Solar energy driven photo catalytic action and antimicrobial activities of Iron oxide nanoparticles

Every year loss of crop yield (at least 20–40%) occurs by pathogenic infections that leads to loss of billions of dollars worldwide. Usage of antibiotics are limited in numerous countries for controlling bacterial diseases / infections in agricultural field. Therefore, alternative protocol is necessary to combat with microbial pathogens and to overcome the requirement to suppress use of conventional antibiotics in plant production. Nanoparticles (NPs) having antimicrobial properties can have potential to combat the bacteria and can protect the plant / crop production. Moreover, such NPs may also have potential to suppress the plant pathogens. Sol-gel method is used for synthesis of iron oxide NPs with variation in pH (1, 2, 3, 4, 5, 6, 7, 8 and 9). Magnetic field annealing (MFA) of NPs at different temperatures (200 and 300 °C) is done. 300 °C MFA samples show efficient results. X-ray Diffraction (XRD) results show magnetite phase (at pH 1, 2 and 6), mixed phases (i.e. hematite and maghemite) at pH 3–5, maghemite phase (at pH 7-8) and hematite phase (at pH 9) of iron oxide. Scanning Electron Microscopy (SEM) analysis shows particle size of ~50 nm for MFA iron oxide NPs (at pH 6). Raman spectroscopy results show the formation of iron oxide NPs. Furthermore, 300 °C MFA magnetite nanoparticles (at pH 6) proved to be potential candidate against bacteria (E. coli with inhibition zone ~31 mm) and against methylene blue with enhanced photo catalytic action. In-vitro activity of magnetite NPs expressively inhibited the growth of Fusarium oxysporum after 3^rd and 7^th day of incubation in a dose-dependent way. In-vivo studies also exhibited improved plant growth parameters after treatment with different concentrations of magnetite NPs. This work suggests that iron oxide NPs can be used in agricultural sector for protection of plant.