Molecular precursors are suitable starting compounds for preparation of semiconductor nanoparticles (NPs), which allow for control of atomic ratio, composition, monodispersity, and particle size of nanoscaled metal sulfides/oxides. In the present study, we carried out a one-pot synthesis of ZnS NPs in aqueous triethanolamine medium at room temperature, from molecular precursor zinc xanthate as a source of both Zn2+ and S2- ions. Furthermore, we compared the products obtained from zinc ethylxanthate (Zn(C2H5OCS2)2) and zinc amylxanthate (Zn(C5H11OCS2)2). The as-prepared ZnS NPs were found to crystallize in cubic phase, which usually forms at low temperatures, with the dimension dependent on the xanthate precursor used. The long carbon-chain xanthate Zn(C5H11OCS2)2 gave spherically shaped NPs with an average diameter of 19 nm, while the NPs that originated from zinc ethylxanthate had a mean size of ~26 nm. Both nanomaterials had surface sulfur vacancies that extended their absorption spectra toward the visible region and reduced the band gap. This allowed both materials to demonstrate photocatalytic performance under visible-light irradiation. Photodegradation of methylene blue over newly prepared ZnS NPs was tested under visible light, demonstrating efficiency of 50%-60% after 180 min.
Keywords: ZnS nanoparticles; photocatalysis; triethanolamine; zinc xanthate.