Eric de Vries
Daily Supervision: L. Zheng
Group Leader: Prof. Dr. A. Herrmann
Polymer Chemistry and Bio-engineering Group
2

Physical properties dependent on specific
structure of the nanotubes

Separate enantiomers to use it for chiral
applications

Chiral single-walled carbon nanotubes
(SWNTs) can be used for:
• Asymmetric catalysis
• Chiral resolution (e.g. drugs)
• Chirality sensing
3


Chiral molecules will have different
interactions towards left-handed and righthanded SWNT species
Proven by near-IR fluorescence
measurements towards amino-acids
4
Towards lysine
1400000
CNT only
CNT+DL
CNT+LL
1200000
1000000
NT only
NT+DL
NT+LL
1200000
800000
Intensity
Intensity
1000000
600000
800000
600000
400000
400000
200000
200000
0
800
900
1000
1100
1200
Wavelength (nm)
(P)-(6,5) SWNT
1300
0
800
900
1000
1100
1200
1300
Wavelength (nm)
Racemic (6,5) SWNT
5


By non-linear DGU it is possible to extract
these species from a CoMoCat solution
Enantiomers have different buoyant densities
ρ upon interaction with chiral surfactant
Ultracentrifugation
Nano Res. 2, 69 (2009), Nat. Nanotechnol. 5, 443 (2010)
6
Absorbance (A.U.)
2.5
2.0
1.5
1.0
0.5
0.0
400
500
600
700
800
900
1000
wavelength (nm)
The specific absorption peaks of (6,5) SWNTs are at 570 nm and 984 nm
7
30
25
(-) (6,5)
(+)
(6,5)
(P)-(6,5)
20
(M)-(6,5)
15
CD
10
5
0
-5
-10
-15
-20
500
550
600
650
700
Wavelength (nm)
Nature Nanotech. 5, 443 (2010), JACS 132, 31 (2010),
Nano Res. 2, 69 (2009)
8

•
•
Idea: Use chiral discrimination by chemical
force microscopy (CFM)
Modify AFM tips by chiral molecules
Different interactions between chiral tip and
SWNT enantiomers
9



Adhesion force ~ 1nN
We expect that the ‘chirality force’ from a
single-molecule interaction is between 50100 pN
Minimize other adhesion forces to see
difference in chirality
10

Au AFM tip modification

Measure in water to minimize capillary forces
11


Relatively short spacer distance will lead to
tip-substrate interactions
Probable broadening of the tips due to tip
immobilization  reduced lateral resolution
In water it is possible to flush away SWNTs
 Use highly-oriented pyrolytic graphite

12

Use sharper Si3N4 tips and a larger spacer to
avoid non-specific interactions
Y. Zhang et al. Langmuir 23,
7911-7915 (2007)
13


Chiral SWNTs can be extracted with an
enantiomeric excess of 97% by non-linear
DGU
Ideas towards realization of absolute
quantification of enantiomeric excess by CFM
14

Lifei Zheng

Pavlo Gordiichuk
Kranthi Bannuru
Vladimir Derenskyi (Group Loi)

Prof. Dr. A. Herrmann

Polymer Chemistry and Bio-engineering Group


15