Scalable single-step deposition of recyclable TiO2@Au monolayer coatings for enhanced visible-light photocatalysis of methylene blue dye

Abstract

Titanium dioxide@gold (TiO₂@Au) nanocomposite monolayers with enhanced visible-light photocatalysis were synthesized via an air–water interfacial self-assembly and pyrolysis strategy. This method simultaneously embeds Au nanoparticles (5–20 nm) within TiO₂ and reduces the bandgap from 3.02 eV to 2.66 eV via interfacial charge redistribution. In a 200 ml aqueous reaction system, the TiO₂@Au monolayers demonstrated a visible-light-driven methylene blue degradation rate of 0.0054 min⁻¹-3.6-fold higher than pure TiO₂, attributed to Au's localized surface plasmon resonance (LSPR) enhancing visible-light absorption and interfacial electron transfer. The system maintained 99.2% activity retention over five cycles, showcasing unprecedented stability in large-volume wastewater treatment scenarios. This method leverages self-limiting assembly at the air–water interface to orchestrate the molecular packing of organometallic precursor films, which upon pyrolysis yield centimeter-scale nanocomposite monolayers. The developed methodology provides a practical pathway for industrial photocatalytic wastewater purification.