Synthesis and Characterization of Functional Iron and Germanium Nanomaterials Open Access

[摘要] Germanium nanomaterials have many potential applications based on their size-tunable optical and electronic properties, for example in photodetectors, photovoltaics and non-volatile memory. In this work, the synthesis of Ge nanoparticles by two different methods based on tailorability through the substituent chemistry of the Ge precursors is explored. In Chapter Two, the effect of the organic substituent upon thermal decomposition of organogermanium oxides (RGeO1.5)n to yield oxide-embedded germanium nanocrystals (Ge-NCs) is investigated. Substituents with stable radical formation or the presence of !-hydrogen are found to facilitate NC formation at lower temperatures. Lower temperature limits germanium production to a pathway based on disproportionation only, and not – as previously – also on hydrogen reduction of germanium oxides. The organic substituent also introduces tailorability of organogermanium oxide properties, such as melting points. For R = n-butyl, benzyl, these are lowered below the disproportionation temperature, yielding melts containing Ge-NCs. The knowledge gained in the substituent study is applied to solution synthesis of Ge-NCs in Chapter Three. The n-butyl substituent, which formed Ge- NC from (nBuGeO1.5)n at 300 °C, can eliminate by radical and !-hydride elimination pathways. In the molecular compounds nBuxGeH4-x (x = 1-4), reductive elimination also becomes possible. We propose this leads to the decrease in decomposition temperature of nBuxGeH4-x from x = 4 to x = 1. In the second section of this thesis, Chapter Four, the catalytic activity of metal-decorated iron/iron-oxide core-shell nanoparticles (M/Fe@FexOy) in Heck and Suzuki couplings is investigated. Electroless deposition of noble metals on Fe@FexOy generates the catalyst. The catalytic activity of Pd/Fe@FexOy is improved over standard heterogeneous catalysts (e.g., Pd/C) in Heck coupling of styrene and bromobenzene. Leaching studies in Suzuki coupling of bromobenzene with phenylboronic acid show elevated Pd levels in solution during reaction, suggesting Pd is solvated during catalysis in a quasi-homogeneous mechanism. Less Pd is found in the final product, suggesting Pd is deposited back onto the Fe@FexOy support after catalysis. In Chapter Five, a summary of our findings regarding the effects of organic substituents on Ge-NC synthesis and catalysis employing metal-decorated Fe@FexOy is presented, followed by a detailed discussion of future research directions.

[发布机构] University of Alberta

[效力级别] Chemistry