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

Using simple and eco-friendly ethanol solvothermal treatment, dual-emission biomass carbon quantum dots (D-BCQDs) were synthesized from biomass Viburnum awabuki leaves. The dual emission peaks appeared at 490 and 675 nm under excitation with 413 nm wavelength light. D-BCQDs could be tuned to emit crimson, red, purplish red, purple and blue-gray fluorescence, respectively by changing the solvothermal temperature (140, 160, 180, 200 and 240 °C). XPS and FTIR characterization indicated that the fluorescence color was mainly ascribed to surface oxidation defects, nitrogen element and sp²-C/sp³-C hybridized structural domains. D-BCQDs can not only detect Fe³⁺ or Cu²⁺, but also quantify the concentration ratio of Fe³⁺ to Cu²⁺ in a mixed solution containing both, demonstrating their potential applications in the simultaneous detection of Fe³⁺ and Cu²⁺ ions.