Bio-inspired fluorescent agent derived from Mucuna pruriens for PeT-mediated sensitive detection of Cu(II) ions in environmental water.

Copper contamination in water and irrigation sources is an essential environmental exposure pathway that can affect ecosystem health and, indirectly, food safety. Here, we present a sustainable optical sensing platform based on bio-inspired carbon quantum dots (CQDs) synthesized from Mucuna pruriens seeds via a green hydrothermal route. The synthesis yields uniformly dispersed nanoparticles (∼2.5 nm) enriched with oxygen- and nitrogen-containing surface functionalities, imparting strong colloidal stability and efficient photoluminescence with a quantum yield of 18.70%. These CQDs exhibit excitation-dependent fluorescence that is selectively quenched by Cu2+ ions via a photoinduced electron transfer (PeT) mechanism, achieving detection limits of 0.34 μM. The CQDs enable both solution-based and filter paper-mediated visual detection. Low phytotoxicity in seed germination assays underscores their environmental compatibility. This study demonstrates that Mucuna pruriens-derived CQDs provide a promising, sustainable fluorescent agent for sensitive, portable monitoring of Cu2+ ions in aqueous environments.