Eco-Friendly Reduction of Graphene Oxide via Satureja calamintha L. Butanolic Fraction: Structural Characterization and Antioxidant Functionality

Abstract In this study, we report a one-step green reduction of graphene oxide using the butanolic fraction of Satureja calamintha L. extract, obtained via methanol/water extraction, which serves as an efficient natural reducing agent. This fraction is particularly rich in bioactive compounds, exhibiting high total phenolic content (51.6 mg GAE/g extract) and flavonoid content (17.3 mg QE/g extract). The successful transformation of graphene oxide (GO) into plant-reduced graphene oxide (Sc-rGO) was comprehensively confirmed by FTIR, XRD, SEM, XPS, and Raman spectroscopy analyses. In addition, the antioxidant activity of the obtained materials was evaluated using the DPPH radical scavenging assay. The results demonstrated a marked enhancement in antioxidant capacity following reduction, as evidenced by a decrease in IC50 values from 103.4 µg/mL for GO to 87.6 µg/mL for Sc-rGO. In parallel, XPS analysis revealed a significant increase in the carbon-to-oxygen (C/O) ratio, rising from 1.80 in GO to 3.07 following reduction, indicating the effective removal of oxygen-containing functional groups. This elevated C/O ratio reflects the partial restoration of the conjugated sp² carbon network, which likely underpins the enhanced radical scavenging activity of Sc-rGO. These findings highlight its promising potential for applications in green nanotechnology and biomedicine.