Physicochemical and antibacterial characterization of Aspergillus sp. filtrate-reduced graphene oxide

Abstract Graphene-based nanomaterials are rapidly emerging as antimicrobial agents against a range of pathogenic microorganisms. In the present study, we have demonstrated the synthesis of reduced graphene oxide (RGO) using Aspergillus sp. filtrate as a reducing agent. The obtained Aspergillus sp. filtrate-RGO (AF-RGO) was characterized by ultraviolet–visible absorption spectroscopy, dynamic light scattering, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and atomic force spectroscopy to obtain details about the size, composition, structure, and morphology. The characterization confirmed the reduction of graphene oxide, the restoration of sp2 conjugation, and the formation of few-layered RGO sheets. The surface charge and stability of the AF-RGO in aqueous media were examined by zeta potential measurements. The thermal stability of AF-RGO was increased significantly due to the restoration of the graphitic sp2 network. The antibacterial activity of AF-RGO was evaluated using the agar well diffusion method, broth microdilution method, and Live/Dead bacterial viability assay. AF-RGO exhibited good antibacterial activities against pathogenic Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 15 and 30 mg/ml, respectively. Therefore, fungal filtrate-mediated synthesis of RGO is a promising antibacterial carbon nanomaterial for a range of biomedical and nano(bio)technological applications.