A fluorescent N-doped carbon dot-hydrogel composite for concurrent selective detection and local hot spot promoted adsorption of uranium(vi)

Developing a highly effective bifunctional platform with concurrent UO₂²⁺ detection and removal from nuclear-contaminated water is highly needed. Here, we report an N-doped carbon dot-embedded cellulose-based fluorescent hydrogel composite (CMH-NCDs) with a 3D hydrophilic hierarchical pore network. The CMH-NCD composites displayed good UO₂²⁺ selectivity with rapid fluorescence quenching (∼0.5 s) and an ultra-low detection limit of 8.4 nM (1.94 ppb), which is far below the maximum contamination standard in drinking water according to the WHO's guidelines (30 ppb). Simultaneously, an extraction capacity of 194 mg g⁻¹ and a removal ratio of over 97% were achieved due to the excellent binding affinity of the CMH-NCD composite towards uranium. Importantly, in the hydrophilic channel of the CMH-NCD composite, the local heating nano-domains derived from the photothermal effect of the NCD heaters would strengthen the convection and diffusion rates of uranyl ions and improve the collision probability with the active sites, allowing improved absorption capacity of the CMH-NCD composites.