silicon and germanium-oxide

Magnesiothermic reduction can directly convert SiO2 into Si nanostructures. Despite intense efforts, efficient fabrication of highly nanoporous silicon by Mg still remains a significant challenge due to the exothermic reaction nature. By employing table salt (NaCl) as a heat scavenger for the magnesiothermic reduction, we demonstrate an effective route to convert diatom (SiO2) and SiO2/GeO2 into nanoporous Si and Si/Ge composite, respectively. Fusion of NaCl during the reaction consumes a large amount of heat that otherwise collapses the nano-porosity of products and agglomerates silicon domains into large crystals. Our methodology is potentially competitive for a practical production of nanoporous Si-based materials.

Topics: Chemistry Techniques, Synthetic; Germanium; Hot Temperature; Nanostructures; Porosity; Silicon; Silicon Dioxide

We demonstrate the temperature-dependent growth of germanium oxide and silicon oxide based composite nanostructures (multiple nanojunctions of Ge nanowires and SiO(x) nanowires, Ge-filled SiO(2) nanotubes, Ge/SiO(2) coaxial nanocables, and a variety of interesting micrometer-sized structures), aligned SiO(x) nanowire assemblies, and SiO(x) microtubes. The structures were characterized by SEM, TEM, energy-dispersive X-ray spectroscopy, and electron diffraction. The combination of laser ablation of a germanium target and thermal evaoporation of silicon monoxide powders resulted in the formation of Ge and SiO(x) species in a carrier gas; the nano/micro-sized structures grow by either a Ge-catalyzed vapor-liquid-solid or a Ge-nanowire-templated vapor-solid process.

Topics: Crystallization; Germanium; Metal Nanoparticles; Microscopy, Electron, Transmission; Molecular Conformation; Nanostructures; Nanotechnology; Nanotubes; Nanowires; Semiconductors; Silicon; Silicon Dioxide; Temperature

Germanium dioxide is found to increase the frequencies of the genetical transformation in Bacillus subtilis 30-40 fold. The increased frequency of transformation was registered in Sil- mutant in contrast to Sil+ strain having the decreased one. Bacillus megatherium strain KU-2 and Bacillus oligonitrophilus KU-1 were isolated from soil. These strains possess better ability to utilize the orthoclase and biotite. Germanium dioxide did not induce the transformation frequencies increase in these strains. Sil mutant of Bacillus oligonitrophilus demonstrated no competence to transformation.

Topics: Bacillus; Bacillus subtilis; Cell Survival; Genes, Bacterial; Germanium; Mutation; Plasmids; Silicon; Soil Microbiology; Transformation, Genetic