Characterization of green-synthesized reduced graphene oxide nanosheets for structural, morphological, and biological properties

Two-dimensional graphene derivatives exhibit excellent biocompatibility, structural robustness, and chemical stability, making them promising candidates for biomedical applications. This study presents a sustainable, phytochemical-assisted green approach for the synthesis of reduced graphene oxide (rGO) using Nigella sativa seed (NSS) extract as a natural reducing and stabilizing agent. Comprehensive characterization using XRD, FTIR, TEM, SEM, EDS, XPS, and DLS confirmed the successful reduction of graphene oxide. XRD analysis revealed a broad diffraction peak at 2θ ≈ 25°, corresponding to the (002) plane of graphitic carbon, while FTIR spectra showed substantial removal of oxygen-containing functional groups with residual biomolecular signatures originating from NSS extract. Electron microscopy demonstrated transparent, crumpled, and wrinkled nanosheets, and EDS analysis confirmed high carbon purity (98.85%). XPS further validated effective deoxygenation and restoration of sp²-hybridized carbon networks. DLS measurements indicated a multimodal size distribution with moderate colloidal stability (ζ = +17 ± 6.58 mV). Biologically, the NSS- rGO exhibited strong antibacterial activity against Bacillus subtilis, Escherichia coli, and Candida albicans. Additionally, MTT assays revealed dose-dependent anticancer activity against MCF-7 and HCT-116 cell lines, with IC₅₀ values of 3.125 and 1.56 mg/mL, respectively. These results highlight the potential of NSS-rGO as a sustainable and effective material for biomedical applications. KEY WORDS: rGO, Nanosheets, Phytochemical synthesis, NSS, Antibacterial, Anticancer Bull. Chem. Soc. Ethiop. 2027, 41(1), 133-147. DOI: https://dx.doi.org/10.4314/bcse.v41i1.10