Preparation of Ge@Organosilicon core-shell structures and characterization by solid state NMR and other techniques

Many core-shell materials having a protecting outer layer have lately been proposed. In such materials it is not uncommon that chemical or thermal stability issues of the core material are resolved by a proper choice of the shell material. We report here the formation of core-shell structures by pyrolysis of a mixture of tetraethyl germanium and tetramethyl silicon at 750 C in a simple one-step reaction without the use of catalysts under "RAPET" conditions. The composite product, germanium-core/ organosilicon-shell (Ge@Organosilicon), is formed in two morphologies, rods and spheroids. The rods radial distribution is rather narrow while the spheroids exhibit a broader distribution due to their tendency to agglomerate. The germanium core phase is crystalline covered by a disordered organosilicon layer. The contribution of each of the precursors to the final product is shown by selected-area EDS and solid state NMR spectroscopy and further corroborated by RAMAN, EPR, and powder X-ray diffraction analysis.