Room temperature synthesis of thioglycolate-coated zinc sulfide (ZnS) nanoparticles in aqueous medium and their physicochemical characterization

This article considers the room temperature (25 C) synthesis and characterization of water-dispersible zinc sulfide (ZnS) nanoparticles, coated with thioglycolic acid in order to shed new light on the mechanism of nanoparticle formation and to optimize the conditions for nanoparticle preparation. The ZnS nanoparticles were prepared by a facile one-pot synthesis procedure from alkaline solution of zinc thioglycolate and sodium sulfide, and were characterized by transmission electron microscopy with electron diffraction, X-ray powder diffraction and UV-vis absorbance spectroscopy. Slight nanocrystal growth and focusing of size distribution was observed soon after mixing of precursors at room temperature, while further storage of the dispersion resulted in ripening process and broadening of the size distribution. The obtained nanoparticles were spheroid in shape, of cubic crystal structure and average size of around 2.2 nm. A new semi-empirical equation based on attenuated quantum confinement was derived, which allowed determining the true nanocrystal size directly from the absorbance spectrum. The effects of the molar ratio of precursors and precursor concentrations on the UV-vis absorbance properties and nanoparticle stability were also investigated. It is expected that the obtained results could be useful for researchers in the field of quantum dot synthesis and characterization. (C) 2013 Elsevier B.V. All rights reserved.