Sulfur-Capped Germanium Nanocrystals: Facile Inorganic Ligand Exchange

The development of applications for germanium nanocrystals has been hindered by the limited availability of synthetic methods coupled with poorly understood ligand-exchange chemistry. Herein we describe the synthesis of germanium nanocrystals and ligand exchange experiments designed to establish facile routes toward ligand replacement and, consequently, layers that are amenable to charge-transfer. After assessing thiols, carboxylates, and dithiocarbamates, sulfur dissolved in 1-ocatadecene was determined to be the most amenable to ligand exchange, with over 95% of the initial alkylamine ligand replaced as determined by Fourier transform infrared spectroscopy (FTIR). These results were in good agreement with density functional theory calculations showing a strong preference for Ge–S bonding. The materials were fully characterized via powder X-ray diffraction, FTIR, transmission electron microscopy, and X-ray and UV photoelectron spectroscopy. This new ligand exchange procedure provides a possible route toward the fabrication of thin films that may be employed in such applications as photovoltaic devices.