D-Mannose-derived carbon dots and their application to plant growth

This study aimed to investigate the application potential of carbon dots (CDs) synthesized with D-mannose as a carbon source precursor and its nitrogen-doped derivatives (GCDs and GLCDs) in plant growth. GCDs and GLCDs were successfully synthesized using hydrothermal methods, and their morphology, structure, and optical properties were detailed. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) showed that the prepared CDs had uniform spherical nanostructures with particle sizes of 2.63 nm and 1.22 nm, respectively. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analysis revealed that the surface of CDs was rich in functional groups, such as hydroxyl, carbonyl, and nitrogen functional groups introduced by nitrogen doping. Ultraviolet–visible absorption spectroscopy and fluorescence spectra showed that GCDs and GLCDs had high quantum yields of 2.39 % and 6.60 %, respectively. In plant growth experiments, GCDs and GLCDs significantly affected the growth of mung bean sprouts, especially at a concentration of 0.08 mg/mL. The increase in chlorophyll content suggests that CDs may promote plant growth by increasing the efficiency of photosynthesis. The results show that D-mannose-derived carbon dots have great potential for application as a new type of plant growth regulator.