Enhanced photocatalytic gold recovery with concurrent near-IR fluorescence turn-on sensing: N,S-doped CDs in functionalized dendritic silica as a dual-mode platform

Abstract

The concurrent gold detection and extraction in aqueous medium is crucial for gold exploration and resource recovery. While using a single material for dual purposes offers distinct advantages, it remains relatively underexplored. This study introduces a rationally engineered heterojunction material that enables selective fluorescence-based turn-on gold detection in the near-IR region, coupled with photocatalytic enhanced adsorption. The hybrid composite material (NSCD@DFNS@BMB-AO) consists of dendritic fibrous silica integrated with in situ grown N,S-doped carbon dots (NSCDs) as a fluorescence indicator in the silica matrix and covalently attached amidoxime ligands for gold binding. The incorporation of NSCDs enables photoluminescence in near-IR regions while also promoting photocatalytic activity. The material uniquely enables turn-on gold-ion detection in the near-IR region through photoinduced electron transfer (PET) disruption, offering an ultra-low detection limit (LOD) of 9.9 nM with excellent selectivity. The adsorption potential of the material (780 mg g⁻¹) was enhanced through the photocatalytic reduction of Au(III) to Au(0). Furthermore, the ROS (reactive oxygen species) activity contributes to the material's antimicrobial properties, which are essential to prevent biofouling in aquatic environments. With its rapid response, fast kinetics, effective adsorption capability, and nearly complete gold recovery (∼98%) from e-waste, this material demonstrates significant potential for gold extraction and recovery.