Facile Synthesis of Germanium Nanoparticles with Size Control: Microwave versus Conventional Heating

Significance Statement

In a follow-up work published recently in Chemistry of Materials, dodecanethiol was explored as a capping ligand for the germanium NCs. The thiol ligand was observed to yield more stable Germanium Nanoparticles dispersions and increased resistance against oxidation. Surface photovoltage measurements were carried out on thin films of thiol-capped Germanium Nanoparticles and their band-gaps were ascertained. More information is available in this article at http://pubs.acs.org/doi/abs/10.1021/cm4042154. Current work in our group is focused on extending the methodology to prepare doped-Germanium Nanoparticles

Figure Legend: TEM image of Germanium Nanoparticles

Journal Reference

Chem. Mater., 2013, 25 (8), pp 1416–1422.

Elayaraja Muthuswamy , Andrew S. Iskandar ,Marlene M. Amador , and Susan M. Kauzlarich.

Department of Chemistry, University of California, One Shields Ave, Davis, California 95616, United States.

Abstract

A commercially viable colloidal synthetic method for germanium nanocrystals (NCs) is reported. Oleylamine serves as a solvent, a binding ligand, and a reducing agent in the synthesis. Reactions were carried out with microwave-assisted heating, and the results have been compared with those produced by conventional heating. Germanium iodides (GeI₄, GeI₂) were used as the Germanium precursor, and size control in the range of 4–11 nm was achieved by controlling the ratio of Ge⁴⁺/Ge²⁺ in the precursor mix. Longer reaction times and higher temperatures were also observed to have an effect on the nanocrystals size distribution. Microwave heating resulted in crystalline particles at lower temperatures than conventional resistive heating as observed with many other nanocrystals systems. The reported approach for germanium nanocrystals preparation avoids the use of strong reducing agents (LiAlH₄, n-BuLi, NaBH₄) and HF for etching and, thus, can be considered simple, safe, and amenable to industrial-level scale up. The as-prepared NCs are a stable dispersion (hexane or toluene) for weeks when stored under an inert atmosphere (N₂/Ar). The stability of the colloidal dispersion was observed to be dependent on the nanocrystals size, with smaller nanocrystals exhibiting longer stability. On exposure to ambient conditions, oxidation occurs over a period of time and results in slow precipitation of the nanocrystals.

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Facile Synthesis of Germanium Nanoparticles with Size Control: Microwave versus Conventional Heating

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