Photocatalytic degradation using Bi-doped SnS Quantum dots and phytotoxicity evaluation of treated effluents through seed germination

Abstract

Quantum dots (QDs) are employed in photocatalytic applications because of their distinctive optical characteristics, such as high absorption coefficients and tunable bandgaps, enabling efficient visible light absorption and charge carrier generation. This study focuses on synthesizing homogeneous bismuth-doped tin sulfide (Bi-doped SnS) QDs for environmental remediation. Bi-doped SnS QDs with varying Bi concentrations are prepared via a facile, cost-effective chemical method, and their structural, optical, and morphological characteristics are analyzed through X-ray diffraction (XRD), UV–Vis spectroscopy, and transmission electron microscopy (TEM). TEM results confirm that the catalysts are highly homogeneous and tiny (<5 nm). Photocatalytic activity is assessed through the breakdown of Crystal Violet (CV) and Methylene Blue (MB) when exposed to visible light. High efficiencies of 89.0 % and 95.8 % are achieved for CV and MB, respectively, outperforming undoped SnS. Kinetic analysis reveals a pseudo-first-order reaction, providing insights into the underlying degradation kinetics. A plausible mechanism is proposed, elucidating how Bi-ion doping enhances photocatalytic performance and facilitates dye degradation. Additionally, toxicity evaluation using Vigna radiata seeds demonstrates the efficacy of the degradation process. Treated dye solutions (D-CV and D-MB) show no significant changes in intracellular ROS levels compared to untreated dye and control solutions, confirming reduced toxicity. These findings highlight the enhanced photocatalytic performance of Bi-doped SnS QDs and their potential in environmental purification, advancing the understanding of QD-based photocatalysts for sustainable applications.