Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique (original) (raw)
Related papers
2019 16th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE)
Zinc oxide (ZnO) thin films were deposited on soda lime glass substrates by using the RF magnetron sputtering technique. The deposition process was carried out in a system initially evacuated at 7x10-5 torr and a working pressure of 10-3 torr in a pure argon atmosphere, at room temperature. A 2" diameter and ¼" thick ZnO target (99.999%) was used. A target-substrate distance of 10 cm, and a working power of 125 W were kept constant. The films were deposited at different thicknesses, 50 to 400 nm. The thickness, the optical, structural and morphological properties were analyzed by profilometry, UV-Vis spectrophotometry, x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Additionally, three ZnO thin films were used to analyze the photocatalytic performance by using an 1x10-5 molar aqueous methylene blue (MB) solution, under the irradiation of ultraviolet light with a wavelength of 232 nm, during 5 h. The degradation of MB was carried out by absorbance measurements in the range of 400 to 800 nm every 30 min. The ZnO films showed a wurtzite hexagonal structure with a preferential growth in the (002) planes and good homogeneity. The results obtained from the study of the degradation of methylene blue showed that the ZnO film with a thickness of 400 nm presented the best photocatalytic response.
Materials Science in Semiconductor Processing, 2014
The crystallographic phase, surface features and photocatalytic properties in the reaction of decolorization of Malachite Green dye over TiO 2 (0-100 mol%) doped ZnO films have been investigated. The films have been prepared by polymer modified spray pyrolysis. The crystallization degree and the size of the crystallites comprising the films have been found to be influenced by the TiO 2 content in the spraying solution. The undoped ZnO film has little porosity. The titania dopant causes formation of hexagonal nanorods on the ZnO surface. The increase in TiO 2 content results in enhancement of both size and crystallization degree of the nanorods. When the TiO 2 content is increased (i) the Zn2p, O1s and Ti2p peaks are shifted to lower binding energies, (ii) the atomic ratio of O L /Zn is decreased and (iii) the amount of adsorbed hydroxyl (OH À ) species is increased. All the TiO 2 doped ZnO films manifested higher photocatalytic activity than that of the undoped ZnO and TiO 2 samples. The films obtained from solutions with 50 mol% TiO 2 showed the fastest decoloration of the dye.
Morphological effect of ZnO nanoflakes and nanobars on the photocatalytic dye degradation
Catalysis Today, 2017
ZnO films with nanoflake and nanobar morphologies were obtained by spray pyrolysis by changing the precursor salt and without any structure-directing agents. Nanoflakes were obtained from zinc acetate while nanobars with zinc chloride. Both films presented ZnO hexagonal wurtzite structure, a transmittance above 80% and band gap of 3.2 eV. The photocatalytic activity of the films was evaluated by the degradation of methyl orange and indigo carmine dyes in different concentrations. The film with nanoflake morphology showed the best performance in discoloration (96%) and it achieved a 51% in mineralization. The film with nanobars attained only a 67% in discoloration whereas it failed to mineralize the dye solution. The principal factors involved in the best performance of the nanoflake films were the less defective surface in the ZnO structure that diminished the electron-hole recombination, allowing the generation of hydroxyl radicals in a sufficient amount. The nanoflake film showed also a high stability after 10 degradation cycles, indicating a promising material for photocatalytic water treatment.
Journal of Nanomaterials, 2008
Glass plate-supported nanostructure ZnO thin films were deposited by sol-gel spin coating. Films were preheated at275∘Cfor 10 minutes and annealed at 350, 450, and550∘Cfor 80 minutes. The ZnO thin films were transparent ca 80–90% in visible range and revealed that absorption edges at about 370 nm. Thec-axis orientation improves and the grain size increases which was indicated by an increase in intensity of the (002) peak at34.4∘in XRD corresponding to the hexagonal ZnO crystal. The photocatalytic degradation of X6G an anionic monoazo dye, in aqueous solutions, was investigated and the effects of some operational parameters such as the number of layer and reusability of ZnO nanostructure thin film were examined. The results showed that the five-layer coated glass surfaces have a very high photocatalytic performance.
The effect of oxygen pressure on structural, morphological and photocatalytic properties of ZnO nanostructured films deposited on glass substrates via RF magnetron sputtering was investigated. The structural, morphology and oxidation states of the films were investigated by x-ray diffraction, scanning electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy. UV–vis spectroscopy and photoluminescence spectroscopy were used to analyze the degradation and optical properties of ZnO thin films. The grown films showed wurtzite hexagonal crystalline nanostructures with a favored orientation along the direction of (0 0 2) lattice plane. The morphology images showed a hierarchical ZnO nanostructured films with various shapes from circulars to foils and even much more multifaceted circular shapes and triangular sheets-like shapes by varying the oxygen pressure. The foil type ZnO nanostructured films showed significant photocatalytic activity concerning the degradation of methyl orange, mainly due to their surface-tovolume ratio
tDoubly (Sn + F) doped zinc oxide (ZnO:Sn:F) thin films were deposited onto glass substrates using asimplified spray pyrolysis technique. The deposited films were annealed at 400◦C under two differentambiences (air and vacuum) for 2 h. The photocatalytic activity of these films was assessed through pho-tocatalytic decolorization kinetics of Methylene Blue (MB) dye and the decolorization efficiency of theannealed films was compared with that of their as-deposited counterpart. The photocatalytic studiesreveal that the ZnO:Sn:F films annealed under vacuum environment exhibits better photocatalytic effi-ciency when compared with both air annealed and as-deposited films. The SEM and TEM images depictthat the surface of each of the films has an overlayer comprising of nanobars formed on a bottom layer,having spherical grains. The studies show that the diameter of the nanobars plays crucial role in enhancingthe photocatalytic activity of the ZnO:Sn:F films. The structural, optical and electrical studies substantiatethe discussions on the photocatalytic ability of the deposited films.
Importance of precursor type in fabricating ZnO thin films for photocatalytic applications
Materials Science in Semiconductor Processing, 2018
Here, the importance of choosing an appropriate precursor with right molarity for the fabrication of zinc oxide (ZnO) films by spray pyrolysis for the photocatalytic application is reported. Films were grown on glass substrates by using three different zinc precursors such as zinc acetate, zinc chloride, and zinc acetylacetonate. The structural, morphological, and optical characterizations were performed on the ZnO films. A preferential orientation along (002) plane, crystallite size distribution in the range 21-59 nm, and the nanostructures such as nanothorns, hexagonal nanorods, hexagonal layers and elongated grains, were acquired from the characterization studies. Further, the photocatalytic activity was tested using indigo carmine dye, obtaining 100% of dye degradation using the ZnO thin films deposited with zinc acetate, whereas films from zinc chloride and zinc acetylacetonate precursors showed 20% and 10% of degradation respectively.
Thin ZnO films have been successfully prepared on glass substrates by the sol-gel method using two different solutions of zinc acetate with complexat- ing agent (monoethanolamine, MEA) or polymer additive (polyvinyl alcohol, PVA). The films have been characterised by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and UV-Vis spectroscopy. The films prepared by the complexating agent solution possess many sep- arate ganglia on the surface, while the polymer modified solutions lead to the formation of some ganglia aggregates. The films morphology has significant influence on the photocatalytic properties. The higher photocatalytic activity and the faster degradation of the organic dye (94% degree of conversion after 3 h under illumination) over the ZnO samples obtained from complexating agent solution could be attributed to the greater number of active sites on the surface, while the polymer solution leads to aggregation of the ganglia. This results in a lower pho...
Photocatalytic Performance of ZnO: Al Films under Different Light Sources
International Journal of Photoenergy, 2012
ZnO and Al doped ZnO films were produced by spray pyrolysis. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectroscopy, and photoluminescence. Their photocatalytic activity was evaluated by the decomposition of the methyl orange dye using different light sources: ultraviolet light, artificial white light, and direct sunlight. The films were also tested under darkness for comparison. The ZnO films were able to degrade the test pollutant under UV and sunlight in more than a 60% after 180 min of irradiation and a scarce degradation was obtained using white light. However, the Al doped ZnO films presented a very high degradation rate not only under UV and sunlight (100% degradation), but also under white light (90% degradation after the same irradiation time). An unexpected high degradation was also obtained in the dark, which indicates that a nonphotonic process is taking place parallel to the photocatalytic process. This can be du...