Thermolysis of organogermanium oxide sol-gel polymers yields germanium oxide-embedded germanium nanocrystals. In the present study, we investigate the influence of different organic substituents, R, on the sol-gel chemistry of organotrichloro- and organotrialkoxygermane precursors and the thermal behavior of the resulting organogermanium oxides (RGeO1.5)n. The organic substituent affects the structure of the sol-gel product, with bulky R groups hindering network polymer formation. Cage-like sol-gels formed in the presence of bulky substituents are volatile, while network polymers experience thermolytic cleavage of the Ge–C bond. This cleavage produces a Ge-rich oxide (GeO1.5)n, that undergoes thermally induced disproportionation into GeO2 and elemental Ge. The onset temperature of the disproportionation reaction is profoundly influenced by the nature of the organic substituent. We propose the change in onset temperature arises from a shift in R-group cleavage pathways from radical to β-hydride elimination.
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Understanding the Formation of Elemental Germanium by Thermolysis of Sol-Gel Derived Organogermanium Oxide Polymers
Melanie Hoffman and Jonathan G. C. Veinot
Chemistry of Materials Article ASAP
Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2 Canada
Publication Date (Web): March 12, 2012
Copyright © 2012 American Chemical Society