Carbon dots as light converter for plant photosynthesis: Augmenting light coverage and quantum yield effect

Carbon dots (CDs) with gradient-changed quantum yield (QY) were prepared by regulating the graphitic N and hydroxyl group contents. Then, the QY effect of CDs on plant photosynthesis was studied using chloroplasts and rice plants. After incubation for 2 h in the dark, CDs entered into the chloroplasts and converted ultraviolet radiation to photosynthetically active radiation. By this mechanism, CD1:0.2 (300 μg·mL−1) with a moderate QY of 46.42% significantly increased the photosynthetic activity of chloroplast (200 μg·mL−1) to reduce DCPIP and ferricyanide by 43.77% and 25.45%, respectively. After spraying on rice seedlings, CD1:0.2 (300 μg·mL−1) was evenly distributed in the leaves and resulted in maximum increases in the electron transport rate and photosynthetic efficiency of photosystem II by 29.81% and 29.88%, respectively. Furthermore, CD1:0.2 significantly increased the chlorophyll content and RuBisCO carboxylase activity of rice by 64.53% and 23.39%, respectively. Consequently, significant increases were observed in the growth of CD1:0.2-treated rice, including 18.99%, 64.31%, and 61.79% increases in shoot length, dry weights of shoot and root. These findings contribute to the exploitation of solar energy and agricultural production using CDs in the future. As an artificial light convertor, carbon dots with a quantum yield of 46.42% can promote plant growth by improving photosynthesis. [Display omitted] •Carbon dots (CDs) with gradient-tunable quantum yield (QY) were prepared.•The surface graphite N and hydroxyl group determine the changed QYs of the CDs.•CDs in chloroplasts could convert UV into the light coverage of photosynthesis.•CDs with QY of 46.42% showed the best promotion to plant photosynthesis.•The enhanced photosynthesis by the CDs significantly increased the rice growth.