Schottky-type magneto-plasmonic Fe3O4–Au heterostructures as highly efficient photocatalysts for the degradation of commercial oxamyl

Harnessing light-driven processes to combat environmental pollution represents a sustainable approach to wastewater treatment. In this study, Schottky-type magneto-plasmonic heterostructures were engineered as magnetic assemblies composed of superparamagnetic Fe 3 O 4 nanoparticles decorated with 18.5 nm Au nanoparticles at nominal concentrations of 2, 5, and 10 mol%. These hybrid materials exhibited outstanding photocatalytic activity in the degradation of highly concentrated aqueous solutions of the commercial pesticide Oxamyl (up to 1 × 10 4 ppm) under both UV and solar irradiation. The Fe 3 O 4 –Au heterostructures containing 5 mol% Au showed the best performance, achieving 66% degradation within 30 min of sunlight exposure, significantly outperforming the efficiency under UV irradiation (39%). Liquid chromatography with mass-spectrometric detection in the ion positive ionization mode revealed a substantial reduction in the oxamyl peak compared with other product components, indicating extensive decomposition into a hydroxy derivative (C 5 H 10 N 2 O 2 S) and a secondary product (C 3 H 5 NO 3 ) under both irradiation conditions. Interestingly, the tatrazine colorant present in the commercial formulation degraded simultaneously with Oxamyl, evidencing the capacity of the catalyst for handling complex pollutant mixtures at high contaminant concentrations. The findings highlight the synergistic effect of magnetic-plasmonic coupling in Fe 3 O 4 -Au Schottky heterostructures, establishing them as promising photocatalysts for efficient solar-driven pollutant remediation.