Photothermal Degradation of Pollutants Using a Ag@ZnNP/TiO₂ Composite

The design of sustainable wastewater treatment strategies for recalcitrant pollutants, including per- and polyfluorinated alkyl substances (PFAS) and pesticides, remains a critical challenge. In this study, silver-zinc core-shell nanostructures (Ag@ZnNP), consisting of a zinc core and silver shell, were dispersed on TiO₂ and investigated as photothermal materials for the degradation of perfluorooctanoic acid (PFOA) and fipronil. Ag@ZnNP nanoparticles (Ag@ZnNP) were synthesized via pulsed laser ablation in liquid of a zinc target in the presence of silver nitrate. By tuning silver nitrate concentration, materials with optical and photothermal properties comparable to pure silver nanoparticles were obtained while reducing the silver content. X-ray diffraction confirmed a crystalline silver shell and a zinc core, while atomic emission spectroscopy indicated a composition of 67% ± 4% Ag and 33% ± 4% Zn. The Ag@ZnNP/TiO₂ composite exhibited PFOA degradation efficacy comparable to Ag/TiO₂ via blue light-initiated photothermal sulfate radical formation, achieving 85% degradation after 7 h. The Ag@ZnNP/TiO₂ composite achieved 88% fipronil removal within 1 h under blue light irradiation (455 mW cm^-2) without sulfate radicals. These results demonstrate the potential of Ag@ZnNP/TiO₂ as an efficient, lower-silver photothermal material for degrading persistent environmental contaminants.