Abstract
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.
Highlights
During the last decades, semiconductor nanoparticles (NPs) have been extensively explored because such nanomaterials often demonstrate unique properties that are attractive for applications in various fields, such as optics, electronics, biomedicine, sensing, photocatalysis, and so on
Pradham et al reported on the production of metal sulfide crystalline particles with tunable size and shape via metal alkyl xanthates by employing alkylamines as solvents, which were found to play a crucial role in the synthesis, significantly lowering the decomposition temperature of metal xanthate precursors [23]
The dry powders of samples ZnS(1) and ZnS(2) were used for X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and photocatalytic tests. They were redispersed in ethanol by means of sonication, after which they were drop-cast onto Si wafers for XRD, XPS, and SEM measurements, while more diluted dispersions were used for UV–Vis absorption spectroscopy
Summary
Semiconductor nanoparticles (NPs) have been extensively explored because such nanomaterials often demonstrate unique properties that are attractive for applications in various fields, such as optics, electronics, biomedicine, sensing, photocatalysis, and so on. Pradham et al reported on the production of metal sulfide crystalline particles with tunable size and shape via metal alkyl xanthates by employing alkylamines as solvents, which were found to play a crucial role in the synthesis, significantly lowering the decomposition temperature of metal xanthate precursors [23] This finding stimulated us to explore the effect of hydroxyl alkyl amines on the formation of metal sulfide NPs with metal xanthate as a molecular precursor. In this work, we studied the preparation of ZnS NPs from a molecular precursor zinc ethylxanthate (Zn(C2 H5 OCS2 )2 ) or zinc amylxanthate (Zn(C5 H11 OCS2 )2 ) as a source of sulfide and zinc ions in reaction with triethanolamine (N(C2 H4 OH)3 ), which acted as both nucleophile and a capping agent at room temperature. Considering the remarkable interest in applying ZnS nanostructures in diverse photocatalytic reactions under visible-light irradiation [37,38], upon characterizing them properly, we tested the performance of the as-prepared nanomaterials in degradation of methylene blue (MB), which was used as a model compound simulating organic pollutants in wastewaters
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