Optical properties of ZnS nanoparticles precipitated at various molar ratios of sulphide and zinc ions and stabilized by CTAB

Abstract

ZnS nanoparticles were precipitated by the reaction of zinc and sulphide ions in aqueous media and stabilized by cetyltrimethylammonium bromide (CTAB). The nanoparticles size (diameter) was calculated using the relationship between band-gap energy and radius as a result of the quantum size effect. Depending on the molar ratio of precursors S2-/Zn2+ = 0.25–2.0 and time elapsed from their preparation t = 0–5 h, nanoparticles with sizes of 3.5–4.8 nm were obtained. The absorption of UV radiation and photoluminescence (PL) of the nanoparticles dispersions were studied. The nanoparticles growth dependent on time and the S2-/Zn2+ ratio were indicated by changes in UV absorption and PL spectra. The stabilization effect of CTAB was observed for all S2-/Zn2+ ratios up to 5 hours. At longer time intervals (3 a 4 days) flocs of ZnS nanoparticles and CTAB were observed.