Novel microbial synthesis of rGO nanosheets for effective photocatalytic remediation of Acid Blue 113 dye, improved seed germination, antimicrobial and antioxidant applications

•Isolation of Bacillus cabrialesii RIRD-SK from Lonar lake, Maharashtra.•Bacterial synthesis rGO nanosheets (NS).•Biophysical characterization of rGO NS.•Biosynthesized rGO NS enhanced photocatalysis of Acid Blue 113 dye 90.10 % decolourization and degradation within 45 min, degraded dye product analysis and proposed degradation pathway. Phytotoxicity studies of degraded products show enhanced growth rate of the test seeds.•rGO NS exhibited excellent antibacterial and antioxidant activity. We report for the first time reduction of graphene oxide (GO) nanosheets (NS) by an isolated bacterium from Lonar lake Bacillus cabrialesii RIRD-SK (MCC 4670). Facile, rapid, ecofriendly, and cost-effective biological approach makes it advantageous over physical and chemical methods. Isolated bacterial strain is deposited in Gene Bank accession number MMZ151886. The physiochemical characterization of rGO NS revealed formation of dark black precipitate within 8 h. UV–Visible spectra of rGO shows absorption peak mainly at 269 nm. Fourier-transform infrared spectroscopy (FTIR) revealed presence of functional biomolecules involved in capping and stabilization of NS. X- ray diffraction (XRD) pattern of rGO confirms pure crystal structure. Scanning electron microscopy (SEM) of rGO showed ultrathin graphene NS morphology having thickness less than 3.5 nm. The elemental composition of graphene oxide (GO) and rGO was studied by energy dispersive spectroscopy (EDS) confirms bacterial reduction GO. Specific surface area rGO about 139.53 m2/g was measured by Brunauer-Emmett-Teller (BET) technique. Raman spectroscopy indicates decrease oxygen containing functional group after bacterial reduction with unique fingerprint of material. The rGO NS showed 90.10 % degradation of Acid Blue 113 diazo dye within 45 min. Bioremediation was confirmed with the help of UV–Visible spectroscopy, thin layer chromatography (TLC), FTIR, High-performance liquid chromatography (HPLC) and Liquid chromatography mass spectroscopy (LCMS). Reduced toxicity of the degraded products was observed by the phytotoxicity experiment. A mechanistic degradation pathway has been proposed. rGO NS also exhibit good antimicrobial and antioxidant properties emphasizing its role in biomedical field.