Growth of ZnO films via spray pyrolysis deposition route for methylene blue photodegradation
Growth and photodegradation acitvity of zinc oxide films deposited via spray pyrolysis were investigated. Raman spectroscopy of the samples displayed the phonon modes with E2(high) at 437cm-1 as the most prominent mode confirming wurtzite structure of ZnO. The vibration due to E1(LO) mode indicated that the sample grown at 250°C had exhibited a presence of defects in the film. Scanning electron microscopy images revealed that the films deposited at different substrate heating temperatures have distinct surface morphologies. The grain size and grain structures can determine the surface area to volume ratio which is important in the photocatalytic reaction. UV-visible spectroscopy have showed that the transmittance of the films at the visible region increased with growth temperature. The ZnO films have an onset of absorption at around 390-411 nm which can be related to its calculated band gap from 3.01-3.15 eV. The sample grown at a substrate temperature of 250°C exhibited the highest absorbance in the UV region among the grown ZnO films. It also performed the highest degradation of methylene blue solution with the highest degradation efficiency of 91% and the highest rate of degradation in one hour irradiation.