Biosynthesis of hematite (α-Fe2O3) nanostructures: Size effects on applications in thermal conductivity, catalysis, and antibacterial activity

Abstract Hematite nanoparticles, being stable and comparatively less toxic, have remarkable contributions in biomedical as well as other interdisciplinary fields of research. A facile, efficient and environmentally-friendly protocol has been developed for the synthesis of hematite nanoparticles exploiting the reducing and capping potential of the aqueous leaf extract of Anacardium occidentale . Nanoparticles of different sizes obtained by optimizing the precursor to extract ratio have been investigated for their size-dependent catalytic, nanofluid and antibacterial activities. The nanoparticles have been characterized by XRD, TEM, SEM, EDX, UV-visible, Raman and FTIR techniques. The XRD, UV–visible, FTIR and Raman spectral analysis demonstrated the formation of pure hematite nanoparticles. Thermal analysis of the as synthesized product has been carried out to determine the proper annealing temperature. Magnetic hysteresis measurement carried out using Vibrating Sample Magnetometer shows weak ferromagnetism at room temperature. The biosynthesized nanoparticles could effectively degrade hazardous pollutants including methyl red and eosin yellowish within a short span. The synthesized nanoparticles have also been found to enhance thermal conductivity of conventional base fluids; water and ethylene glycol at room temperature. Dose dependent antibacterial activity of the nanoparticles against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus have been depicted through agar-well diffusion method.