New horizons for the synthesis of nanoparticles: Germanium nanoparticles from metastable GeBr-solutions

We present the synthesis and characterization of halide-terminated colloidal Ge nanoparticles of 2–10 nm with a narrow size distribution, synthesized via a novel reaction route. The nanoparticles are prepared by the disproportionation reaction of metastable Ge(I)X solutions and are obtained in a maximum yield of 79%. Control of the nanoparticle size is achieved by varying the aging time and/or temperature. The halide termination of the nanoparticles is a perfect prerequisite for further surface functionalization but also leads to a high sensitivity of the germanium nanoparticles to water and air.

Effects of Temperature on the Morphology and Optical Properties of Spark Discharge Germanium Nanoparticles

We report the spark discharge synthesis of aerosol germanium nanoparticles followed by sintering in a tube furnace at different temperatures varying from 25 to 800 °C. The size, structure, chemical composition and optical properties were studied. We have demonstrated a melting mechanism of nanoparticles agglomerates, the growth of the mean primary particle size from 7 to 51 nm and the reduction of the size of agglomerates with a temperature increase. According to transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) data, primary nanoparticles sintered at temperatures from 25 to 475 °C basically have a structure of Ge crystals embedded in a GeOx amorphous matrix, as well as visible photoluminescence (PL) with the maximum at 550 nm. Pure germanium nanoparticles are prepared at temperatures above 625 °C and distinguished by their absence of visible PL. The shape of the experimental UV-vis-NIR extinction spectra significantly depends on the size distribution of the germanium crystals. This fact was confirmed by simulations according to Mie theory for obtained ensembles of germanium nanoparticles.

Effect of temperature on B(C6F5)3-catalysed reduction of germanium alkoxides by hydrosilanes – a new route to germanium nanoparticles

The reaction of Ge(OBu)4 with PhMe2SiH in the presence of B(C6F5)3 carried out at temperatures above 100 °C provides a simple one-pot method for Ge NPs synthesis under mild conditions.