Quercetin supported Bi2S3 nanoparticles: A versatile photocatalyst for treatment of harmful bacteria and mixture of toxic cationic dyes in water

In this study, we present the successful fabrication of quercetin-stabilized Bi2S3 nanoparticles (QBi2S3 NPs), which have been used to degrade three toxic cationic dyes and kill harmful bacteria. Herein, QBi2S3 NPs were prepared using a facile precipitation method under ambient conditions. HRTEM, SEM, XRD, UV-visible and EDX were employed to characterize their average size, morphology, crystallinity, degradation efficiency and elemental composition percentage, respectively. Stabilization of NPs using quercetin was confirmed by DFT based IR and binding energy calculations. Visible light assisted photocatalytic activity of QBi2S3 NPs was eval-uated against methylene blue (MB), brilliant green (BG), rhodamine-B (Rh-B), and mixture of all three (MB, BG and Rh-B) at different pH ranges (pH 2, 4, 6 and 8) up to 120 min. QBi2S3 NPs effectively degraded all three cationic dyes, the maximum degradation of BG and Rh-B was recorded in 120 min, while that of MB in 60 min. Antibacterial findings reveal that the combination of quercetin and Bi2S3 NPs displayed significantly higher antibacterial activity compared to pristine quercetin. Low MIC values (20 +/- 2, 30 +/- 3 and 40 +/- 3 mu g/mL for E. coli, E. faecalis and B. subtilis respectively) of QBi2S3 NPs compared to native quercetin indicate its synergistic antibacterial effects. Cytotoxicity study of QBi2S3 NPs on HaCat and HeLa cell lines confirmed its non-toxicity up to a concentration of 200 mu g/mL. Furthermore, the phytotoxicity assay of QBi2S3 NPs, MB, BG, and Rh-B on green gram plants was compared and showed the minimal toxic effects of BG compared to MB and Rh-B.