Green photodeposition of Au/TiO2 nanocomposites for wide-range photocatalytic degradation of pharmaceuticals.

Modifying photocatalytic materials by depositing noble metal nanoparticles is an effective strategy to enhance solar energy conversion. This study developed a UV-driven, one-pot photodeposition method to synthesise Au/TiO2 nanocomposites without chemical reducing agents. The influence of gold loading on physicochemical and photocatalytic properties was investigated. Structural, morphological, and optical analyses confirmed successful Au deposition without altering the TiO2 crystalline structure and also revealed improved colloidal stability and visible-light absorption due to Au surface plasmon resonance. The nanocomposites showed significant generation of reactive oxygen species under UV irradiation, with consistent hydroxyl radical production and increasing singlet oxygen formation at higher gold content. Photocatalytic performance was evaluated by degrading ciprofloxacin, chloroquine phosphate, diclofenac sodium, paracetamol, and fluconazole under UV light and simulated sunlight. A gold loading of 0.5 wt% achieved the highest efficiency, with up to 90% degradation of ciprofloxacin under both irradiation sources. Degradation of other pharmaceuticals ranged from 84% (chloroquine phosphate) to 45% (diclofenac sodium), depending on molecular structure and affinity for the catalyst. This work presents a simple and reproducible UV-driven approach to fabricating Au/TiO2 nanocomposites for the photocatalytic degradation of pharmaceutical pollutants.