May 21-23, 2008 – Lecce (ITALY)
Museo Sigismondo Castromediano di Lecce
Viale Gallipoli 28
I-73100 Lecce hosted by the National Nanotechnology Laboratory of CNR‐INFM and the SA‐NANO European project (Contract No. STRP013698) Organizers: Liberato Manna and Roman Krahne (National Nanotechnology Laboratory) Wolfgang J. Parak (Philipps Universität Marburg) NaNaX 3 is supported by the following companies and institutions:
2M STRUMENTI
NaNaX 3 Program Wednesday May 21 9:00 – 9:10 Welcome chaired by Uri Banin Session I: Growth (1) 9:10 ‐ 9:40 A1: Artificial molecules built from colloidal nanocrystals Paul Alivisatos (invited) University of California‐Berkeley, USA 9:40 ‐ 10:10 A2: Electronic structure of graphene: the effect of quantum confinement Alessandra Lanzara (invited) 10:10 – 10:30 A3: Blue Luminescence and Superstructures from Magic Size Clusters of CdSe Michael Krueger, F. S. Riehle, R.Bienert, R. Thomann, G. Urban Freiburg Materials Research Center (FMF), University of Freiburg, Freiburg, Germany; Institute for Microsystems Technology (IMTEK), University of Freiburg, Freiburg, Germany; Institute of Physical Chemistry, University of Freiburg, Freiburg, Germany University of California‐Berkeley, USA 10:30 – 10:50 10:50 – 11:10 11:10 – 11:40 11:40 – 12:00 A4: Gel electrophoresis as a tool for size and shape selective nanocrystal preparation Carsten Soennichsen, Matthias Hanauer, Sebastien Pierrat, Inga Zins, Alexander Lotz Institute for Physical Chemistry, University of Mainz, Mainz, Germany. Coffee break A5: Co based nano ‐objects Katerina Soulantica (invited) CNRS Toulouse, France A6: Colloidal magnetic‐semiconductor oxide heterostructures: site‐selective epitaxial growth of spherical γ‐Fe2O3 domains onto phase‐controlled TiO2 nanorods Raffaella Buonsanti, Elvio Carlino, Fabia Gozzo, Vincenzo Grillo, Cinzia Giannini, Liberato Manna, Miguel Angel Garcia, Roberto Cingolani, Davide Cozzoli Nanotechnologie Laboratory of CNR‐INFM, Unità di Ricerca IIT, Distrett Tecnologico ISUFI, Lecce, Italy; TASC‐
INFM‐CNR National Laboratory, Area Sciente Park‐Basovizza, Trieste, Italy; CNR Istituto di Cristallografia (IC), Bari, Italy;Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland; Institute of Applied Magnetism and Departement of Materials Physiks, Las Rozas, Madrid, Spain 12:00 – 12:20 A7: Synthesis and characterisation of coated ferrite nanoparticles for theranostic application Claudio Sangregorio, Adriano Boni, Maria F. Casula, Patrizia Floris, Claudia Innocenti, Alessandro Lascialfari, Massimo Marinone, Wolfgang J. Parak, Costanza Ravagli Dipartimento di Chimica and INSTM, Università di Firenze, Sesto Fiorentinono , Italy; Dipartimento di Scienze Chimiche and INSTM, Università di Cagliari, Monserrato , Italy; Istituto di Fisiologia e Chimica Biologica, Università di Milano, Milano, Italy; Philipps Universitaet Marburg,Marburg, Germany; Centro Ricerche Colorobbia, Sovigliana, Vinci,Italy 12:20 – 12:40 A8: Amine‐borane derivatives as new reagents for the synthesis of core‐shell magnetic nanoparticles Catherine Amiens, Diana Ciuculescu, Gilles Alcaraz, ,A. Falqui,Marc Respaud, Pierre Lecante, Robert E. Benfield, Linqin Jiang,Kai Fauth, Alevtina Smeckova,Fabrice Wilhelm, Andrei Rogalev, Bruno Chaudret Laboratoire de Chimie de Coordination, CNRS‐UPR8241, Toulouse, France; Laboratoire de Physique et Chimie des Nano‐Objets, INSA,Toulouse, France; Centre d’Elaboration des Matériaux et d’Etudes Structurales, CNRS,Toulouse, France; Functional Materials Group, School of Physical Sciences, University of Kent, Canterbury, U.K; Max‐Planck‐Institut fuer Metallforschung,Stuttgart, Germany; European Synchrotron Radiation Facility,Grenoble Cedex, France 12:40 – 13:00 A9: Manipulation and electroluminescence of individual CdSe nanocristals on carbon‐based surfaces Geneviève Comtet,Elizabeth Boer‐Duchemin, Gérald Dujardin, Edern Tranvouez Laboratoire de Photophysique Moléculaire, Université Paris‐Sud,Orsay, France 13:00 – 14:30 Lunch chaired by Liberato Manna Session II: Optics 14:30 – 15:00 A10: Ultrafast dynamics in nanostructures Guglielmo Lanzani (invited) Politecnico di Milano, Italy 15:00 – 15:30 A11;: White light emitting semiconductor nanocrystals Andrey Rogach (invited) Ludwig‐Maximilian‐Universitaet, Germany 15:30 – 15:50 A12: Hybrid colloidal nanocrystal‐organics based LEDs Aurora Rizzo, Marco Mazzeo, Yanqin Li, and Giuseppe Gigli 15:50 – 16:10 A13: Novel Multi‐photon Microscopy based on Resonant Nonlinear Optics of Colloidal Quantum Dots Francesco Masia, Wolfgang Langbein, Paola Borri National Nanotechnology Laboratory of CNR‐INFM, 73100 Lecce, Italy School of Physics and Astronomy, Cardiff University, Cardiff, UK; School of Biosciences, Cardiff Univerity, Cardiff, UK 16:10 – 16:30 A14: Stable and tunable quantum dot‐dye hybrids: Preparation, transient absorption and single particle spectroscopy Thomas Basché, Ting Ren, Liu, Prasun Mandal, Victor Matylitsky, Wolfgang Erker, Gerald Hinze, Yuri Avlasevich, Klaus Muellen, Josef Wachtveitl Institut für Physikalische Chemie, Johannes Gutenberg‐ Universitaet, Mainz, Germany; Max Planck‐Institut für Polymerforschung, Mainz, Germany; Institut für Physikalische und Theoretische Chemie, Universität Frankfurt, Frankfurt, Germany 16:30 – 16:50 Coffee break 16:50 – 17:20 A15: Mesoscopic enhancement of emission and scattering of light in nanostructures S. V. Gaponenko (invited) 17:20 – 17:40 A16: Charge carrier dynamics of individual semiconductor nanostructures Alf Mews, Anton Myalitsin, Zhen Li, Zhe Wang, Jessica Voelker, Ma Xuedan, Maxime Tchaya, Andreas Kornowski B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Belarus Department of Chemistry‐Biology, University of Siegen, Siegen, Germany; Institute of Physical Chemistry, University of Hamburg, Hamburg, Germany 17:40 – 18:00 A17: Linearly polarized light emission of single CdSe/CdS tetrapod‐shaped nanocrystals Christian Mauser , Thomas Limmer, Enrico Da Como, Andrey Rogach, Jochen Feldmann, Dimitri V. Talapin Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig‐Maximilian‐Universität, Muenchen, Germany;Department of Chemistry, The University of Chicago, Chicago, Illinois, USA 18:00 – 18:20 A18: Synthesis and optical spectroscopy of highly luminescent type‐II CdTe/CdSe and ZnTe/CdSe colloidal heteronanocrystals Celso de Mello Donegá, Veronique Gevaerts, Esther Groeneveld, Patrick T.K.Chin, Rolf Koole, Evelien M. van Schrojenstein Lantman Condensed Matter and Interfaces – Debye Institute, Utrecht University, Utrecht, The Netherlands 18:20 – 18:40 A19: Energy transfer from CdSe quantum dots to oriented CdSe quantum rods Patrick T. K. Chin, Rifat A. M. Hikmet, Stefan C. J. Meskers, René A. J. Janssen Molecular Materials and Nanosystems, Eindhoven University of Technology, Eindhoven, The Netherland; Photonic Materials & Devices, Philips Research Laboratories Eindhoven, High Tech Campus, Eindhoven,The Netherlands 18:40 – 19:00 A20: Coherent X‐ray Diffraction Imaging of non periodic single objects Cinzia Giannini, Liberato De Caro, Antonella, Guagliardi, Daniele Pelliccia, Stefano Lagomarsino, Alessia Cedola, Christian Mocuta, Till Hartmut Metzger Istituto di Cristallografia – Consiglio Nazionale delle Ricerche (IC‐CNR), Bari, Italy; Istituto di Fotonica e Nanotecnologie – CNR (IFN‐CNR), Roma, Italy; ESRF, BP 220, Grenoble Cedex, France; Institut für Synchrotronstrahlung ‐ ANKA‐ Forschungszentrum Karlsruhe ,Eggenstein‐Leopoldshafen, Germany 19:00 – 19:20 A21: Inkjet printed nanocrystal photodetectors operating up to 3 micrometer wavelength Wolfgang Heiss, M. Böberl, M. V. Kovalenko, S. Gamerith, E. J. W. List Institute of Semiconductor and Solid State Physics University Linz, Linz, Austria; C.Doppler Laboratory Advanced Functional Materials, Institute of Solid State Physics, Graz University of Technology, Graz, Austria; Institute of Nanostructured Materials and Photonics, Johanneum Research, Weiz, Austria 19:20 – 19:40 A22: Fabrication and optical characterization of Photonic Crystal Nanocavities with Colloidal Nanocrystals Luigi Martiradonna, L.Carbone, A. Tandaechanurat , M.Kitamura, B.Antonazzo, S. Iwamoto, L.Manna, R. Cingolani, Y. Arakawa, M. De Vittorio IIS, INQIE, RCAST, the University. of Tokyo; NNL‐ISUFI, Università del Salento, Italy 20:00 Memorial lecture of Paul Alivisatos for Giulia Adesso Thursday May 22 Session III: Bio applications and surface functionalization (1) chaired by Wolfgang Parak 9:00 – 9:30 A23: Infrared Emitting quantum Dots for in‐vivo Imaging: Opportunities in the clinic? Marcel Bruchez (invited) Carnegie Mellon University, USA 9:30 – 9:50 A24: Au nanoparticles integrated and bi‐metal – clad waveguide biosensors A.S. Batti, H. M. Quddusi, M. Yasar 9:50 – 10.10 A25: Exploring interfactions between Nanoparticels and Biological Systems Neus G. Bastús, Joan Comenge, Scorro Vàzquez‐Campos, Eduald Casals, Miriam Varon, Victor Puntes Department of Physics COMSATS Institute of Information Technology, Islamabad, Pakistan Institut Català de Nanotecnologia, Campus UAB Bellaterra,Barcelona,Spain; Institut Català de Recerca i Estudis Avançats (ICREA) Barcelona, Spain 10:10 – 10:30 A26: Incorporation of Polyelectrolyte Multilayer Capsules by living Cells Pilar Rivera Gil, A. Muñoz Javier, P. del Pino, M. Bedard, A. Skirtach, O. Kreft, G. Sukhoruko, W. J. Parak Fachbereich Physik, Phillips Universität Marburg, Marburg, Germany; Max‐Planck ‐Institut für Kolloid‐und Grenzflächenforschung, Golm, Germany 10:30 – 10:50 Coffee break 10:50 – 11:20 A27: Effect of nature, size and coating on biochemical applications of magnetite nanoparticles Maria Del Puerto Morales, A. G. Roca, R. Costo, S. Veintemillas‐Verdaguer, C.J. Serna (invited) 11:20 – 11:40 A28: Rod shaped semiconductor nanocrystals elicit neuronal activity in vivo Claudia Tortiglione, Maria Ada Malvindi, Alessandra Quarta, Luigi Carbone, Angela Tino, Liberato Manna, Teresa Pellegrino Instituto de Ciencia de Materiales de Madrid, Madrid (Spain) CNR, Istituto di Cibernetica “E Caianiello”Pozzuoli, Italy; National Nanotechnology Laboratory of CNR‐INFM, Unità di ricerca IIT and Scuola Superiore ISUFI, Lecce, Italy 11:40 – 12:00 A29: Bioconjugation strategies and temperature controlled cell uptake of gold nanoparticles obtained by laser ablation in liquid solution Vincenzo Amendola, Moreno Meneghetti 12:00 – 12:20 A30: Bioimaging using less‐toxic Quantum Dots Thomas Nann, Salam Massadeh, Shu Xu, Alexei Merkoulov 12:20 – 12:40 A31: Bifunctional Nanocomposites: Synthesis, Surface Functionalization and Application S.Tamil Selvan, Alex W. H. Lin, Pranab K. Patra, Chung Yen Ang, Shujun Gao, Georgia C. Papaefthymiou, Jackie Y. Ying Department. of Chemical Sciences, University of Padova, Padova, Italy School of Chemical Sciences and Pharmacy University of East Anglia(UEA), Norwich, UK Institute of Bioengineering and Nanotechnology, The Nanos, Singapore; Department of Physics, Villanova University, Villanova, Pennsylvania, USA 12:40 – 13:00 A32: Surface chemistry of colloidal PbSe nanocrystals Iwan Moreels, Bernd Fritzinger, David De Munck, Frank Vanhaecke, José C. Martins, Zeger Hens Physics and Chemistry of Nanostructures, Ghent University, Ghent, Belgium; NMR Structure Analysis Unit, Ghent University, Ghent, Belgium; Laboratory of Analytical Chemistry, Ghent University, Ghent, Belgium 13:00 – 14:30 Lunch Session IV: Bio applications and surface functionalization (2) 14:30 – 15:00 A33: Formation of Tissue by Nanoactions of Cells Joachim Spatz (invited) chaired by Marcel Bruchez University of Heidelberg, Germany 15:00 – 15:20 A34: A general one‐step biofunctionalization of magnetic nanoparticles: chemistry and surface characterization. Davide Prosperi, Laura Polito, Diego Monti Department of Organic and Industrial Chemistry, University of Milan, Milan, Italy; Nanobiotechnology Laboratory of CNR‐ISTM, Milan, Italy 15:20 – 15:40 A35: Biotemplates for nanoparticle deposition Nadja C. Bigall, Manuela Reitzig, Paul Simon, Wolfgang Naumann, Karl‐Heinz van Pée, Alexander Eychmüller Physical Chemistry, TU Dresden, 01062 Dresden, Germany; Biochemistry, TU Dresden, 01061 Dresden, Germany; MPI Chemical Physics of Solids, 01187 Dresden, Germany 15:40 – 16:00 A36: Colloidal quantum dot ligand characterization by solution NMR Zeger Hens,Bern Fritzinger, Petra Lommens, Rolf Koole, Ivan Moreels, Jose C. Martins Physics and Chemistry of Nanostructures, Ghent University, Ghent, Belgium; Organic Chemistry Department, Ghent University, Ghent, Belgium; Condensed Matter and Interfaces, Utrecht University, Utrecht, The Netherlands 16:00 – 16:20 A37: Size determination water‐soluble colloidal nanoparticles ‐ a comparison of different techniques Ralph A. Sperling, Feng Zhang, Marco Zanella, Wolfgang J. Parak Phillips Universitaet Marburg,AG Biophotonics, Marburg, Germany 16:30 – 19:00 20:30 ‐ …. Poster session and Coffee Conference dinner at Torre del Parco / nomination of best student poster‐award winner Friday May 23 Session V: Growth (2) chaired by Katerina Soulantica 9:00 – 9:30 A38: Semiconductor nanoparticles‐carbon nanotubes composites Beatriz H. Juárez, C. Klinke, A. Kornowski, A.B. Hungría, P.A.Midgle, and H. Weller (invited) Institute of Physical Chemistry, University of Hamburg, Department of Materials Science. University of Cambridge 9:30 – 10:00 A39: Cadmium‐free highly luminescent semiconductor nanocrystals Peter Reiss (invited) 10:00 – 10:20 A40: Defect‐induced transformation of lamellar regions of silver nanoprisms from fcc to hcp crystal structure Damian Aherne, Deirdre Ledwith, Matthew Gara, John M. Kelly School of Chemistry, Trinity College Dublin, Ireland A41: Effector‐controlled growth of silver shells on gold nanoparticles in batch and under micro flow‐through conditions P. Mike Guenther, J. Michael Koehler, Henry Romanus CEA Gernoble, France 10:20 – 10:50 Technische Universität Ilmenau, Ilmenau, Germany 10:50 – 11:10 11:10 – 11:30 Coffee break A42: On the Incorporation Mechanism of Hydrophobic Quantum Dots in Silica Spheres by a Reverse Microemulsion Method Rolf Koole, Matti van Schooneveld, Jan Hilhorst, Celso de Mello Donega, Dannis’t Hart, Alfons Van Blaaderen, Daniel Vanmaekelbergh, Andries Meijerink CMI, Debye Institute, Utrecht University, Utrecht, The Netherlands; Soft Condensed Matter, Debye Institute, Utrecht University, Utrecht, The Netherlands 11:30 – 11:50 A43: Size Distribution of Superparamagnetic Particles and Clusters Determined by Magnetic Sedimentation J.‐F. Berret, O. Sandre, A. Mauger Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris‐VII, Bâtiment Condorect, Paris, France; Laboratoire Liquides Ioniques et Interfaces Chargées, UMR7612 CNRS Université Pierre et Marie Curie Paris‐VI, Paris, France; Dépatement Mathématique Informatique Physique Planète et Université, CNRS, Paris, France 11:50 – 12:20 12:20 – 12:50 A44: Hybrid metal‐ semiconductor nanoparticles: a new type of functional materials Uri Banin (invited) Hebrew University, Jerusalem, Israel A45: Carbon Nanotubes: useful templates for hybrid materials production Miguel A. Correa‐Duarte (invited) University of Vigo, Spain 12:50 – 13:10 A46: 2D and 3D Nanocrystal Systems: Applications between Optics and Electronics Jessica Pacifico, Paul Mulvaney, Luis M. Liz‐Marzán Departamento de Química Física, Universidade de Vigo,Vigo, Spain; BIO21 Institute, University of Melbourne, Parkville, Australia 13:10 – 14:30 Lunch chaired by Roman Krahne Session VI: Electronics and Devices 14:30 – 15:00 A47: Proximity effects and collective phenomena in nanocrystalline semiconductor systems Oded Millo, Dov Steiner, Hadar Levi, Doron Azulay, Isaac Balberg, Assaf Salant, Assaf Aharoni, Uri Banin (invited) Racah Institute of Physics and the Center for Nanoscience and Nanotechnology; Institute of Chemistry and the Center for Nanoscience and Nanotechnology; The Hebrew University of Jerusalem, Israel 15:00 – 15:20 A48: Memory and photoconductivity effects in zinc oxide nanoparticle films Neil C. Greenham, Jianpu Wang, Yizheng Jin 15:20 – 15:50 A49: PbSe quantum dots: single‐particle energy levels and quantum mechanical coupling measured with Scanning Tunneling Microscopy K. Overgaag, P. Liljeroth, B. Grandidier, D. Vanmaekelbergh Cavendish Laboratory,Cambridge, U.K. Condensed Matter and Interfaces Debye Institute, Utrecht University, Utrecht, The Netherlands; Institut d'Electronique, de Micro‐électronique et de Nanotechnology, ISEN, Lille, France; IBM Zuerich Research Laboratory,Rueschlikon, Switzerland. 15:50 – 16:10 A50: Dipolar Structures in Colloidal Dispersions of PbSe and CdSe Quantum Dots Arjan Houtepen, M. Klokkenburg, R. Koole, B.H. Erné, D. Vanmaekelbergh Condensed Matter and Interfaces, Utrecht University, Utrecht,The Netherlands; Van ’t Hoff Laboratory for Physical and Colloid Chemistry, Utrecht University,Utrecht, The Netherlands ; Opto‐electronic Materials, Delft University of Technology, The Netherlands 16:10 – 16:40 A51: Electrical transport and Raman scattering of a single organic molecule Israel Bar‐Joseph (invited) Weizmann Institute, Israel 16:40 – 17:00 Coffee break chaired by Israel Bar‐Joseph Session VII: Theory 17:00 ‐ 17:30 A52: Distribution of carrier multiplication rates in nanocrystals Eran Rabani (invited) University of Tel Aviv, Israel 17:30 – 17:50 A53: Implications of CoPt3‐Au interface properties on the growth of colloidal CoPt3‐Au nanocrystal heterodimers: an ab initio study Letizia Chiodo, Fabio Della Sala, Teresa Pellegrino, Roberto Cingolani, Liberato Manna 17:50 – 18:10 A54: Plasmon Coupling Between Gold Nanorod and Adsorbed Organic Molecule Anushree Roy, Goutam Chandra, Gautam Mukhopadhyay National Nanotechnology Laboratory of CNR‐INFM, Lecce, Italy Indian Institute of Technology, Kharapur, India;Department of Physics, Indian Institute of Technology Mumbai India 18:10 – 18:30 A55: Excited state properties of functionalized Silicon Quantum Dots: A theoretical investigation based on time‐dependent DFT Thomas A. Niehaus , Xian Wang, Quansong Li, Ruiqin Zhang, Thomas Fraunheim Bremen Center for Computational Materials Science Bremen, Germany; Centre of Super‐Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China Session VIII: Assembly chaired by Oded Millo 18:30 – 18:50 A56: Micrometer‐scale assembly of colloidal CdSe/CdS nanorods Concetta Nobile, Luigi Carbone, Milena De Giorgi, Giovanni Morello, Roberto Cingolani, Liberato Manna, Roman Krahne Scuola Superiore ISUFI and National Nanotechnology Laboratory of CNR‐INFM, Distretto Tecnologico, Lecce, Italy; 18:50 – 19:10 A57: Colloidal nanocrystal based nanocomposites as novel functional materials M. Striccoli, C. Ingrosso, A. Panniello, C. Sciancalepore, T. Placido, A. Agostiano, M.L. Curri,R. Comparelli, A. Convertino, G. Leo V. Fakhfouri, J. Y. Kim J. Brugger, R. Tommasi, T. Cassano A. Voigt, F. Reuther, G. Gruetzner, D. Mecerreyes, J. A. Alducin, N. Kehagias, V. Reboud, C. M. Sotomayor Torres Dipartimento di Chimica, Università di Bari, Italy; CNR‐IPCF Bari Division, Italy;CNR‐ISMN Roma Division, Italy; Microsystems Laboratori, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland ;Dipartimento di Biochimica Medica, Biologia Medica e Fisica Medica, Università di Bari,Italy; Micro Resist Technology GmbH, Berlin,Germany; CIDETEC‐Centre for Electrochemical Technologies, San Sebastian,Spain; Tyndall National Institute, Cork, Ireland 19:10 – 19:30 A58: Highly persistent superparamagnetic needles obtained by controlled co‐assembly of iron oxide nanoparticles and polymers Jérôme Fresnais, Jean‐François Berret and Olivier Sandre Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris‐VII, Paris, France; Laboratoire Liquides Ioniques et Interfaces Chargées, UMR 7612 CNRS Université Pierre et Marie Curie Paris‐
VI, Paris, France 19:30 – 20:00 Concluding remarks, nomination of best student oral‐award winner, and farewell cocktail Session I: Growth (1)
ARTIFICIAL MOLECULES BUILT FROM COLLOIDAL NANOCRYSTALS
Paul Alivisatos
Department of Chemistry, University of Berkeley, USA
Colloidal nanocrystals can be thought of as artificial atoms, or units with controllable density of
electronic states. In recent years we have been working on coupled colloidal nanocrystals, to create
artificial molecules. One example involves branched nanocrystals, such as tetrapods, the individual
branches of which can be wired up into a transistor. A more recent example involves the creation of
regularly spaced colloidal quantum dots within a rod shaped semiconductor nanocrystal. In a third
example, we can use DNA to direct the assembly of specific nanoparticle groupings. In all cases,
we are able to observe in solution-grown materials some interesting condensed matter physics
previously observed in materials produced by much more exotic methods.
A1
Session 1: Growth (1)
Quasiparticle dynamics in epitaxial graphene films
Alessandra Lanzara, Shuyun Zhou, David Siegel, Alexei Fedorov
a
Department of Physics, University of California, Berkeley, USA
b
Lawrence Berkeley National Laboratory, Berkeley, California
Corresponding author: Alessandra Lanzara, email: [email protected]
The electronic structure of single and bilayer graphene films is studied by high resolution angle resolved
photoemission spectroscopy. The evolution of the band structure and many body interactions is studied as a
function of sample thickness. By monitoring the film growth with low energy electron microscopy (LEEM)
sample with different domain size are grown. The effect of confinement on the band structure is discussed.
References:
1.
S. Y. Zhou, et al. Nature Physics 2006, (2), 595
2.
S. Y. Zhou et al. Physica E 2007
3.
S. Y. Zhou et al. Nature Materials 2007, (6), 770
A2
Session I: Growth (1)
Blue Luminescence and Superstructures from Magic Size Clusters of CdSe
F. S. Riehle1,2, R.Bienert3, R. Thomann1, G. Urban2, M. Krüger1,2
1
Freiburg Materials Research Center (FMF), University of Freiburg
Stefan Meier Strasse 21, D- 79104 Freiburg, Germany
2
Institute for Microsystems Technology (IMTEK), University of Freiburg,
George Köhler Allee 103, D-79110 Freiburg, Germany
3
Institute of Physical Chemistry, University of Freiburg
Albertstrasse 23a, D-79104 Freiburg, Germany
Corresponding author: Michael Krüger, Fax 00497612034701, email: [email protected]
We present a new method leading to a new type of stable magic size clusters of CdSe with an exceptional
narrow blue emission and a full width at half-maximum (FWHM) of 19nm without size selection. TEM
characterization shows the uniformity of the clusters with a mean diameter of 1.6 nm. Surface modification
of the clusters results in the formation of ultra-thin nanowires demonstrating their potential as building
blocks for highly-ordered superstructures. Moreover their apparent advantages for applications like LEDs
and fluorescent labelling are discussed.
A3
Session I: Growth (1)
Gel electrophoresis as a tool for size and shape selective nanocrystal preparation
Matthias Hanauer, Sebastien Pierrat, Inga Zins, Alexander Lotz, Carsten Sönnichsen ,
a
Institute for Physical Chemistry, University of Mainz, Jakob-Welder-Weg 11, 55128 Mainz, Germany.
Corresponding author: C.S. Fax: +49 6131 3926747 E-mail: [email protected]; http://www.nano-bio-tech.de
The chemical synthesis of inorganic nanoparticles in solution often yields a large distribution of particle sizes
and multiple particle shapes, e.g. rods, spheres and triangles. To use size and/or shape dependent material
properties, such as quantum confinement or plasmon resonances, it is critical to have nanoparticles with the
lowest size and shape dispersion possible. The need for ultra-narrow size and shape distributions becomes
highly important for self-assembly of nanoparticles over large areas which would be required for many
devices, for example solar cells. An alternative to the high-yield synthesis of nanoparticles with ultra-narrow
size distribution is the post-synthetic separation of particles similar to cleaning procedures in organic
synthesis.
We show here how the technique of gel electrophoresis is successfully used to separate nanoparticles
according to size and shape [1]. Gel electrophoresis is commonly used to separate biomolecules and has been
used to sort nanoparticles according to the exact number of attached polymer chains. We separate polymercoated spherical, rod-shaped and triangular gold and silver nanoparticles, which show strong colors induced
by plasmon resonances. The strong influence of size and shape on the frequency or wavelength of the
plasmon resonance would make it desirable to obtain mono-disperse samples for optical applications. The
strong shape/color relationship also allows direct visual or spectroscopic analysis of successful separations,
which appear as multicolored lanes in a gel. Compared to other separation techniques such as centrifugation,
HPLC (High Performance Liquid Chromatography), capillary electrophoresis, diafiltration, or size exclusion
chromatography, gel electrophoresis has the advantage of allowing multiple runs in parallel on the same gel,
which is a considerable advantage at the stage of understanding mechanisms and optimizing conditions.
Figure 4. a) Electrophoretic separation of silver
nanoparticles according to surface coating in a
0.3 % agarose gel run for 30 min at 150 V (15 cm
electrode spacing) in 0.5x TBE buffer (pH ≈ 9). The
coating consists of SH-PEG-X molecules with -X =
-OCH3, -SH, -NH2, or -COOH as indicated. The
different fractions are prepared by mixing different
proportions of SH-PEG-X with SH-PEG-OCH3. The
two horizontal lines mark the position of the gel
wells. b) Comparison of the mobilities of gold
spheres (Ø ≈ 20 nm, BBI) deduced from analyzing
gels with those measured by dynamic light
scattering (DLS). The zeta potential is calculated
from the measured mobilities using the Henry
formula. Those mobilities agree within the errors of
the experiments, except for an offset caused by
electro-osmotic flow in the gel as shown by the
mobility of vitamin B12.
References:
[1] M. Hanauer, S. Pierrat, I. Zins, A. Lotz, C.
Sönnichsen Nano Lett., 7, 2881 (2007)
A4
Session I: Growth
Cobalt based nano-objects
K. Soulantica LPCNO-INSA Toulouse France
Due to their magnetic properties, Co containing nano-objects, are interesting for a number of
applications. Several forms of cobalt nanocrystals can be synthesised by reduction of a coordination
cobalt compound under H2 in the presence of a long chain acid and a long chain amine. Among them,
monocrystalline cobalt nanorods are especially interesting thanks to their high anisotropy
(magnetocrystalline and of shape). Superlattices of Co nanorods are obtained by spontaneous
organisation in solution during the synthesis. The long axes of the nanorods correspond to the easy
magnetisation axis of the nanocrystals and such organisations expose a surface of tips 1 (photo).
These nanorod superlattices are ferromagnetic at r.t. and they are characterized by a strong coercive
field. Therefore this system can be considered as a good candidate for high density magnetic
recording.
However, in order to render these objects useful in a real application, several issues have to be
addressed. Some examples are the mechanical stability (attachment on a flat substrate), the
conservation of the magnetic properties, which may deteriorate due to the oxidation and the
organisation over large areas in a reproducible and controlled way.
The functionalisation of these nanorods may facilitate their implementation in real devices by offering
solutions for some of these problems. One way of functionalisation is the controlled growth of another
metal on the surface of Co. The growth of Au nanoparticles either on the tips of cobalt nanorods in a
selective way, or on the whole body can be achieved by controlling the nanarods surface coverage by
ligands 2 . Pt on the other hand gives rise to Co@Pt core-shell objects which could be resistant towards
oxidation.
Finally a different kind of cobalt containing nano-objects, are CdSe nanorods with Co tips, either
spherical or elongated, which could be of interest for biological applications.
1
F. Wetz, K. Soulantica, M. Respaud, A. Falqui, B. Chaudret, Mater. Sci. Eng. C, 2007, 27,
1162
2
Wetz, K. Soulantica, A. Falqui, M. Respaud, E. Snoeck, B. Chaudret Angew. Chem. Int.
Ed., 2007, 46, 7079.
A5
Session I: Growth (1)
Colloidal magnetic-semiconductor oxide heterostructures: site-selective epitaxial growth of
spherical γ-Fe2O3 domains onto phase-controlled TiO2 nanorods
Raffaella Buonsanti,1* Vincenzo Grillo,2 Elvio Carlino,2 Cinzia Giannini,3 Fabia Gozzo,4 Miguel Angel Garcia,5
Liberato Manna,1 Roberto Cingolani,1 and P. Davide Cozzoli1
1
National Nanotechnology Laboratory of CNR-INFM, Unità di Ricerca IIT, Distretto Tecnologico ISUFI, via per
Arnesano km 5, I-73100 Lecce, Italy.
2
TASC-INFM-CNR National Laboratory, Area Science Park - Basovizza, Bld MM, SS 14, Km 163.5, I-34012 Trieste,
Italy
3
CNR-Istituto di Cristallografia (IC), via Amendola 122/O, I-70126 Bari, Italy
4
5
Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
Institute of Applied Magnetism and Department of Materials Physics, UCM, P. O. Box 155, 28230 Las Rozas,
Madrid, Spain
* To whom all correspondence should be addressed: Phone:+39-0832-298271. Fax: +39-0832-298238. Email: [email protected]
The recognition of the dimensionality-dependent physical-chemical properties of nanoscale inorganic matter
has stimulated efforts toward the fabrication of nanostructured materials in a controlled and systematic
manner. Colloidal routes have now advanced to the point of allowing facile access to a variety of finely sizeand shape-tailored nanocrystals (NCs) by adjusting thermodynamically and kinetically-limited growth
processes in liquid media. While refinement of this synthetic ability is far from being exhausted, the
increasing demand for multi-purpose nano-objects has recently oriented efforts of nanochemistry research to
envision first prototypes of hybrid nanocrystals (HNCs) with a topologically controlled composition.1 Here,
we describe surfactant-assisted seeded-growth approaches to fabricate elaborate noncentrosymmetric HNCs,
which comprise semiconductor/magnetic sections interconnected together through small inorganic interfaces.
The nanocrystal heterostructures are fabricated by heterogeneous nucleation of γ-Fe2O3 onto crystal-phasecontrolled TiO2 nanorod seeds.2-3 The latter can be decorated at either of their tips or at their longitudinal
sidewalls, sharing epitaxial heterointerfaces that can tolerate rather large large lattice mismatch. The
heterostructure topology can be controlled by switching the TiO2 seeds between the anatase and the brookite
crystal phase. Our results illustrate how the surfactant-controlled reactivity of the exposed seed facets, the
interfacial strain involved at the relevant junction regions, and local lattice distortion mechanisms interplay at
the nanoscale and dictate the final heterostructures topology. These studies suggest useful criteria for the
rational design of novel generations of HNC with high structural complexity and increased functionality.
[1] P. D. Cozzoli, T. Pellegrino, L. Manna, Chem. Soc. Rev. 2006, 35, 1195.
[2] R. Buonsanti, V. Grillo, E. Carlino, C. Giannini, M. L. Curri, C. Innocenti, C. Sangregorio, K.
Achterhold, F. G. Parak, A. Agostiano, P. D. Cozzoli, J. Am. Chem. Soc. 2006, 128, 16953.
[3] R. Buonsanti, V. Grillo, E. Carlino, C. Giannini, F. Gozzo, M. A. Garcia, L. Manna, R. Cingolani, P. D.
Cozzoli, in preparation
A6
Session I: Growth (1)
Synthesis and chacarterisation of coated ferrite nanoparticles for theranostic application
Adriano Bonia, Maria F. Casulab, Patrizia Florisb, Claudia Innocentia, Alessandro Lascialfaric, Massimo Marinonec,
Wolfgang J. Parakd, Costanza Ravaglie, Claudio Sangregorioa
a
Dip. di Chimica and INSTM, Univ. di Firenze, via della Lastruccia, 3 Sesto F.no 50019, Italy
Dip. di Scienze Chimiche and INSTM, Univ. di Cagliari, Cittadella Universitaria, Monserrato 09042, Italy
c
Ist. di Fisiologia e Chimica Biologica, Univ. di Milano, Via Trentacoste 2, 20134, Milano, Italy
d
Philipps Univ. Marburg, Renthof 7, 35032 Marburg, Germany
e
Centro Ricerche Colorobbia, via Pietramarina 53, Sovigliana, Vinci, 50053 (FI), Italy
b
Corresponding author: Claudio Sangregorio, Fax 00390554573336, email: [email protected]
In the last few decades magnetic nanoparticles had a large impact in biomedicine, the interest extending onto
many areas, including contrast agents for magnetic resonance imaging, drug targeting, diagnostics, molecular
biology, cell separation and purification, and hyperthermia therapy (MFH).1, 2 In this widespread scenario we
started a project aimed to design a new biocompatible material based on magnetic nanoparticles allowing a
two-fold anticancer action, i.e. combining the therapeutic effect of targeted drug-delivery with hyperthermia
for the treatment of widespread diseases. Moreover the possession of enhanced relaxometric properties was
also pursed in order to track the path and the deposition of the carriers inside human body and tumoral cells
by MRI.
In this contribution we present the synthesis, the investigation of the static and dynamic magnetic properties
and of the hyperthermic and relaxometric efficacy of highly monodisperse ferrite particles with average size
of few nanometers embedded in different chemical environments and coated by properly designed grafting
molecules.
Monodisperse ferrite nanoparticles, MFe2O4, M = Mn, Fe and Co, were prepared by rapid decomposition of
metalcarbonyl into a hot solvent in the presence of a coordinating surfactant, followed by an oxidation step.
The size of the particles was tuned in the 4-15 nm range, by varying the metalcarbonyl/surfactant molar
ratio. This allowed to systematically investigate the dependence of the relaxometric and hyperthermic
efficacy on the magnetic properties of the nanoparticles, which in turn, depends on the particles dimension,
on the coating and on the composition. In particular the comparison between the magnetic behaviour of the
three materials considered allowed to clarify the role of magnetic anisotropy in the shortening of the
relaxation times and in increasing the heat release capability. The understanding of such relations allowed to
attain the capability of tailoring the properties of the nanomaterials and to select the best promising products
for the proposed biomedical applications.
A7
Session I : Growth (1)
Amine-borane derivatives as new reagents for the synthesis of core-shell magnetic nanoparticles
Diana Ciuculescu,a Gilles Alcaraz,a Catherine Amiens,a A. Falqui,b Marc Respaud,b Pierre Lecante,c Robert E.
Benfield,d Linqin Jiang,eKai Fauthe, Alevtina Smeckova,f Fabrice Wilhelm,f Andrei Rogalevf and Bruno
Chaudreta
a
Laboratoire de Chimie de Coordination, CNRS-UPR8241, 205 Route de Narbonne, 31077 Toulouse, France
Laboratoire de Physique et Chimie des Nano-Objets, INSA, 135 Avenue de Rangueil, 31077 Toulouse, France
c
Centre d’Elaboration des Matériaux et d’Etudes Structurales, CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse,
France
d
Functional Materials Group, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, U.K.
e
Max-Planck-Institut fu¨r Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart, Germany
f
European Synchrotron Radiation Facility, BP 220, F-38043, Grenoble Cedex France
b
Corresponding author: Catherine Amiens, Fax 0033561553003, email: [email protected]
Remarkable control over the size, shape, organization and surface chemistry of colloidal nanocrystals
of different materials: semiconductors, metals or even bimetallic systems, is now reach. This allows
already a fine control of their physical properties. However, in the case of bimetallic nanocrystals, the
control over the inside chemical distribution is still a challenge. As their properties will greatly depend
on the chemical distribution: statistical or ordered alloy, core-shell distribution of both elements, it
needs to be adjusted as a function of the application envisaged (catalysis, microelectronics or for
biological applications). A first typical example is the FePt system, which presents in the bulk state the
highest magnetic anisotropy known only when it adopts the ordered tetragonalL1,0 phase.1 When this
chemical order is reached, the material is the best suited for applications such as ultrahigh density
magnetic data storage. Unfortunately, this situation is never reached via solution phase synthesis.2
Another example is the coating of ferromagnetic seeds by noble metals in a core-shell arrangement to
afford air protection, biocompatibility and allow for further functionalization of the nanoparticles.
Here again, no straightforward route is available. It is thus of crucial importance to develop new routes
for the control of the chemical distribution inside bimetallic nanoparticles.
This report will present our strategy for the synthesis of core-shell bimetallic nanocrystals based on a
kinetic control of the chemical distribution. On a test system, FeRh, we have already demonstrated that
taking advantage of the faster hydrogenation of olefinic complexes versus amido complexes, it was
possible to produce Rh@Fe nanoparticles.3 Here, we will show that the reverse chemical distribution,
i.e. with the noble metal at the surface, can also be reach. For the synthesis of the corresponding
Fe@Rh nanoparticles, a process based on the use of amine-borane (AB) derivatives has been
designed, which will be discussed into details. In agreement with their different chemical distribution,
the structure of the nanoparticles as probed by WAXS, and EXAFS varies from one system to the
other. As well, Mössbauer spectroscopy and XMCD measurements evidence very different magnetic
behaviors. Generalization of this method to various systems such as CoRh, NiFe, FePt, FeAu … will
be discussed.
Fe@Rh
Rh@Fe
Fig. 1: Schematic representation of the influence of reaction conditions on structural and magnetic properties of
FeRh nanosystems
References:
1.
Sun, S.; Murray, C. B.; Weller, D.; Folks, L.; Moser, A. Science 2000, 287, 1989.
2.
Delalande, M.; Marcoux, P. R.; Reiss, P.; Samson, Y. J. Mater. Chem. 2006, 17, 1579.
3.
Ciuculescu, D.; Amiens, C.; Respaud, M.; Falqui, A.; Lecante, P.; Benfield, R. E.; Jiang, L.; Fauth, K.;
Chaudret, B. Chem. Mater. 2007, 19, (19), 4624-4626.
A8
Session I: Growth (1)
Manipulation and electroluminescence of individual CdSe nanocristals on carbon-based surfaces
Elizabeth Boer-Duchemin, Geneviève Comtet, Gérald Dujardin, Edern Tranvouez
Laboratoire de photophysique Moléculaire, Bât. 210, Université Paris-Sud, 91405 Orsay, France
Corresponding author: Genevieve Comtet, Fax 0033169156697, email: [email protected]
Carbon-based surfaces such as graphite and diamond have unique structural and electronic
properties for studying the manipulation and electroluminescence of individual CdSe nanocristals.
When deposited under ultrahigh vacuum on an HOPG graphite surface, CdSe elongated
nanocristals (nanorods) capped with phosphonate ligands are all aligned along the three C-C bond
directions of the graphite surface. Manipulation of individual CdSe nanorods with the atomic force
microscope (AFM) indicates that (i) friction is strongly anisotropic on the graphite surface and (ii)
dynamic friction is markedly smaller than static friction most probably due to the disordering of the
molecular ligands during manipulation.
Conductive AFM has been used to investigate electronic excitation of individual CdSe
nanocristals on hydrogenated diamond surfaces through electron-hole pair injection. This relies on the
unique electronic properties of hydrogenated diamond surfaces which display strong p-type doping.
These studies open interesting perspectives for using an individual CdSe nanocristal as a
photon nanosource.
A9
Session II: Optics
Ultrafast electron-hole dynamics in CdSe/CdS nanorods
Maria Grazia Lupo, Dario Polli, Margherita Zavelani-Rossi, Guglielmo Lanzani
Dipartimento di Fisica, Politecnico di Milano (Italy)
Angela Fiore, Fabio della Sala, Roberto Cingolati, Liberato Manna
National Nanotechnology Laboratory of CNR-INFM, Lecce (Italy)
Sub-ps pump-probe experiments are carried out in CdSe/CdS dot/rod nanocrystals, in which the CdSe dot is
embedded into the CdS rod. Samples are colloidal nanorods in solution, kept at room temperature.
Photobleaching dynamics due to state filling is explored upon tuning the pump photon energy and intensity.
A picture for the electron-hole dynamics at the interface, within the nanostructure, is obtained together with a
model for band alignment and wavefunction delocalization, supported by theoretical calculations. Stimulated
emission and saturation phenomena are explored in view of nanocrystals applications.
A10
Session II: Optics
White light emitting semiconductor nanocrystals
Andrey L. Rogach
Photonics & Optoelectronics Group, Physics Department and Center for NanoScience (CeNS), Ludwig-MaximiliansUniversität München, Amalienstr. 54, 80799 München, Germany
Fax 00498921803441, email: [email protected]
Solid state white light emitting devices have a great potential to reduce the global electricity consumption.
Luminescent semiconductor nanocrystals are potentially useful candidates for white lightening applications.
We present two bright white light emitting semiconductor nanocrystal based systems. CdS nanocrystals emit
white light due to the presence of surface states over the entire range of the visible spectrum, while onion
like CdSe/ZnS/CdSe/ZnS core-shell-shell-shell NCs are designed to emit white light as a result of the
combination of blue and orange emissions from the CdSe shell and the CdSe core, respectively (Fig. 1). The
shade of the white light can be controlled during synthesis by varying the thickness of the CdSe shell. The
relative intensities of both emission lines are additionally determined by intra-nanocrystal energy transfer.
Fig. 1: White light emission from core-shell-shell semiconductor nanocrystals.
References:
1. S. Sapra, S.; Mayilo, S.; Klar, T. A.; Rogach, A. L.; Feldmann, J. Bright white light emission from
semiconductor nanocrystals: by chance and by design, Adv. Mater. 2007, 19, 568.
A11
Hybrid colloidal nanocrystal-organics based LEDs
A. Rizzo, M. Mazzeo, Yanqin Li, and G. Gigli
National Nanotechnology Laboratory of CNR-INFM, 73100 Lecce, Italy
Corresponding author: Aurora Rizzo, Fax 00390832298270, email: [email protected]
Light emitting devices (LEDs) based on colloidal semiconductor nanocrystals represent a matter of technological
interest for the development of flat panel display and lighting systems.[1] The appealing features of these materials are
the high fluorescence efficiency, narrow ban edge emission, potential chemical stability, and tunable light emission
across the visible spectrum. These characteristics open the way to a new class of hybrid devices in which the flexible
technology of organic LEDs can be combined with the long operating lifetime of inorganic semiconductor devices.
We demonstrate the first efficient hybrid light-emitting device, with white emission from chemically and optically
stable ternary nanocrystal composites dispersed in an organic matrix. White bright emission is obtained from
homogenous blends, exploiting the energy transfer and charge-trapping properties of the different species. The
maximum brightness of the device is 1050 cd m-2 at 58 mA cm-2, which corresponds to a current efficiency of 1.8cd A-1,
and a turn-on voltage of 6V are measured in air atmosphere. (Figure 1a) The proposed approach is a new general
method for the fabrication of potential long operating lifetime, high efficiency white light-emitting devices.[2]
Subsequently we worked in the development of a new QD depositions technique. Spin-coating,[1,2] drop-casting,[3]
electrodeposition[4] and Langmuir-Schafer[5] techniques are all reported methods for QDs wet deposition.
Nevertheless using wet method is possible to deposit only a two layer device structure by means phase separation or by
using different solvents for QDs and organic molecules. Consequently the integration of these materials in the Light
Emitting Devices (LEDs) is limited by the lack of an appropriate deposition technique that can allows for the
fabrication of high efficiency and multilayered devices. In this scenario we developed two dry, simple, and inexpensive
deposition techniques to transfer colloidal semiconductor QDs onto organic substrates. These innovative techniques are
modification of the standard microcontact printing (μCP) and combines the ease of wet deposition processes with the
possibility to grow a heterojunction QDs-LED using thermal evaporation. We exploit these methods to integrate QDs in
multilayer organic light emitting diodes. White and red (Figure 1b) electroluminescence from colloidal QDs has been
obtained demonstrating that these deposition techniques are fully compatible with OLED technology. [6]
Fig. 1 a) top: Photoluminescence spectra corresponding to isolated lake blue, green and red quantum dots, which
measured in solid state; bottom: Electroluminescence spectrum for the device: ITO//PEDOT:PSS//CBP:QDs(B,G,R,
c%=18:2:1)//Alq3//Ca/Al; inset: a picture of the working device. b) Electroluminescence (EL) (solid line) and
photoluminescence (PL) (dashed line) spectra of the red hybrid light emitting device by μCP technique; inset: a picture
of the working device.
References:
1. S. Coe, W. K. Woo, M. G. Bawendi, V. Bulović, Nature (London), 420 800 (2002)
2. Y. Q. Li, A. Rizzo, R. Cingolani, G. Gigli, Adv. Mater., 18 2545 (2006)
3. X. M. Lin, H. M. Jaeger, C. M. Sorensen, K. J. Klabunde, J. Phys. Chem. B.,105 3353 (2001)
4. M. A. Islam, I. P. Herman, I. P. Appl. Phys. Lett., 80 3823 (2002)
5. V. Santhanam, J. Liu, R. Agarwal, R. P. Andres, Langmuir, 19 7881 (2003)
6. A. Rizzo, M. Mazzeo, M. Palumbo, G. Lerario, S. D’Amone, R. Cingolani, and G. Gigli, Advanced Materials
adma.200701480 in press.
A12
Session II: Optics
Novel Multi-photon Microscopy based on Resonant Nonlinear Optics of Colloidal Quantum Dots
Francesco Masiaa*, Wolfgang Langbeina, and Paola Borrib
a
School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK.
b
School of Biosciences, Cardiff University, Cardiff CF10 3US, UK.
Corresponding author: Francesco Masia, Fax 004429 2087 4056, email: [email protected]
z position (μm)
FWM Intensity (arb. units)
-1
-1
Absorption (cm μM )
FWM Intensity (arb. units)
y position (μm)
Colloidal quantum dots (CQDs) have been investigated intensively in the last years as innovative
fluorophores for applications in microscopy owing to their unique optical properties.1 Differently from
standard organic dyes, CQDs exhibit a broad band absorption increasing towards shorter wavelengths, and
yet a narrow emission spectrum. CQDs emitting at different wavelengths can therefore be excited by a single
monochromatic light source, greatly simplifying multiple marker imaging. Moreover, CQDs exhibit high
photostability as compared to organic dyes.2 However, fluorescence microscopy is often severely limited by
background fluorescence that can originate from endogenous object constituents (autofluorescence) or from
unbound or non-specifically bound fluorescent probes (reagent background).
In this work we have developed of a novel coherent multiphoton microscopy which is not based on
fluorescence but exploits resonant four-wave mixing (FWM) signal from CQDs. This method joins the
inherent 3D sectioning capability of multiphoton microscopy with the coherent nature of the FWM signal,
which can be detected interferometrically free from any incoherent autofluorescence background. As a proof
of principle, we have demonstrated FWM imaging on TOPO-capped CdSe/ZnS colloidal quantum dots
emitting at 610nm which were drop cast on a glass coverslip. In the experiment, two 130fs laser pulses excite
the CQDs in resonance with the ground-state absorption peak at 590nm. High numerical aperture (NA=1.25)
objectives are used to excite and collect the FWM in transmission. A heterodyne detection scheme allows for
frequency selection of the FWM signal instead of directional selection.3 Figure (a) shows the FWM intensity
4
4
as a function of position in an xy scan (pixel
1
b)
a)
0.9
size 0.1μm×0.1μm) for an incident power of
0.8
3
3
0.7
3.2 ⋅10 4 Wcm −2 .
Regions with different
0.6
concentration of QDs are clearly visible. The
0.5
2
2
0.4
maximum intensity in the image (red in the
0.3
colour scale) is three orders of magnitude
0.2
1
1
0.1
greater than the non-resonant background
4E-4
0
0
(blue). Figure (b) shows an xz scan of the same
0
1
2
3
4
0
1
2
3
4
region for y = 0.2μm, demonstrating the optical
x position (μm)
x position (μm)
sectioning capability. We measured a spatial
1.5
resolution below the diffraction limit, as
d) 4
c)
expected due to the nonlinear nature of the
1.0
3
FWM signal, resulting in about 180nm lateral
FWHM=180nm
resolution (see figure (c)) and ~550nm axial
2
resolution. We have determined the sensitivity
0.5
1
of our technique from the measured saturation
of the FWM field amplitude and the number of
0.0
0
dots in the focal volume estimated by their
-0.2
0.0
0.2
500
550
600
650
Wavelength (nm)
absorbance. We infer a minimum of
x position (μm)
~ 10 CQDs Hz detectable in the focal volume (limited by shot noise). We have also investigated the
dependence of the FWM emission on the excitation wavelength. The FWM has a clear resonant behavior
with maximum emission for an excitation wavelength at the ground-state absorption peak (see figure (d)).
With the present development of bio-compatible CQDs, our results open the perspective to apply this new
imaging modality to cell microscopy with high sensitivity and spatial resolution.
References:
1.
Michalet, X.; Pinaud, F. F.; Bentolila, L. A.; Tsay, J. M.; Doose, S.; Li, J. J.; Sundaresan, G.; Wu, A. M.;
Gambhir, S. S.; Weiss, S. Science 2005, 307, (5709) ,538-544.
2.
Wu, X.; Liu, H.; Liu, J.; Haley, K. N.; Treadway, J. A.; Larson, J. P.; Ge, N.; Peale, F.; Bruchez, M.P. Nature
Biotechnology 2003, 21, (1), 41-46.
3.
Borri, P.; Langbein, W.; Mørk, J.; Hvam, J. M. Optics Communication 1999, 169, (1-6), 317-324.
A13
Session II: Optics
Stable and tunable quantum dot-dye hybrids: Preparation, transient absorption and single particle
spectroscopy
Thomas Baschéa, Ting Rena, Liub, Prasun Mandala, Victor Matylitskyc, Wolfgang Erkera, Gerald Hinzea, Yuri
Avlasevichb, Klaus Müllenb, Josef Wachtveitlc
a
Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz
b
Max Planck-Institut für Polymerforschung Mainz
c
Institut für Physikalische und Theoretische Chemie, Universität Frankfurt
Corresponding author: [email protected]
Hybrid materials composed of inorganic semiconductor quantum dots (QD) and organic dye molecules
(Dye) are being increasingly considered for sensing and photovoltaic applications. As these strongly rely on
excitation energy transfer (EET) and/or electron transfer (charge separation) between the two components, it
is mandatory to get an improved understanding of electronic coupling at the inorganic/organic interface.
Based on the versatile surface chemistry of the QDs a number of approaches have been developed to prepare
QD-dye conjugates, which can serve as relatively simple model systems for such studies [1, 2].
Fig. 1: Emission spectra of a single CdSe/CdS/ZnS-Perylenecarboxyimide complex embedded in a PMMA host as a
function of time. In spectrum 1 QD emission is almost completely quenched by two dye molecules attached to QD.
After sequential bleaching of the dye molecules (spectra 2, 3) QD emission (~ 535 nm) dominates the spectra
(recording-time per spectrum: 2 s).
In the present work we have prepared complexes from CdSe/CdS/ZnS core/shell QDs and rylenecarboximide dyes. Complex formation was mediated by carboxylate moieties directly attached to the dye
molecules. These bi-dentate anchors give rise to stable complex formation by chelate type coordination to
Zn2+-ions at the QD surface. After the complexes have formed in solution they can be precipitated, purified
and re-dissolved which demonstrates the high stability and processability of these novel QD/Dye conjugates.
Further advantageous features are the rather well-defined binding geometries and EET efficiencies which can
be tuned by size quantization of QD and Dye. EET from QD to Dye has been studied by steady state
absorption and emission, transient absorption and single molecule spectroscopy. From transient absorption
spectroscopy the time scale of the EET process in solution can be directly deduced which lies in the range of
several hundred picoseconds depending on the actual composition of the QD/Dye complex. At the single
particle level we simultaneously measure spectra, fluorescence lifetimes and correlation functions which give
further insight into the ET dynamics. A typical sequence of spectra is shown in Fig. 1. QD emission
quenching can be satisfactorily modeled by a FRET type process, yielding QD/Dye distances being close to
those estimated from the binding model. Because we can quite accurately control QD/Dye distances and
spectral overlaps our approach promises to quantitatively check for the limits of a Förster type description of
EET in QD/Dye complexes.
References:
1. O. Schmelz, A. Mews, Th. Basché, A. Herrmann, K. Müllen, Langmuir 17 (2001) 2861-2865.
2. A. Clapp, I. Medintz, H. Mattousi, ChemPhysChem 7 (2006) 47-57.
A14
Session II: Optics
Mesoscopic enhancement of emission and scattering of
light in nanostructures
S. V. Gaponenko
Stepanov Institute of Physics, Minsk 220072, Belarus
[email protected]
Interaction of a quantum system with electromagnetic field experiences strong modification in
mesoscopic structures with topological singularities of dielectric function, e.g. in microcavities, photonic
crystals, complex dielectrics metal-dielectric nanostructures. The latter offer superior enhancement
factors because of surface plasmon resonance. The highest enhancement of 1015 times is reported and
provides single molecule detection by means of Raman scattering.
The present contribution will provide state-of-the-art and outlook for the variety of mesoscopic
enhancement effects on atoms, molecules and quantum dots. Elementary photon emission and scattering
events are considered alike [1]. Enhancement mechanisms then break into two groups of effects, namely:
incident field enhancement by means of localization of electromagnetic field at the absorption frequency,
and local density of photon states enhancement by means of electromagnetic field redistribution at the
emission frequency. Model mesoscopic structures are reviewed (metal colloids, nanoshells, aggregates,
nanotextured surfaces) both in experimental and theoretical aspects and the resulting factor of 1015 as
limiting theoretical estimate is shown to be affordable. Favorable estimates are directly applicable to
enhanced Raman and Rayleigh scattering which have no finite lifetimes and therefore do not obey
sensitivity to undesirable competitive processes of quenching. Unlike scattering, spontaneous emission of
photons by an excited quantum system bear unwanted sensitivity to non-radiative energy transfer to metal
which by no means allow observation of superior luminescence enhancement. One order of the magnitude
is a typical performance of surface enhanced luminescent structures. Possible positive balance of local
field enhancement, density of states enhancement and non-radiative energy transfer is discussed. Surface
nanoengineering to control dielectric spacing between light emitting species and metal surface is
reviewed with emphasis at polyelectrolytes[2] as appropriate spacers. Experiments with semiconductor
nanocrystals[3] are discussed in detail.
The work has been supported by the FP6 “SA-NANO” Project.
1. S. V. Gaponenko, Physical Review B 65, 140303 (R) (2002).
2. O.Kulakovich et al., Nanotechnology, 17, 5201 (2006).
3. O. Kulakovich et al., Nanoletters 2, 1449 (2002).
A15
Session II: Optics
Charge carrier dynamics of individual semiconductor nanostructures
Alf Mewsa*, Anton Myalitsina, Zhen Lia, Zhe Wanga, Jessica Voelkera, Ma Xuedana, Maxime Tchayaa, Andreas
Kornowskib
a
Department of Chemistry-Biology, University of Siegen, 57068 Siegen, Germany
Institute of Physical Chemistry, University of Hamburg, 20146 Hamburg, Germany
b
Corresponding author: Alf Mews, Fax 004902717402805, email: [email protected]
Fluorescence spectroscopy of individual CdSe nanostructures like nanocrystals (NCs) and nanowires (NWs)
can be used as a tool to investigate their charge carrier dynamics. While the emission wavelength is
depending on the size (diameter) of the nanocrystals (nanowires), the emission intensity is strongly related to
their (molecular) surface modification and/or their charging state. As a model it is discussed, that photo
generated charge carriers are trapped at the surface or in the surrounding of the nanostructures, which
changes the charging state and hence their fluorescence properties.
Here we present several methods to chemically and physically tune the charging state of the nanostructures
to manipulate their fluorescence properties. Firstly we will show how functional metal complex ligands with
tunable molecular energy levels will affect the fluorescence of CdTe nanocrystals. Upon metal complexation
a hole transfer from the NCs to the ligands is blocked and the fluorescence is increased. Thus, these NCligand complexes might be useful as a senor for metal ions. Further we show how the fluorescence of
individual NCs can be investigated in conductive Polymer matrices. While the fluorescence in hole
conducting polymers (TPD) is completely quenched, the particles are clearly visible in an electron
conducting matrix (PBD). These experiments might lead to a detailed understanding of the recombination
mechanism of NCs in polymer LEDs and also shed light on the fluorescence mechanism of single particles
with a defined charging state. Eventually, these mechanisms can also be used to explain the fluorescence of
individual CdSe-NWs. Those NWs can be prepared by a seeded growth mechanism and have macroscopic
dimensions in length (> μm) but a diameter below that of the bulk exciton (< 10 nm). Hence there is a
similarity between NCs and NWs and several features which have recently been observed for NCs are also
present for the NWs. (e.g. the fluorescence intensity fluctuations of single emitters). Here we show results of
fluorescence spectroscopy from single CdSe NWs which have also been characterized by AFM to establish a
structure-property relationship. Finally we show first results on the fluorescence properties of NWs which
are integrated into a field effect transistor (FET) device, such that the charging state can be manipulated
through the macroscopic contacts.
Fig. 1: a) Nanocrystals with functional ligands. b) Fluorescence of individual nanocrystals in a PBD matrix. c) Force
and fluorescence microscopy of individual nanowires
A16
Session II: Optics
Linearly polarized light emission of single CdSe/CdS tetrapod-shaped
nanocrystals
Christian Mauser1, Thomas Limmer1, Enrico Da Como1, Andrey Rogach1, Jochen Feldmann1, Dmitri V. Talapin2
1
Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universität München,
Amalienstr. 54, 80799 Munich, Germany
2
Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
Corresponding author: Christian Mauser, Fax 0049(0)8921803441, email: [email protected]
Branched semiconductor nanocrystals have been considered as active materials in optoelectronic devices
such as photovoltaic cells [1,2]. Shape control during particle synthesis provides a large potential for
wavefunction engineering [3]. We have recently reported on highly luminescent CdSe/CdS tetrapod
heterostructures (Figure 1a), where wurtzite CdS arms were grown on CdSe zinc-blend nuclei [4]. Due to
the peculiar energy band alignment the holes remain trapped in the CdSe core, whereas electrons in ideal
tetrapods are expected to delocalize symmetrically into the four CdS arms. However, polarization
dependent photoluminescence experiments on single tetrapods show asymmetric localization effects for
electrons. Whereas in optical excitation nearly no polarization anisotropy is observed, high polarization
degrees, described by (Imax – Imin/ Imax + Imin), are present in the emission process, as shown in Figure 1b,c.
(b)
50
40
5nm
(a)
30
20
10
Absorption
50
40
Occurence
PL Intensity
0
(c)
30
20
10
350
400
450
500
550
600
650
700
750
Wavelength (nm)
0
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
Polarization anisotropy
Fig1: (a) Absorption (green line) and photoluminescence (PL) (blue line) spectra for a dilute solution of tetrapods.
Red bars represent a histogram for single tetrapods PL spectra. The inset in (a) shows a TEM picture of a single
tetrapod. Polarization anisotropy histograms in excitation (b) and emission (c) for a total of more than 200 single
tetrapods. Both anisotropies were measured at 5 K.
Calculations based on the effective mass approximation show that the wavefunction confinement is very
sensitive to changes in the shape of the tetrapods. In particular, they highlight the role of arm thickness in
the localization process. Therefore, breaking the symmetry by increasing the thickness of one arm gives rise
to a strongly asymmetric localization of the electron and leads to high polarization degrees in emission. The
related changes in electron-hole wavefunction overlap result in a correlation between emission intensity and
polarization anisotropy in agreement with our experimental findings. The CdSe/CdS tetrapods provide an
ideal system to explore and observe wavefunction symmetry breaking in branched nanocrystals.
References:
[1] Liberato Manna, Delia J. Milliron, Andreas Meisel, Erik C. Scher, A. Paul Alivisatos, Nature Materials 2, (6), 382-385 (2003).
[2] Ilan Gur, Neil A. Fromer, Chih-Ping Chen, Antonios G. Kanaras, A. Paul Alivisatos, Nano Letters 7, 409 (2007).
[3] J. Müller, J. M. Lupton, P. G. Lagoudakis, F. Schindler, R. Koeppe, A. L. Rogach, J. Feldmann, D. V. Talapin, H.
Weller, Nano Letters. 5, 2044 (2005).
[4] Dmitri V. Talapin, James H. Nelson, Elena V. Shevchenko, Shaul Aloni, Bryce Sadtler, and A. Paul Alivisatos,
Nano Letters 7, 2951 (2007).
A17
Session II: Optics
Synthesis and optical spectroscopy of highly luminescent type-II CdTe/CdSe and ZnTe/CdSe colloidal
heteronanocrystals
Veronique Gevaertsa, Esther Groenevelda, Patrick T.K. Chinb, Rolf Koolea, Evelien M. van Schrojenstein Lantmana, and
Celso de Mello Donegáa*,
a
Condensed Matter and Interfaces - Debye Institute, Utrecht University, 3508TA Utrecht, The Netherlands
Molecular Materials and Nanosystems, Eindhoven University of Technology, 5600MB Eindhoven, The Netherlands
b
*Corresponding author: Celso de Mello Donegá, Fax: 0031302532403, email: [email protected]
Semiconductor heterostructures can show different behavior regarding charge carrier localization after
photoexcitation (type-I or type-II), depending on the energy offsets between the valence and conduction band
levels of the materials that are combined at the heterointerface.1 In the type-I case both carriers are primarily
confined in the same part of the heterostructure, while in the type-II case electrons and holes are spatially
separated on different sides of the heterojunction, leading to the formation of an indirect exciton. The relative
energy offsets in heteronanocrystals can be tuned by controlling the composition, size and shape of each
component, since the energy levels of semiconductor nanocrystals (NCs) are strongly size- and shapedependent, and may also be affected by electronic coupling between the components. This offers the
possibility of directly controlling the degree of electron-hole wavefunction overlap, and consequently the
material optoelectronic properties (e.g. emission wavelength, exciton radiative lifetimes, etc.), with important
consequences for a number of potential applications. In this work we investigate the optical properties of
CdTe/CdSe and ZnTe/CdSe colloidal heteroNCs by a number of spectroscopic techniques (viz. absorption,
emission and excitation spectra, PL quantum yields, exciton lifetimes). The CdTe-CdSe system is chosen
because it offers the possibility to tune the behavior from type-I to type-II, making it a convenient model
system to investigate the formation of indirect excitons. The ZnTe-CdSe system is interesting because it is
chemically and structurally similar to CdTe-CdSe, while providing larger energy offsets and a much smaller
lattice mismatch. The preparation methodology developed yields highly efficient (PL QY up to 80% at 300
K) anisotropic heteroNCs, with shapes tunable from prolate to rod or branched heteroNCs. Depending on the
growth conditions quasi-spherical core/shell QDs can also be obtained. The exciton PL gradually shifts to
lower energies as the dimension of the CdSe part increases (e.g. from 2.25 eV for 2.8 nm CdTe cores to 1.60
eV for bipods consisting of 10 nm long CdSe arms on a 3 nm core,2 Figure 1). The emission red-shift is
accompanied by a large increase in the exciton radiative lifetime (e.g., from 15 ns to 300 ns for the NCs
shown in fig.1) and a decrease in the absorption oscillator strengths at the emission energies, clearly
indicating the gradual decrease of the
electron-hole wavefunction overlap
and the formation of an indirect
exciton. High PL QYs associated
with long (indirect) exciton lifetimes
imply low defect concentrations,
therefore attesting the high-quality of
the heteroNCs prepared in this work.
Fig. 1: Left:: TEM image of CdTe/CdSe heteroNCs.2 Right: Absorption and emission spectra of the
CdTe/CdSe heteroNCs shown in d (red) and the CdTe cores from which they were grown (blue).
References:
1.
Hatami, F.; Grundmann, M.; Ledentsov, N.N.; Heinrichsdorff, F.; Heitz, R.; Böhrer, J.; Bimberg, D.; Ruvimov,
S.S.; Werner, P.; Ustinov, V.M.; et al.; Physical Review B 1998, 57, 4635.
2.
Chin, P.T.K.; de Mello Donegá, C.; van Bavel, S.S.; Meskers, S.C.J.; Sommerdijk, N. A. J. M.; Janssen,
R.A.J.; Journal of the American Chemical Society 2007, 129, 14880.
A18
Session II: Optics
Energy transfer from CdSe quantum dots to oriented, CdSe quantum rods
Patrick T. K. China*, Rifat A. M. Hikmetb, Stefan C. J. Meskersa, and René A. J. Janssena
a
Molecular Materials and Nanosystems, Eindhoven University of Technology, 5600MB Eindhoven, The Netherlands
Photonic Materials & Devices, Philips Research Laboratories Eindhoven, High Tech Campus 4, 5656 AE Eindhoven ,
The Netherlands
b
*
Corresponding author: Patrick T.K. Chin, email: [email protected]
Rod-shaped crystals can be macroscopically aligned by dispersion and subsequent stretching in polymer
films, or by rubbing a layer with a velvet cloth.1,2 This opens the opportunity to create composites with
intrinsically anisotropic optical and electronic properties, functioning as polarized light sources. Such light
sources can have a significant energy-saving advantage over conventional backlight systems in LCDs where
absorbing polarizers that discard at least 50% of the incident light intensity are used. In such an application
one can make use of a lamp emitting unpolarized light and use a polarized light emitter to convert the
unpolarized light into polarized light.
Here we explore the energy transfer from spherical quantum dots (QDs) to aligned quantum rods (QRs) in
solid films.3 CdSe/CdS core shell QDs are used as donor and highly-luminescent CdSe/CdS QRs with a
fluorescence quantum yield up to 45% and an aspect ratio of 4.4 as acceptor. The QRs can be aligned on a
macroscopic scale by rubbing a thin film of the QR-QD mixture deposited on a polymer layer The
orientation of the rods is evidenced by linearly polarized luminescence with a degree of polarization of 35%
The absorption of light by the QDs remains unpolarized upon rubbing. In the film, energy transfer form QD
to QR is evidenced by a quenching of the QD emission and a shortening of its excited state lifetime. The
energy transfer converts unpolarized light absorbed by the QD into linearly polarized luminescence emitted
by the QR. This novel nanophosphor composite has therefore polarizing properties and may be useful in e.g.
LC displays as a converter unpolarized backlight into polarized emission.
Fig. 1: Schematic representation of the energy transfer from QD tot QR upon excitation perpendicular
to the QR orientation; electron microscope photo of CdSe/CdS QRs
References:
1.
2.
3.
Peng, X.; Manna, L.; Yang, W.; Wickham, J.; Scher, E.; Kadavanich, A.; Alivisatos, A. P.; Nature 2000, 404,
59.
Hikmet, R. A. M.; Chin, P. T. K.; Talapin, D. V.; Weller, H. Adv. Mater. 2005, 17, 1436.
Chin, P.T.K.; Hikmet, R.A.M.; Meskers, S.C.J.; Janssen, R.A.J. Adv. Funct. Mater. 2007, ASAP.
A19
Session II: Optics
Coherent X-ray Diffraction Imaging of non periodic single objects
Cinzia Gianninia*, Liberato De Caroa, Antonella Guagliardia, Daniele Pellicciab,+, Stefano Lagomarsinob, Alessia
Cedolab, Christian Mocutac, Till Hartmut Metzgerc
a
Istituto di Cristallografia – Consiglio Nazionale delle Ricerche (IC-CNR), via Amendola 122/O, I- 70126 Bari, Italy
b
Istituto di Fotonica e Nanotecnologie – CNR (IFN-CNR), via Cineto Romano 42, I-00156 Roma, Italy
c
ESRF, BP 220, F-38043 Grenoble Cedex, France
+
present address: Institut fur Synchrotronstrahlung - ANKA- Forschungszentrum Karlsruhe in der HelmholtzGemeinschaft Herman-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen Germany
Corresponding author: Cinzia Giannini, Fax 00390805929170, email: [email protected]
Coherent X-ray diffraction imaging (CXDI) is one of the most promising techniques to study the structure
and behaviour of non periodic single objects or non periodic assembly of objects at the nanoscale. The first
CXDI experiments were performed using planar incident waves1,2 while the significance of CXDI with
curved wavefronts has been demonstrated by Williams et al3 using a zone plate as primary optics to produce
a coherent X-rays point-like source.
A successfully Fresnel CXDI experiment with hard x-rays was recently performed using two planar crossed
waveguides as optical elements, leading to a virtual point-like source4. The coherent wavefield obtained with
this novel set-up, was used to illuminate a test single object (butterfly). This pioneering work first brought
together three concepts - the use of waveguides to produce a coherent X-rays point-like source, X-ray in-line
holography, and iterative retrieval of X-ray diffraction phases in Fresnel geometry. A digital twodimensional in-line holographic reconstruction of the test object was straightforwardly obtained via Fast
Fourier Transform of the raw data at a source size limited resolution of 200 nm. A 50 nm diffraction limited
spatial reconstruction of the single object was achieved by phase retrieval techniques. Perspectives to
nanosized single objects will be discussed.
Fig. 1: data and
encoded formation
References:
1.
J. Miao, P. Charalambous, J. Kirz, and D. Sayre, Nature (London) 400, 342 (1999)
2.
J. M Zuo, I. Vartanyants, M. Gao, R. Zhang, and L.A. Nagahara. Science 300, 1419, (2003); D. Shapiro, P.
Thibault, T. Beetz, V. Elser, M.R. Howells, C. Jacobsen, J. Kirz, Lima, J. Miao, Nieman & D. Sayre, Proc. Nat.
Acad. Sci. USA 102, 15343 (2005)
3.
H. M. Quiney, A. G. Peele, Z. Cai, D. Paterson, and K. A. Nugent, Nature Phys. 2 101 (2006); G. J. Williams, H.
M. Quiney, B. B. Dhal, C. Q. Tran, K. A. Nugent, A. G. Peele, D. Paterson, and M. D. de Jonge, Phys. Rev. Lett.
97, 025506 (2006).
4.
L. De Caro, C. Giannini, D. Pelliccia, C. Mocuta, T.H. Metzger, A. Guagliardi, A. Cedola, I. Burkeeva, S.
Lagomarsino (unpublished).
A20
Session II: Optics
Inkjet printed nanocrystal photodetectors operating up to 3 micrometer wavelength
W. Heissa, M. Böberla, M. V. Kovalenkoa, S. Gamerithb, E. J. W. Listb,c
(a)
(b)
Institute of Semiconductor and Solid State Physics, University Linz, A-4040 Linz, Austria
Christian Doppler Laboratory Advanced Functional Materials, Institute of Solid State Physics, Graz University
of Technology, A-8010 Graz, Austria
(c)
Institute of Nanostructured Materials and Photonics, Johanneum Research, A-8160 Weiz, Austria
We demonstrate the first inkjet-printed electro-optical nanocrystal devices, namely infrared
photodetectors operating at room temperature in the whole visible spectral region as well in the infrared.
The photodetectors are based on HgTe nanocrystals synthesized in aqueous solutions via a room
temperature reaction between Hg(ClO4)2 and H2Te gas1. After exchanging the hydrophilic thioglycerol
ligands by hydrophobic dodecanethiol, a 2 wt% HgTe nanocrystal/chlorobenzene solution was inkjet
printed on top of interdigitate electrode structures as shown in Fig. 1a2. It is emphasized that the inkjetprinting of colloidal nanocrystals is a mass-effective and a highly reproducible technique. The inkjetprinted HgTe photodetectors exhibit a current increase by two orders of magnitude with respect to the
dark current under monochromatic illumination at 1.4 m and powers of only 42 W (see Fig. 1b). The
cut-off wavelength of the HgTe nanocrystal detectors with 3 nm large nanocrystals is found at 2 m
(see sensitivity spectra in Fig. 1c). By increasing the number of successive printed layers the sensitivity
can be increased. At small illumination powers a maximum sensitivity of 4.4 A/W is achieved for small
bias voltages of 10V. The maximum observed sensitivity corresponds to a room temperature detectivity
of D*=3.2*1010 cmHz1/2W-1 measured at a wavelength of 1.4 m, which is about 3 orders of magnitude
higher as is obtained for epitaxially grown quantum dot photoconductors operating at the same
wavelength. The long-wavelength cut-off of the photoresponse can be tuned by the size of the used
HgTe nanocrystals. The HgTe nanocrystal photodetectors show distinct photoconductance up to
wavelength of 3 m, which is the longest wavelength so far achieved with solution-processable
materials.
[1] M. V. Kovalenko, E. Kaufmann, D. Pachinger, J. Roither, M. Huber, J. Stangl, G. Hesser, F.
Schäffler, W. Heiss, J. Am. Chem.. Soc. 2006, 128, 3516
[2] M. Böberl, M. V. Kovalenko, S. Gamerith, E. List, W. Heiss, Adv. Mat. 2007, 19, 3574
-6
10
Current [A]
80
42 μW
-7
1 μW
-8
10
-9
10
dark current
-10
10
10
b)
-11
0
2
4
6
Voltage [V]
8
Sensitivity [mA/W]
10
10
6 layer
60
HgTePD1
(3 nm)
4 layer
40
2 layer
1 layer
20
c)
0
1.4
2.0
1.6
1.8
Wavelength [μm]
2.2
Fig. 1: (a) Top view of the nanocrystal photodetector consisting of interdigitated finger-like electrodes and an
array of 16 printed HgTe nanocrystal stripes on top of the electrodes. (b) I-V characteristics of a sample with 6
printed layers in dark and under illumination with 1 W and 42 W. (c) Sensitivity spectra of inkjet-printed
HgTe nanocrystal photodetectors with varying number of printed layers, measured at a bias of 10 V.
A21
Session II: Optics
Fabrication and optical characterization of Photonic Crystal Nanocavities with Colloidal Nanocrystals
L. Martiradonna1,2, L.Carbone2, A. Tandaechanurat 1 , M.Kitamura1, B.Antonazzo2, S. Iwamoto1, L.Manna2,
R. Cingolani2, Y. Arakawa1, M. De Vittorio2
1IIS, INQIE, RCAST, the Univ. of Tokyo、2NNL-ISUFI, Univ. del Salento, Italy
Corresponding author: Luigi Martiradonna, Fax 00390832298238, email: [email protected]
The development of photonic devices based on wet-chemically synthesized semiconductor nanocrystals (NCs) is nowadays
one of the main research topics in international laboratories, due to their broad excitation spectra and narrow emission bands
also at room temperature, tunable optical gain from the UV to the NIR spectral range, high photochemical stability. The
insertion of these nanoemitters into photonic crystal (PC) cavities with localized optical modes having high quality factor (Q)
and small modal volume can be exploited to develop high performing optical devices such as single photon sources, ultra-low
threshold lasers and non-linear devices. At present, several works have been proposed in order to couple colloidal NCs to 2DPC structures fabricated on Si or AlGaAs membrane layers. In this case, the transfer of the nanometric pattern on the rigid
membrane layer through high-resolution etching steps (which could introduce fabrication imperfections on the structure)
deteriorates the optical quality of the photonic crystal; moreover, the absorption of Si and AlGaAs in the visible spectral
range limit the use of these devices to the infrared spectral range.
In this work, we propose the fabrication of semiconductor nanocrystal based 2D-PC nanocavities by directly patterning and
releasing a thin membrane of a functional material composed by NCs dispersed in a positive electronic resist. No pattern
transfer from the resist to underlying membrane layers is required, since the resist itself acts as the suspended waveguiding
layer. Therefore the optical quality of the resonating structure is only determined by a single high-resolution lithographic step,
while it is not affected by any etching process. Moreover, the absence of absorbing backing layers allows the use of NCs
emitting in both the visible and the infrared spectral range, thus giving a broader applicability to our technique.
Fig. 1(a) shows a Scanning Electron Microscopy (SEM) image of the pattern layer composed by an e-beam resist and
colloidal nanocrystals. The chosen pattern is a PC nanocavity in square lattice with modulated air hole radii: this design allows
to obtain high Q-factor localized modes also in low-index contrast slab surrounded by air. Fig. 1(b) shows a sharp peak, with a
Q-factor ~ 700, collected from the suspended resist cavity with micro-photoluminescence measurements at room temperature.
The polarization dependence of the fundamental mode was also studied: degenerated modes with an average spectral splitting
~ 1 nm, comparable to their FWHM, were detected, as shown in Fig. 1(c). The minimum measured spectral splitting was as
low as 0.4 nm. Moreover, the degenerated modes showed orthogonal polarization (see the polar diagram of the two modes in
Fig. 1(d)), as expected from the 3D-FDTD calculations. The high repeatability of the process and the good matching between
the optical measurements and the theoretical predictions demonstrates the effectiveness of this new simple two-step
processing (EBL pattern definition, wet etching of the sacrificial layer).
FIG. 1. (a) SEM image of the fabricated nanocavity; (b) Emission detected from the nanocavity at room temperature,
showing a sharp resonance peak with Q-factor ~ 700; (c) photoluminescence spectra detected from the same nanocavity
through a polarizer, at different angles: two degenerated modes are observed; (d) polar diagram of the degenerated
modes, showing orthogonal polarization.
A22
Session III: Bio applications and surface functionalization (1)
Infrared Emitting Quantum Dots for in-vivo Imaging: Opportunities in the clinic?
Marcel Bruchez
Carnegie Mellon University, USA
A number of potential clinical applications have been demonstrated with infrared quantum dots in animal
model systems. Existing IR-emitting quantum dots are prepared from toxic heavy metals, and hence have
some safety concerns. We have found that CdSe/CdTe nanoparticles can be used for a variety of
applications, including cell tracking, lymph node identification, tumor targeting, and blood-pool imaging.
However, current materials show some evidence of degradation over long-term in-vivo exposure. We have
explored a number of alternative approaches and dosing methods to reduce the amount of material delivered
in these applications.
A23
Session III: Bio applications and surface functionalization (1)
Au nanoparticles integrated and bi-metal – clad waveguide biosensors
H. M. Quddusi, M. Yasar, A. S. Bhatti
Department of Physics
COMSATS Institute of Information Technology,
Park Road, Islamabad 44000. Pakistan.
Corresponding author: A. S. Bhatti, Fax 0092514442805, e-mail: [email protected]
Optical waveguide sensors have widely been used for biosensing and are being actively studied
for sensitivity enhancement. In comparison to metal waveguide biosensors which use single metal film,
the Au nanoparticles were added to the cladding layer and improvements in the sensitivity of the
biosensing device were observed. The addition of nanoparticles on top of the cladding layer has found to
sharpen and narrow the reflectivity minima due to confinement of electrons which enhances the plasmon
resonances, thus making the device highly sensitive to the minute changes in the cover or detecting
medium. Moreover, bimetallic layer of Au/Ag was also studied instead of single Au layer. These
configurations incorporate better evanescent field enhancement and higher resolution in the resonance due
to Ag film and stability to Au film. These two configurations were used to detect e-coli and results are
being discussed for single, bi-metallic and nanoparticles integrated metal – clad waveguide sensors.
A24
Session III: Bio applications and surface functionalization (1)
EXPLORING INTERACTIONS BETWEEN NANOPARTICLES AND BIOLOGICAL
SYSTEMS
Joan Comenge1, Neus G. Bastús1, Socorro Vázquez-Campos1, Eudald Casals1, Miriam Varon1, Victor
Puntes1, 2 *
1 Institut Català de Nanotecnologia, Campus UAB Bellaterra,,08193 Barcelona, Spain.
2 Institut Català de Recerca i Estudis Avançats (ICREA) Barcelona, Spain
[email protected]
Nanomaterials have received enormous attention for their potential applications in biology and
medicine[1] (a revolutionary technology to address single molecules and work inside the cell).
This coming revolution in life sciences may exceed our current expectations and new to come.
However fundamental studies in molecular mechanics, biodistribution, immune barrier
trespassing, remote and local[2] activation and health/environment impact among others are
needed in a simultaneous approach to ensure sustained and successful breakthroughs. Thus,
nanoparticles (NP) can be tailored with different properties such as fluorescence or magnetic
moment. These properties can be harnessed to use them as local nano-probes or nanomanipulators in biological and medical applications (e.g. fluorescence labelling of cellular
compartments, use of fluorescent or magnetic particles as contrast agents, magnetic separation,
targeted drug delivery). Besides, NP derivatized with biological molecules have successfully
been applied in materials science and biological research in recent years. NP biopolymer (like
proteins or DNA) conjugates hold great promise both for biological diagnostics, where the NP
can provide unique detection signatures, and for nanotechnology, where the information content
of the biomolecule can be harnessed for spatial patterning of NPs. There are many strategies
available for bioconjugation of NP, including attachment to biopolymers like elastin, antisense,
biotin-avidin, antigen-antibodies, peptides, proteins, etc. Among the many biological polymers
that can be coupled to NP, proteins are of particular interest, because of their inherent
programmability and biological activity.
Transmission Electron Microscopy images of cells and internalized NP. Top) Bacillus + Amyloid +
Au NPs. Medium) Au NP + Hela cells. Bottom) Macrophages + AuNP. The two first have been
passively internalized via cell membrane recycling, and the third actively via TLR4. Medium pictures in
collaboration with Silvia Pujals and Ernest Giralt (PCB-UB). Bottom pictures in collaboration with Ester
S. Tilló and A. Celada.
[1] A.P. Alivisatos, Scientific American 285 (2001) 66.
[2] M.J. Kogan, N.G. Bastus, R. Amigo, D. Grillo-Bosch, E. Araya, A. Turiel, A. Labarta, E. Giralt,V.F.
Puntes, Nano Letters 6 (2006) 110.
A25
Session III: Bio applications and surface functionalization (1)
Incorporation of Polyelectrolyte Multilayer Capsules by living Cells
P. Rivera Gil1, A. Muñoz_Javier1, P. del Pino1, M. Bedard2, A. Skirtach2, O. Kreft2, G. Sukhoruko2, W. J.
Parak1*
1
Fachbereich Physik, Philipps-Universität Marburg, Marburg, Germany
2
Max-Plank-Institut für Kolloid- und Grenzflächenforschung, Golm, Germany
*
corresponding author: Prof. Dr. Wolfgang Parak, Fachbereich Physik, Philipps Universität Marburg,
Renthof 7, 35037 Marburg, Germany, email: [email protected]
The nanotechnology offers a broad range of applications to the medicine, cell biology,
pharmaceutics, and other disciplines. Specially in controlled-cargo release and targeted drug
delivery find nano- and microparticles a novel role as controlled microenviroments. In the
context of this work, functionalized polymer microcapsule made by layer-by-layer absortion of
oppositely charged macromolecules are being used as delivery system. Firstly, the uptake of
micrometer-sized polyelectrolyte capsules (which are modified by quantum dots, magnetic and
metallic nanoparticles) by living cells is investigated. Secondly, the intracellular localization of
the capsules is also analysed. Finally, the controlled release of the cargo upon the incorporation
process is characterized. The great advantage of these microcapsules in comparison to other
carrier systems is that they can be simultaneously loaded/functionalized with the above
mentioned components, allowing for the combination of their properties in a single object.
A26
Session III: Bio applications and surface functionalization (1)
Effect of nature, size and coating on the biomedical applications of magnetite nanoparticles
M.P. Morales, A. G. Roca, R. Costo, S. Veintemillas-Verdaguer, C.J. Serna
Instituto de Ciencia de Materiales de Madrid, CSIC, C) Sor Juana Inés de la Cruz 3,
Cantoblanco, 28049 Madrid (Spain)
Corresponding author: Maria del Puerto Morales, Fax 003413720623, email: [email protected]
Magnetic nanoparticles have received a growing interest in biomedicine for their possible applications as
magnetic resonant imaging (MRI), delivery of anticancer therapeutic agents to solid tumors and cancer
treatments by magnetic hyperthermia induction [1, 2]. This talk will be divided in three parts showing first,
the effect of the nature of the magnetic nanoparticles on the relaxivity properties of the dispersions and the
contrast in “in vivo” NMR images. Secondly, the effect of the nanoparticle size on the specific absorption
rate produced after applying an alternating magnetic field, which indicates the heat evolution rate in
hyperthermia treatments, will be presented. Finally, the last results on the effect of the coating on the
biocompatibility of the nanoparticles will be described.
Magnetic nanoparticles with improved magnetic properties consisting of core/shell particles of Fe/Fe2O3
have been prepared by laser pyrolysis and evaluated as contrast agents for NMR imaging. Colloidal
suspensions prepared from these iron alloys coated with dextran consist of magnetic particles-aggregates
with hydrodynamic sizes of 75 nm. Magnetic resonance images of rats taken after the intravenously
administration of these Fe colloidal dispersions showed a contrast improvement of 60% in the liver with
respect to the commercial sample [3, 4].
On the other hand, an aqueous route for the preparation of magnetite nanoparticles with sizes around 30
nm and stable in aqueous media at pH 7 and concentrations of 10 mg/ml has been recently developed [5].
Those particles are just around the critical diameter for monodomain behaviour, which could lead to high
power absorption of magnetic fields. According to that, calorimetric experiments resulted in specific power
absorption rates of 80-95 W/g, which are among the highest values reported in literature and make these
nanoparticles very interesting for alternating magnetic field cancer therapy.
Finally, taking into account that an essential condition for applications in vivo is the biocompatibility of
the nanoparticles and the absence of toxic effects in the organism. Magnetic iron oxide nanoparticles with
neutral, positive and negative surface charge coverage have been synthesized by coprecipitation of iron salts
in the presence of dextran, amino dextran and heparine. The biological evaluation was performed using two
human tumor cell lines, HeLa (cervix carcinoma) and A-549 (lung carcinoma) [6]. It will be shown that
nanoparticles are first attached to the plasma membrane and, only when the particles are positively or
negatively charged, they are internalized into the cells. On the other hand, the degree of internalization was
dependent on both, concentration and incubation time. Finally, large amount of positively charged particles
inside the cells does not alter the normal morphology and distribution of interphase microtubules. Mitotic
spindles and chromosomes distribution were also similar to the metaphase of the control cells. Cell viability
was not altered by these particles under our experimental conditions. Different results were found for
negatively charged particles.
References:
4. O. Bomatí-Miguel, P. Tartaj, M. P. Morales, P. Bonville, U. Golla-Schindler,X. Zhao and S.VeintemillasVerdaguer. Small, 2 (2006) 1476-1483
5. M. Andrés Vergés, R. Costo, A.G. Roca, J.F. Marco, G. F. Goya, C.J. Serna and M.P. Morales, “Uniform magnetite
nanoparticles with diameters around the monodomain-multidomain limit”, J. Phys. D: Apply. Phys., Accepted 2007
6. M. Cañete, A. G. Roca, S. Veintemillas-Verdaguer, C. J. Serna, M. P. Morales, A. Villanueva. In preparation 2008
A27
Session III: Bio applications and surface functionalization (1)
Rod shaped semiconductor nanocrystals elicit neuronal activity in vivo
Maria Ada Malvindia, Alessandra Quartab, Luigi Carboneb, Angela Tinoa, Liberato Mannab,
Teresa Pellegrinob and Claudia Tortiglionea*
a
CNR, Istituto di Cibernetica “E Caianiello”, Via Campi Flegrei, 34, 80078 Pozzuoli, Italy
b
National Nanotechnology Laboratory of CNR-INFM, Unità di ricerca IIT and Scuola Superiore ISUFI, Via per
Arnesano, 73100 Lecce, Italy
Corresponding author: Claudia Tortiglione, [email protected]
The mechanism of interactions of nonfunctionalised nanoparticles with biological systems, ranging from
single cells to whole animals is a fundamental requirement for their use as diagnosis, imaging, and biosensor
tools. The small freshwater coelenterate Hydra vulgaris has been shown to be an amenable model system to
be approached by fluorescent semiconductor nanocrystals1. Here we report the effect of a new generation of
colloidal semiconductor nanoparticles, asymmetric core/shell CdSe/CdS Quantum Rods (QRs), on Hydra
vulgaris. PEG coated QRs, synthesised using recently reported procedures2,3, elicit in Hydra an unexpected
tentacle writhing behaviour, which is Ca2+ dependent and relies on the presence of tentacle neurons.
Moreover, this activity is inhibited by gap junction blockers, indicating the need of cell electric coupling to
transmit the QR stimuli along the tentacle. The absence of functional ligands on QR external surface suggest
that nanoparticle intrinsic properties could be responsible for the elicitation of the activity. We suggest the
existence of local electrical fields produced by QR dipole moments, which may be of sufficient intensity to
stimulate membrane-bound voltage dependent ion channels, thus eliciting an action potential resulting in
tentacle activity (Fig.1).
These results suggest for the first time QR as neuronal stimulator and propose their use in nanobiodevices to
interface with the nervous system.
c
QR
Ca2+
Fig.1 a) elicitation of tentacle writhing by QRs. Whithin seconds from addition of QRs to the culture medium polyp’s
tentacle begin to writhe, bending toward the mouth. Contractions are not syncronous for all tentacles. b) normal hydra
behavior. c) Hypothesis of QR dipole moment for the activation of a membrane-bound voltage dependent ion channel
References
1.
Tortiglione, C., Quarta, A., Tino, A., Manna, L., Cingolani, R., Pellegrino, T. Bioconjug Chem. 2007, 18, 829835.
2.
Carbone, L., Nobile, C., De Giorgi, M., Sala, F.D., Morello, G., Pompa, P., Hytch, M., Snoeck, E., Fiore, A.,
Franchini, I.R., Nadasan, M., Silvestre, A.F., Chiodo, L., Kudera, S., Cingolani, R., Krahne, R., Manna, L. Nano
Lett. 2007, 7, 2942-2950.
3.
Pellegrino, T., Manna, L., Kudera, S., Liedl, T., Koktysh, D., Rogach, A.L., Keller, S., Radler, J., Natile, G.
and Parak, W.J. Nano Lett. 2004, 4, 703-707.
A28
Session III: Bio applications and surface functionalization (1)
Bioconjugation strategies and temperature controlled cell uptake of gold nanoparticles
obtained by laser ablation in liquid solution.
V. Amendola and M. Meneghetti*
Dep. of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy)
Corresponding author: Moreno Meneghetti; [email protected]
Surface accessibility to functionalization or bioconjugation are key points for gold
nanoparticles (AuNP) applications. Often, synthesis methods based on chemical reduction require long
and expensive processes to obtain the desired AuNP functionalization.
An alternative is represented by laser ablation synthesis of metal nanoparticles in liquid
solution (LASiS).[1-3] LASiS provides stable colloidal solutions in water or in organic solvents,
without any ligands or chemicals. Therefore AuNP surface is usually free and functionalization with a
wide range of organic and bio-molecules occurs in one step. Also AuNP multi-conjugation can easily
be obtained. Moreover the real time monitoring of the surface coverage is possible by UV-Vis
spectroscopy. [1-3]
The size of AuNP obtained by LASiS can be further manipulated by a chemical free laser
techniques inspired by top down and bottom up approaches. Gold nanoparticles (AuNP) with average
radii of 4.5 nm were obtained in this way, which allowed the sensing of AuNP bioconjugation with
bovine serum albumin (BSA) down to a ratio of 10:1 for AuNP:BSA.[4]
The conjugation of AuNP with the thermo-responsive polymer poly-N-isopropylacrylamide
was exploited for the temperature controlled cellular uptake of AuNP. An 86 fold increase in the
AuNP loading was found by switching the temperature from 34°C to 40°C in human breast
adenocarcinoma MCF7 cells. Irradiation experiments with 532 nm (9 ns) laser pulses produced the
preferential death of AuNP loaded cells, indicating a new strategy for the photothermal therapy of
cancerous tissues combined with temperature responsive plasmonic nanostructures.[5]
20
15
ΔSPA (nm)
3
10
2
5
1
0
ΔA (%)
a
4
Figure 1: Monitoring AuNP bioconjugation
with bovine serum albumin (BSA). Surface
plasmon absorption (SPA) red shift (ΔSPA
in nm, filled symbols) and absorbance (A)
difference (ΔA in percentage, open symbols)
at increasing AuNP : BSA ratio.
Measurements for two solutions of AuNP:
with average radius of 4.5 nm (grey
triangles) and of 14.5 nm (black circles).
0
10
-1
10
0
10
1
2
3
10 10
CBSA/CAuNP
10
4
10
5
References:
1. V. Amendola, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2006, 110, 7232 – 7237.
2. V. Amendola, S. Polizzi, M. Meneghetti; Langmuir 2007, 23, 6766 – 6770.
3. V. Amendola, G. A. Rizzi, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2005, 109, 23125 – 23128.
4. V. Amendola, M. Meneghetti; J. Mater. Chem. 2007, 17, 4705-4710.
5. S. Salmaso, P. Caliceti, V. Amendola, M. Meneghetti, G. Pasparakis, A. Cameron; Submitted.
A29
Session III: Bio applications and surface functionalization (1)
Bioimaging using less-toxic Quantum Dots
Salam Massadeh, Shu Xu, Alexei Merkoulov, Thomas Nann
School of Chemical Sciences and Pharmacy, University of East Anglia (UEA), Norwich NR4 7TJ, UK
Corresponding author: Thomas Nann, Fax 00441603592003, email: [email protected]
Semiconductor Quantum Dots (QDs) are a promising option for biolabelling and bioimaging. Typical QDs
have a relatively stable luminescence intensity, and tunable (size-dependent) optical properties. A major
drawback of the frequently used cadmium-chalcogenide based QDs is the toxicity of cadmium. Even though,
many efforts have been made to prevent cadmium from leaking out of these nanoparticles, the possibility can
not be ruled out completely. A more elegant alternative is the exploitation of QDs which do not contain highly
toxic elements.
We have successfully prepared InP and InP/ZnS QDs with optical properties comparable to those of
CdSe-based ones. 1,2 Luminescence quantum yields can reach values of about 65% and are typically between
40 and 50%. Full width at half maxima (FWHM) are about 70 nm and luminescence maxima ranging from 500
to 800 nm, depending on the QD's size. Thus, these nanoparticles are a well-suited, less-toxic alternative for
CdSe-based QDs.
We will present a straightforward method for the phase transfer of InP/ZnS nanoparticles to aqueous buffers.
The resulting water-dispersible QDs are colloidally stable in high ionic-strength solutions, and can be
functionalised for further conjugation (cf. figure below). Furthermore, the characterisation of the nanoparticles
and their protein-conjugates will be discussed. Finally, the results are compared with those obtained with toxic
CdSe/ZnS QDs.
Figure: (left): 2% agarose gel on UV table. Samples in pockets from left to right 1) InP/ZnS/ME nanoparticles in DMSO,
2) InP/ZnS/ME nanoparticles in Trisglycine buffer, 3) BSA coated InP/ZnS nanoparticles, 4) dark spot is BSA 10
mg/mL, 5) InP/ZnS nanoparticles conjugated to (NHS-biotin-avidin) complex. (Right): Coomasie blue stained agarose
gel showing 1) BSA conjugated particles, 2) BSA 10 mg/mL, 3) nanoparticles +NHS-biotin-avidin complex.
References:
1
Xu, S.; Kumar, S; Nann, T. J. Am. Chem. Soc. 2006, 128, 1054-1055.
Xu, S.; Nann, T. 2007, submitted.
2
A30
Session III: Bio applications and surface functionalization (1)
Bifunctional Nanocomposites: Synthesis, Surface Functionalization and Application
S. Tamil Selvan,† Alex W. H. Lin,† Pranab K. Patra,† Chung Yen Ang,† Shujun Gao,† Georgia C.
Papaefthymiou,‡ and Jackie Y. Ying†
†
Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore 138669.
Department of Physics, Villanova University, Villanova, Pennsylvania 19085, USA. E-mail:
[email protected]
‡
Nanocomposites consisting of semiconductor quantum dots (QDs) and magnetic particles
(MPs) are of interest for biolabeling/imaging and cell sorting/separation applications. We
have developed several strategies to the fabrication of a bifunctional nanocomposite system
consisting of Fe2O3 MPs and CdSe QDs. These magnetic quantum dots (MQDs) can be
prepared in the form of heterodimers using either a seed-mediated (with Fe2O3 MPs as the
seeds) route or a simple one-pot synthesis. The resulting MQDs exhibited tunable emission
properties, and superconducting quantum interference device (SQUID) data illustrated that
the MQDs were superparamagnetic. To render the particles with water solubility and less
cytotoxicity, we used a silica coating approach. This talk will describe a general silica coating
method developed in our laboratory for the hydrophobic nanocrystals of either QDs or
MQDs. The plain QDs and MQDs (without ZnS capping) were coated with thin layers of
silica, and used for the labeling of different live cell membranes (HepG2 human liver cancer
cells, NIH-3T3 mouse fibroblast cells, and 4T1 mouse breast cancer cells) through a simple
bioconjugation method.
1. S. T. Selvan, P. K. Patra, C. Y. Ang and J. Y. Ying, “Synthesis of Silica-Coated Semiconductor and
Magnetic Quantum Dots and Their Use in the Imaging of Live Cells,” Angew. Chem. Int. Ed. (2007),
46, 2448–2452.
2. D. K. Yi, S. T. Selvan, S. S. Lee, G. C. Papaefthymiou, D. Kundaliya and J. Y. Ying, “Silica-Coated
Nanocomposites of Magnetic Nanoparticles and Quantum Dots,” J. Am. Chem. Soc. (2005), 127,
4990–4991.
3. S. T. Selvan, T. T. Tan and J. Y. Ying, “Robust, Non-Cytotoxic, Silica-Coated CdSe Quantum Dots
with Efficient Photoluminescence,” Adv. Mater. (2005), 17, 1620–1625.
4. T. T. Tan, S. T. Selvan, L. Zhao, S. Gao and J. Y. Ying, “Size Control, Shape Evolution, and Silica
Coating of Near-Infrared-Emitting PbSe Quantum Dots,” Chem. Mater. (2007), 19, 3112–3117.
A31
Session III: Bio applications and surface functionalization (1)
Surface chemistry of colloidal PbSe nanocrystals
Iwan Moreelsa, Bernd Fritzingerb, David De Munckc, Frank Vanhaeckec, José C. Martinsb and Zeger Hensa
a
Physics and Chemistry of Nanostructures, Ghent University, B-9000 Ghent, Belgium
b
NMR Structure Analysis Unit, Ghent University, B-9000 Ghent, Belgium
c
Laboratory of Analytical Chemistry, Ghent University, B-9000 Ghent, Belgium
Corresponding author: Iwan Moreels, Fax 0032-9-264 4871 email: [email protected]
In contrast to the physical properties (optical, conductive…) of semiconductor nanocrystals, their (physico)chemical properties have received little attention over the last ten years. Yet, most colloidal nanocrystals are
synthesized in the presence of organic ligands, which determine the nanocrystal size and shape. Furthermore,
the ligands determine for instance the nanocrystal luminescence, their stability in suspension and the distance
between nanocrystals in close-packed quantum dot solids.
We present a quantitative study on the composition of PbSe nanocrystals (Q-PbSe), addressing both the
semiconductor core and organic ligand shell. The Pb:Se ratio of the nanocrystals is determined with
inductively coupled plasma mass spectrometry (ICP-MS). Although they are synthesized with an excess of
Se, we find that the nanocrystals contain an excess of Pb atoms. Detailed structural modeling shows that this
Pb excess agrees with Q-PbSe consisting of a stoichiometric PbSe core, terminated by a pure Pb surface
shell. The ligands are studied with nuclear magnetic resonance spectroscopy (NMR). Detailed analysis using
different NMR techniques (diffusion ordered spectroscopy, heteronuclear single quantum coherence
spectroscopy) allows us to distinguish the nanocrystal ligands from unbound molecules and permits
identification of the ligands. We find that the ligand shell is composed almost entirely of oleic acid (OA).
Tri-n-octylphosphine is also used during synthesis, yet it represents less than 5% of the nanocrystal ligands.
A procedure is derived to determine the number of ligands per nanocrystal from quantitative NMR data. We
find an OA grafting density of 4.2 ligands per nm2. This value corresponds almost exactly to the number of
excess Pb atoms added to the nanocrystal surface. Combination of the ICP-MS and NMR results therefore
allows us to build a complete structural model of PbSe nanocrystals.
Fig. 1: Left: Pb:Se ratio as measured with ICP-MS (black dots) compared to a
structural Q-PbSe model without (green dots) and with (red and blue dots)
addition of surface Pb atoms. The experimental Pb:Se ratio is well represented
by the Pb terminated nanocrystal model. Right: 1H NMR spectrum of a QPbSe suspension. The broad resonances can be identified with OA ligands.
Inset: Representation of the nanocrystal model. It consists of a stoichiometric
core of Pb (grey dots) and Se (red dots) atoms, terminated by a Pb surface
shell (black dots).
A32
Session III: Bio applications and surface functionalization (2)
Formation of Tissue by Nanoactions of Cells
Joachim P. Spatz
Max-Planck-Institute for Metals Research, Department of New Materials and Biosystems, Stuttgart & University
of Heidelberg, Department of Biophysical Chemistry, Heidelberg
Engineering of cellular environments has become a valuable tool for guiding cellular activity such as
differentiation, spreading, motility, proliferation or apoptosis which altogether regulates tissue
development in a complex manner. The adhesion of cells to its environment is involved in nearly
every cellular decision in vivo and in vitro.
Our approach to engineer cellular environments is based on self-organizing spatial positioning of
single signaling molecules attached to inorganic or polymeric supports, which offers the highest
spatial resolution with respect to the position of single signaling molecules. This approach allows
tuning cellular material with respect to its most relevant properties, i.e., viscoelasticity, peptide
composition, nanotopography and spatial nanopatterning of signaling molecule. Such materials are
defined as “nano-digital materials” since they enable the counting of individual signaling molecules,
separated by a biologically inert background. Within these materials, the regulation of cellular
responses is based on a biologically inert background which does not trigger any cell activation, which
is then patterned with specific signaling molecules such as peptide ligands in well defined nanoscopic
geometries. This approach is very powerful, since it enables the testing of cellular responses to
individual, specific signaling molecules and their spatial ordering. Detailed consideration is also given
to the fact that protein clusters such as those found at focal adhesion sites represent, to a large extent,
hierarchically-organized cooperativity among various proteins. Moreover, “nano-digital supports” are
capable of involvement in such dynamic cellular processes as protein ordering at the cell’s periphery
which in turn leads to programming cell responses.
A33
Session III: Bio applications and surface functionalization (2)
A general one-step biofunctionalization of magnetic nanoparticles: chemistry and surface
characterization.
Laura Politoa, Diego Montib, Davide Prosperib*
a
Dept. of Organic and Industrial Chemistry, University of Milan, 20133 Milan, Italy
Nanobiotechnology Laboratory of CNR-ISTM, via G. Fantoli 16/15, 20138 Milano, Italy
b
Corresponding author: Davide Prosperi, Fax 00390250314061, email: [email protected]
We present the potentials of a new method based on a tandem combination of diazo transfer reaction and
Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction for the efficient conversion of amino iron
oxides to carbohydrate and protein derived nanoparticles with highly conserved bioactivity.1
The need for new technologies to realize bioactive organic-inorganic hybrid nanomaterials (including those
involving surface alteration of preexisting substrates) is now widespread in fields such as material science,
biophysics, molecular biology, pharmacology and molecular medicine.2,3 Our method is rapid, efficient and
potentially applicable to every organic and biomolecular structure without apparent loss of biological
activity, which usually represents a severe obstacle in the fabrication of bioinspired hybrid materials. To
demonstrate the reliability of our strategy, we have successfully examined a group of alkyne bearing
polyether and saccharide structures. It should be noted that our method makes use of common amino
nanoparticles as starting materials, leading to the biocolloids in one-pot. Therefore, the same protocol is
well-suited to be immediately applied to many other kinds of currently available nanomaterials.
Moreover, we demonstrate that our method is particularly suitable for protein immobilization, resulting in a
site-specific anchorage onto the nanoparticle surface, which prevents loss of protein bioactivity. We have
evaluated the residual activity of a human plasma protein (human serum albumin, HSA) immobilized onto
the surface of iron oxide nanoparticles by TEM and relaxivity measurements of the particulate behaviour in
the presence of a specific antibody.
Besides usual FTIR spectroscopy, high resolution magic angle spinning (HRMAS) NMR spectrometry is
proposed as a clever tool for the direct characterization of anchored organic molecules, otherwise very
difficult with magnetic nanoparticles using conventional NMR techniques, particularly when the solvent is
water. Our data suggest that this method has the potential to allow an accurate structure-resolved
determination of the organic coating, avoiding particle decomposition.
On the whole, by exploiting the unique magnetic properties of MNP, this approach may lead to the
generation of a new class of diagnostic probes for active targeting.
References:
1.
Polito, L.; Monti, D.; Caneva, E.; Delnevo, E.; Russo, G.; Prosperi, D. Chem. Commun., 2008, in press.
DOI:10.1039/B716113A.
2.
Kell, A. J.; Simard, B. Chem. Commun., 2007, 1227-1229.
3.
Lewin, M.; Carlesso, N.; Tung, C.-H.; Tang, X.-W.; Cory, D.; Scadden, D. T.; Weissleder, R. Nat. Biotechnol.,
2000, 18, 410-414.
A34
Session IV: Bio applications and surface functionalization (2)
Biotemplates for nanoparticle deposition
Nadja C. Bigalla, Manuela Reitzigb, Paul Simonc, Wolfgang Naumannb, Karl-Heinz van Péeb, Alexander Eychmüllera
a
Physical Chemistry, TU Dresden, 01062 Dresden, Germany
b
Biochemistry, TU Dresden, 01061 Dresden, Germany
c
MPI Chemical Physics of Solids, 01187 Dresden, Germany
Corresponding author: Alexander Eychmüller, Fax +4935146337164, email: [email protected]
Hybrid systems consisting of life forms and micro-1 or nanotechnological materials have moved increasingly
into the focus of interest. New materials are generated e.g. incorporating semiconductor or magnetic
nanoparticles into bacterial superstructures2. Functionalized gold nanoparticles have been assembled onto
bacteria. For example, highly electrically conducting materials were obtained by assembling lysine coated
gold nanoparticles3 and even CTAB terminated gold nanorods4 onto bacteria. Another successful approach
was the assembly of oligonucleotide-functionalized gold nanoparticles onto diatoms5 and fungi6.
This poster presents a different technique for the combination of biological materials and metal
nanoparticles. Noble metal nanoparticles are synthesized in aqueous solution with sodium citrate and sodium
borohydride. The nanoparticles are characterized by high resolution transmission electron microscopy and by
absorption spectroscopy. The as prepared solutions are inoculated with different fungi. The citrate containing
nanoparticle solutions act as growth media for the fungi. After incubation for several weeks, the fungi have
grown to macroscopic size. Nanoparticles are assembled onto the fungal mycelium. The as obtained
superstructures are dried by a critical point drying technique with conservation of their morphology. These
hybrid structures are characterized via scanning electron microscopy and EDX. Possible applications for
these systems are discussed.
500 nm
50 µm
Fig. 1: Left: Scanning electron micrograph of the alloy structure in higher resolution. Right: SEM of the
dried alloy structure.
References:
1.
Zeck, G.; Fromherz, P. Proceedings of the National academy of science of the United States of America 2001,
98 (18), 10457-10462
2.
Davis, S. A.; Patel, H. M.; Mayes, E. L.; Mendelson, N. H.; Franco, G.; Mann, S. Chemistry of Materials 1998,
10, 2516-2524
3.
Berry, V.; Rangaswamy, S.; Saraf, R. F.; Nano Letters 2004, 4, (5), 939-942
4.
Berry, V.; Gole, A.; Kundu, S.; Murphy, C. J.; Saraf, R. F. Journal of the American Chemical Society 2005,
127, 17600-17601)
5.
Rosi, N. L.; Thaxton, C. S.; Mirkin, C. A. Angewandte Chemie, International Edition 2004, 43, 5500 –5503
6.
Li, Z.; Chung, S.-W.; Nam, J.-M.; Ginger, D. S.; Mirkin, C. A. Angewandte Chemie, International Edition
2003, 42, 2306
A35
Session III: Bio applications and surface functionalization (2)
Colloidal quantum dot ligand characterization by solution NMR
Zeger Hens*, Bern Fritzinger#, Petra Lommens*, Rolf Koole$, Iwan Moreels*, Jose C. Martins#
*
Physics and chemistry of nanostructures, Ghent University, Krijgslaan 281-S12, B-9000 Gent, Belgium.
#
Organic chemistry department, Ghent University, Krijgslaan 281-S4, B-9000 Gent, Belgium.
$
Condensed matter and interfaces, Utrecht University, PO box 80000, 3508 TA Utrecht, The Netherlands.
Corresponding author: Zeger Hens, Fax +32-9-2644971, email:[email protected]
1.0
0.9
−
18.5
z
kJ mol-1
P
O
P
O
0.8
Q-InP
0.7
0.00
0.05
0.10
0.15
0.20
[free ligand]
Fig. 1: Solution NMR on colloidal TOPO|InP quantum dots. Left: DOSY
spectrum showing resonances of residual toluene, free TOPO and bound
TOPO with different values of the diffusion coefficient. Right: Integration of
the bound and free TOPO CH3 resonance leads to the adsorption isotherm of
TOPO at InP Qdots. The fit to a Fowler isotherm yields the free energy of
adsorption and of ligand-ligand interaction.
References
1
2
Z. Hens, I. Moreels, J.C. Martins, ChemPhysChem 6, 2578 (2005).
I. Moreels, J.C. Martins, Z. Hens, ChemPhysChem 7, 1028-1031 (2006).
A36
− 22 kJ mol -1
P
O
ligand surface coverage
Colloidal semiconductor quantum dots (Qdots) are a widely used building block in bottom-up
nanotechnology. Very often, they consist of an inorganic, crystalline core surrounded by a monolayer of
organic ligands. As these ligands can be modified or exchanged for others, they are key to tailor the physical
and chemical properties of Qdots. Nevertheless, few techniques have been established to identify and
quantify colloidal nanoparticle ligands in situ at the nanoparticle surface. Here, we show that solution NMR
is a powerful tool to address the most important aspects of this organic|inorganic interface.
We use the examples of InP [1] and PbSe to show that for tightly bound ligands, ligand identification is
possible by combining one dimensional 1H NMR with 1H-13C HSQC spectroscopy and pulsed field gradient
diffusion NMR. Apart from ligand identification, this approach leads to the determination of the diffusion
coefficient of the suspended Qdots. Next, by calibrating the surface area of the 1H NMR resonances using a
solute of known concentration, the density of ligands at the nanocrystal surface can be quantified. In the case
of InP, this enables us to demonstrate a dynamic equilibrium between bound and free trioctylphosphine
oxide ligands and to determine the corresponding adsorption isotherm [2]. In the case of PbSe, this provides
a complete picture of the stoichiometry of the interface, where oleic acid ligands and excess Pb are present in
a 1:1 ratio.
With loosely bound ligands, 1D 1H NMR and pulsed field gradient diffusion NMR cannot distinguish free
from bound ligands. Using data on amine capped CdTe and ZnO quantum dots, we show that the nuclear
Overhauser effect (NoE) effect can be exploited to identify nanocrystal ligands in this case. Moreover, this
identification comes with an estimate of the exchange rate between the bound and the free states.
0.25
0.30
0.35
Session III: Bio applications and surface functionalization (2)
Size determination water-soluble colloidal nanoparticles
- a comparison of different techniques Ralph A. Sperling, Feng Zhang, Marco Zanella, Wolfgang J. Parak
Philipps University Marburg, AG Biophotonics, Renthof 7, 35032 Marburg, Germany
Corresponding author: Wolfgang Parak <[email protected]>
For colloidal nanoparticles, size is one of the basic properties used for characterization. For inorganic, e.g.
metallic or semiconductor nanoparticles, transmission electron microscopy (TEM) is a widely used technique
to obtain information about the size of the particle core.
In general, nanoparticles are coated with one or more layers of organic molecules that provide colloidal
stability to the particles. These molecules are usually referred as surfactants or ligand molecules, can in
general not be observed by TEM because their lack of contrast which is due to their organic nature, while
they contribute nevertheless to the effective overall particle radius.
For many applications in e.g. biological systems, the nanoparticle surface has to be modified in order to
render the particles hydrophilic[1,2], biocompatible and functional[3], generally by the conjugation with the
appropriate (bio-) molecules. The binding of these molecules is often monitored by the increase of the
particle size.
Such complex, functional particles often consist of multiple layers of coatings, which all contribute to the
effective (or hydrodynamic) radius which is in fact the property determining the interaction of the particle
with its environment. However, such layers of organic molecules are in general not well organized, soft
compared to the inorganic particle cores and not trivial to characterize.
The size of inorganic colloidal nanoparticles that were coated with organic layers of varied thickness has
been measured with different techniques including TEM, gel electrophoresis, size exclusion chromatography
(SEC), fluorescence correlation spectroscopy (FCS), and thermophoresis[4]. While all methods yield selfconsistent results, the obtained values differ when comparing the different methods. The results are critically
compared and both the advantages and disadvantages of the respective methods are discussed.
References:
1.
2.
3.
4.
T. Pellegrino, L. Manna, S. Kudera, T. Liedl, D. Koktysh, A. L. Rogach, S. Keller, J. Rädler, G. Natile, W. J.
Parak, Nanoletters 2004, 4, 703.
C.-A. J. Lin, R. A. Sperling, J. K. Li, T.-Y. Yang, P.-Y. Li, M. Zanella, W. H. Chang, W. J. Parak, SMALL,
accepted.
R. A. Sperling, T. Pellegrino, J. K. Li, W. H. Chang, W. J. Parak, Advanced Functional Materials 2006, 16,
943.
R. A. Sperling, T. Liedl, S. Duhr, S. Kudera, M. Zanella, C.-A. J. Lin, W. Chang, D. Braun, W. J. Parak,
Journal of Physical Chemistry C 2007, 111, 11552.
A37
Semiconductor nanoparticles-carbon nanotubes composites
Beatriz H. Juárez, C. Klinke, A. Kornowski, A.B. Hungría, †† P.A.Midgley†† and H. Weller
Institute of Physical Chemistry, University of Hamburg
††
Department of Materials Science. University of Cambridge
e-mail: [email protected]
The design of composite materials including light harvesting and charge transport
components provides a suitable strategy for the development of solar cells.1 The combined
optical and electrical transport properties of nanoparticles and carbon nanotubes respectively
can lead to improvements in the efficiency of photoelectric devices.2 In order to maintain their
electrical properties, unfuntionalized CNTs are desirable. In this work, unfunctionalized carbon
nanotubes have been used to attach CdSe and ZnO nanoparticles at very high degree of
coverage. In the case of CdSe nanoparticles, the attachment to the carbon lattice involves shape
change from rod-like to pyramildal-like3 (see figure 1). The crystallographic structure of the
pyramidal-shaped CdSe nanoparticles has been elucidated by means of HRTEM and HAADF
STEM Electron Tomography4 (figure 2). The presented non-covalent attachment (according to
Raman spectroscopy) should, furthermore, be most advantageous in order to combine the
outstanding electrical properties of CNTs with the unique possibility of bandgap tuning of
quantum dots. The attachment is observed on both, singlewall and multiwall CNTs and the
obtained composite materials exhibit photoelectrical response.
a
b
Figure 2.-(a) Surface rendered reconstructed nanoparticle. (b), (c)
Model particle at different orientations.
Figure 1.- (a) CdSe rod-like nanoparticles and carbon nanotubes obtained after 1 hour of reaction.
(b) Shape transformed nanoparticles in direct contact to singlewall carbon nanotubes
[1]P. V. Kamat, Journal of Physical Chemistry C 2007, 111, 2834; B. Q. Sun, E. Marx, N. C. Greenham, Nano Letters 2003, 3, 961; S. A.
McDonald, G. Konstantatos, S. G. Zhang, P. W. Cyr, E. J. D. Klem, L. Levina, E. H. Sargent, Nature Materials 2005, 4, 138.
[2] (a) Robel, I.; Bunker, B.; Kamat, P. V. Adv. Mater. 2005, 17, 2458-2463. (b) Sheeney-Haj-Khia, L.; Basnar, B.; Willner, I. Angew. Chem.,
Int. Ed. 2005, 44, 78-83; Feng, W., Feng, Y., Wu, Z., Fujii, A., Ozaki, M. & Yoshino, K. J. Phys.: Condens. Matter 2005, 17, 4361.
[3] B. H. Juárez, C. Klinke, A. Kornowski, H,. Weller. NanoLett 2007, 7, 3564.
[4]A. B. Hungria, B. H. Juárez, C. Klinke, H. Weller, P.A. Midgley. Submitted
A38
Session V: Growth (2)
Cadmium-free highly luminescent semiconductor nanocrystals
Liang Lia, Myriam Protièrea, Toufic Jean Daoub, Isabelle Texier-Nogues b, Peter Reissa*
a
CEA Grenoble INAC/SPrAM (UMR 5819), 17 rue des martyrs, 38054 Grenoble, France.
b
CEA Grenoble LETI/DTBS, 17 rue des martyrs, 38054 Grenoble, France.
Corresponding author: Peter Reiss, Fax 0033438785113, email: [email protected]
The meeting of nano-materials with biology has produced a new generation of technologies that can
profoundly impact biomedical research.1 The NIR spectral window (650-900 nm) is appealing for in vivo
optical imaging because of the low tissue absorption and scattering in this wavelength range. Therefore the
design of high-quality NIR-emitting quantum dots, with outstanding optical properties in comparison to
organic dyes, should lead to novel contrast agents with improved performance (higher fluorescence quantum
yields and photo-stability).
While certain types of cadmium and lead chalcogenide quantum dots show appropriate optical
properties for in vivo imaging, they suffer from the low acceptability due to their intrinsic toxicity. Indium
phosphide nanocrystals could be an interesting alternative provided that synthesis methods for the
reproducible production of high quality samples are developed.2 We present novel wet-chemical routes to
indium phosphide core, related core/shell and core/shell/shell nanocrystals. The obtained samples exhibit
size-dependent fluorescence in the visible and near infrared spectral range (480-720 nm, FWHM 40-70 nm).
Their quantum yield can reach 40-70% after the shell growth and an excellent photo-stability is observed. At
the same time their hydrodynamic diameter remains small (sub-10 nm), which is of crucial importance for
their bio-distribution. Our results indicate that the speed of first pass extraction of quantum dots towards the
reticulo-endothelial system (liver, spleen, bone marrow) depends strongly on the particle size and surface
coating (cationic, anionic, neutral, zwitterionic). Therefore the surface coating of quantum dots and their
hydrodynamic diameter are shown to be the critical parameters in the development of new diagnostic agents.
b)
a)
Fig. 1: a) Photos of InP/ZnS nanocrystals excited with a UV lamp (365 nm). b) Photoluminescence spectra of selected
samples (Excitation wavelength: 400 nm).
References:
1.
Medintz, I. L.; Uyeda, H. T.; Goldman, E. R.; Mattoussi, H., Quantum dot bioconjugates for imaging, labelling
and sensing. Nature Materials 2005, 4, (6), 435-446.
2.
Haubold, S.; Haase, M.; Kornowski, A.; Weller, H., Strongly luminescent InP/ZnS core-shell nanoparticles.
Chemphyschem 2001, 2, (5), 331-334.
A39
Session V: Growth (2)
Defect-induced transformation of lamellar regions of silver nanoprisms from fcc to hcp crystal
structure
Damian Ahernea*, Deirdre Ledwitha, Matthew Garaa, John M. Kellya*
a
School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
Corresponding authors: Damian Aherne and John M. Kelly, Fax: 0035316712826, email: [email protected],
[email protected]
We present a rapid and readily reproducible seed-based method for the production of triangular silver
nanoplates in high yield which is a modification of a previously published procedure from our lab. 1 The
edge-length of the nanoplates can be readily controlled through adjustment of reaction conditions. Lattice
fringes with a 2.5 Å spacing are typically reported for <111> orientated (flat-lying) triangular silver
nanoprisms and are usually attributed to formally forbidden 1/3{422} reflections. 2,3,4,5,6 Recently this has
been explained as the result of a hexagonally close packed (hcp) structure arising from many lamellar defects
within the crystal along <111>. 7 Here, direct TEM evidence is presented, confirming this explanation, and
illustrates how multiple defects can combine to give rise to continuous lamellar regions with a hcp
arrangement of silver atoms. This has implications for our understanding of anisotropic growth in such
systems.
d = 2.35 Å
ABABABA
d = 2.50 Å
}
{111 {10
0}
Figure 1. Left, TEM image of flat-lying
triangular silver nanoplates. Right, High
resolution TEM image of a <110> oriented
nanoprism exposing the internal crystal
structure. A series of intrinsic stacking faults
has resulted in a hexagonally close packed
pattern emerging and gives rise to an
arrangement of atoms that is aligned
perpendicular to the surface with a spacing
of 2.50 Å.
d = 2.35 Å
40 nm
1 nm
900
Seeds
I II III IV V VI VII VIII IX
850
X
800
Wavelength / nm
Absorbance
1
A
0.8
0.6
0.4
0.2
0
300
400
500
600
700
800
Wavelength / nm
900
1000
B
750
700
650
600
1.2
Absorbance / A.U.
1.2
550
500
450
1
0.8
0.6
0.4
0.2
0
300 400 500 600 700 800 900 1000
Wavelength / nm
400
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
D/T
Figure 2. A) Normalized spectra of a series of samples obtained using different volumes of seed solution: I) 650 μl,
II) 500 μl, III) 400 μl, IV) 260 μl, V) 200 μl, VI) 120 μl, VII) 90 μl, VIII) 60 μl, IX) 40 μl, X) 20 μl. B) Plot of data
(squares) for the position of the plasmon band against diameter divided by thickness for four samples. The dashed line
is a linear fit to the data. The diameter and thickness were obtained by measuring the lateral dimensions of vertically
oriented nanoprisms. The inset shows the absorption spectra of the four samples.
References:
1.
2.
3.
4.
5.
6.
7.
D. M. Ledwith, A. M. Whelan, J. M. Kelly, J. Mater. Chem. 2007, 17, 2459.
V. Germain, J. Li, D. Ingert, Z. L. Wang, M. P. Pileni, J. Phys. Chem. B 2003, 107, 8717.
C. Lofton, W. Sigmund, Adv. Funct. Mater. 2005, 15, 1197.
J. L. Elechiguerra, J. Reyes-Gasga, M. J. Yacaman, J. Mater. Chem. 2006, 16, 3906.
J. E. Millstone, G. S. Métraux, C. A. Mirkin, Adv. Funct. Mater. 2006, 16, 1209.
B. Rogríguez-González, I. Pastoriza-Santos, L. M. Liz-Marzán, J. Phys. Chem. B 2006, 110, 11796.
T. C. R. Rocha, D. Zanchet, J. Phys. Chem. C 2007, 111, 6989.
A40
Session V: Growth (2)
Effector-controlled growth of silver shells on gold nanoparticles in batch and under micro flowthrough conditions
J. Michael Köhlera, Henry Romanusa, P. Mike Günthera
a
Technische Universität Ilmenau, 98684 Ilmenau, Germany
Corresponding author: P. Mike Günther, Fax 00493677693179, email: [email protected]
Despite a lot of knowledge about the electronic and optical properties [1, 2] of Au/Ag core/shell and alloy
nanoparticles, there is a lack of information about the kinetics of nucleation and growth of such binary metal
nanoparticles and their effect on the nanoparticle properties. Investigations on the formation of this particle
class in micro flow-through synthesis showed a strong dependency on mixing order and flow conditions [3].
Therefore, the growth of silver shells on gold nanoparticles was studied in dependence on concentration of
reducing agent and surface active additives.
In addition to the known effect of reduction of growth rate by dissolved polymers and surfactants, an
enhancement of growth rate by addition of a copper salt was observed. The growth of silver shell in case of
ascorbic acid as reducing agent was monitored by cyclic UV/VIS spectrophotometry and by micro flowthrough photometry. Spectrophotometry allows to distinguish at least to different processes. Their rates are
modulated by the dissolved components of growth solution and by the conditions of gold nucleation.
Significant differences in the shell growths processes and in the optical spectra of colloidal product solutions
were found in case of constant silver-to-gold ratio, if different dillutions of tetrachloroauric acid during
nucleation were applied (Fig. 1, both experiments: 20 nmole HAuCl4, 240 nmole ascorbic acid, 20 nmole
copper sulphate, 50 nmole AgNO3 in 0.6 mL aqueous solution, a) higher, b) lower concentration in gold
nuleation). In parallel, flow-through experiments with different absolute flow rates but constant reactant
ratios lead to large differences in the character of product solution due to the specific process kinetics (Fig.
2).
The obtained nanoparticles were characterized by centrifugal sedimentation spectroscopy, AFM and SEM
imaging. In result, the size, the size distribution and the plasmon absorption of obtained nanoparticles can be
influenced by the composition of reactants as well as by the process design. The control of flow and mixing
conditions as well as the choice of additives give the possibility to vary the optical properties of Au/Ag
core/shell nanoparticles to a large extend.
Figure 2
Figure 1
References:
[1]
Link, S.; El-Sayed, M.A. J. Phys. Chem. 1999, 103, 8410-8426
[2]
Moskovitch, M.; Srnouvá-Sloufová, I.; Vlckova, B. J. Chem. Phys. 2002, 116, 10435-1044
[3]
J.M. Köhler, J. Wagner, J. Albert, G. Mayer, 5th Internatl. Conf. on unsteady-state processes in catalysis,
2006, Nov, 22-26, Suita City, Japan, 43-44
A41
Session V: Growth (2)
On the Incorporation Mechanism of Hydrophobic Quantum Dots in Silica Spheres by a
Reverse Microemulsion Method
Rolf Koolea*, Matti van Schoonevelda, Jan Hilhorsta, Celso de Mello Donegaa, Dannis ‘t Hartb, Alfons van Blaaderenb,
Daniel Vanmaekelbergha, and Andries Meijerinka,
a
CMI, Debye Institute, Utrecht University, The Netherlands,
b
Soft Condensed Matter, Debye Institute, Utrecht University, The Netherlands,
Corresponding author: Rolf Koole, Fax 0031-30-2532403, email: [email protected]
In the past decade, the incorporation of metal1, semiconductor2, or insulating3 nanoparticles into silica
spheres has been studied extensively. Silica coated nanocrystals have several advantages over their bare
counterparts, especially regarding their potential end-use in applications like (opto-) electronics, photonic
crystals, or as contrast agent in bio-imaging. The silica coating can provide both chemical and physical
stability, reduce toxic effects and facilitate modifications of the composite particles for further use.
In the present study, we have elucidated the mechanism at which hydrophobic quantum dots (QDs) are
incorporated in silica spheres using a reverse microemulsion method.4 The resulting silica particles are
highly monodisperse (37.2 ± 1.5 nm in diameter), and have one QD incorporated exactly in the centre
(Figure A). This control is surprising since the silica nucleation and growth occurs within the small water
droplets of the microemulsion, where one would expect the hydrophobic QDs to agglomerate or not to be
present at all. We have investigated the optical properties of the QDs during each step of the microemulsion
synthesis using (time-resolved) fluorescence spectroscopy. We found that tetraethoxyorthosilicate (TEOS)
has a high affinity for the QD-surface, and that it is responsible for the emission quenching that is generally
observed for QDs that are incorporated in silica spheres (Figure C). It is shown that hydrolyzed TEOS
rapidly replaces the hydrophobic amine-ligands of the QDs, which facilitates their transfer to the hydrophilic
interior of the micelles where silica growth takes place. The TEOS coated QDs are effective and isotropic
nucleation centers for silica growth, which explains the high homogeneity of the final particles (Figure A).
However, the exchange by hydrolyzed TEOS molecules could be deliberately hindered by attaching stronger
binding thiolated ligands (i.e. dodecanethiol) on the QD surface. In that case, silica growth takes place on
only a part of the QD-surface (anisotropic growth), resulting in QDs that are incorporated off-centre (Figure
B), attached to the outside of the silica surface (not shown), or not association with the silica particles at all,
depending on the concentration of thiolated ligands in the reaction mixture.
It is likely that the proposed mechanism also applies to the incorporation of other hydrophobic nanocrystals
in silica using the same method. In conjunction with our findings, we were able to make QD/silica particles
with an unprecedented quantum efficiency of 35 %.
References:
(1)
Graf, C.; Vossen, D. L. J.; Imhof, A.; van Blaaderen, A. Langmuir 2003, 19, (17), 6693-700.
(2)
Nann, T.; Mulvaney, P. Angewandte Chemie-International Edition 2004, 43, (40), 5393-96.
(3)
Philipse, A. P.; Vanbruggen, M. P. B.; Pathmamanoharan, C. Langmuir 1994, 10, (1), 92-99.
(4)
Osseo-Asare, K.; Arriagada, F. J. Colloids and Surfaces 1990, 50, 321-39.
A42
Session V: Growth (2)
Size Distribution of Superparamagnetic Particles and Clusters
Determined by Magnetic Sedimentation
J.-F. Berreta, O. Sandreb and A. Maugerc
a
Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris-VII, Bâtiment Condorcet
10 rue Alice Domon et Léonie Duquet, 75205 Paris, France
b
Laboratoire Liquides Ioniques et Interfaces Chargées, UMR 7612 CNRS Université Pierre et Marie Curie Paris-VI
4 place Jussieu, F-75252 Paris Cedex 05 Franc
c
Département Mathématique Informatique Physique Planète et Univers,
CNRS, 140 rue de Lourmel, F-75015 Paris France
Corresponding author: J.-F. Berret, email: [email protected]
We report on the use of magnetic sedimentation as a means to determine the size distribution of dispersed
magnetic particles. The particles investigated here are i) single anionic and cationic nanoparticles of diameter
D ~ 7 nm and ii) nanoparticle clusters resulting from electrostatic complexation with polyelectrolytes and
polyelectrolyte-neutral copolymers. A theoretical expression of the sedimentation concentration profiles at
the steady state is proposed and it is found to describe accurately the experimental data. When compared to
dynamic light scattering, vibrating sample magnetometry and cryogenic transmission electron microscopy,
magnetic sedimentation exhibits a unique property : it provides the core size and core size distribution of
nanoparticle aggregates [1].
Photographs and concentration profiles of a
magnetic dispersion at t he initial (a) and final
(b) stages of the sedimentation process. The
magnet is located at the bottom of the cell and
the field gradient is constant over the height of
the sample.
[1] J.-F. Berret, O. Sandre and A. Mauger, Size Distribution of Superparamagnetic Particles Determined by Magnetic
Sedimentation, Langmuir 2007, 23, 2993 – 2999.
A43
Session V: Growth (2)
Hybrid metal-semiconductor nanoparticles; A new type of functional materials
Uri Banina, Ronny Costia, Einat Elmalema, David Mocattaa, Asaf Salanta, Aaron E. Saunders+
a
Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem,
Jerusalem 91904, Israel
+
present address: Department of Chemical Engineering, University of Colorado, Boulder, CO USA
Corresponding author: Uri Banin, Fax 0097226584148, email: [email protected]
An important frontier in nano-materials research concerns nanoparticles with different materials in the same
nanostructure as means of increasing functionality. One particularly interesting combination of materials is
that of a metal and semiconductor in the same nanoparticle where metal tips grown on a semiconductor rod
can provide anchor points for electrical connections and for self assembly. This was demonstrated by the
growth of Au tips on CdSe nanorods forming ‘nano-dumbbells’ (NDB’s) 1 . By increasing the concentration
of gold in the reaction, rods with a metal tip on one side are formed by a unique Electrochemical ripening
mechanism 2 . The Au-CdS system shows a similar behavior but requires different reaction conditions for Au
growth. However, reacting Au with InAs nanoparticles provides a completely different behavior of diffusion
of the gold into the nanoparticle. Other growth modes of metal-semiconductor hybrid particles will be
discussed, showing the richness of the reaction possibilities of metals and semiconductor nanoparticles.
The functionality of the hybrid system is demonstrated in several ways. First, the use of the tips for
assembly with biomolecular linking is demonstrated, forming chains of NDBs linked via the gold tips. 3
Additionally, upon metal growth, the fluorescence of the semiconductor nanoparticles is generally quenched.
This is assigned to the process of charge separation at the nanoscale semiconductor-metal junctions. This
indicates the potential use of such hybrid systems in visible light photocatalysis. A first step in this direction
is the demonstration of visible light induced reduction of a model acceptor dye with both Au-CdSe
nanohybrids 4 and Pt-CdSe systems (see scheme in Figure 1). The latter case shows interesting morphology
dependent photocatalytic behavior.
Figure 1: Scheme of a light induced
charge separation mechanism in a
nanodumbbell in which the
photogenerated electron-hole pair
separates so that the electron resides
at the gold tip and the hole at the
CdSe nanorod. The scheme also
depicts the transfer of the hole to the
scavenger, and the reduction of the
MB molecule upon electron transfer
from the gold tip. The inset shows
the energy band alignment between
CdSe (4nm dots) and Au.
References:
1. T. Mokari, E. Rothenberg, I. Popov, U. Banin, Science 304, 1787 (2004).
2. T. Mokari, C. G. Sztrum, A. Salant, E. Rabani, U. Banin, Nature Materials 4, 855 (2005).
3. Asaf Salant, Ela Amitay-Sadovsky, Uri Banin, J. Am. Chem. Soc. 128, 10006 (2006).
4. R. Costi, A. E. Saunders, E. Elmalem, A. Salant, U. Banin, Nano Lett. 8, 637 (2008).
A44
Session V: Growth (2)
Carbon Nanotubes: useful templates for hybrid materials production
Miguel A. Correa-Duarte
Departamento de Química Física and Unidad Asociada CSIC-Universidade de Vigo, 36310 Vigo, Spain.
e-mail: [email protected]
CNTs can be considered as ideal templates for the formation of one dimensional nanoparticle
assemblies. Despite their relative chemical inertness, several strategies have been followed for the
preparation of CNT–nanoparticle composites, either through in situ nanoparticle synthesis or by the
assembly of pre-formed nanoparticles. In both cases surface modification is required, sometimes
implying the chemical development of defect-sites and subsequent covalent functionalization or noncovalent adsorption of macromolecules on the side walls.
Herein, we report on the fabrication of one dimensional nanomaterials based on the non-covalent
functionalization of CNTs by means of a combination of polymer wrapping and layer-by-layer
assembly (figure 1a) through the deposition of nanoparticles of different nature (magnetic, metallic
semiconductor) and the description of the properties of the resulting hybrid materials. [1-5]
As a second approach it will be shown the covalent functionalization based on the acidic chemical
oxidation of the CNTs surface, which can be used for the self assembly of CNTs on colloidal
templates. Additionally it will be shown how these composites help for the synthesis of particles with
an increased complexity and functionality through the surface modification of the adsorbed CNTs
either through nanoparticles assembly or through uniform surface coating [6-7].
A
B
Figure 1: Schematic illustration of the synthetic procedures comprising the polymer wrapping of
CNTs, the electrostatic self-assembly of pre-synthesized Pt nanoparticles and the Ni salt reduction
with the consequent formation of Ni/NiO nanowires supported onto the CNTs (A); and the
polyelectrolyte coating of PS spheres (a), adsorption of Fe3O4 nanoparticles (b), adsorption of CNTs
(c, d), and SiO2 coating of the individual CNTs (B).
[1] M. A. Correa-Duarte et al., Adv. Mater. 2004, 16, 2179
[2] M. A. Correa-Duarte, L. M. Liz-Marzán, J. Mater. Chem. 2006, 16, 22.
[3] M.A. Correa-Duarte, M. Grzelczak et al., J. Phys. Chem. B 2005, 109, 19060.
[4] M. Grzelczak, M.A. Correa-Duarte et al., Adv. Mater. 2006, 18, 415.
[5] M. Grzelczak, M.A. Correa-Duarte, et al. Ang. Chem. Int. Ed. 2007, 46, 7026.
[6] M.A. Correa-Duarte, A. Kosiorek et al., Chem. Mater. 2005, 17, 3268.
[7] M. Sanles-Sobrido, V. Salgueiriño-Maceira et al., Small 2007, in press.
A45
Session V: Growth (2)
2D and 3D Nanocrystal Systems: Applications between Optics and Electronics
Jessica Pacificoa,b, Paul Mulvaneyb, Luis M. Liz-Marzána
a
Departamento de Química Física, Universidade de Vigo, Campus de Lagoas-Marcosende, 36310 Vigo, Spain
b
BIO21 Institute, University of Melbourne, Parkville VIC 3010, Australia
Corresponding author: Jessica Pacifico, email: [email protected]
The goal is to measure and understand the properties of nanoparticles, both as individual islands and as
closely packed entities adsorbed, embedded or encapsulated into a surface. From single nanoparticles to a
more dense population, randomly organized but relatively close to each other, for finally extending torwards
organized 2D or 3D structures. They are synthesized by colloid chemistry methods and assembled using
surface chemistry techniques on different substrates. The materials used include semiconductors but also
metallic nanosystems, of various types, shapes and sizes. In this work, the idea is to combine the existing 2D
and 3D structured materials made of CdSe@ZnS with different nanoparticles systems like Au, Au@Pt@Ni,
goethite or goethite@Au. The potential applications using the optical properties and energy transfer
possibilities are quite wide.
The following analysis techniques were carried out to study the fabricated systems: confocal microscopy,
and various scanning probe microscopy (SPM) techniques such as atomic force microscopy (AFM),
magnetic force microscopy (MFM), electric force microscopy (EFM) and scanning near-field optical
microscopy (SNOM).
2D and 3D structures can lead to the formation of electrochemically interesting devices with an application
in electrochemical force microscopy.
Fig. 1 Cumulative emission spectra given by a succession of six CdSe@ZnS QD layers on a patterned
surface surface
References:
1. J.Jasieniak, J. Pacifico, R. Signorini, A. Chiasera, M. Ferrari, A. Martucci, P. Mulvaney, Adv. Funct. Mat., 2007,
17(10), 16541662
2. J. Pacifico, J. Jasieniak, D. Gomez, P. Mulvaney, Small, 2006, 2(2), 199-203.
A46
Session VI: Electronics and Devices
Proximity effects and collective phenomena in semiconductor nanocrystalline semiconductor systems
Oded Milloa*, Dov Steinera, Hadar Levia, Doron Azulaya, Isaac Balberga, Assaf Salantb, Assaf Aharonib, Uri Baninb
a
Racah Institute of Physics and the Center for Nanoscience and Nanotechnology
b
Institute of Chemistry and the Center for Nanoscience and Nanotechnology
The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
*Corresponding author: Oded Millo, Fax +972-2-6586784, email: [email protected]
I will give an overview of our scanning tunneling spectroscopy and electrical transport studies of hybrid
semiconductor nanocrystals (NCs) and NC assemblies. The following topics will be addressed:
1. The electronic properties of metal-semiconductor nanojunctions, where in-gap states are induced in the
semiconductor side of the interface.
2. The level structure of semiconductor NCs within arrays. Here we found a systematic reduction of the
band-gap compared to the corresponding isolated NCs. This proximity-induced reduction was found to
depend on three main factors: The effective masses of the charge carriers and the distance between and
number of nearest neighbors. The effect of the capping molecules on the band-gap will also be discussed.
We have also observed, for the densest NC assemblies, a (surprising) emergence of collective twodimensional array level structure.
3. An anomalous photovoltaic effect in films of Si NCs embedded in SiO2 where, close to the percolation
threshold of the Si crystallites phase, photovoltages much larger than the Si band-gap were observed. The
photo-induced built-in electrical field appeared to be along the size (and concentration) gradients of the Si
NCs, and the photovoltage increased as the concentration (and NC size) reduced towards the percolation
threshold. These phenomena may be due to charge separation of excited electron-hole pairs governed by the
size-dependent quantum confinement and charging energies.
A47
Session VI: Electronics and Devices
Memory and photoconductivity effects in zinc oxide nanoparticle films
Jianpu Wang, Yizheng Jin, Neil C. Greenham,
Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
Corresponding author: Neil Greenham, Fax +44 1223 764515, email: [email protected]
Electrical conduction in films of nanoparticles is controlled by a complicated combination of hopping,
disorder, coulomb blockade, and trapping effects. Here, we study the device properties of films of zinc oxide
nanoparticles. In sandwich structures where a ZnO nanoparticle film is deposited between indium tin oxide
and aluminium electrodes, interesting hysteresis effects are observed which may have applications in
memory devices. As the voltage is increased, the device is initially in a high conductivity state, but then
switches to a low conductivity state which persists as the voltage is decreased (Figure 1). These effects are
only seen when the devices are under ambient conditions, indicating that adsorbed oxygen is important in
trapping free carriers. They also only appear several hours after deposition of the aluminum electrode, and
are much more prominent when short (octylamine) ligands are used. We present a mechanism for the
hysteresis which involves the modification of the injection barrier at the aluminium/ZnO interface by
trapping of electrons at surface states.
1
Current density (A/cm2)
10
-1
10
-3
10
-5
10
-7
10
-1
0
1
Voltage (V)
2
3
Figure 1. Current-voltage scan for a 100 nm thick film of 6 nm diameter ZnO nanocrystals with
octylamine ligands between ITO and Al electrodes.
We have also studied these films using interdigitated in-plane gold electrodes. These devices show a very
large ultraviolet photoconductivity, with a responsivity of 79 A/W at 370 nm under a bias of 120 V. The
large photoconductive gain is attributed to the UV-assisted desorption of oxygen from the nanoparticle
surfaces, thus reducing trapping of electrons and also reducing the barrier to charge injection through
modification of surface states. These devices have potential as visible-blind ultraviolet photodetectors.
A48
Session VI: Electronics and Devices
PbSe quantum dots: single-particle energy levels and quantum mechanical coupling measured with
Scanning Tunneling Microscopy
K. Overgaaga, P. Liljerotha+, B. Grandidierb, D. Vanmaekelbergha.
Condensed Matter and Interfaces, Debye Institute, Utrecht University, P.O. Box 80 000, 3508 TA Utrecht, The
Netherlands
b
Institut d'Electronique, de Micro-électronique et de Nanotechnology, ISEN, 41 boulevard Vauban, F-59046 Lille,
France
+
present address: IBM Zurich Research Laboratory, CH-8803 Rüschlikon, Switzerland.
a
Corresponding author: Karin Overgaag, Fax 0031 30 2532403, email: [email protected]
Scanning Tunneling Spectroscopy (STS) is a nearly ideal method to measure the energy and spatial
probability of the levels of atoms, molecules and semiconductor quantum dots (QDs)1,2. The method probes
resonant electron transitions between the Fermi level of a tip electrode and the energy levels of the system
under investigation. STS has certain advantages with respect to optical spectroscopy in the sense that
transition selection rules do not play a role (all energy levels can be probed) and the spatial resolution can be
enhanced up to the atomic scale.
Generally, QDs have to be chemically attached to a conducting substrate to obtain a stable tip/QD/substrate
configuration in STS. Here, we present an alternative method of stabilizing individual QDs and QD
molecules by embedding the QDs of interest in a monolayer-matrix of wider band gap nanocrystals of about
the same size. We demonstrate this approach by studying PbSe QDs embedded in a monolayer of CdSe
nanocrystals where the PbSe QDs can be identified by both topographic (STM) and spectroscopic (STS)
measurements4. With STS we investigate electron (hole) transport through individual PbSe QDs, small
aggregates and larger 2D arrays of PbSe QDs. The results are compared to single QDs chemically linked to a
substrate.
Individual PbSe QDs show a set of s, p, d..-type electron and hole levels1. The energy spacing and the
HOMO-LUMO gap depend sensitively on the crystal size due to quantum confinement. Detailed
spectroscopy allows us to better understand the results from optical spectroscopy1. In small aggregates, the
spectra change with respect to that of an individual QD due to quantum mechanical interaction, i.e. electron
(hole) delocalization over the QDs in the molecular island: the HOMO-LUMO gap reduces and the features
in the energy level spectrum broaden4. In 2-D arrays of PbSe, the spectrum taken at a given QD site in the
array varies from site to site, reflecting a site-variable quantum mechanical interaction3,4. In some cases, a
step-like density of states of a 2-D electron gas is observed. QD arrays with two different types of building
blocks can be quantitatively studied, it is possible to measure the local "atomic" configuration together with
the LDOS, a promising prospect for further study of ordered binary QD solids.
Fig. 1: Schematics of electron tunneling processes (arrows) in a single PbSe QD (left), an individual PbSe QD in an
inert matrix (middle) and in a PbSe trimer (right) where due to quantum mechanical coupling, the electron can
delocalize over three QDs.
References:
1
Liljeroth, P.; Zeijlmans van Emmichoven, P. A.; Hickey, S. G.; Weller, H.; Grandidier, B.; Allan, G.;
Vanmaekelbergh, G. Physical Review Letters 2005 95, 086801/1-086801/4.
2
Liljeroth, P.; Jdira, L.; Overgaag, K.; Grandidier, B.; Speller, S.;. Vanmaekelbergh, D. Physical Chemistry
Chemical Physics 2006 8, 3845-3850.
3
Liljeroth, P.; Overgaag, K.; Urbieta, A.; Grandidier, B. Hickey, S.G.; Vanmaekelbergh, D. Physical Review
Letters 2006 97, 096803/1-096803/4.
4
O vergaag, K.; Liljeroth, P.; Grandidier, B.; Vanmaekelbergh, D. ACS Nano, 2007 submitted.
A49
Session VI: Electronics and Devices
Dipolar Structures in Colloidal Dispersions of PbSe and CdSe Quantum Dots
A.J. Houtepen*‡, M. Klokkenburg†, R. Koole*, B.H. Erné†, D. Vanmaekelbergh*
*
Condensed Matter and Interfaces, Utrecht University, The Netherlands
Van ’t Hoff Laboratory for Physical and Colloid Chemistry, Utrecht University, The Netherlands
‡
Present address: Optoelectronic Materials, Delft University of Technology, The Netherlands
†
Corresponding author: Arjan Houtepen, email: [email protected]
We show by cryogenic transmission electron microscopy that PbSe and CdSe nanocrystals of
various shapes in a liquid colloidal dispersion self-assemble into equilibrium structures that have
a pronounced dipolar character, to an extent that depends on particle concentration and size.
Analyzing the cluster-size distributions with a one-dimensional (1D) aggregation model yields a
dipolar pair attraction of 8-10 kBT at room temperature. From this pair attraction we determine a
dipole moment of >300 Debye, which is significantly larger than has been determined previously
by electrical impedance measurements.
These results are important for all measurements on relatively concentrated dispersions of
nanocrystals because the distribution of chain lengths can influence the response of the system to
optical and electrical signals. For example, efficient energy-transfer may occur within clusters.
Understanding the chain formation and the distribution of chain lengths is also important for the
synthesis of anisotropic nanocrystals such as wires, stars and rings. Finally, the presence of a
large dipole moment has a strong effect on the electronic properties of the nanocrystals. The
dipole moments we determine correspond to a potential drop of several tens of a Volt over the
nanocrystals. This will distort the electronic wave functions and will likely lift the degeneracy of
non spherically symmetric levels.
Figure 1 Cryo TEM images of spherical (A), cubic (B) and star-shaped (C) PbSe nanocrystals. All crystal
shapes exhibit pronounced linear aggregation, which is indicative of strong dipolar interactions
Klokkenburg, M., Houtepen, A.J., Koole, R., de Folter, J.W.J., Erne, B.H., van Faassen, E., and
Vanmaekelbergh, D., Dipolar structures in colloidal dispersions of PbSe and CdSe quantum dots. Nano
Lett., 2007. 7(9): p. 2931.
A50
Session VI: Electronics and Devices
Electrical transport and Raman scattering of a single organic molecule
I. Bar-Joseph
Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot, Israel
Recently we have introduced a novel new technique to contact single organic molecules. The
technique is based on forming a dimer structure, in which the molecule under study is attached to
two metal nanoparticles. We have shown that the dimer structure allows us to measure the
conductance of a single organic molecule, and conducted measurements of a few short (~1 nm)
molecules [1]. In this work we show that this dimer structure significantly enhances the Raman
cross section and allows measurement of the Raman spectrum of a single organic molecule. We
investigate the origin of this enhancement and show that it is related to surface plasmons excited
in the metal nanoparticles by the incoming and outgoing radiation. We find that the enhancement
in these dimeric structures can not be understood within the simple dipolar approximation, and
could only be explained if one considers higher multipoles in the plasmon spectrum, which
appear due to retardation effects in the dimers.
[1] T. Dadosh et al. Nature 436, 677 (2005)
A51
Session VII: Theory
Theory of self-assembly of nanorods
Eran Rabani (invited)
University of Tel Aviv, Israel
A new theoretical approach is developed to study drying-mediated self-assembly of nanorods. The
approach is based on a coarse-grained lattice-gas model that couples dynamically two different phasetransformations, one in solvent density (evaporation, or liquid-gas phase transition) and the other in
nanorod density (self-assembly, or liquid-solid phase transition). The nanorods and the solvent are
described on a coarse level while their interactions are described on a denser grid. Within the new
approach, the nanorods have no preferred orientation in the presence of the solvent, during and after its
evaporation, while the computational effort is still manageable. Two different scenarios are discussed
for self-assembly of nanorods. The first is the standard drying-dynamics, where diffusional and
rotational dynamics of the nanorods compete with the evaporation timescale. In the other, capillary
forces pre-align the nanorods in the solution, and the fast drying dynamics only pack the nanorods
together. We analyze the nanorods angle distribution, and the effects of the different timescales and
length scales on this distribution. The main conclusion that can
Be drawn from our work is that, unlike the case o nanocrystals, where drying dynamics and solvent
fluctuations determine the final morphology, for nanorods, one requires pre-ordered array (via
capillary forces, external fields, or perhaps liquid crystals) and the drying dynamics do not change
this pre-ordered structure.
A52
Session VII: Theory
Implications of CoPt3-Au interface properties on the growth of colloidal CoPt3-Au
nanocrystal heterodimers: an ab initio study
Letizia Chiodo, Fabio Della Sala, Teresa Pellegrino, Roberto Cingolani, Liberato Manna
National Nanotechnology Laboratory of CNR-INFM, 73100 Lecce, Italy
Corresponding author: Letizia Chiodo, Fax +390832298238, email: [email protected]
The theoretical investigation of solid-solid interfaces is of fundamental importance in several areas of
research and technology, and the new challenging field of fabrication and interconnection of inorganic
nanostructures is giving new strength to the study of interfacial properties, in view of realizing integrated
optical, electronic and magnetic devices.1 In materials chemistry, one recent exciting direction is represented
by the development of colloidal inorganic nanocrystals that can be synthesized with control over their size,
shape and chemical composition.1,2 Understanding the parameters that govern the hetero-interface formation
represents an important step towards a higher control over the synthesis of novel combinations of materials
and ultimately towards modeling and tailoring of their physical and chemical properties.
On the light of the recently reported formation of colloidal CoPt3-Au nanocrystal heterodimers 3 that have
been synthesized by wet-chemical approaches and that share conductive and magnetic properties, we report
here an ab initio Density Functional Theory study of the structural properties of Au/CoPt3 interfaces. We
investigate the structure of different bulk CoPt3 facets and of Au atoms adsorbed on CoPt3 facets. We
calculate CoPt3 and Au surface energies, Au/CoPt3 interfacial energies as well as adsorption energies of Au
atoms on CoPt3. We find that the most reactive CoPt3/Au interface is the (111) one, which should help to
explain the preferred growth of Au on the (111) facet of CoPt3. An important contribution to this effect
should be given by the strain developing at the heterointerface. Further experimental and theoretical work is
required for a complete understanding of the properties of hetero-nanocrystals. In particular we are
investigating the electronic and magnetic properties of CoPt3 dimers.
b)
Fig. 1: Panel a) Transmission electron microscopy (TEM) high-resolution image of a CoPt3-Au heterodimer
surrounded by unreacted CoPt3 nanocrystals. The large domain in the heterodimer is made of gold. Panel b)
Structure of the (111) CoPt3-Au interface modelled by a supercell.
References:
1. Rao, C. N. R.; Vivekchand, S. R. C.; Biswasa, K.; Govindaraja, A., Dalton Trans. 2007, (34), 3728-3749.
2. Cozzoli, P. D.; Pellegrino, T.; Manna, L., Chem. Soc. Rev. 2006, 35, (11), 1195-1208.
3. Pellegrino, T.; Fiore, A.; Carlino, E.; Giannini, C.; Cozzoli, P. D.; Ciccarella, G.; Respaud, M.; Palmirotta, L.;
Cingolani, R.; Manna, L., J. Am. Chem. Soc. 2006, 128, (20), 6690-6698.
A53
Session VII: Theory
Plasmon Coupling Between Gold Nanorod and
Adsorbed Organic Molecule
Goutam Chandraa, Anushree Roya*,Gautam Mukhopadhyayb
a
Department of Physics, Indian Institute of Technology Kharagpur, Pin- 721302
Department of Physics, Indian Institute of Technology Mumbai, Pin -400076
b
Corresponding author: Anushree Roy, email: [email protected]
Localized surface plasmons in metal nanorods can couple with optical fields efficiently, and thereby, leads to a
strong modification in optical absorption and the scattering cross section of the adsorbed molecules on metal
surface. The metal-ligand interaction strongly depends on molecular orientation with respect to the local field
generated by the plasmon resonance in the anisotropic metal body. Recently, an analytical theory has been proposed
to explain the dipolar response of ellipsoidal plasmonic particles covered by anisotropic molecular layers [1].
In this work, we have investigated plasmon coupling between gold nanorod (Au NR), prepared by chemical
route. The aspect ratio of the rod, as estimated from Transmission Electron Microscopic images and the plasmon
resonance bands for longitudinal and transverse modes, is 4.5±02 nm . Fig.1 shows the changes in surface plasmon
resonance bands of metal particles, induced by adsorbed benzonitrile (BN) molecules on the rod surface. On the
other hand, Fig. 2 exhibits, the dispersion in vibrational mode of the adsorbed molecule upon adsorption on gold
rod surface. To understand the effect of surface coverage, we have carried out the experiment for different
concentrations of ligand molecules.
3
x10
Au nanorod
0.1M BN
0.07M BN
0.03M BN
0.8
Intensity (arb. unit)
Absorbance (Normalized)
1.0
0.6
0.4
0.2
6
0.03M BN
0
2200
8
2240
0.07M BN
0
16
8
2200
2240
0.1M BN
0
2200
0.0
400
2240
8
600
BN
800
Wave length (nm)
0
2200
2240
-1
Fig. 1 Optical absorption spectrum of colloidal
solution of bareAu NR (black) and after adsorption of
0.1 M (red), 0.07 M (green) and 0.03M (red) of BN
molecule
Raman shift (cm )
Fig. 2 Raman spectrum of BN molecule after
adsorption on Au NR surface.
For calculating the optical response of Au NR on ligand molecule and to understand our experimental observations,
first, we have carried out density functional theory calculations to estimate the vibrational frequencies of the
chemisorbed molecule for different orientation on [111] and [100] plane of Au NR surface. It is to be noted that
[100] is expected to be the axial growth direction of gold nanorod along with a strips of [111] facets. Next, we use
the microscopic analytical model, proposed in [1], to include the effect of plasmon coupling on the chemisorbed BN
molecule on Au NR.
Reference:
[1] Tobias Ambjornsson, Gautam Mukhopadhyay, S.Peter Apell and Mikael Käll, Phys. Rev. B, 73, 085412 (2006).
A54
Session VII: Theory
Excited state properties of functionalized Silicon Quantum Dots:
A theoretical investigation based on time-dependent DFT
Thomas A. Niehausa, Xian Wangb, Quansong Lib, Ruiqin Zhangb, Thomas Frauenheima
aBremen Center for Computational Materials Science, Bremen, Germany
bCentre of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City
University of Hong Kong, Hong Kong SAR, China
Corresponding author: Thomas A. Niehaus, Fax 00494212184764 email: [email protected]
Excited-state properties of silicon quantum dots (SiQDs) from Si5 to Si199 are studied using a time-dependent
density-functional tight-binding method (TD-DFTB) [1] and compared with available experimental data.
Several functionalizations ranging from simple hydrogen passivation up to capping with amine [2],
allyamine [3] and propionic acid [4] groups are discussed. Signatures in vibrational and optical absorption
spectra are revealed, which show the detailed effect of surface modification of the SiQDs. It is verified that
the modification could be expected to not only reduce the surface oxidation rate but also maintain an
efficient electronic transition feature that facilitates blue emission. The obtained absorption spectra show a
significant size dependence. In the case of allylamine capping, the increase in the number of attached
molecules only results in a slight red shift of emission spectra. The latter are calculated by means of full
geometry optimization in the excited state and reveal huge Stoke shifts in contrast to simple quantum
confinement models [5].
References:
[1] T.A. Niehaus, S. Suhai, F. Della Sala, P. Lugli, M. Elstner, G. Seifert, and T. Frauenheim, Phys. Rev. B, 63, art.no.
085108, 2001.
[2] Q.S. Li, R.Q. Zhang, S-T. Lee, T.A. Niehaus, and Th. Frauenheim, J. Phys. Chem. C, submitted.
[3] X. Wang, R.Q. Zhang, T.A. Niehaus, and Th. Frauenheim, J. Phys. Chem. C, 111, 2394, 2007.
[4] Q.S. Li, R.Q. Zhang, T.A. Niehaus, Th. Frauenheim, and S.-T. Lee, J. Chem. Theo. Comp., 3, 1518, 2007.
[5] X. Wang, R.Q. Zhang, S.T. Lee, T.A. Niehaus, and Th. Frauenheim, Appl. Phys. Lett., 90, 123116, 2007.
A55
Session VIII: Assembly
Micrometer-scale assembly of colloidal CdSe/CdS nanorods
Concetta Nobilea,b*, Luigi Carboneb, Milena De Giorgib, Giovanni Morelloa,b, Roberto Cingolanib, Liberato Mannab,
Roman Krahneb
a
Scuola Superiore ISUFI, Distretto Tecnologico, Via per Arnesano Km 5, 73100 Lecce, Italy
b
National Nanotechnology Laboratory of CNR-INFM, IIT Research Unit, Via per Arnesano km 5, 73100 Lecce, Italy
*
Presenting author: Concetta Nobile, Fax +39 0832 298230, email: [email protected]
Ordered assemblies of inorganic nanostructures are relevant both to fundamental research, as they present
new platforms on which chemical and physical interactions among proximal particles can be investigated,
and to the bottom-up engineering of new materials and devices. Significant progress has been recently made
in the organization of colloidal nanorods into well defined “superlattice” geometries. To this purpose various
methods have been exploited, such as, for example, the use of external fields, the control of inter-particle
interactions and/or of interfacial energy in binary solvent/non-solvent mixtures.1
In this work we present two different types of ordered assemblies of rod-shaped CdSe/CdS core/shell
colloidal nanocrystals, which have been obtained onto suitable solid surfaces.2 In particular, we demonstrate
the lateral alignment of nanorods mediated by electric fields as well as their vertical close-packed alignment
over areas of several tens of square microns. The vertically oriented arrays have been obtained by inducing
self-assembly under controlled solvent evaporation either at aqueous/organic interfaces or upon the
application of electric fields.
The large scale assemblies that are presented here have allowed us to study relevant optical properties arising
from coupling effects among neighbouring nanorods in organized superstructures, which we demonstrated to
be strongly correlated with the geometry and the degree of alignment achieved.2,3
Figura 1. (a) SEM image of lateral alignment of nanorods, and (b) TEM image of vertically oriented nanorods obtained
under the assistance of electric fields.
References:
1.
Böker, A.; Jinbo, H.; Emrick, T.; Russell, P. T. Soft Matter 2007, 3, (10), 1205-1320
2.
Carbone, L.; Nobile, C.; De Giorgi, M. ; Carbone, L.; Della Sala, F.; Morello, G.; Pomap, P.; Hytch, M.;
Snoeck, F.; Fiore, A.; Franchini, I.; Nadasan, M.; Silvestre, A. F.; Chiodo, L.; Kudera, S.; Cingolani R.;
Krahne, R.; Manna, L. Nano Letters 2007, 7, (10), 2942-2950
3.
Nobile, C.; Fonoberov V.A.; Kudera, S.; Della Torre, A.; Ruffino, A.; Chilla, G.; Kipp, T.; Heitmann, D.;
Manna, L.; Cingolani, R.; Balandin, A. A.; Krahne, R. Nano Letters 2007, 7, (2),476-479.
A56
Session VIII: Assembly
Colloidal nanocrystal based nanocomposites as novel functional materials
A.
C. Ingrosso, A. Panniello, C. Sciancalepore, T. Placido, A. Agostiano
B.
M.L. Curri, M. Striccoli, R. Comparelli,
C.
A. Convertino, G. Leo
D.
V. Fakhfouri, J. Y. Kim J. Brugger,
E.
R. Tommasi, T. Cassano
F.
A. Voigt, F. Reuther, G. Gruetzner
G.
D. Mecerreyes, J. A. Alducin
H.
N. Kehagias, V. Reboud, C. M. Sotomayor Torres
A
Dipartimento di Chimica, Università di Bari, Italy
B
CNR-IPCF Bari Division, Italy
C
CNR-ISMN Roma Division, Italy
D
Microsystems Laboratori, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
E
Dipartimento di Biochimica Medica, Biologia Medica e Fisica Medica, Università di Bari,
F
Micro Resist Technology GmbH, Berlin (Germany)
G
CIDETEC-Centre for Electrochemical Technologies, San Sebastian (Spain)
H
Tyndall National Institute, Cork, (Ireland)
Corresponding author: M. Striccoli, Fax +39 080 5442128, email: [email protected]
The unique size- and shape-dependent electronic properties of semiconductor and metal nanocrystals (NCs)
make them extremely attractive as novel structural building blocks for constructing a new generation of
innovative materials and solid-state devices. Recent advance in chemical synthesis allows to synthesize
colloidal NCs in a wide range of compositions with an excellent control on size, shape and uniformity. In
addition, the NC surface can be properly engineered by ligand exchange and surface functionalization, and
they can be thus placed in almost any chemical environment. Therefore such colloidal nano-objects can be
envisioned as an innovative class of chemical macromolecules, which can be organised using the wellassessed techniques of organic chemistry. In this contribution different approaches will be presented as
distinctive opportunities for exploitation of colloidal NC properties in micro and nanofabrication processes
towards their use in devices for photonic and sensing applications. The incorporation in polymers of such
nanostructures in mesoscopic materials can be achieved by choosing NCs differing in size and/or
composition, as well as tuning the interaction between NCs and surrounding environment. The possibility to
improve the processability and tune the reactivity of the particles without altering their structural and
chemical-physical properties will be demonstrated. The original characteristics of hybrid materials based on
polymers and colloidal NCs, able to combine the optoelectronic and chemical properties of the inorganic
moiety with the processability of the host matrix, will be discussed. Selected cases of micro and
nanofabrication of such composite materials for patterning either by conventional lithographic techniques [1]
and emerging patterning tools, such as nanoimprinting lithography (NIL) [2] and ink jet printing will be
illustrated (Figure 1 and 2), pointing out their technological impact on the development of new
optoelectronic and sensing devices. [3,4]
Figure 1: Luminescent NCs modified
epoxy resist for the fabrication of 3-D high
aspect ratio microstructures. [1]
Figure 2: NC based luminescent polymer
nanocomposites for Nano Imprinting
Lithography for photonic devices. [2]
A57
Session VIII: Assembly
Acknowledgement
The EC-funded projects NaPa (NMP4-CT-2003-500120) and NOVOPOLY (STRP 013619) and the National
project SYNERGY (FIRB RBNE03S7XZ) within the Italian MIUR funding programme are gratefully
acknowledged.
References:
1. C. Ingrosso, V. Fakhfouri, M. Striccoli, A. Agostiano, A. Voigt, G. Gruetzner, M. L. Curri, J. Brugger
(2007) Adv. Funct. Mater. 17, 2009–2017
2. M. Tamborra, M. Striccoli, M. L. Curri, J. A. Alducin, D. Mecerreyes, J. A. Pomposo, N. Kehagias, V.
Reboud, C. M. Sotomayor Torres, A. Agostiano (2007) Small 3, 822 – 828.
3. V. Reboud, N. Kehagias, M. Zelsmann, M. Striccoli, M. Tamborra, M. L. Curri, A. Agostiano, M. Fink, F.
Reuther, G. Gruetzner, C. M. Sotomayor Torres (2007) Applied Physics Letter 90, 011115;
4. Convertino, G. Leo, M. Tamborra, C. Sciancalepore, M. Striccoli, M. L. Curri, A. Agostiano (2007) Sensors
and Actuators B, 126 138–143
A57
Session VIII: Assembly
Highly persistent superparamagnetic needles obtained
by controlled co-assembly of iron oxide nanoparticles and polymers
Jérôme Fresnaisa, Jean-François Berreta and Olivier Sandreb
a
Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris-VII, Bâtiment Condorcet
10 rue Alice Domon et Léonie Duquet, 75205 Paris, France
b
Laboratoire Liquides Ioniques et Interfaces Chargées, UMR 7612 CNRS Université Pierre et Marie Curie Paris-VI
4 place Jussieu, F-75252 Paris Cedex 05 Franc
Corresponding author: J.-F. Berret, email: [email protected]
During the past years, we have investigated the complexation between nanocolloids and oppositely charged
polymers. The nanocolloids examined were ionic surfactant micelles [1] and inorganic oxide nanoparticles
[2]. For the polymers, we used homopolyelectrolytes or block copolymers with linear or branched
architectures. The attractive interactions between oppositely charged species are strong and in general the
simple mixing of disperse solutions yield to a precipitation, or to a phase separation. We have developed
means to control the electrostatically-driven attractions and at the same time, to preserve the stability of the
dispersions. Using this approach we also designed novel nanostructures, as those obtained recently with iron
and cerium oxide nanoparticles [2]. In this presentation, we give an account of the formation of micrometric
needles made from the co-assembly between 7 nm particles and copolymers. The length of the elongated
structures can be varied at will between 5 and 100 μm, with a diameter of the order of 500 nm. The number
of nanoparticles per micrometer of needles was estimated at 106. By application of an external magnetic
field, the needles can be easily oriented along the field direction. Preliminary micro-rheology experiments on
test fluids have demonstrated the potential use of these needles to determined locally the viscoelastic
response of complex fluids.
[1] J.-F. Berret, P. Hervé, O. Aguerre-Chariol and J. Oberdisse, Colloidal Complexes obtained from Charged Block
Copolymers and Surfactants : A comparison between Small-Angle Neutron Scattering, Cryo-TEM and Simulations,
Journal of Physical Chemistry B 107, 8111 – 8118 (2003)
[2] J.-F. Berret, A. Sehgal, M. Morvan, O. Sandre, A. Vacher, M. Airiau
Stable Oxide Nanoparticle Clusters Obtained by Complexation, Journal of Colloid and Interface Science 303 (2006)
315–318
A58
Efficient photo-electron extraction from colloidal quantum dots
Michel Saba, Agnieszka Gocalinska, Francesco Quochi, Andrea Mura, Giovanni Bongiovanni
Dipartimento di Fisica, Università di Cagliari, I-09042 Monserrato (CA), Italy
Corresponding author: Michele Saba, Phone +39 070 675 4872, email: [email protected]
Colloidal quantum dots are an increasingly popular choice for photovoltaic applications, given their tuneable
absorption covers most of the solar spectrum and the quantum confinement could help converting the energy
of a single photon into multiple excited electrons, a process known as carrier multiplication. Further,
quantum dots in combination with organic matrices happen to have simple fabrication procedures and
therefore represent a low cost route to efficient solar cells, as demonstrated by promising prototypical
devices.
The crucial step for generating a photocurrent is charge separation after optical absorption, and this is the
area whose workings we investigate. We study the time needed to extract photoexcited electrons from
quantum dots and transfer them into organic matrices. PbS quantum dots with different passivation layers
were embedded in organic matrices or organic solutions that act as good electron acceptors. We timeresolved the optical emission from the quantum dots with ps resolution to infer by the shortening of the
luminescence decay the time needed for electrons to be extracted from the quantum dots. Photocurrent
measurements confirmed the luminescence quenching was indeed linked to separation of excitons.
P1
Water solubilization of different hydrophobic nanocrystals by means of an amphiphilic
polymer and their characterization
Riccardo Di Corato*, Alessandra Quarta, Philomena Piacenza, Andrea Ragusa, Albert Figuerola, Raffaella Buonsanti,
Roberto Cingolani, Liberato Manna and Teresa Pellegrino
National Nanotechnology Laboratory of CNR-INFM, 73100 Lecce, Italy
*Corresponding author: Riccardo Di Corato, Fax 00390832298238, e-mail: [email protected]
A simple and general strategy to water-solubilize hydrophobic nanoparticles, by means of the amphiphilic
polymer poly(maleic anhydride-alt-1-octadecene), is here presented.
Poly(maleic anhydride-alt-1-octadecene), a cheap and commercially available polymer, was used to transfer
in water colloidal nanocrystals with different composition (gold, iron oxide, CdSe based semiconductor1,
FePt@FexOy heterodimers2) morphology (rod, sphere or heterostructure), and size. A previously reported
procedure3 had to be substantial modified in order to efficiently substitute a similar polymer not
commercially available anymore. Highly pure nanoparticles with homogeneous distribution of sizes and
surface charges were obtained after a single purification step by ultracentrifugation, saving precious time
compared to the old procedure. The resulting water-soluble nanocrystals preserved the same physical,
chemical, and optical properties of their hydrophobic counterparts. The characterization of the nanocrystals
was carried on by means of transmission electron microscope, spectroscopy analysis (absorption spectra,
quantum yield measurement, FT-IR analysis), gel electrophoresis, dynamic light scattering and zeta-potential
measurements.
Fig. 1 Comparison of the effect of
ultracentrifugation on different types of
nanocrystals coated either with C14-P (a) or
with C18-P (b). This was carried out on the
following nanocrystals: Au spheres (6 nm
diameter, a1-b1), γ-Fe2O3 spheres (both 8 nm
and 13 nm diameter, a2-b2 and a3-b3,
respectively), heterodimers made of FePtFexOy2 (9 nm total length, a4-b4) and
CdSe/CdS nanorods1 (5 nm diameter × 38 nm
length, a5-b5).
References:
1.
Carbone, L.; Nobile, C.; De Giorgi, M. ; Della Sala, F.; Morello, G.; Pompa, P.; Hytch, M.; Snoeck, E.; Fiore,
A.; Franchini, I. R.; Nadasan, M.; Silvestre, A. F.; Chiodo, L.; Kudera, S.; Cingolani, R.; Krahne R.; Manna, L.
Nano Letters, 2007, 7, 2942-2950.
2.
Figuerola, A.; Fiore, A.; Di Corato, R.; Falqui, A.; Giannini, C.; Micotti, E.; Lascialfari, A.; Corti, M.;
Cingolani, R.; Pellegrino, T.; Cozzoli, P. D.; Manna, L. JACS 2007, in press
3.
Pellegrino, T.; Manna, L.; Kudera, S.; Liedl, T.; Koktysh, D.; Rogach, A. L.; Keller, S.; Radler, J.; Natile G.;
Parak, W. J. Nano Letters, 2004, 4, 703-707.
P2
Exploiting surface functionalization of colloidal nanocrystals for biological applications
Andrea Ragusa*, Riccardo di Corato, Alessandra Quarta, Angela Fiore, Roberto Cingolani, Liberato Manna, Teresa
Pellegrino
National Nanotechnology Laboratory of CNR-INFM, Distretto Tecnologico ISUFI, Via Arnesano, 73100 Lecce, Italy
Corresponding author: Andrea Ragusa, Tel +390832298236, email: [email protected]
Fluorescent nanocrystals have already proven to be very important tools for a variety of biological
applications, such as detection and imaging.1-3 However, to be used in a biological environment, such
nanocrystals have to be biocompatible, e.g. water-soluble and not cytotoxic. To that aim, nanocrystals can be
synthesized directly in aqueous solution with water-soluble capping ligands. However, this approach does
not yield nanocrystals with the same physico-chemical properties of those synthesized by colloidal hightemperature methodologies, which, on the other hand, are passivated by a layer of hydrophobic ligands.
Several strategies have been developed to make the latter nanocrystals water-soluble, such as ligandexchange, creation of an outer silica shell, or intercalation of an amphiphilic polymer.3 A step forward can be
reached targeting a particular cell or tissue by further functionalizing the nanocrystal surface with specific
ligands, such as antibodies, peptides, receptor ligands, etc.
Here we show how to exploit surface functionalization for a variety of applications, such as specific targeting
of tumor cells, creation of assembled dimers and site-selective functionalization of nanocrystals through the
use of polymeric beads. Folate receptor is overexpressed in many tumor cells,4, 5 thus conjugation of folic
acid to nanorods and quantum dots yielded cell-targeting fluorescent probes. On the other hand, conjugation
of nanocrystals to polymeric microbeads yielded an efficient way of linking together inorganic clusters in a
controlled way with spatial control over assembly, giving also the possibility for site-selective
functionalization.
References:
1.
Bruchez, M., Jr.; Moronne, M.; Gin, P.; Weiss, S.; Alivisatos, A. P. Science 1998, 281, 2013-2016.
2.
Chan, W. C. W.; Nie, S. Science 1998, 281, 2016-2018.
3.
Medintz, I. L.; Uyeda, H. T.; Goldman, E. R.; Mattoussi, H. Nat. Mater. 2005, 4, 435-446.
4.
Leamon, C. P.; Low, P. P. Proc. Natl. Acad. Sci. U.S.A. 1991, 88, 5572-5576.
5.
Wang, S.; Low, P. S. J. Controlled Release 1998, 93, 39-48.
P3
Production of 3D structures of semiconductor nanocrystals
Stefan Kuderaa, Eva Bocka, Isabella Franchinib, Liberato Mannab, Joachim Spatza
a
Max Planck Institute for metals research, Department New Materials and Biosystems, Stuttgart and University of
Heidelberg, Biophysical Chemistry, Heidelberg, Germany
b
National Nanotechnology Laboratory of CNR-INFM, Lecce, Italy
Corresponding author: Stefan Kudera, Fax +49(0)711-689-3612 , email: [email protected]
Colloidal nanocrystals are considered as promising candidates for the enhancement of solar cells. In a
mixture of nanocrystals and conducting polymer or electrolyte the role of these nanocrystals is to first absorb
light and thus generate electron-hole pairs.1 The charges are then separated on the interface between
nanocrystals and surrounding medium and transported to the relative electrodes. In this talk we will present
possible improvements of the structure of the nanocrystals in the solar cells.
The first approach relies on the cross-linking of shape controlled semiconductor nanocrystals. In a deviation
for the synthesis scheme for the production of gold tipped semiconductor nanorods2 complex networks of
these structures can be formed. These networks provide a large surface and still one can expect to find
conductive pathways through these networks, so that the generated charges are transported towards the edges
of the network and thus to an electrode.
In a second approach we start from patterned surfaces. Gold dots of defined size and with controllable
distances are deposited with a self-assembly technique onto silicon surfaces.3 With a solution-liquid-solid
approach4 we were able to grow CdSe nanowires onto the immobilized dots. The advantage of this technique
resides in the firm anchoring of the wires on the surface. Through the control of the density of the gold dots
we can furthermore control the density of the nanowires, which might be an important parameter in the
tuning of the performance of the solar cells.
References:
1.
Grätzel, M. Nature 2001, 414, (6861), 338.
2.
Mokari, T.; Rothenberg, E.; Popov, I.; Costi, R.; Banin, U. Science 2004, 304, 1787-1790.
3.
Glass, R.; Moller, M.; Spatz, J. P. Nanotechnology 2003, 14, (10), 1153-1160.
4.
Trentler, T. J.; Hickman, K. M.; Goel, S. C.; Viano, A. M.; Gibbons, P. C.; Buhro, W. E. Science 1995, 270,
(5243), 1791-1794.
P4
Investigation of the molecular ordering of tetrakis-(isopropoxy-carbonyl)-copperphthalocyanine to target towards advanced technological applications
Chiara Ingrossoa,b, Maria Lucia Curria, Paola Finia, Gabriele Giancanec, Ludovico Vallic, Angela Agostianoa,b
a
Chemistry Department of Bari University, via Orabona 4, 70126 Bari, (Italy)
CNR-IPCF Bari Section c/o Chemistry Department of Bari University, via Orabona 4, 70126 Bari, (Italy).
c
Material Science Department of Lecce University, via Arnesano 1, 73100 Lecce, Italy.
b
Corresponding author: Angela Agostiano, Fax 00390805442128, email: [email protected]
Phthalocyanines (Pcs) and Metal Phthalocaynines (MPcs) are highly flexible compounds in terms of
design of the chemical and physical functionalities by properly choosing and varying the metal ion at the
centre of the aromatic macroring and/or the peripheral groups1. Owing to the large π aromatic system, these
compounds show a strong tendency to stack in H- or J-type aggregates detrimentally affecting the
outstanding functionalities of the corresponding monomer2. Accordingly, an extensive spectroscopic and
chemical-physical investigation of such compounds, with particular attention to the molecular selforganization, appears fundamental to orient them towards advanced technological applications and
rationalize the achieved performances.
Among MPcs, Copper-Phthalocyanines (CuPcs) represent a class of largely investigated compounds,
whose peculiarity resides in the fact that the singly occupied Cu-derived outer level is predicted to lie in the
HOMO-LUMO ligand gap and the corresponding orbital can be addressed as singly occupied molecular
orbital3. Solid oligomers of CuPc evidenced in fact high dielectric constant values4 and were used to develop
highly dielectric organic composites5.
Thin films of CuPc and relative hybrid junctions formed with a wide range of metals and inorganic
semiconductors shown interesting electronic properties that can be exploited in photoelectrochemical
applications, light-emitting diodes and gas sensing devices4. In particular, the conjunction of MPcs with
inorganic colloidal nanocrystalline (NC) semiconductors provided to achieve photoelectrochemical6 and
sensing performances7 superior than those obtained with single component based devices thanks to the
synergy of properties of the diverse materials. In particular, the functionalities of TiO2 NCs were widely
explored and tested in a variety of photochemical8 and sensing applications9, from which the outstanding
properties of TiO2 nanorods (NRs) 8b-c emerged.
Numerous and interesting papers on the photoconversion properties of MPc sensitized NC
semiconductor based hybrid junctions can be found6 while the sensing properties of these systems were
studied only in few recent papers7. In these works, the role of the molecular organization of the organic layer
in affecting the device performance was discussed, therefore, it appears evident how mastering the factors
that affect the molecular ordering represent a great challenge to reach a complete understanding of the
processes occurring at the organic-inorganic interfaces.
Copper tetrakis-(alkoxycarbonyl)-phthalocyanines constitute a class of macrocycles largely
investigated in the form of thin film. Almost all studies were carried out on derivatives containing n-alkyl
radicals bound to the –COO- group10. The behaviour of films of derivatives with four symmetrical branched
and bulky substituents (3,3-dimethyl-1-butoxycarbonyl groups) has been already studied and rationalised in
our group10d,11.
In this work we reported an extensive physical-chemical characterization of a novel phthalocyanine,
the tetrakis -(isopropoxy-carbonyl)-copper-phthalocyanine (TIPCuPc), whose macrocycle is functionalised
with simpler branched substituents with minor sterical hindrance (isopropoxycarbonyl radicals) which
provide the dissolution of the phthalocyanine in several organic solvents and its transfer in thin film by
means of Langmuir- Blodgett (LB), spin-coating and casting procedures. Herein, the properties of TIPCuPc
were investigated in solution of different solvents (DMSO, DMF, CHCl3 and Pyridine) by means of UV-vis
Spectroscopy (Absorption, Photoluminescence and Resonance Light Scattering) and in real time at the
air/water interface by the combined use of advanced Brewster Angle Microscopy (BAM) and Reflection
Spectroscopy. Such investigations pointed out the strong intrinsic tendency of TIPCuPc to arrange mainly in
H-type stacks which aligns forming 3D bulky domains.
The spectroscopic and morphological properties of thin films of TIPCuPc were characterized by
means UV-vis Spectroscopy (Absorption, Reflectance and Photoluminescence) and Atomic Force
Microscopy (AFM) by evaluating different issues: i) type of substrate (mica, TiO2 NR film, hydrophobic
quartz), ii) concentration of TIPCuPc, iii) solvent (DMSO, DMF, CHCl3 and Pyridine), iv) temperature of
P5
post deposition thermal treatment and vi) transferring technique (spin-coating, casting and LangmuirBlodgett). The discussion supported also by DSC investigations and ATR-FTIR analyses of TIPCuPc
powders shown that all the examined factors strongly modify the functionalities and self-organization of
TIPCuPc.
Such extensive characterization resulted essential to properly optimize the operating conditions of
TIPCuPc and address it and related hybrid junctions formed of TiO2 NRs, towards photoelectrochemical
cells and Quartz Crystal Microbalance (QCM) sensing of halogen phenol pollutants. We have extended the
application to QCM phenol sensing in liquid phase based on LB films of phthalocyanines using a homedeveloped flow-injection/QCM apparatus.
The interesting properties that TIPCuPc shown in chloroform, namely a reduced aggregation both in
solution and film and high stability against UV-light degradation leaded to process the phthalocyanine from
such solvent for photoelectric and QCM sensing experiments. The charge transfers occurring at the
organic/inorganic interfaces were found to improve, as expected, the photoelectric performance of the hybrid
junctions and the conditions which optimize the photoelectric activity were determined. Interestingly, such
charge transfers were found also to improve the QCM sensing response towards halogen phenols.
Fig. 1: Spectroscopical, (photo)electrochemical, morphological investigation and technological
potential of TIPCuPc for advanced applications
References:
(a) Nyokong, T. Coord. Chem. Rev. 2007, 251, 1707. (b) Durmuş, M.; Nyokong, T. Polyhedron 2007, 26,
2767.
2
Miroslav, K.; Zimcik, P.; Miletin, M.; Klemera, P.; Kopecky, K.; Musil, Z. J. Photochem. Photobiol. A:
Chem. 2006, 178, 16.
3
Evangelista, F.; Carravetta, V.; Stefani, G.; Jansik, B.; Alagia, M.; Stranges, S.; Ruocco, A J. Chem. Phys.
2007, 126, 124709.
4
Shi N.; Ramprasad, R. Appl. Phys. Lett. 2006, 89, 102904.
5
Zhang, Q. M.; Li, H.; Poh, M.; Xia, F.; Cheng, Z.-Y.; Xu, H.; Huang, C. Nature 2002, 419, 284.
6
(a) Giribabu, L.; Kumar, C. V.; Reddy, V. G.; Reddy, P. Y.; Rao, C. S.; Jang, S.-R.; Yum, J.-H.;
Nazeeruddin, M. K.; Grätzel, M. Sol. Energy Mat. Sol. Cells 2007, 91, 1611.
7
(a) Siviero, F.; Coppedè, N.; Pallaoro, A.; Taurino, A. M.; Toccoli, T.; Siciliano, P.; Iannotta, S. Sens.
Actuators B 2007, 126, 214.
8
(a) Duncan, W. R.; Prezhdo, O. V. Annu. Rev. Phys. Chem. 2007, 58, 143. (b) Nelson, J.; Haque, S. A.;
Klug, D. R.; Durrant, R. J. Phys. Rev. B 2001, 63, 2053211. (c) Nelson, J. Curr. Opin. Solid State Mat. Sci.
2002, 6, 87.
9
(a) Karunagaran, B; Uthirakumar, P.; Chung, S. J.; Velumani, S.; Suh, E.-K. Mater. Charact. 2007, 58,
680. (b) Yawale, S. P.; Yawale, S. S.; Lamdhadeb, G. T. Sens. Actuators A 2007, 135,388.
10
(a) Rella, R.; Serra, A.; Siciliano, P.; Tepore, A.; Valli, L.; Zocco, A. Langmuir 1997, 13, 6562.
11
(a) S. Capone, S. Mongelli, R. Rella, P. Siciliano, L. Valli, Langmuir 1999, 15, 1748.
1
P5
Chemical Assembly of Colloidal Nanocrystals
Albert Figuerola a*, Isabella R.Franchini a*, Angela Fiore a, Roberto Cingolani a,
Davide Cozzoli a, Teresa Pellegrino a, Liberato Manna a
a
National Nanotechnology Laboratory of CNR-INFM, 73100 Lecce, Italy
Corresponding authors: Albert Figuerola, email: [email protected];
Isabella R.Franchini, email: [email protected]
Recently, molecularly bridged nanocrystals (NCs) have attracted growing interest as a result of their
potentially novel electronic, optical and magnetic properties, which are different from those of a
corresponding collection of individual NCs or from the bulk solid.
Our aim is to exploit gold domains grown on selected regions of colloidal NCs that will act as “glue” for
creating specific and useful assemblies and superstructures of NCs. For this study, we chose different hybrid
nanostructures with optical and magnetic properties in which one of the domains is composed by metallic
gold (Au).
State of the art of the gold nanoparticles shows the role of the iodide to fuse and assembly the colloidal gold
NCs in solution. 1 However, in our preliminary experiments, iodine seems to have a comparable effect using
the nanostructures that have a gold domain. In particular the NCs (which had been previously synthesized
and purified) are dissolved in an organic solvent (such as toluene or chloroform), together with a gold
precursor (AuCl3) and an alkyl ammonium bromide which is required to reach complete dissolution of the
gold precursor. The presence of iodide or iodine, even in trace amounts, was found sufficient to glue together
the Au domains that had nucleated at the tips of the nanorods, for example. Different ratios of gold NCs and
nanostructures are investigated to find the optimal conditions to fabricate these assemblies.
It is believed that strong adsorption of iodine molecules or of iodide ions to the gold surface could suppress
the competitive binding of organic surfactant molecules which would eventually lead to inter-particle
aggregation. The real role of the surfactant nature in the aggregation process is also being investigated.
Such type of chemical assembly approach could be also performed on particular substrates as well. Regularly
patterned gold substrates are being tested to see if it is possible to obtain ordered assemblies. Such
functionalized substrates could find interesting applications as chemical sensors, thin-film photovoltaics and
memory devices.
References:
1
Wenlong Cheng, Shaojun Dong, and Erkang Wang Angew. Chem. Int. Ed. 2003, 42, No. 4 449-452; Akhilesh Rai,
Amit Singh, Absar Ahmad, and Murali Sastry, Langmuir 2006, 22, 736-741
P6
NanoFRET® pH sensing of nanocrystal internalization into live cells
Camilla Luccardinia, Aleksey Yakovlevb, Wolfgang Parakc, Martin Oheima and Anne Feltzb
a
Neurophysiology & New Microscopies laboratory, Inserm U603, 75006 Paris, France
b
Neurobiology Lab ENS CNRS, UMR 8544, 75005 Paris, France
c
Department of Physics, Biophotonics, Philipps University of Marburg, D-35032 Germany
Corresponding author: Camilla Luccardini, Fax 00330142864151, email: [email protected]
Due to their superior optical properties compared with organic fluorophores, semiconductor nanocrystals
(NCs) are increasingly being used as point-like emitters in biological imaging and tracking applications.
However, NCs have mainly been used as extracellular markers for labeling and tracking membrane
receptors1, while their application for tagging cytoplasmic targets remains sporadic. Intracellular labeling is
hampered by the difficulty of reversibly permeabilizing the cell membrane to allow NC entry and the nonspecific sequestration of NCs into vesicular organelles.
Different strategies have been explored to deliver nanocrystals inside the cells2, however, a quantitative
assessment if the NCs are really inside the cell has been lacking. In response to this need we developed a
nanoFRET® sensor, based on the non-radiative energy transfer between a single functionalized
semiconductor NC donor and a small number of organic SNARF acceptors that stably attached to the NC
surface. This sensor is taken up by HEK or COS cells following loading with different techniques in analogy
to traditional NCs. Depending on the subcellular localization and compartmentalization of the internalized
nanoFRET sensor, its pH dependent fluorescence provides a unique time-dependent signature to trace its
extracellular, cytroplasmic or vesicular final localization.
References:
1.
Dahan, M.; Lévi, S.; Luccardini, C.; Rostaing, P.; Riveau, B.; Triller, A.. Science 2003: 302 442 - 445
2.
Derfus, AM.; Chan, WCW., Bhatia, SN.; Advanced Materials. 2004;16(12) 961-966
P7
Charge carrier dynamics in thin films of colloidal CdSe quantum rods
Anna Persanoa*, Adriano Colaa, Arianna Cretìa, Mauro Lomascoloa, Liberato Mannab, Gabriella Leoc
a
IMM-CNR, Istituto per la Microelettronica e Microsistemi, I-73100 Lecce, Italy
b
National Nanotechnology Laboratory of CNR-INFM, I-73100 Lecce, Italy
c
ISMN-CNR, Istituto per lo Studio dei Materiali Nanostrutturati, I-00016 Monterotondo St. (Roma), Italy
*
Corresponding author: Anna Persano, Fax 00390832422552, email: [email protected]
Quantum rods (QRs) are currently investigated due to the ability to tune their operating wavelength in the
visible spectral range through the control of the rod diameter. Additionally linearly polarized emission1 and
efficient one-dimensional electrical transport2 have been detected for such nanorods which are thus
becoming attractive for optoelectronic applications. For the development of QR based devices it is essential
to investigate the process of charge separation of a photogenerated excitation created within a QR as well as
the transport of charge carriers through QR films. In particular, a crucial role in the electrical properties of
thin QR films is played by the exposure to air, due to the large surface-to-volume ratio and the presence of
the oxide potential barrier for carriers tunneling from a rod to the adjacent one.
In this work the phototransport properties of CdSe colloidal QR thin films have been investigated under
ambient conditions. Organic capped CdSe QRs have been prepared by pyrolisis of organometallic precursors
in a hot coordinating solvent of trioctylphosphine oxide (TOPO)3, obtaining narrow dispersed nanoparticles
with average diameter and length of 3.5 nm and 30 nm, respectively. QR thin films have been deposited by
spin coating on SiO2/Si substrates which have been patterned with interdigitated contacts having both finger
width and gap of 1-2 µm. The surface morphology of the deposited QR film has been investigated by atomic
force microscopy (AFM) measurements. Steady photocurrent measurements have been performed as a
function of both the excitation energy and the applied voltage allowing to evaluate the responsivity of the
measured devices. Discrete features due to S and P interband transitions in the quantum confined QRs are
clearly observable in the spectral responsivity measurements. The process responsible for the escape of the
carriers from the QRs has been investigated by current-voltage cycles performed under optical excitation
resonant to QR band-edge. These measurements have pointed out an important and irreversible degradation
process of the phototransport in CdSe QRs which appears to be accelerated by the flowing of the current. By
applying a resonant tunneling model, the observed degradation has been ascribed to an increase in the height
of the tunneling barrier. Finally, transient photocurrent measurements have been also performed enabling the
mechanism of the current quenching to be inferred and the recombination processes of the charge carriers in
the oxide barrier to be investigated in detail.
(b)
Φ1
Φ2 > Φ1
Φ2
(c)
Barrier height Φ (eV)
(a)
0.96
0.92
0.88
0.84
1
2
3
4
5
Voltage sweep
Fig. 1: Schematics of the processes involving the electrons originated from the electric field assisted
ionization of the electron-hole pairs photogenerated within the QRs. (a) The electrons escaping from the
QRs through the barrier Φ1 can be trapped by the defect states of the QR surface oxide. (b) As the current
value becomes greater, the charge stored in the barrier enhances leading to an increase of the barrier height
to Φ2 > Φ1 and, consequently, recombination pathways compete with tunneling process which is inhibited.
(c) In agreement with this picture, by applying a tunneling model to reproduce successive experimental I-V
curves, an increase of the barrier height has been found to cause the observed degradation.
References:
1.
Hu, J.; Li, L.; Yang, W.; Manna, L.; Wang, L.; Alivisatos, A. P. Science 2001, 292 (5524), 2060-2063.
2.
Huynh, W. U.; Dittmer, J. J.; Alivisatos, A. P. Science 2002, 295 (5564), 2425-2427.
3.
Manna, L.; Scher, E. C.; Alivisatos, A. P. Journal of the American Chemical Society 2000, 122 (51), 1270012706.
P8
Fast ligand exchange in amine-capped iron oxide nanoparticles
Sara Mondinia, Simone Cenedesea, Nadia Santob, Alessandro Pontia
a
Consiglio Nazionale delle Ricerche, Istituto di Scienze e Tecnologie Molecolari, via Golgi 19, 20133 Milano, Italy.
b
Università di Milano, Centro Interdipartimentale Microscopia Avanzata, via Celoria 26, 20133 Milano, Italy.
Corresponding author: Alessandro Ponti, Fax 00390250314280, email: [email protected]
Long-chain aliphatic carboxylic acids are the surfactant of choice for the solvothermal synthesis of iron
oxide nanoparticles since their use affords single-crystal mono-disperse nanoparticles.1,2 The use of longchain aliphatic amines as surfactants, well-established for manganese oxide nanoparticles, is rather rare in
the synthesis of iron oxide nanoparticles. It was briefly mentioned upon by Sun et al.3 and recently resumed
by P. O’Brien et al.4 who synthesized single-crystal, nearly mono-disperse hexadecylamine-capped
magnetite nanoparticles.
Since iron(III) has a marked preference for O-donor as opposed to N-donor ligands,5 we conceived that
exchanging the amine surfactant with a carboxylic acid could be a fast and complete process even at room
temperature, as opposed to the tedious and sometimes problematic exchange between different carboxylic
acids usuaally carried out (e.g. exchanging oleic acid with a temperature-sensitive, functionalized acid).
As an example, we chose to use a short PEGylated carboxylic acid {2-[2-(2-methoxyethoxy)ethoxy]acetic
acid} since exchange would lead to a dramatic variation in the nanoparticle solubility that could be visually
appreciated. When the nanoparticles dispersed in hexane were treated with a small quantity of 2-[2-(2methoxyethoxy)ethoxy]acetic acid, they instantaneously precipitated out. If the hexane dispersion floated
over a layer of water, addition of the PEGylated acid transferred the nanoparticles into the water layer within
seconds, forming a stable aqueous dispersion. (See Figure 1).
Thus, this exchange procedure seems very promising for easy and fast capping of iron oxide nanoparticles
with functionalized carboxylic acids. We are currently working on the following issues: (i) improving the
morphological properties of the as-synthesized nanoparticles; (ii) extending the exchange procedure to other
functionalized carboxylic acids and their mixtures; (iii) characterizing the details of the exchange process.
Fig. 1: Oleylamine-capped iron oxide nanoparticles form a stable dispersion in
hexane (left vial). Upon addition of 2-[2-(2-methoxyethoxy)ethoxy]acetic acid,
the nanoparticles quickly form a stable dispersion in water (right vial).
References:
1.
Lu, A.-H.; Salabas, E. L.; Schüth, F. Angewandte Chemie 2007, 46, 1222-1244.
2.
Hyeon, T. Chemical Communications 2003, 927-934.
3.
Sun, S.; Zeng, H.; Robinson, D. B.; Raoux, S.; Rice, P. M.; Wang, S: X.; Li, G. Journal of the American
Chemical Society 2003, 126, 273-279.
4.
Li, Y.; Afzaal, M.; O’Brien, P. Journal of Materials Chemistry 2006, 16, 2175-2180
5.
Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements, 1985, Pergamon Press, Oxford (UK), p.1265.
P9
Synthesis and Characterization of Bi-magnetic Branched Nanocrystal Heterostructures
Marianna Casavola,1,2* Andrea Falqui,3 Liberato Manna,2 Roberto Cingolani,1,2 and Pantaleo Davide Cozzoli1,2
1
Scuola Superiore ISUFI, University of Salento, Distretto Tecnologico, via per Arnesano km 5, I-73100 Lecce, Italy.
2
National Nanotechnology Laboratory of CNR-INFM, Unità di Ricerca IIT, Distretto Tecnologico ISUFI, via per
Arnesano km 5, I-73100 Lecce, Italy.
3
Laboratoire de Physique et de Chimie des Nanoobjets-INSA, 135, Avenue de Rangueil, F-31077 Toulouse, France
* Presenting author, to whom all correspondence should be addressed: Phone:+39 0832 298271. Fax: +39 0832 298238.
E-mail: [email protected]
Current efforts of nanoscience research are devoted to design and fabricate novel generations of complex
nanostructures with enhanced technological potential and increased functionalities. One strategy to achieve
this goal has been recently devised with the chemical synthesis of hybrid nanocrystals, which are particles
consisting of two or more domains of different materials grouped together through an inorganic interface.1-2
As a result of their higher structural complexity and of the combination of the properties that distinguish each
crystalline section, such composite nanocrystals hold promise as first prototypes of “smart” nano-objects,
potentially able to perform multiple tasks, such as in biomedical engineering, diagnostics, sensing, and
catalysis.3-6
Herein, we report a colloidal two-step approach to fabricate a new type of bi-magnetic hybrid nanocrystal,
consisting of one iron oxide branched central section onto which one or more metallic Co domains are
attached. The synthesis of these heterostructures has been performed by seeding Co nucleation with
preformed iron oxide tetrapods with finely tuned geometric parameters(7). The adjustment of the reaction
conditions has allowed us to control the average number and the location of the metal domains that can be
nucleated on each tetrapod seed. A detailed chemical-topological, structural, and magnetic characterization
of the as-prepared Co-decorated iron oxide branched nanocrystals has been carried out by combining powder
X-ray Diffraction, Raman spectroscopy, high angle annular dark field (HAADF) imaging, high-resolution
transmission electron microscopy (HRTEM), and superconducting quantum interference device (SQUID)
magnetic analyses. The relevant size and shape dependent magnetic properties associated with these new
topologically controlled metal/oxide hybrid nanocrystals are presented and discussed.
Fig. 1 TEM images of iron oxide tetrapods before (left) and after decoration with Co domains (right).
References:
1. P. D. Cozzoli, T. Pellegrino, L. Manna Chem. Soc. Rev. 2006, 35, 1195.
2. M. Casavola, R. Buonsanti, G. Caputo, P. D. Cozzoli, Eur. J. Inorg. Chem. 2007, in press.
3. D.V. Talapin, I. Mekis, S. Gotzinger, A. Kornowski, O. Benson, H. Weller, J. Phys. Chem. B 2004, 108, 18826.
4. H. Wang, D. W. Brandl, F. Le, P. Nordlander, N. J. Halas, Nano Lett. 2006, 6, 827
5. T. Pellegrino, A. Fiore, E. Carlino, C. Giannini, P. D. Cozzoli, G. Ciccarella, M. Respaud, L. Palmirotta, R.
Cingolani, L. Manna, J. Am. Chem. Soc. 2006, 128, 6690.
6. M. Casavola, V. Grillo, E. Carlino, C. Giannini, F. Gozzo, E. F. Pinel, M. A. Garcia, L. Manna, R. Cingolani, and
P. D. Cozzoli, Nano Lett. 2007, 7(5), 1386.
7. P. D. Cozzoli, E. Snoeck, M. A. Garcia, C. Giannini, A. Gagliardi, A. Cervellino, F. Gozzo, A. Hernando, K.
Achterhold, N. Ciobanu, Fritz G. Parak, R. Cingolani, L. Manna, Nano Lett. 2006, 6, 1966.
P10
Photocatalytic activity of novel nanocrystal-based catalysts under UV and solar light irradiation
R. Comparellia, M. Corricellia, A. Panniellob, E. Fanizzab, M.Striccolia, G. Mascoloc, A. Agostianoa,b, M. L. Curria
a
CNR-IPCF Sez. Bari, c/o Dip. Chimica – Via Orabona 4, Bari, I-70126, Italy, [email protected]
b
Università di Bari – Dip. Chimica, Via Orabona 4, Bari, I-70126, Italy
c
CNR-IRSA – Sez. Bari, Viale De Blasi, Bari, I-70100, Italy
Corresponding author: Roberto Comparelli, Fax 00390805442128, email: [email protected]
The photocatalytic degradation of organic pollutants assisted by semiconductors represent one of the most
attractive techniques among the Advanced Oxidation Processes (AOPs). Anatase TiO2 is broadly accepted as
the most photoactive catalyst, although ZnO appears very promising for degradation of organic compounds
in aqueous systems.1,2 Coupling noble metals with active oxides can increase the efficiency of the electronhole pair separation by exploiting the accumulation of the photogenerated electrons in the noble metal.3
Furthermore, the energy range able to photo-excite wide band gap catalysts can be extended by coupling
semiconductor with suitable band gap thus providing an interesting way to increase the efficiency of a
photocatalytic process by increasing the charge separation.
Herein, we present a comprehensive study of photocatalytic activity of colloidal nanocrystal based films
deposited onto suitable substrates as catalysts.
The nanosized materials are expected to have a beneficial behaviour on the catalytic properties, in terms of
active sites and possibly size dependent redox properties, although some detrimental behaviour is likely to
occur if their are immobilized onto substrates.4 In this paper nanocrystalline (NC) semiconductor oxides
(TiO2 and ZnO), coupled semiconductor system (CdS/TiO2) and noble metal-semiconductor heterostructures
(TiO2/Ag)5 have been tested under UV and Visible irradiation for the degradation of several target
compounds such as azo dyes (Methyl Red and Methyl Orange) textile dyes (Uniblu A) and pesticides
(Carbofuran) in water matrices. The experiments have been monitored by absorption, photoluminescence,
HPLC-MS and TOC measurements
The obtained results show that nanocrystalline oxides present higher photoactivity than their commercial
counterparts. The presence of CdS NCs has been demonstrated to increase the photoresponse of TiO2 NCs
under solar light. Moreover, the novel TiO2-NC/Ag based catalyst have presented an interestingly higher
photoactivity then the bare TiO2 NC. The obtained results evidence in all cases the complete degradation of
the dyes and their by-products.
Acknowledgment
This work was financially supported by MIUR SINERGY programme (FIRB RBNE03S7XZ) and by
Explorative Project “Photocatalytic degradation of organic pollutants in aqueous solution by nanostructured
semiconductors” funded by Apulia Region within the Scientific Research Framework Program 2006.
References:
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Comparelli R.; Fanizza E.; Curri M. L.; Cozzoli P. D.; Mascolo G.; Passino R.; Agostiano A. Applied
Catalysis B: Environmental 2005, 55, (2), 81- 91.
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Comparelli R.; Fanizza E.; Curri M. L.; Cozzoli P. D.; Mascolo G.; Agostiano A. Applied Catalysis B:
Environmental 2005, 60, (1-2), 1 - 11.
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Bedja I.; Kamat P. V. Journal of Physical Chemistry 1995, 99, (22) 9182 - 9188.
4.
Mascolo G.; Comparelli R.; Curri M. L.; Lo vecchio G.; Lopez A.; Agostiano A. Journal of Hazardous
Materials 2007, 142, (1-2), 130 - 137
5.
Cozzoli P.D.; Comparelli R.; Fanizza E.; Curri M. L.; Agostiano A.; Laub D. J. Journal of the American
Chemical Society 2004, 126, (12), 3868 - 3879
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