Sunlight-mediated photocatalytic uranium extraction from seawater: a bioresistant heterojunction for highly selective uranium sensing and extraction with in vivo application

Uranium's dual role in energy production and environmental pollution necessitates simultaneous monitoring and remediation, where the designing philosophy of the material is crucial for achieving multifunctional properties. A novel composite material, CD@WFNS@DAB-AO, has been engineered to incorporate dual functional activities of uranium detection and extraction, with anti-biofouling properties. This material utilizes worm-shaped fibrous nano-silica (WFNS) as a substrate, photoactive nitrogen and phosphorus-doped carbon dots (NPCDs) as a fluorescence tag, and an amidoxime-based ligand (DAB-AO) for uranium specificity. The worm-like fibrous silica offers a high-surface-area platform with radial channels for effective surface functionalization. NPCDs within the silica matrix exhibit excitation-independent red photoluminescence and photocatalytic activity. The surface immobilization of amidoxime ligands on CD-incorporated silica results in fluorescence quenching of the CDs due to electron transfer from the electron-rich amidoxime system. However, this process is subsequently hindered (PET breakdown) upon binding with the uranyl ion, leading to fluorescence recovery of the CDs showing turn-on red-emission, which is rarely reported for uranium and favorable for environmental and biological samples. This material also enables enhanced uranium extraction via photocatalytic uranium reduction and prevents biofouling by generating reactive oxygen species (ROS). The material shows an ultra-low detection limit (7.4 nM) and high adsorption capacity (Qmax = 710 mg g-1) in batch mode with 98% extraction efficiency. It achieves a uranium adsorption capacity of 12.13 mg g-1 from natural seawater in 30 days, surpassing the UES standard (6 mg g-1). Uranium biosensing in Artemia salina is assessed through fluorescence imaging. The material demonstrates excellent reusability, selectivity, and fast adsorption kinetics, making it a distinct platform for UES technologies.