Carbon dots synthesized from cabbage and nettle: characterization and biological activity

Biomass waste derived from food processing poses environmental problems. Cabbage and nettle are valuable biomass sources having natural heteroatoms (S, N) in their structures. In this study, cabbage and nettle biomass waste were used as precursors in the synthesis of S- and N-doped carbon dots (CDs). The effects of synthesized carbon dots (CNCDs) on seed germination, seedling development and fluorescent emission behavior in response to heavy metals (Cr⁶⁺, Pb²⁺, Sn⁴⁺, Zn²⁺) have been studied. It was expected that CNCDs modified with heteroatoms from their precursors would increase germination and contribute to plant growth because of their large surface areas. The seeds were primed with CNCDs at different concentrations (0, 0.05, 0.1, 0.2, 0.5, 1 and 2 mg mL^-1) for 18 h. To assess the effect of priming on the seeds, scanning electron microscopy, thermogravimetric analysis, energy-dispersive X-ray analysis and contact angle measurements were performed. The effects of CD concentrations on root and shoot length and mass, as well as chlorophyll (chl) and carbohydrate content in leaves, were investigated. Antioxidant activity, antibacterial activity, biological oxygen demand (BOD) and chemical oxygen demand (COD) were investigated.

CNCDs deformed the hydrophobic layer on the seed surface, creating cracks. Seeds prepared with CNCDs at concentration of 0.1 mg mL^-1 germinated faster and had better root and shoot lengths compared to other CNCD concentrations. The greatest fluorescence quenching in CNCDs occurred for Cr⁶⁺. The synthesized CNCDs showed excellent antioxidant and antibacterial activities. BOD and COD to be of 21 ± 1 mg L^-1 and 30 ± 1 mg L^-1, respectively.

Based on these results, priming CNCDs at appropriate concentrations positively affects seed germination rates, root and shoot development. CDs doped with heteroatoms, at the appropriate concentration, can be considered as an alternative to traditional chemical fertilizers. The effects of CNCDs on plant growth require further investigation from various perspectives. © 2026 Society of Chemical Industry.