Gold plasmon-enhanced TiO2 and ZnO nanocomposites for rapid photodegradation of dyes, pharmaceuticals, and real textile wastewater

In this study, plasmon-enhanced Au@TiO 2 and Au@ZnO nanocomposites were synthesized via controlled reduction routes and systematically evaluated for photocatalytic degradation under UV irradiation. Structural and optical characterization confirmed the successful deposition of well-dispersed Au nanoparticles on semiconductor supports, promoting interfacial charge transfer and suppressing electron–hole recombination. The photocatalytic performance was investigated using a range of model dyes (methylene blue, methyl orange, rhodamine B, and cresol red), pharmaceutical contaminants (ciprofloxacin and caffeine), and real textile wastewater. Both nanocomposites exhibited high degradation efficiencies; however, Au@TiO 2 demonstrated significantly faster reaction kinetics, achieving rapid degradation within 30 min, while Au@ZnO required extended irradiation to reach comparable efficiencies. Kinetic analysis based on a pseudo-first-order model revealed a higher apparent rate constant for Au@TiO 2 , confirming its superior catalytic activity. Mechanistic investigations using radical scavengers indicated that superoxide radicals (O 2 ·− ) play a dominant role in the degradation process, with hydroxyl radicals and photogenerated holes contributing synergistically. The enhanced performance of Au@TiO 2 is attributed to more efficient charge separation and electron trapping at the Au@TiO 2 interface. Importantly, the photocatalyst maintained high activity in complex systems, including mixed dyes and untreated industrial wastewater, achieving substantial removal without pre-treatment.