NiS-ZnS quantum dots as visible-light photocatalysts for enhanced dye degradation in sustainable wastewater treatment

Abstract

Nickel Sulfide–Zinc Sulfide Quantum Dots (NiS-ZnS QDs) have gained attention as efficient photocatalysts for breaking down organic dyes due to their adjustable optoelectronic characteristics and improved photocatalytic efficiency. In the present work, NiS, ZnS, and NiS-ZnS QDs were prepared using a chemical precipitation approach and thoroughly analysed through characterization techniques. The incorporation of Ni into the ZnS lattice was found to significantly modulate the band gap, facilitating improved visible light absorption. The photocatalytic performance of the synthesized NiS-ZnS QDs was evaluated through the degradation of Methylene Blue (MB) and Rose Bengal (RB) under visible-light irradiation. The results demonstrated a substantial enhancement in dye degradation efficiency compared to ZnS QDs and NiS, attributed to the suppression of electron-hole recombination, increased generation of reactive oxygen species (ROS), and improved charge carrier separation. Remarkably, the NiS-ZnS QDs achieved degradation efficiencies of 96.91 % for MB and 97.12 % for RB under visible light exposure, showcasing their superior photocatalytic activity. These findings highlight the potential of NiS-ZnS QDs as a highly efficient and economically viable photocatalyst for sustainable wastewater treatment applications. Furthermore, the efficient degradation of mixed dye solutions highlights the practical applicability of the photocatalyst, underscoring its potential for real-world wastewater treatment applications. Tuning the optical and electronic properties of these quantum dots via nickel doping offers promising opportunities for designing advanced photocatalytic materials aimed at environmental cleanup.