Synergistic effects of nitrogen-doped carbon dots on pepper and lettuce growth via irrigation enhancement

Nitrogen-doped carbon dots (NCDs) with an average diameter of 3.25 nm were prepared by a hydrothermal process from betel leaves as a single source of carbon and nitrogen. FTIR analysis attested to the presence of amine, carbonyl, and hydroxyl groups in the NCD surface. The obtained aqueous solutions were applied to enhance the growth of pepper and lettuce plants in a greenhouse and a growing room, respectively. The growth of these two plants was observed and analyzed at different stages, indicating significantly higher fresh and dry weights of roots and peppers, compared to the control. The healthy growth results from hydrophilic groups on the surface of the CDs, and the hydroxyl and carbonyl groups provide abundant binding sites for water molecules, which penetrate the plant along with NCDs. It promotes the absorption and utilization of water and nutrients via ROS, which leads to improved nitrogen fixation. The supply of carbon dots stimulates and enhances the growth of both lettuce and pepper, illustrating the benefit of NCDs with minimal cytotoxicity in the enhanced production of other plants.