Light-nutrition coupling effect of degradable fluorescent carbon dots on lettuce

The increasing application of carbon dots (CDs) inevitably leads to environmental leakage. To be environmentally friendly, degradable CDs will become a mainstream agricultural application in the future. We prepared three CDs with different functional groups. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis showed that -C&z.dbd;C-H and C&z.dbd;O groups on the CD surfaces are major sites for oxidative degradation of the CDs. The pyridine N is responsible for photoproduction of &z.rad;OH and &z.rad;O 2 − , which will self-induce degradation. By liquid chromatography-mass spectrometry (LC-MS) method, the routes for N-doped CDs degrading into carboxylic acid compounds, CO 2 , NH 4 + , and H 2 O are clearly illustrated. After spraying fluorescent CDs on lettuce leaves, only the group of lettuce that combined the light conversion function of N3-CDs and the final degradation products of N3-CDs exhibited a significant enhancement of the net photosynthesis rate by 1.13 times, acceleration of the ETR by 1.19 times, and improved expression of genes related to CO 2 fixation in the C 4 cycle and carbon assimilation in the C 3 cycle. Degradable fluorescent N-doped CDs are oxidized and degraded into substances that can be used for lettuce growth. Their excellent light conversion characteristics promote the utilization of the CD degradation products by lettuce.