A Facile Solid-Phase Synthesis of Scandium-Modified Carbon Dots for Fluorescent Sensing of Cu2+

Scandium-modified carbon dots (Sc-oCDs) were synthesized in this work through a solid-phase approach. The prepared Sc-oCDs exhibited excitation-independent emission properties, as well as photostability against pH, ionic strength, and UV irradiation. Their fluorescence quantum yields significantly exceeded those of unmodified counterparts, confirming effective Sc modification. The Sc-oCDs also possessed upconversion fluorescence at 542 nm with 980 nm excitation. Additionally, the as-prepared Sc-oCDs functioned as an effective fluorescent sensor for Cu2+, demonstrating selective fluorescence quenching. A linear correlation was observed between the quenching efficiency and Cu2+ concentration from 1 to 600 μM, achieving a detection limit of 0.167 μM. Operating via dynamic quenching, this sensing system achieved highly selective and rapid (<1 min) detection of Cu2+, enabling sensitive Cu2+ monitoring in aqueous samples.