Activity Of TiO2 Thin Films Research Articles

Characterization and photocatalytic activity of TiO2 thin films prepared by sol-gel method for NOx degradation

Titanium dioxide (TiO2) thin film photocatalysts for the elimination of nitrogen oxides (NOx) were prepared by the dip-coating process using the sol–gel method. To prepare the sols, titanium (IV) butoxide (Ti(OBu)4), diethanolamine (DEA), butanol, and HCl were chosen. The TiO2 coatings were prepared using sols with varying volume ratios of Ti(OBu)4:DEA:Butanol. Additionally, three withdrawal speeds from the sol were employed. Subsequently, the TiO2 thin films were sintered at 500 and 700 °C. The obtained thin films were characterized using SEM to determine thickness, AFM to determine roughness, and the Step 500 platform for the adhesion test. NOx was found to be efficiently eliminated by TiO2 thin film photocatalyst. It is possible to obtain a TiO2 coating that is capable of degrading 300 ppb of NO in real time under specific conditions: a relative humidity of 30 %, a UV intensity of 20 W/m2, a gas flow rate of 1 dm3/min.

Impact of Cu on structural, optical, dielectric properties and antibacterial activity of TiO2 thin films

In this work, Copper-doped TiO2 thin films were synthesized on glass substrates using a sol-gel dip-coating technique with varied molar concentrations of copper precursor (1,3,5,7,9 at. wt. %). Cu affected the structural, morphological, dielectric, antibacterial, and optical properties of TiO2 films. The formation of the anatase phase was confirmed by XRD. The morphology of all synthesized thin films was spherical grains with slight aggregation. The hopping process explained dielectric characteristics that obeyed the Maxwell-Wagner model and Koop's theory. These films were ideal for high-frequency devices because of their low dielectric constant. It was observed that as Cu concentration increased, the optical band gap energy reduced, which was beneficial for improving solar cell efficiency. Cu-doped TiO2 produced the best antibacterial agent. The photocatalysts with the highest photo activities were those containing 9 wt% Cu. The increased light absorption in the UV-VIS range and the lower recombination rate of the photoinduced electron hole pair of Cu-doped TiO2 thin films were responsible for the improved photocatalytic activity. Methylene blue degraded in the presence of sunshine, making it a potential material for the treatment of water.

Antibacterial Activity of Silver and Gold Particles Formed on Titania Thin Films.

Metal-based nanoparticles with antimicrobial activity are gaining a lot of attention in recent years due to the increased antibiotics resistance. The development and the pathogenesis of oral diseases are usually associated with the formation of bacteria biofilms on the surfaces; therefore, it is crucial to investigate the materials and their properties that would reduce bacterial attachment and biofilm formation. This work provides a systematic investigation of the physical-chemical properties and the antibacterial activity of TiO2 thin films decorated by Ag and Au nanoparticles (NP) against Veillonella parvula and Neisseria sicca species associated with oral diseases. TiO2 thin films were formed using reactive magnetron sputtering by obtaining as-deposited amorphous and crystalline TiO2 thin films after annealing. Au and Ag NP were formed using a two-step process: magnetron sputtering of thin metal films and solid-state dewetting. The surface properties and crystallographic nature of TiO2/NP structures were investigated by SEM, XPS, XRD, and optical microscopy. It was found that the higher thickness of Au and Ag thin films results in the formation of the enlarged NPs and increased distance between them, influencing the antibacterial activity of the formed structures. TiO2 surface with AgNP exhibited higher antibacterial efficiency than Au nanostructured titania surfaces and effectively reduced the concentration of the bacteria. The process of the observation and identification of the presence of bacteria using the deep learning technique was realized.

Enhanced Photocatalytic Activity of TiO2 Thin Film Deposited by Reactive RF Sputtering under Oxygen-Rich Conditions

TiO2 thin films are promising as photocatalysts to decompose organic compounds. In this study, TiO2 thin films were deposited by reactive radio-frequency (RF) magnetron sputtering under various flow rates of oxygen and argon gas. The results show that the photocatalytic activity decreases as the oxygen-gas ratio is increased to 30% or less, while the activity increases under oxygen-rich conditions. It was observed that the crystal structure changed from anatase to a composite of anatase and rutile, where the oxygen-gas ratio during RF sputtering is more than 40%. Interestingly, the oxygen vacancy concentration increased under oxygen-rich conditions, where the oxygen-gas ratio is more than 40%. The sample prepared under the most enriched oxygen condition, 70%, among our experiments exhibited the highest concentration of oxygen vacancy and the highest photocatalytic activity. Both the oxygen vacancies and the composite of anatase and rutile structure in the TiO2 films deposited under oxygen-rich conditions are considered responsible for the enhanced photocatalysis.

Application of surface acoustic wave to enhance the photocatalytic degradation efficiency of methylene blue

The TiO2 thin film was grown on a [Formula: see text] Y-axis cut, X-axis propagation lithium niobate substrate by radio frequency magnetron sputtering to fabricate a surface acoustic wave device. The sputtering ratios of argon to oxygen at 20% and post-annealing temperature at [Formula: see text]C for 3 h were controlled to improve the photocatalytic activity of TiO2 thin film. The effects of work frequency and input voltage of the surface acoustic wave device on the methylene blue photocatalytic degradation efficiency of the TiO2 thin film were investigated. The TiO2 thin film was vibrated at radio frequency by surface acoustic wave device to increase the scattering and reactive frequency for methylene blue in liquid. The surface acoustic wave device operated at 28.65 MHz work frequency and 0.95 V input voltage revealed the highest photocatalytic degradation efficiency of methylene blue. Compared to the TiO2 thin film combined with and without surface acoustic wave device, the surface acoustic wave device enhanced the TiO2 thin film photocatalytic degradation efficiency to 46%.

The study of the applicability of ionizing radiation to increase the photocatalytic activity of TiO2 thin films

The paper presents the results of studying the efficiency of using ionizing radiation to modify the surface morphology and structural properties of TiO2 thin films, and the effect of ion modification on the photocatalytic activity of Rhodamine B. decomposition. Structural and morphological changes in thin films were characterized by irradiation with doses of 1014–1016 ion/cm2 using scanning electron microscopy, atomic force microscopy, energy-dispersive analysis and X-ray diffraction. Modification by ion irradiation of thin films leads to a change in grains orientation, a decrease in their size, and an increase in the active surface area. Formation of grains preferred orientation at high radiation doses is caused both by grains rotation as a result of distorting and deformation factors caused by radiation, and by grains partial fragmentation. It was shown that in the case of modified samples of thin films, not only an increase in the rate decomposition reaction constant by 2–4.5 times compared with the initial samples, but also the degree of mineralization is observed. According to the data obtained, the maximum value of mineralization as a result of photocatalytic reactions for initial films was no more than 75–76%. While for irradiated samples, this value varies from 83 to 90% depending on the irradiation dose. For modified films, an increase in crack resistance and resistance to degradation to prolonged tests of photocatalytic activity is observed.

Thickness Effect on Photocatalytic Activity of TiO2 Thin Films Fabricated by Ultrasonic Spray Pyrolysis

In this study, TiO2 thin films were deposited by ultrasonic spray pyrolysis from solutions with concentrations of 0.1 and 0.2 M. The deposition temperature was adjusted at 350 °C and all samples were annealed at 500 °C for 1 h in air. The thickness of TiO2 films was changed in the range of 50 to ca. 800 nm by varying the number of spray cycles from 1 to 21 and the solution concentration. The results showed that the mean crystallite size of the anatase structure, the surface roughness, and light absorption increased with the film thickness. The effect of film thickness on the photocatalytic activity was investigated with the photodegradation of stearic acid under UV-A irradiation. The optimal thickness of TiO2 films fabricated by ultrasonic spray pyrolysis for photocatalytic self-cleaning applications was in the range of 170–230 nm, indicating a ca. 2.6 times-higher photocatalytic self-cleaning activity compared to the reference sample, Pilkington ActivTM. The photocatalytic results showed that the 190 nm-thick TiO2 film deposited from the 0.1 M solution applying seven spray cycles exhibited the finest grain structure and maximum photocatalytic activity, leading to 94% of stearic acid degradation in 180 min under UV-A light with the reaction rate constant k = 0.01648 min−1.

Enhanced Visible and Ultraviolet Light-Induced Gas-Phase Photocatalytic Activity of TiO2 Thin Films Modified by Increased Amount of Acetylacetone in Precursor Solution for Spray Pyrolysis

TiO2 thin films, modified by acetylacetone (AcacH) in solution, were deposited on glass substrate by ultrasonic spray pyrolysis and tested for photocatalytic activity in a multi-section continuous flow reactor by degradation of acetone and acetaldehyde under ultraviolet and visible light. The increase in molar ratio of AcacH in respect of titanium (IV) isopropoxide (TTIP) from 1:5 to 1:8 modified the electronic structure of the films, favoring enhanced photocatalytic activity. The photocatalytic activity was enhanced approximately twofold on the film with molar ratio 1:8 under both irradiations; the film completely oxidized 10 ppm of acetone and acetaldehyde. The photocatalytic efficacy of TiO2 films in oxidation of air pollutants was three times higher compared to the industrial glass Pilkington ActivTM. Moreover, all the synthesized films indicate antibacterial efficiency against E. coli of over 99% under ultraviolet. TiO2 film, with TTIP:AcacH molar ratio 1:8 having great possibility for its commercial use as a material for indoor air purification.

Grain size effect on photocatalytic activity of TiO2 thin films grown by atomic layer deposition

We have studied the effect of grain size on the photocatalytic activity of TiO2 thin films grown by atomic layer deposition technique. A number of thin films of different crystallinity (anatase, rutile, amorphous) and grain sizes (55 nm to 715 nm) were grown on Si substrates under different processing conditions, by varying the reactor temperature, deposition time or buffer layers. The films are characterized by scanning electron microscopy, grazing incidence x-ray diffraction, x-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy. The photocatalytic activity was examined by measuring the degradation rates of methylene blue in aqueous solutions under the ultraviolet light irradiation. The photocatalytic activity exhibits a maximum for grains of average size of 200 nm, indicating existence of two competing effects, which occur when the average grain size decreases: increase of active surface area (which promotes a high photocatalytic activity) and increase of grain boundaries (which degrades the photocatalytic activity).

Effect of the Titanium Isopropoxide:Acetylacetone Molar Ratio on the Photocatalytic Activity of TiO2 Thin Films.

TiO2 thin films with different titanium isopropoxide (TTIP):acetylacetone (AcacH) molar ratios in solution were prepared by the chemical spray pyrolysis method. The TTIP:AcacH molar ratio in spray solution varied from 1:3 to 1:20. TiO2 films were deposited onto the glass substrates at 350 °C and heat-treated at 500 °C. The morphology, structure, surface chemical composition, and photocatalytic activity of the obtained TiO2 films were investigated. TiO2 films showed a transparency of ca 80% in the visible spectral region and a band gap of ca 3.4 eV irrespective of the TTIP:AcacH molar ratio in the spray solution. TiO2 films consist of the anatase crystalline phase with a mean crystallite size in the range of 30–40 nm. Self-cleaning properties of the films were estimated using the stearic acid (SA) test. A thin layer of 8.8-mM SA solution was spin-coated onto the TiO2 film. The degradation rate of SA as a function of irradiation time was monitored by Fourier-transform infrared spectroscopy (FTIR). An increase in the TTIP:AcacH molar ratio from 1:4 to 1:8 resulted in a ten-fold increase in the photodegradation reaction rate constant (from 0.02 to the 0.2 min−1) under ultraviolet light and in a four-fold increase under visible light.

Photocatalytic Degradation of Different VOCs in the Gas-Phase over TiO2 Thin Films Prepared by Ultrasonic Spray Pyrolysis

In this study, we deposited TiO2 thin films onto borosilicate glass by ultrasonic spray pyrolysis at 350 and 450 °C. The aim of study is to determine the effect of deposition temperature on photocatalytic activity of TiO2 thin films and to investigate the performance of TiO2 thin films on photocatalytic degradation of methyl tert-butyl ether (MTBE), acetone, acetaldehyde, and heptane as functions of different operating parameters. TiO2 thin films deposited at 350 and 450 °C have a thickness value of 190 and 330 nm, respectively. All as-prepared TiO2 films possess an anatase crystalline structure. According to the X-ray photon spectroscopy (XPS) study, the TiO2 thin film deposited at 350 °C showed a higher amount of oxygen vacancies and hydroxyl groups on the film surface after UV treatment. The aged-TiO2 thin film deposited at 350 °C showed a water contact angle (WCA) value of 0° after 10 min UV irradiation, showing superhydrophilic surface behavior. The TiO2 film deposited at 350 °C exhibited the highest amount of conversion of MTBE (100%). The results also showed that TiO2 films are capable of photocatalytic degradation of MTBE (100%) and acetaldehyde (approx. 80%) in humid air conditions and high airflow rate. The visible-light-activity of TiO2 thin films was tested with 5 ppm MTBE and acetone. TiO2 thin films deposited at 350 °C with a surface area of 600 cm2 showed 60% of MTBE and 33% of acetone degradation under VIS light.

Effect of Er doping on the microstructural, optical, and photocatalytic activity of TiO2 thin films

Nanostructured Er3+ doped TiO2 thin films are deposited onto glass substrate via sol-gel dip-coating followed by calcination at 450 °C for 1 h. X-ray diffraction analysis confirms that the films crystallized within single tetragonal anatase phase. Atomic force microscopy observations reveal that the surface of pure TiO2 is characterized by ninepins then becomes smooth and porous for Er-doped TiO2 thin films, while the roughness decreases drastically from 17.2 to 2.6 nm with increasing Er3+ percentage. Wettability tests show a super-hydrophilicity character of 0.2 and 0.3%Er doped TiO2 thin films. UV–vis analysis reveals high transmittance above 85% with the presence of interferences indicating the high quality of films. Meanwhile, the energy band gap decreases slightly from 3.31 eV for un-doped to 3.26 eV for 0.4%Er, with a red-shift in the optical absorption edge. High photocatalytic activity using methylene blue indicator has been achieved for 0.2% Er3+–TiO2 thin film, reaching 95% for 3 h.

Strongly Enhancing Photocatalytic Activity of TiO2 Thin Films by Multi-Heterojunction Technique

The photocatalysts of immobilized TiO2 film suffer from high carrier recombination loss when compared to its powder form. Although the TiO2 with rutile-anatase mixed phases has higher carrier separation efficiency than those with pure anatase or rutile phase, the single junction of anatase/rutile cannot avoid the recombination of separated carriers at the interface. In this study, we propose a TiO2/SnO2/Ni multi-heterojunction structure which incorporates both Schottky contact and staggered band alignment to reduce the carrier recombination loss. The low carrier recombination rate of TiO2 film in TiO2/SnO2/Ni multi-heterojunction structure was verified by its low photoluminescence intensity. The faster degradation of methylene blue for TiO2/SnO2/Ni multi-junctions than for the other fabricated structures, which means that the TiO2 films grown on the SnO2/Ni/Ti coated glass have a much higher photocatalytic activity than those grown on the blank glass, SnO2-coated and Ni/Ti-coated glasses, demonstrated its higher performance of photogenerated carrier separation.

Influence of the number of layers on photocatalysis activity of TiO2 thin films

Titanium oxide (TiO2) is one of the most important semiconductors because of their properties. This study was carried out to investigate the influence of the number of layers of Co -doped TiO2 thin films obtained by sol–gel method on the photocatalytic activity. The crystalline structure of films is characterised by means of X-ray diffraction and Raman spectroscopy. All the films were of anatase phase and the particle size was in nanoscale. The surface morphology was studied by atomic force microscopy. The optical properties were investigated by UV-visible spectroscopy. The photocatalytic properties of the samples were tested on the degradation of methylene blue dye solution. The results indicated that photocatalysis is more important when the number of dipping of films increases.Keywords: Photocatalysis, X-ray diffraction, TiO2, thin films, methylene blue.

The Role of Concentration Ratio of TTiP:AcAc on the Photocatalytic Activity of TiO2 Thin Film in Reducing Degradation Products of Used Frying Oil

The TiO2 thin film has been applied to reduce degradation products (free fatty acid/FFA and peroxide value/PV) in used frying oil under ultraviolet (UV) light irradiation. FFA and PV are degradation products in used frying oil that can cause various diseases in human. In this study, the TiO2 thin films were made from precursor solution with concentration ratio of titanium tetraisopropoxide (TTiP) and acetylacetone (AcAc) of 1:1, 1:2, 2:1, 2:3, and 3:2. The aim of this study is to investigate the effect of concentration ratio of TTiP and AcAc on the photocatalytic activity of TiO2 thin film in reducing FFA and PV of used frying oil. The spray coating method was used to deposit precursor solution of TiO2 onto glass substrate at 450 oC. All TiO2 thin films consist of spherical-like grain with dominant structure of TiO2 rutile. The band gap energy of TiO2 thin films was in the range 3.11-3.16 eV. Concentration ratio of TTiP and AcAc of 2:3 results in TiO2 thin film with highest photocatalytic activity in reducing FFA and PV of used frying oil.

Prediction of Photocatalytic Activity of TiO2 Thin Films Doped by SiO2 using Artificial Neural Network and Fuzzy Model Approach

Background: In the current study, nanocrystalline thin films of TiO2:xSiO2 (x: mole percentage) with high photocatalytic activity were grown on glass surfaces using sol-gel method. The films were then treated under high temperature of 500°C for the crystal growth. The synthesized films presented high photocatalytic activity when they were in contact with methyl orange (MO) solution and UV irradiation. Due to complexity and nonlinearity photocatalytic features of TiO2 films doped by SiO2, Artificial Neural Network (ANN) and Fuzzy Logic (FL) models have been applied to predict and calculate the MO concentration variations with SiO2 concentration and MO degradation time. Results: The simulations have resulted in accurate and reliable predictive models since the squared correlation coefficient (R2) and the standard squared error (SSE) have been R2>0.99, 0.004, R2 >0.96, and 0.14 for ANN and FL models, respectively. The reported figures have shown that the independent predicted values of MO concentration are extremely close to their corresponding experimental data. Conclusion: The results of simulations have shown that ANN and Fuzzy models are reliable predictive models to study the photocatalytic activity of TiO2 thin film doped by SiO2. Keywords: Sol-gel, photocatalytic activity, fuzzy logic, artificial neural network, organic materials, TIO2.

Structural and optical properties of Er-doped TiO2 thin films prepared by dual-frequency magnetron co-sputtering

Er-doped TiO2 thin films have been prepared by dual-frequency magnetron co-sputtering with two targets composed of TiO2 and Er2O3. The structural and optical properties of these thin films were investigated using various characterization techniques. X-ray photoelectron spectroscopy measurements show that the content of Er increases when the power on Er2O3 target increases. X-ray diffraction patterns indicate that the anatase TiO2 peaks become weaker with the increasing power on Er2O3 target and the films tend to form amorphous structure. Scanning electron microscopy results show that the grain size decreases with the rise in Er content. UV–vis spectrophotometric analyses reveal that the values of band gap decrease from 3.35±1.3% eV to 3.02±1.3% eV with the increasing amount of Er from 0 at.% to 3.2 at.%. The red shift in the optical adsorption edge may contribute to a higher photocatalytic activity of TiO2 thin films.

Electrophoretic Deposition of Titanium Dioxide Thin Films for Photocatalytic Water Purification Systems

In this study, electrophoretic deposition (EPD) technique was used to deposit titanium dioxide (TiO2) thin films on conducting glass substrates for application in water purification from organic contaminants. Phenol was used as a model pollutant. The EPD suspension related parameters and deposition conditions were first optimized for good quality film deposits. The suspension stability and deposition conditions that result in good adherence of TiO2 particles to the substrate with homogeneous film coatings, is ethanol with a pH of 3.0, a TiO2 solid loading of 4.0 wt%, a 0.2 wt% iodine concentration in the solvent and a deposition voltage of 20.0V in a time of 210.0s. The photocatalytic activity of TiO2 thin films decreases exponentially with the ultraviolet light (UV) illumination time and it is also dependent on film thickness, sintering temperature and the intensity of the UV light. Highest rate of photocatalytic activity is observed at an optimal film thickness of 95.0 ± 2.0µm sintered at 300.0°C. The implications of these results are discussed for design of inexpensive waste water purification systems for light industries before discharge into the ecosystem.

New prototype for the treatment of falling film liquid effluents by gliding arc discharge part II: Plasmacatalytic activity of TiO2 thin film deposited by magnetron sputterin

A new prototype of Gliding Arc Discharge (GAD) generating cold plasma at atmospheric pressure and ambient temperature was performed to treat pollutant liquid films. This study focuses on the intensification of the electrical process by the immobilization of a thin layer of TiO2 inside the GAD reactor by magnetron sputtering technology. The deposited film was analyzed by X-ray photoelectron spectroscopy (XPS) and the wettability was estimated by measuring the water contact angle (WCA).Plasmacatalytic activity of the GAD-plate-immobilized TiO2 was evaluated by the plasma-treatment of AG25 anthraquinonic dye dispersed in aqueous solution. The discoloration and the degradation rates have been largely improved by the synergetic effect between the plasma of humid air and the deposited TiO2.In the end of three successive cycles (3×120min) of plasma-treatment, the TiO2 depletion rate was between 2 and 3%, which means a good stability of the coated plate. No significant Fe, Cr and Ti concentrations were found after 360min of GAD-discharge.The electrical plasma-discharge intensified by the magnetron sputtering technology seems to be adapted to the degradation of organic compounds such as AG25 dye.

Effect of annealing temperature on the structural, optical and photocatalytic activity of TiO2 thin films by chemical bath deposition technique

In this report, we have synthesized nanocrystalline of TiO2 thin films by simple chemical bath deposition technique. The as-deposited films were annealed at different temperatures (300, 500 and 700 °C) for 5 h in ambient atmosphere in order to improve crystallinity and structural perfection. The structural, morphological and optical properties were analyzed by using X-ray diffraction (XRD), Atomic force micrograph, Fourier Infrared spectra, UV–Vis transmission spectra and photoluminescence (PL) spectra analysis. XRD results showed that formation of anatase phase for all the annealed samples. The average crystalline size was found to be increased from 35 nm to 46 nm with increasing the annealing temperature. Band gap energy of the 300 °C sample was found to be 3.42 eV, further it was decrease to 3.33, 3.27 eV for 500 and 700 °C annealed samples respectively. The decreasing in the band gap energy and oxygen related vacancies were analyzed by PL analysis. The photocatalytic activity of the TiO2 films were studied by monitoring the degradation of methylene blue rhodamine B in an aqueous solution under visible light irradiation and were empirical that TiO2 film 700 °C samples exhibited excellent photocatalytic activities, when compared with other TiO2 film.