Fig. 1. Schematic illustration for the preparation of CDs with persimmon leaves

Fig. 2. HR-TEM image (a) and size distribution histogram (b) of CDs

Fig. 3. XRD patterns of CDs

Fig. 4. FTIR (a) and UV-Vis absorption (b) spectra of CDs (the inset in Fig.(b) shows the photograph of CDs in aqueous solutions under 365 nm UV light)

Fig. 5. Emission spectra of CDs excited with different wavelengths

Fig. 6. (a) Excitation (λ_em=498 nm) and emission (λ_ex=410 nm) spectra of CDs and (b) Fluorescent decay curve of CDs

Fig. 7. Fluorescent intensity difference of CDs after mixing with different metal ions

Fig. 8. (a) Dependence of Fe³⁺ concentration on the fluorescence intensity of CDs; (b) Linear relationship between F₀/F and Fe³⁺ concentration