Commercial Wheat and Oat Flour Derived Fluorescent Carbon Quantum Dots through Sustainable Hydrothermal Synthesis and Their Biological Activities

In this study, we utilized processed edible commercial wheat and oat flours to synthesize highly fluorescent carbon dots using green hydrothermal synthesis. The as-synthesized carbon quantum dots (CQDs) were characterized using UV-vis spectrophotometry, photoluminescence spectrophotometry, high-resolution transmission electron microscopy, and Fourier transform infrared spectroscopy. The synthesized wheat-CQDs (W-CQDs) and oat-CQDs (O-CQDs) had monodispersed spherical shapes with average sizes of 3–8 and 5–10 nm, respectively, and exhibited strong fluorescence intensity and excitation-dependent photoluminescence. The W-CQDs and O-CQDs were highly dispersed in aqueous solutions and exhibited bright green and blue fluorescence, respectively, under UV light (λ_ex=380 and 370 nm). Both CQDs contained abundant functional groups, including amino, hydroxyl, and carboxyl groups, which may play a major role in biological applications. The W-CQDs and O-CQDs showed good free-radical scavenging capacity in the 2,2-diphenylpicrylhydrazyl (DPPH) and H₂O₂ assays. The anti-inflammatory activities of W-CQDs and O-CQDs were more effective than that of the standard, with EC₅₀ values of 1.8 and 1.3 mg/mL, respectively, in the protein denaturation assay. Additionally, the CQDs exhibited low cytotoxicity toward NIH3T3 fibroblast and human HeLa cervical cancer cells when treated with a 5-mg/mL concentration. Therefore, green-synthesized W-CQDs and O-CQDs are easily available, less cytotoxic, and applicable to therapeutic and cell nanocarrier purposes.