Preparation of fluorescent carbon dots from mint leaves and its performance of photocatalytic degradation of organic dyes

The green fluorescent N-doped carbon dots (N-CDs) and (B ,N )-doped carbon dots (B ,N- CDs) were prepared from mint leaves by one-step hydrothermal method. The morphology structure, elementary composition,surface functional groups, and fluorescence properties of CDs were characterized by TEM, XRD,FT-IR,XPS, UV-Vis, and XRF. The results show that CDs are uniform in size and have hydrophilic groups such as -OH and -COOH on the surface. N-CDs and B,N-CDs are typical aromatic systems, with the maximum fluorescence emission peaks at 490 nm and 440 nm, respectively, exhibiting excitation light-dependent characteristics. After 120 min of simulated solar light, the degradation rate of methylene blue by N-CDs and B, N-CDs are 84 degrees 0 and 67 degrees 0. The capture experiment result shows that h+ ,<middle dot>O (-)(2) ,and e- are the main active substances produced by N-CDs, and h+ and <middle dot>O (-)(2) are the main active substances produced by B,N-CDs in the photocatalytic process. The type and intensity of reactive oxygen species are verified using electron spin resonance (ESR ) spectroscopy, and <middle dot>O (-)(2) is detected in both carbon dots. The photocatalytic process of N-CDs also produced more (1) O (2) than B, N-CDs, which resulted in a higher efficiency of N-CDs in photocatalytic degradation of MB than that of B, N-CDs.