Non-Plasmonic Oxidase-Like Gold Nanocatalysts on Hydrogel Beads for Broad-Spectrum Water Decontamination

The efficient and sustainable remediation of contaminated water calls for catalytic systems that must clean broadly, endure widely, and last repeatedly. In this regard, we report the development of sulfonate-functionalized core–shell hydrogel beads embedded with in situ synthesized gold nanoparticles (AuNPs) that exhibit intrinsic oxidase-like activity without requiring external light or chemical oxidants. The sulfonate ligands modulate the surface electronic environment of the AuNPs, facilitating singlet oxygen generation via a nonplasmonic, radiationless mechanism. These AuNPs, confined to the bead surface, provide rapid substrate access, eliminating diffusion barriers and enabling efficient catalytic oxidation of a broad spectrum of contaminants. The AuNP@Beads demonstrate excellent activity toward phenolic pollutants, azo dyes, and biologically relevant catecholamines such as dopamine and epinephrine. They also exhibit potent antibacterial efficacy against both Gram-negative and Gram-positive pathogens through ROS generation. The catalytic beads are reusable, structurally stable under ionic stress, and show negligible nanoparticle leaching. Furthermore, the treated wastewater supports healthy plant growth, underscoring its environmental compatibility. This study introduces a robust, multifunctional catalytic platform for water purification that combines oxidase-like catalysis, antibacterial action, and biosensing potential. The light-independent operation and broad-spectrum efficacy make it highly promising for real-world environmental remediation applications.