Development of N-doped carbon dots from citronella grass solid waste as a potential bioimaging and phototherapeutic agent

Nitrogen-doped carbon dots (N-CCDs) were synthesized from citronella grass solid waste via a rapid microwave-assisted method using EDTA as a nitrogen source. The resulting N-CCDs were water-dispersible and photostable nanoparticles with an average size of ∼9 nm and a photoluminescence quantum yield of 41.83 ± 1.72% (n = 3). Structural and surface analyses confirmed effective nitrogen incorporation and abundant surface functional groups. The N-CCDs exhibited low intrinsic cytotoxicity toward HeLa and MCF-7 cells under dark conditions, while showing significant dose-dependent cytotoxicity upon blue-light irradiation, indicating photodynamic-like activity. The IC 50 values under irradiation were >200 μg/mL for HeLa cells and ∼62.41 μg/mL for MCF-7 cells. Confocal microscopy revealed efficient cellular uptake and preferential localization in cytoplasmic lipid-rich regions, with exclusion from the nucleus. These findings demonstrate the potential of citronella-derived N-CCDs as sustainable, light-responsive nanomaterials for combined bioimaging and phototherapeutic applications.