Size tailoring of aqueous germanium nanoparticle dispersions.

We demonstrate a practical route to synthesize Ge nanoparticles (NPs) in multi-gram quantities via the laser pyrolysis of GeH4 gas. The size of the as-produced Ge NPs can be precisely controlled in the range of 19.0 to 65.9 nm via a subsequent etching procedure using a dilute H2O2 solution. Stable water dispersions of Ge NPs yield particles with a Ge/GeO2 core-shell structure, however, the oxide shell can easily be removed and passivated by treatment with HCl. The feed materials used in this process are readily available and lead to non-toxic, water-based dispersions of Ge NPs. The scalability and convenience of this procedure make it attractive as a method to obtain Ge NP dispersions for use in applications such as optoelectronic devices and biosensors.