The promotion effect of carbon quantum dots derived from maize stalks on the photosynthesis of maize growth.

This study described the preparation of water-soluble carbon quantum dots (CQDs) from maize stalks via a hydrothermal method at 200 °C for 10 h. The prepared CQDs exhibited an average particle size of 2.03 nm with a graphene structure, and the surfaces contained hydroxyl and carboxyl functional groups. For the aqueous solution of CQDs at a concentration of 100 mg/L, the optimal excitation wavelength was 410 nm, and the maximum emission wavelength was 495 nm. By utilizing the down-conversion luminescence properties of CQDs to enhance photosynthesis in maize growth, it was found that the optimal CQD concentration was 25 mg/L when maize seedlings were sprayed with CQDs at different concentrations for 7 days. The maize plant height, leaf area, leaf length, leaf circumference, chlorophyll content, Hill reaction activity, total photosynthetic rate, and net photosynthetic rate significantly increased by 43.2%, 25.6%, 31.2%, 27.3%, 35.2%, 45.5%, 29.8% and 46.6% compared with the CK, respectively. This work developed and demonstrated a feasible strategy for synthesizing cost-effective CQDs and may offer a potential benefit for early-stage corn seedling growth under controlled conditions.