The antibacterial efficacy of reduced graphene oxide (rGO) and rGO/ZnO composites produced through thermal pyrolysis method against various bacterial strains

Abstract Antibacterial agents are essential to maintain the health of living beings. The misuse and overuse of antibiotics have led to the development of resistance against antibiotics in microbes. To address this issue, efficient, cost-effective, and biocompatible alternatives for conventional antibiotics need to be developed. Reduced graphene oxide (rGO), ZnO, and their composite have been identified as being efficient in disinfecting bacterial strains. The synthesis of rGO, ZnO, and their composite is usually a multi-step, time-consuming process that uses harmful reagents and catalysts. In this study, we prepared rGO from sucrose and rGO/ZnO composite from sucrose and zinc acetate by a single-step heating process. The method is green, eco-friendly and only uses commonly available non-hazardous precursors for preparation. The characterisation techniques, XRD, XPS, FE-SEM, and HR-TEM, displayed the formation of rGO and ZnO in the samples. The antibacterial efficiency of the samples rGO, the composites ZG-10, ZG-40, ZG-60 and ZnO (ZG-100) were evaluated against Gram-positive and Gram-negative bacterial strains using the agar disc diffusion method. The samples showed remarkable bactericidal activity against all the tested bacterial strains, and their zone of inhibition was comparable to that of conventional antibiotics. Different samples are proven to be effective for different bacterial strains. The sample rGO was found to be more efficient in inhibiting Escherichia coli with a zone of inhibition of 19.5 mm, whereas the ZG-10 composite exhibited superior efficiency against Pseudomonas aeruginosa with a zone of inhibition of 20.5 mm. The sample ZG-100 showed high disinfection efficiency against Staphylococcus aureus and Salmonella enteritidis with zones of inhibition of 22.8 and 23 mm, respectively. The minimum inhibitory concentration and cytotoxicity of the samples were also tested. From the analysis, the tested samples demonstrate strong antibacterial efficacy and less cytotoxicity, positioning them as a promising material for biomedical applications.