Titanium dioxide thin films: the effect of the preparation method in their photocatalytic properties (original) (raw)
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Journal of Physics: Conference Series, 2014
TiO 2 thin films were deposited by reactive DC-magnetron sputtering at different Ar/O 2 ratios in the gas mixture. The photocatalytic activity (under UV light irradiation) of these films was evaluated upon degradation of aqueous solutions of methylene blue (MB), a model organic pollutant. Upon photocatalysis, the TiO 2 films showed structural, morphological and compositional changes that were characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and energy dispersive X-ray (EDX).
A short review is presented on the authors, investigations on the influence of the crystal structure and the morphology on the sorption ability and photocatalytic activity under UV-irradiation of thin TiO2 films produced by spray-deposition process. Commercially available TiO2 (Degussa P25 and Tronox), titania modified by mechanoactivation as well as TiO2 doped with gold and, mainly, with lanthanides (produced by sol–gel process or from mixed-metal citric complexes) are used as starting materials. Organic dyes, phenol, oxalic acid and pesticides were used as model pollutant. Conclusions are drawn for the effect on the photocatalytic activity of films morphology, anatase content, substrate chemical nature, deposition conditions (temperatures of deposition and post-deposition annealing, suspension medium nature, additives presented and its ultrasonic treatment), type of titania used and its modifi- cation by mechanochemical treatment and by doping with gold or lanthanides (lanthanum, gadolinium and neodymium).
Journal of Physics: Conference Series, 2012
Thin nano-sized TiO 2 films were deposited on aluminum foil substrates by the spray pyrolysis method, using Ti(i-OPr) 4 (TIP) and TiCl 4 (TC) as precursors. The films were characterized by means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). According to the XRD patterns the as-deposited films appear to be amorphous. The thermal treatment at 400 o C leads to the formation of anatase nano-crystallites. The XPS analyses showed that the Ti2p broad photoelectron peak of as-deposited TC films indicated a mixture of Ti 3+ and Ti 4+ oxidation states. After treatment at 400 o C the Ti2p peak displays only Ti 4+ oxidation state for both TIP and TC films. The number of hydroxyl groups on the surface is decreased after the thermal treatment. The photocatalytic activity of the films was studied towards degradation of azo dye Reactive Black 5 (RB5) as model wastewater pollutant under visible light illumination. It was found out that the films obtained from TC were more active than those obtained from TIP films. The thermally treated samples are better photocatalysts than those non-treated, because they posses anatase crystalline phase and stoichiometric TiO 2 . The TOC measurements showed minimal concentration of total organic carbon in the dye solution after 180 min of visible light irradiation.
Thin Solid Films, 2006
Titanium dioxide (TiO 2 ) thin films were prepared using Titanium [bis(dipiraloymethanate) diisopropoxide] (Ti(dpm) 2 (OPr i ) 2 ) and Titanium isopropoxide (Ti(OPr i ) 4 ) complex compound precursors by Chemical Vapour Deposition (CVD) and photo-assisted CVD. Structural information on TiO 2 thin films was obtained in synchrotron radiation experiments: high-resolution Grazing Incidence X-ray Diffraction (GIXRD) and h -2h XRD experiments were performed on the high-resolution powder diffractometer at the Hamburg Synchrotron Laboratory. Chemical composition of thin films was studied by high-resolution Laser Ionization Mass Spectrometry technique, surface composition by X-ray Photoelectron Spectroscopy, and surface morphology by Atomic Force Microscopy. Photocatalytic activity of TiO 2 thin films was studied using a photocatalytic reactor. The fungicide Fenarimol was chosen as chemical indicator and its degradation kinetics was followed by High Performance Liquid Chromatography. D
Photocatalytic TiO2 thin film deposited onto glass by DC magnetron sputtering
Thin Solid Films, 2001
A high performance photocatalytic TiO thin film was successfully obtained by reactive DC magnetron sputtering. The film was 2 deposited onto SiO-coated glass at a substrate temperature of 220ЊC using a titanium metal target in O 100% atmosphere. The 2 2 film showed good uniformity of thickness in a large area with the optical transmittance of ; 80% in the visible region. The Ž. decomposition ability of acetaldehyde CH CHO of the film under UV irradiation was almost the same as that of the 3 sol᎐gel-derived TiO thin film but the sputtered film showed a much higher mechanical durability. The characterization of the 2 films was carried out using XRD, SEM, AFM, XPS and SIMS, and the electronic structures of the films were calculated using a first-principle calculation method based on the density functional theory. It was found that the amount of incorporated 18 O into the film was larger for the films with lower photocatalytic activity when the films were annealed in 18 O rN atmosphere. This 2 2 result indicates that the amount of oxygen vacancies, which were occupied by incorporated 18 O, was larger for the films with lower photocatalytic activity. Furthermore, the introduction of structural defects associated with oxygen vacancies was found to create some energy levels around the mid-gap, indicating that they could work as recombination centers of photo-induced holes and electrons, causing the decrease in photocatalytic activity. Therefore, the decrease in the structural defects associated with oxygen vacancies is important for improving the photocatalytic activity of the films.
Photocatalytic activity of sprayed TiO2 films deposited on different substrates
Thin photocatalytically active TiO2 fi lms are successfully deposited on glass and alumina foil substrates by spray pyrolysis method. The films are characterized by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Thermal Analyses (TG-DTA). The XRD spectra of TiO2 thin fi lms, treated at 400◦C showed formation of nanosize anatase phase. The fi lms were studied with respect to the photo-initiated bleaching of azo dye Reactive Black 5 (RB5) under UV illumination. The influence of the substrate, treatment conditions and pH of the dye solution on the decoloration were investigated. It was found that the films, deposited on alumina foil revealed a better photocatalytic activity than those on glass substrates, due to the furrowed surface of the alumina substrate. The highest rate of decoloration was obtained at low pH value of the dye solution for fi lms treated at 400◦C.
Nanostructured low crystallized titanium dioxide thin films with good photocatalytic activity
Powder Technology, 2010
Transparent TiO2 thin films were deposited on soda lime glass at different substrate temperatures by a simple and reproducible spray pyrolysis technique from aqueous peroxo-polytitanic acid. Both the as-prepared and annealed films (3 h thermal treatment in air at 500 °C) were characterized by AFM, SEM, TEM, XRD, FT-IR and UV–visible spectroscopy. The as-prepared films present predominant low crystallized structure, low porosity, high surface roughness and grain agglomerates while the annealed films exhibit slightly better polycrystalline structure of brookite phase. The as-deposited TiO2 films prepared at low substrate temperatures (280 °C) show the best photocatalytic activity, against methylene-blue, due principally to their small grain size and high surface area.In this work, transparent and low crystallized TiO2 thin films were deposited on soda lime glass at different substrate temperature by spray pyrolysis technique from aqueous peroxo-polytitanic acid. The as-prepared films (at 280 °C substrate temperature) have exhibited good photocatalytic activity against aqueous methylene-blue solution. TiO2 particle size measured by TEM for this material was around 7 nm.
Influence of the structural and surface properties on photocatalytic activity of TiO2:Nd thin films
Polish Journal of Chemical Technology, 2015
Titanium dioxide thin films doped with the same amount of neodymium were prepared using two different magnetron sputtering methods. Thin films of anatase structure were deposited with the aid of Low Pressure Hot Target Magnetron Sputtering, while rutile coatings were manufactured using High Energy Reactive Magnetron Sputtering process. The thin films composition was determined by energy dispersive spectroscopy and the amount of the dopant was equal to 1 at. %. Structural properties were evaluated using transmission electron microscopy and revealed that anatase films had fibrous structure, while rutile had densely packed columnar structure. Atomic force microscopy investigations showed that the surface of both films was homogenous and consisted of nanocrystalline grains. Photocatalytic activity was assessed based on the phenol decomposition. Results showed that both thin films were photocatalytically active, however coating with anatase phase decomposed higher amount of phenol. The t...
In this paper, three types of titanium dioxide structures (anatase, heated amorphous and amorphous) from peroxo titanium complex were deposited on glass and wafer substrates by spraying technique. Influences of crystal structure, morphology and sodium ion on UV induced hydrophilicity were studied. X-ray diffraction revealed that crystalline anatase coatings are extremely hydrophilic (<10°) under UV irradiation (indoor) while the amorphous coatings are still hydrophobic on both glass and wafer substrate with contact angles as high as 70º. When amorphous coating was heated at 450ºC, its structure was converted into crystalline anatase, and hence its UV induced hydrophilicity behavior on wafer substrate became similar to that of anatase. However, this UV induced hydrophilicity was inhibited on heated glass (450ºC), suggesting that sodium ions in the glass might be responsible for the differences between silicon wafer and glass. With increasing coating thickness, such inhibition effect was reduced, but the hydrophilicity still could not reach the level of anatase. After 6 months of outdoor exposure, water contact angle for amorphous, heated amorphous and anatase were 61°, 26.6° and 12.1°, respectively. Also, X-ray diffraction suggested that amorphous is not converted into anatase after long period of UV exposure, although coating morphologies are changed based on Scanning Electron Microscopic observation. It is concluded that the crystal structure, coating morphology and sodium ion concentration have key impact on the photocatalytic properties on glass substrate.
Annals of West University of Timisoara - Physics
Photocatalytic degradation of organic pollutants from wastewater using titanium dioxide is recognized as an efficient process. To be feasible, this process needs to be solar- or visible light -activated, but, due to its wide band gap energy, titanium dioxide can only be activated by ultraviolet radiation. In this paper, thin films of titanium dioxide were deposited by Spray Pyrolysis Deposition using organo-metallic (titanium-iso-propoxide) and inorganic (titanium chloride) precursors, as a first step in optimizing the deposition process of titanium dioxide - carbon composite thin films, active in the visible spectral range. The thin films were characterized to outline the differences when using these two precursor solutions, when deposited on Fluorine doped Tin Oxide-glass, regular glass and microscopic glass, in terms of crystallinity (by using X-ray diffraction), elemental composition (using Energy Dispersive X-ray spectrometry), surface morphology (Scanning Electronic Microscopy...