[Zurück]

J. Ofner, H. Grothe:
"Investigations of Surface Chemistry on Carbonaceous Particles";
Poster: EGU General Assembly 2007, Wien; 15.04.2007 - 20.04.2007; in: "Geophysical Research Abstracts", European Geosciences Union, 9 (2007), Paper-Nr. 07457, 2 S.

The relevance of carbonaceous particles in atmospheric science is increasing. Reasons
for that are their contribution to the urban aerosol, their toxicological importance and
their impact on the global radiation balance. Particle emissions like soot or secondary
organic aerosols like HULIS (humic like substances) are currently a major topic in atmospheric
research. Physical chemistry provides surface analytical methods for these
particles [1,2,3,4], to understand their relevance as part of the atmospheric gas phase
chemistry.
For these surface investigations Diffuse-Reflectance-Infrared-Fourier-Transform-
Spectroscopy (DRIFTS), Temperature-Programmed-Surface-Reaction-Spectroscopy
using a mass spectrometer (TPSR-MS), Temperature-Programmed-Desorption-Mass-
Spectroscopy (TPD-MS) and Electron-Paramagnetic-Resonance (EPR) Spectroscopy
were applied. All of these methods were used to characterize humic substances and
soot. DRIFTS provides detailed information about formation and transformation of
functional surface groups monitoring the characteristic vibration modes. TPD-MS
shows the thermal stability of these groups and TPSR-MS follows up the reaction behaviour
of these particles with gases of atmospheric relevance. Radicals on the surface
could be studied by EPR Spectroscopy. The combination of these four spectroscopic
methods allowed a detailed understanding of heterogeneous reactions with carbonaceous
surfaces at a molecular level. Investigations were done on i) the heterogeneous
reaction with nitrogen oxides and ii) with reactive halogen compounds. Stability and
reactivity of new formed functional groups could be assigned. Single heterogeneous
reaction mechanism could be clarified.
[1] Muckenhuber H., Grothe H., The heterogeneous reaction between soot and NO2
at elevated temperature, Carbon 44 (2006) 546.
[2] Sadezky A., Muckenhuber H., Grothe H., Niessner R., Pöschl U., Raman microspectroscopy
of soot and related carbonaceous materials: Spectral analysis and
structural information, Carbon 43 (2005) 1731.
[3] Muckenhuber H., Grothe H., The reaction between soot and NO2 - investigation
of functional groups using TPD-MS, Topics in Catalysis 30/31 (2004) 287.
[4] Muckenhuber H., Grothe H., A DRIFTS study of the heterogeneous reaction of
NO2 with carbonaceous materials at elevated temperature, Carbon 45 (2007) 321.

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