Endophytic fungus-assisted biosynthesis, characterization and solar photocatalytic activity evaluation of nitrogen-doped Co3O4 nanoparticles

Modified Co3O4 nanoparticles, especially Nitrogen-doped Co3O4 nanoparticles (N-Co3O4 NPs) come to limelight for exhibiting enhanced activity in the fields of biotechnology, advanced materials and catalysis. Currently, Co3O4 NPs are being used as antimicrobial and anticancerous agents, and in catalysis. These properties can be enhanced further with the help of N-Co3O4 NPs. Reported chemical method for N-Co3O4/C nanocube formation requires high temperature and corrosive ammonia gas. To synthesize water dispersible, highly stable N-Co3O4 NPs at room temperature, we screened a range of endophytic fungi. Out of several endophytic fungi screened, only Fusarium oxysporum showed positive result. During the present study, N-Co3O4 NPs were synthesized in ambient temperature by using a facile bio-inspired top-down approach based on endophytic fungus Fusarium oxysporum, and their photocatalytic activity was investigated by the degradation of methylene blue (MB) dye. The shape, size and crystallinity of N-Co3O4 NPs were confirmed by TEM, HRTEM and XRD whereas XPS, FTIR and cyclic voltammetry (CV) were performed for the conformation of nitrogen doping. The biosynthesized N-Co3O4 NPs with average size 25 nm exhibit good photocatalytic activity and degraded 87% MB within 120 min under sunlight irradiation at temperature 32 ± 1 °C. The photo-oxidation, absorbance and band gap of N-Co3O4 NPs were determined by the UV–Vis–NIR spectrophotometry. Thermal properties and enthalpy changes were also investigated by TGA/DSC and the decomposition of synthesized NPs was observed at 700 °C.