SYNTHESIS AND CHARACTERIZATION OF Fe–ZnO THIN FILMS FOR ANTIMICROBIAL ACTIVITY

Abstract

Pure and Fe-doped zinc oxide (ZnO) sol–gel thin films were deposited by spin-coating process. Pure ZnO and Fe–ZnO films, containing Fe of 2–8[Formula: see text]wt.%, were annealed at 500∘C for 2[Formula: see text]h. All prepared thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–visible (UV–vis) spectroscopy. XRD studies show the polycrystalline nature with hexagonal wurtzite structure of pure ZnO and Fe–ZnO thin films. The crystallite size of the prepared samples reduced with increasing Fe doping concentrations. AFM and SEM results indicated that the average grain size decreased as Fe doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300[Formula: see text]nm to 1000[Formula: see text]nm. The films produced yielded high transmission at visible regions. The optical bandgap energy of spin-coated films also decreased as Fe doping concentration increased. In particular, their optical bandgap energies were 3.75, 3.6, 3.5, 3.45 and 3.3 eV at 0-, 2-, 4-, 6- and 8-wt.% Fe concentrations, respectively. Antibacterial activities of pure ZnO and Fe–ZnO against E. coli and S. aureus were evaluated by international recognized test (JIS Z 2801). The results showed that pure and Fe-doped ZnO thin films have antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed be more resistant to pure and Fe-doped ZnO thin films than gram-negative bacteria. The test shows an incremental increase in antibacterial activity of the thin films when dopant ratio increased under UV light.