Structural and chemical characterization of soot particles
I. K. Ortega1, B. Chazallon1, Y. Carpentier1, C. Irimiea1, M. Ziskind1, C. Pirim1, F. X. Ouf2, F. Salm2, D.
Delhaye3, D. Gaffié3, J. Yon4, D. Ferry5 and C. Focsa1
Laboratoire de Physique des Lasers, Atomes et Molécules, Université Lille 1, 59655 Villeneuve d’Ascq, France
2
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Gif-sur-Yvette, 91192, France
3
Onera – The French Aerospace Lab, F-91123 Palaiseau, France
4
CORIA, Université et INSA de Rouen, Av. de l’Université, 76801 Saint-Etienne du Rouvray, France
5 CINaM, Campus de Luminy, 13288, Marseille, France
1
Keywords: combustion aerosols, particle characterization, Raman spectroscopy, mass spectrometry.
Physico-chemical properties of soot
particles play a key role in their impact in both
human health and climate. The two main aims of
this study are: i) find a good surrogate for airplane
soot and ii) provide a systematic characterization
of soot particles that can be used to interpret
future ice nucleation studies planned in our
group. In the present work, we have used three
different techniques to characterize the structure
and the surface chemical composition of soot
samples, collected from three different sources in
the frame of the MERMOSE project (http://
mermose.onera.fr/):
PowerJet
(SNECMA/
Saturn) SaM146 turbofan (four engine regimes),
CAST generator (propane fuel, four different
global equivalence ratios), and Kerosene
laboratory flame.
L2MS, the adsorbed phase is probed by nanosecond
laser desorption (λd=532nm), then the ejected
molecules are ionized with a second ns laser
(λi=266nm) and further mass-separated by ToF-MS.
While in ToF-SIMS the sample is bombarded with a
Bi3+ ion beam and the secondary ions generated are
detected by ToF-MS. Using laser desorption and
ionization in L2MS technique leads to very low
fragmentation of the compounds studied. L2MS is
especially well suited for the study of poly-aromatic
hydrocarbons (PAH) present in the soot surface thanks
to the resonant enhanced multi-photon ionization
(REMPI) of this compounds at 266 nm. ToF-SIMS is
complementary to L2MS since it gives a more uniform
response to various families of compounds, moreover
the higher resolution achieved with this instrument
allows a more precise identification of certain
compounds. On the other hand, the fragmentation
produced in this technique is higher than in L2MS.
Figure 1. Example of band deconvolution of a Raman
spectrum obtained from an airplane soot sample
Figure 2. Example of ToF-SIM positive polarity
mass spectra for an airplane soot sample
To characterize the structure of the studied soot
particles, we have used Raman microscopy. We
studied the spectral parameters of the first-order
Raman band of different soot samples using the five
bands de-convolution approach described by Sadezky
et al. (2005). This approach provides information
about the amount of amorphous carbon and
organization degrees of the samples.
To determine the surface chemical composition
of the samples we use two different mass spectrometry
techniques: Two-Step (Desorption/ Ionization) Laser
Mass Spectrometry (L2MS) and Time of Fight
Secondary Ion Mass Spectrometry (ToF-SIMS). In
This work was supported by the French Civil aviation
Authority (DGAC) through the MERMOSE project.
Sadezky, A., Muckenhuber, H., Grothe, H., Niessner,
R., Pöschl, U. (2005). Carbon, 43, 1731-1742.