Effect of Sm-doping on structural, visible-light activated photocatalytic degradation of crystal violet dye and antifungal activity of ZnO nanoparticles

Industrial wastewater treatment to remove synthetic dyes is a critical environmental issue. In this work, samarium (Sm) (0-3%)-doped zinc oxide (ZnO) nanoparticles (NPs) were synthesized using sol-gel method and examined for their dual functionality in crystal violet (CV) dye degradation and antifungal applications. Hexagonal close packed (HCP) crystal structure, single phase purity, granular nature and functionality have been confirmed by XRD Rietveld refinements, SEM and FTIR analysis. Furthermore, the optical analysis revealed the decrement of band gap with increase in Sm-doping in ZnO NPs i.e. 3.22 eV (ZnO) to 3.10 eV (Sm-3% doped ZnO) which can be ascribed to trap-states formation by Sm 3+ ions. Also, the photoluminescence spectroscopy analysis revealed the variation of defect states with Sm-doping. Photocatalytic experiments revealed the enhanced photocatalytic performance with Sm-doping i.e. 94.8% degradation efficiency for Sm 2%-doped ZnO NPs compared to 84.1% for un-doped ZnO NPs. Antifungal assays against Rhizomucor pusillus demonstrated the highest inhibition zone (15 mm) for Sm 3%-ZnO, followed by Sm 2%-ZnO (12 mm), Sm 1%-ZnO (10 mm), and pure ZnO (8 mm). These findings demonstrate that Sm-doping in ZnO effectively enhances both photocatalytic and antifungal properties, highlighting Sm-doped ZnO NPs a potential candidate for environmental remediation.