Physical properties of nanostructured Mn3O4 thin films synthesized by SILAR method at room temperature for antibacterial application

Nanocrystalline Mn3O4 thin films of thickness 63, 99 and 141 nm were synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrates at room temperature using MnCl2.4H2O and NaOH as cationic and anionic precursors. The grazing incidence X-ray diffraction measurements confirmed that as grown Mn3O4 films are orthorhombic in nature. The FESEM and AFM analysis shows that Mn3O4 films are nanocrystalline in nature with porous morphology. The optical absorption measurements showed that Mn3O4 exhibit direct optical band gap energy that changes from 2.70 to 2.86 eV depending on crystallite size. The electrical resistivity and thermo-emf measurements confirmed that SILAR grown Mn3O4 films are semiconducting in nature with p-type conductivity. The antibacterial efficiency of films against Escherichia coli increases from 18.64% to 94.91% as crystallite size of Mn3O4 increases.