Fluorescence color tuning of dual-emission biomass carbon quantum dots and their application in Fe³⁺ and Cu²⁺ detection

Using simple and eco-friendly solvothermal treatment, dual-emission biomass carbon quantum dots (D-BCQDs) were successfully synthesized from biomass Viburnum awabuki leaves. The resultant dual emission peaks appeared at 490 and 675 nm under a single 413 nm excitation wavelength. Only by changing the reaction temperature (140–240 °C), multicolor D-BCQDs could emit crimson, red, purplish red, purple, and blue-gray fluorescence, respectively. XPS and FTIR characterization indicated that the tunable fluorescence color mechanism was mainly attributed to surface oxidation defects, nitrogen elemental content, and sp²-C/sp³-C hybridized structural domains. D-BCQDs can not only respectively detect Fe³⁺ and Cu²⁺, but also quantify the ratio of Fe³⁺ and Cu²⁺ in mixed solutions, demonstrating their potential application in the simultaneous detection of multiple ions.