Oxide Nanocrystals as Model Systems for Surface Chemistry

Oliver Diwald 1Erich Knoezinger 

1. Institute of Materials Chemistry, Vienna University of Technology (TU), Veterinärplatz 1, Wien 1210, Austria

Abstract

Recent advances in morphology control of unsupported oxide nanostructures allow for the deliberate enhancement or depletion of microstructural characteristics. This opens up new opportunities to relate topographic surface features to their chemical properties. Chemical vapor deposition is an efficient technique for the generation of nanometer-sized MgO particles with characteristic surface defects. After thermal annealing the crystallites adopt cubic shape and the ratio between corner and edge ions depends on the average particle size. Thus, MgO nanocubes represent a powerful model system for molecular spectroscopy studies which aim at the investigation of surface processes on polycrystals.

While on highly dispersed earth alkaline oxides ultraviolet light with energies below 6.2 eV (l>200nm) exclusively addresses the surface, light induced charge separation is initiated in the bulk of TiO2 nanostructures. Under high vacuum conditions, electron and hole trapping processes can be tracked by electron paramagnetic resonance and IR spectroscopy on a time scale of minutes. The generation and chemical reactivity of trapped charges as well as their quantification using the photoadsorption of O2 will be discussed for anatase particles and titanate nanotubes.

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Presentation: Keynote lecture at E-MRS Fall Meeting 2006, Symposium B, by Oliver Diwald
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-06-26 13:45
Revised:   2009-06-07 00:44
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