Fig. 1. Method for preparation of carbon dots and solvent-dependent effect. (a) Illustration of preparation process of fluorescent carbon nanodots; (b) fluorescent photos of carbon dots dispersed in different solvents

Fig. 2. Characterization of carbon quantum dots. (a) AFM image of carbon quantum dots; (b) height profile along line indicated in Fig. 2 (a)

Fig. 3. Spectra of carbon quantum dots. (a) Excitation and emission spectra; (b) fluorescence spectra under different excitation wavelengths

Fig. 4. Spectra of carbon dots with different water contents. (a) Absorption spectra in DMF; (b) fluorescent photos in DMF; (c) fluorescence spectra in DMF excited at 420 nm

Fig. 5. Effect of water content on position of emission peak and fluorescence intensity of carbon dots. (a) Relationship between (F₀-F)/F₀ and water content; (b) relationship between position of emission peak and water content

Fig. 6. Luminescence mechanism of carbon dots. (a) Effect of pH value on fluorescence spectra of aqueous solution of carbon dots; (b) illustration of solvent effect of carbon dots