Efficient one-pot synthesis of monodisperse alkyl-terminated colloidal germanium nanocrystals

An efficient one-pot method for fabricating alkyl-capped germanium nanocrystals (Ge NCs) is reported. Ge NCs with a size of 3.9 +/- 0.5 nm, are formed by co-reduction of germanium tetrachloride in the presence of n-butyltrichlorogermane, producing NCs with butyl-terminated surfaces. The advantage of this method is that it allows rapid synthesis and functionalisation of NCs with minimal post-synthetic purification requirements. TEM imaging showed that the Ge NCs are monodisperse and highly crystalline, while EDX and SAED confirmed the chemical identity and crystal phase of the NCs. FTIR and XPS confirmed that the Ge NCs were well passivated, with some oxidation of the nanocrystal surface. Optical spectroscopy of the NCs showed a strong absorbance in the UV region and an excitation wavelength dependent photoluminescence in the UV/violet. Time resolved photoluminescence measurements showed the presence of two nanosecond lifetime components, consistent with recombination of photogenerated excitons at low lying energy states present at the nanocrystal surface. Photoluminescence quantum yields were determined to be 37 %, one of the highest values reported for organically terminated Ge NCs.