2.6. Photocatalytic Degradation of Organic Dyes

RhB and MB are selected as model dyes to evaluate the photocatalytic ability of our C-dots in this study. Briefly, 3 mg of C-dots and 0.2 mL of aqueous RhB (10 mg/L) solution were mixed, and then 3.8 mL of deionized water were added. The resulted mixture (final concentration of RhB, 0.5 mg/L) was transferred to an UV-Vis cuvette and ultrasonicated for 2 min to disperse the C-dots under dark. Then, the cuvette, vigorously stirred at 200 rpm, was placed in front of the solar simulator (Oriel Instruments, Newport Corporation) with high power mercury-xenon light source set at 310 W (see Supporting Information, Figure S1 for the spectrum of the lamps used). The UV-Vis absorption spectra of RhB were checked every 10 min under irradiation to monitor the degradation of RhB. Similar procedures were carried out for MB except that the amount of MB used was different. Instead of 0.2 mL, 1.0 mL of aqueous MB (10 mg/L) solution was mixed with 3 mg of C-dots. As a result, only 3 mL of deionized water was used later to make the desired mixture solution for test (final concentration of MB, 2.5 mg/L). Same procedures as for RhB were carried out to study and monitor the photocatalyzed degradation of MB by C-dots under light irradiation.