Photocatalytic
ZnO thin films have been deposited onto glass substrate by spray pyrolysis
technique. The sprayed solution consists of 0.1 M of zinc acetate dihydrate dissolved in double distilled water and sprays onto ultrasonically cleaned glass substrates
maintained at 350°C, through an air-atomizing nozzle. The X-ray diffraction
(XRD), scanning electron microscopy (SEM), EDX and UV-VIS spectrophotometer
were applied to describe the structural, morphological, compositional and
optical properties of ZnO catalyst. XRD analysis confirms that the films were
found to be single phase hexagonal wurtzite structure. The SEM micrograph of
the films is shown highly uniform, crack free and found to be
fiber like structures. The optical transmittance spectra of the ZnO thin films
were found to be transparent to visible light and the average optical transmittance
was greater than 85%. The direct optical band gap energy values of the films
shift towards the lower energy as a consequence of the thermal annealing. The
Urbach energy of the films was found to increase with annealing temperature.
The refractive index of the films was calculated and the refractive index
dispersion curve of the films obeys the single oscillator model. The values of
oscillatory energy Eo,
dispersion energy Ed, and static dielectric constant εs for the ZnO thin films were determined. The films were evaluated for their
ability to degrade methylene blue. The Langmuir-Hinshelwood
kinetic model was used to interpret quantitatively the observed kinetic
experimental result. The photocatalytic activity of ZnO thin films was enhanced
by annealing temperature.
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