Co-doped ZnS nanoparticles synthesized via single-source precursor: an efficient photocatalyst for dye degradation

Zinc sulphide nanoparticles (ZnS NPs) with high photocatalytic efficiency, high chemical stability, and resistance to photo-corrosion form promising photocatalysts for the degradation of environmental pollutants like dyes. Doping with transition metals like cobalt (Co) can further improve the photocatalytic efficiency of ZnS NPs by improving light absorption and reducing the recombination rate of photogenerated electron–hole pairs. The decomposition of single-source precursors (SSPs) offers a simple and effective route for obtaining high-quality metal sulphide NPs. In this paper, we explore the synthesis of Co-doped ZnS (Co-ZnS) NPs through the SSP method, offering a novel approach to enhance their photocatalytic properties. The Co-ZnS nanoparticles were prepared via solvothermal decomposition of Zn(II)-L-phenyl alanine dithiocarbamate [Zn-PHEDTC] and Co(II)-L-phenyl alanine dithiocarbamate [Co-PHEDTC] complexes as SSPs in diethylenetriamine (DETA) solvent at 190 °C. The structural, optical, and morphological properties of the synthesized materials were analyzed using UV–Vis spectroscopy, fluorescence spectroscopy, Fourier Transform Infrared Spectroscopy, High-Resolution Transmission Electron Microscopy, and Energy Dispersive X-ray Spectroscopy analysis. The results revealed the formation of NPs of size 3.27 nm with successful doping of Co dopants in the ZnS lattice, altered bandgap, and enhanced light absorption in the visible region. The photocatalytic activity of Co-ZnS NPs was investigated through the degradation of a model pollutant dye, Reactive Blue 81, using visible light irradiation. Co-ZnS was found to achieve a degradation efficiency of 95.98% in 60 min, which was higher than undoped ZnS (92.7% in 90 min). Thus, Co-doping enhanced the degradation efficiency while reducing the degradation time by nearly 33% due to reduced electron–hole recombination and improved charge carrier separation. The present study demonstrates the potential of Co-doped ZnS NPs synthesized through an SSP route as effective photocatalysts for environmental remediation, particularly in the degradation of textile dyes from wastewater. This approach not only overcomes the limitations of conventional water treatment methods but also underscores the environmental and technological benefits of Co-ZnS nanoparticles for sustainable photocatalytic applications.

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