Coconut water-mediated green synthesis of Sm-Gd@ZnO nanoparticles with enhanced photocatalytic and antimicrobial performance

Samarium-Gadolinium doped Zinc Oxide (Sm-Gd@ZnO) nanoparticles (NPs) were synthesized using a simple, green, cost-effective method with coconut water as a natural reducing and stabilizing agent. The synthesized NPs were comprehensively characterized using various techniques including, Thermogravimetry-Differential Thermal Analysis (TG-DTA), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD), Photoluminescence (PL), High-Resolution Transmission Electron Microscopy (HR-TEM), Selected Area Electron Diffraction (SAED), Sanning Electron Microscopy (SEM), Energy-Dispersive X-Ray Spectroscopy (EDAX), X-Ray Photoelectron Spectroscopy (XPS) and UV–visible spectroscopy. XRD pattern confirmed the formation of highly crystalline ZnO with a hexagonal wurtzite structure, while HR-TEM revealed hexagonal and nearly spherical morphology of the NPs with a tendency to form slightly agglomaerated cluster with an average particle size of 25 nm. UV–visible analysis demonstrated enhanced light absorption, and PL spectra indicated reduced charge carrier recombination in co-doped samples. XPS results verified the successful incorporation of Sm and Gd ions into the ZnO lattice in their trivalent oxidation state. BET analysis revealed an increased surface area and N 2 adsorption-desorption studies confirmed mesoporous morphology. The synthesized Sm-Gd@ZnO NPs exhibited remarkable photocatalytic performance, achieving 99 % degradation of MB dye under solar irradiation within 4 h. The reusability tests verified an efficiency retention of 94 % after three cycles. Furthermore, they displayed strong antimicrobial activity against Bacillus subtilis , highlighting the synergistic effect of co-doping in ternary NPs (Sm-Gd@ZnO) compared to bare ZnO and binary NPs. This research contributes significantly to the advancement of eco-friendly technologies in environmental remediation and offers effective solutions for mitigating dye pollution from industrial sources.