Red emissive carbon dots derived from raspberry leaves for enhanced photosynthesis in pea (Pisum sativum L.) seedlings.

Nanomaterials are emerging as promising regulators for boosting crop photosynthesis and plant growth in sustainable agriculture. Herein, red emissive carbon dots (R-CDs) were solvothermally synthesized using waste raspberry leaves as the biomass source. The obtained R-CDs display emission spectra that overlap well with the red-light absorption region of chlorophyll. Pot-cultivation assays on pea seedlings verified that R-CDs exert obvious concentration-dependent growth-promoting effects, with 0.75 mg mL-1 identified as the optimal concentration. At this concentration, seedlings root and shoot lengths, diameter, fresh weight and dry weight were increased considerably, alongside enhanced accumulation of carbohydrates and chlorophyll a/b. R-CDs remarkably boosted key photosynthetic indices (P n, G sw, q P, Φ PSII, and ETR), optimizing gas exchange and photoresponse to enhance photosynthetic efficiency. Structural characterizations identified eight-membered aromatic skeletons and abundant surface oxygen-containing groups in R-CDs. Theoretical simulations further confirmed the 1-2-COOH-3 site as the preferred binding site and reveal directional electron transfer (0.194e) from R-CDs to chlorophyll. This work realizes high-value reutilization of raspberry leaf residues and offers theoretical support for developing eco-friendly nano-agricultural materials.