Carbon dots-mesoporous silica composites for efficient U(Ⅵ) adsorption and in situ fluorescence monitoring

The development of functional materials capable of simultaneous U(Ⅵ) detection and adsorption remains a critical challenge in nuclear waste management. Herein, we present carbon dots (CDs)-functionalized MCM-41 composites (CA@MCM-41 and AA@MCM-41) that synergistically integrate fluorescent sensing and selective adsorption capabilities. Through hydrothermal synthesis of CDs derived from citric acid (CA) and L-aspartic acid (AA), the composites exhibit U(Ⅵ) adsorption selectivity while preserving ordered mesoporosity. The AA@MCM-41 demonstrates higher adsorption capability for U(Ⅵ) under acidic conditions (pH 1–4) leveraging protonated amine-carboxyl synergy. The CA@MCM-41 exhibits better adsorption capacity in pH 5–6. Crucially, the composites exhibit intrinsic fluorescence-U(Ⅵ) adsorption coupling, where uranyl coordination triggers concentration-dependent quenching. The correlation between fluorescence quenching and U(Ⅵ) adsorption is quantitatively analyzed using the Stern-Volmer-type relationship. The excellent linear fits strongly support a static quenching mechanism dominated by the stable complex formation between the anchored CDs and U(Ⅵ). The demonstrated integration of optical feedback positions these composites as transformative solutions for smart nuclear wastewater treatment systems.