Different Kinds of Citric Acid Based Carbon Dots and Their Enhancement of the Growth of Italian Lettuce

Herein, we synthesized different kinds of citric acid based CDs from low-cost citric acid and used them for culturing Italian lettuce. Since they all used citric acid as a precursor, some similarities were observed in terms of optical properties, morphologies, and chemical compositions. In comparison to the control group, they were able to increase the fresh weight of lettuce by 25.53% (CA-CDs), 33.25% (EDA-CDs), and 39.5% (Mg,N-CDs) respectively. Moreover, the three CDs can enhance the nutrient qualities of lettuce. After evaluating the promotion effect of three kinds of CDs on the growth and nutritional qualities of lettuce, we found that the promotion effect of Mg,N-CDs was the best among the three. The results of PAM chlorophyll fluorescence imaging indicate that Mg,N-CDs can promote photosynthesis, thereby increasing weight and accumulating nutrients. This work provides guidance for designing CDs for agricultural production.