Hydrothermal synthesis of <i>Ricinus communis s</i> eed extract-mediated CQDs and their applications as antimicrobial, antioxidant, anti-inflammatory, and photocatalytic agents

Abstract In recent times, carbon-based nanomaterials have garnered consideration for their monumental applications in diversified fields of science. Carbon quantum dots (CQDs) have received a lot of attention for their unusual features, which include strong luminescent properties, biological compatibility, and minimal toxicity. Using renewable resources to synthesize CQDs is an economical and environmentally beneficial method. The current research is the first to demonstrate the synthesis, characterization, and applications of Ricinus communis seed extract-mediated CQDs. GC-MS analysis of the seed extract unveiled the existence of 22 different compounds, which likely contributed towards hydrothermal conversion to CQDs. Color change and fluorescence served as preliminary indicators of CQD fabrication. Successful synthesis was substantiated by UV–vis spectrum (absorbance peaks at 220 and 245 nm), FTIR spectrum (functional groups like O–H, C–N, C–O–C, and C–H), zeta potential measurement (−13.62 ± 1.61 mV), XRD analysis (average particle size = 10.75 nm), EDX analysis (abundance of carbon and oxygen), and SEM (agglomeration of globular particles). The antibacterial activity of CQDs (the largest zone of 20 mm) was far superior to that of the crude extract, and CQDs manifested potential synergy with Gentamicin, in general. CQDs evinced excellent anti-oxidant activity by DPPH assay (IC 50 = 40 μl/ml) and reasonable anti-inflammatory activity by BSA method (IC 50 = 56 μl/ml). As photocatalysts, CQDs elicited higher degradation potentials for four dyes and one of the selected antibiotics than the control. The highest degradation rate (142 × 10 −4 min −1 ) was documented for methyl red. In conclusion, this research reported the first eco-friendly synthesis of CQDs from the seed extract of R . communis . The unique phytochemical composition of the seed extract highlighted the profitable pathway for the creation of novel carbon-based nanomaterials having remarkable biological and photocatalytic properties with potential applicability in biomedicine and environmental remediation.