Abstract
In this paper, we report a new, simple method for the synthesis of CdS and ZnS nanoparticles (NPs) prepared in a basic aqueous medium using metal xanthate as the sulfur source. The structure, morphology, size distribution, optical band gap, and photocatalytic properties of the newly obtained nanomaterials were investigated by UV-Vis spectroscopy, X-ray diffraction, and transmission electron microscopy. The results show that both CdS and ZnS crystallized in cubic phase and formed NPs with average sizes of 7.0 and 4.2 nm for CdS and ZnS, respectively. A blue shift of UV-Vis absorbance band and higher energy band gap values were observed for both materials in comparison with their bulk counterparts, which is in accordance with the quantum confinement effect. The as-prepared nanomaterials were tested in visible-light driven photocatalytic decomposition of methylene blue (MB). After irradiation for 180 min, the degradation rate of MB with a concentration of 8 × 10−6 mol/L mixed with a photocatalyst (CdS or ZnS, both 10 mg in 100 mL solution of MB) was found to be 72% and 61%, respectively. The CdS NPs showed better photocatalytic activity than ZnS, which could be explained by their lower energy band gap and thus the ability to absorb light more efficiently when activated by visible-light irradiation.
Highlights
Semiconductor nanoparticles (NPs) demonstrate unique optical, electronic, photoluminescence, and photocatalytic properties that differ from those of their bulk counterparts because many of these properties are size-dependent at the nanoscale
The photocatalytic performance of metal sulfides can be improved through more efficient light absorption and the reduction of hole-electron recombination—both properties being dependent on the band gap energy and crystal structure of the material
We report the easy synthesis of metal sulfide (CdS and ZnS) NPs from xanthate as a sulfur source without the use of any organic solvents or surfactants
Summary
Semiconductor nanoparticles (NPs) demonstrate unique optical, electronic, photoluminescence, and photocatalytic properties that differ from those of their bulk counterparts because many of these properties are size-dependent at the nanoscale Such a dependence arises from the change in the surface-to-volume ratio, and as a result of the quantum confinement effect at small sizes. The photocatalytic performance of metal sulfides can be improved through more efficient light absorption and the reduction of hole-electron recombination—both properties being dependent on the band gap energy and crystal structure of the material. The reaction is carried out under mild conditions (60–80 ◦ C) and in a basic water medium where metal xanthates decompose to sulfide ions and the formed metal sulfides crystallize into a low-temperature cubic phase Both produced materials are shown to be nano-sized, with average particle sizes around 7.0 and 4.2 nm ZnS, respectively), and demonstrate photocatalytic activity towards methylene blue (MB) under visible light irradiation
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