UC Irvine

The colloidal synthesis and surface modification of germanium and germanium-based nanomaterials is a developing area of research with potential applications in a variety of fields. Colloidal germanium nanocrystal syntheses have improved significantly in recent years, but there has been little exploration into the synthesis of Ge-based nanomaterials, especially metal-germanium nanocrystals. A solution-phase synthesis of nickel germanide nanocrystals was developed to produce colloidal particles possessing an unexpected Ni¬19Ge12 crystal phase. The mechanism of this synthesis was explored to show that the Ni19Ge12 phase formed over a wide range of experimental conditions, but the use of a trioctylphosphine cosolvent allowed formation of a Ni1Ge1 phase that was not thermally stable. Many proposed applications of colloidal Ge nanocrystals require thorough particle surface modification. To this end, surface ligand exchange of Ge nanocrystals was examined and improved through the development of a high-temperature sulfur treatment. Finally, Ge nanocrystal films were cast from solution and their electrical conductivity was characterized.