Fe-doped TiO2 Thin Films Research Articles

Visible-light-mediated antifungal bamboo based on Fe-doped TiO2 thin films

A visible-light-mediated antifungal bamboo based on Fe-doped TiO2 thin films was successfully fabricated through a facile one-step homogeneous precipitation method.

Effect of Aging Time on the Synthesis of Fe-doped TiO2 Thin Films by Spin Coating Method

<p>The synthesis of Fe-doped TiO<sub>2</sub> thin film using spin coating method was studied. Effects of aging time on the deposited thin film were investigated. Titanium butoxide (C<sub>16</sub>H<sub>36</sub>O<sub>4</sub>Ti) as a precursor solution was mixed with the FeCl<sub>3</sub>. Spin coating process was carried out on three types of precursor solution: (1) spin-coating process performed immediately after the precursor solution was made, (2) spin-coating process performed after solution was aged for 24 hours, (3) aged for 24 and (4) spin-coating after aging the precursor for 72 hours. Heating was carried out on the resulting thin film at temperature of 400 °C. The morphology of TiO<sub>2</sub> layers was characterized using Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). Elemental and phase composition of the films was determined using EDX and X-ray diffraction (XRD). We found that the best TiO<sub>2</sub> layer is obtained when spin-coating process is done after aging the precursor for 72 hours. The layer shows a more uniform particle distribution on the substrate and a more monodisperse particle size dominated by the anatase phase.</p>

Effect of Aging Time on the Synthesis of Fe-doped TiO2 Thin Films by Spin Coating Method

<p>The synthesis of Fe-doped TiO<sub>2</sub> thin film using spin coating method was studied. Effects of aging time on the deposited thin film were investigated. Titanium butoxide (C<sub>16</sub>H<sub>36</sub>O<sub>4</sub>Ti) as a precursor solution was mixed with the FeCl<sub>3</sub>. Spin coating process was carried out on three types of precursor solution: (1) spin-coating process performed immediately after the precursor solution was made, (2) spin-coating process performed after solution was aged for 24 hours, (3) aged for 24 and (4) spin-coating after aging the precursor for 72 hours. Heating was carried out on the resulting thin film at temperature of 400 °C. The morphology of TiO<sub>2</sub> layers was characterized using Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). Elemental and phase composition of the films was determined using EDX and X-ray diffraction (XRD). We found that the best TiO<sub>2</sub> layer is obtained when spin-coating process is done after aging the precursor for 72 hours. The layer shows a more uniform particle distribution on the substrate and a more monodisperse particle size dominated by the anatase phase.</p>

Fe doped TiO2 thin film as electron selective layer for inverted solar cells

Inverted P3HT:PCBM based organic solar cells were fabricated by using Fe2+ doped TiO2 films as electron selective layer. Pure and Fe2+ doped TiO2 films were prepared by sol–gel method and the optical as well as the structural properties of the thin films were characterized by UV–Vis spectrophotometer and SEM. The concentration of Fe2+ was varied as 0.5%, 1%, 2% and 3% (w/w) in TiO2 layer and the influence of Fe2+ doping on the solar cell parameters were systemically investigated. Photocurrent density of the solar cells as increased from 8.75 to 13.8mA/cm2, whereas the solar cell efficiency changed from 1.7% to 2.79% by using Fe2+ doped TiO2 electron selective layer. It was experimentally found and demonstrated that charge injection and selection in the TiO2 interlayer was improved by doping of Fe2+ atoms in the TiO2.

Exploring a new phenomenon in the bactericidal response of TiO2 thin films by Fe doping: Exerting the antimicrobial activity even after stoppage of illumination

Antibacterial properties of Fe-doped TiO2 thin films prepared on glass by the sol–gel hot-dipping technique were studied. The films were characterized by X-ray diffraction, field emission scanning electron microscopy, scanning probe microscopy and X-ray photoelectron spectroscopy. The photocatalytic activities were evaluated by measuring the decomposition rate of methylene blue under ultra violet and visible light. The antibacterial properties of the coatings were investigated against Escherichia coli, Staphylococcus aureus, Saccharomyces cerevisia and Aspergillus niger. The principle of incubation methods was also discussed. The results indicated that Fe doping of thin films eventuated in high antibacterial properties under visible light and this performance remained even after stoppage of illumination. This article tries to provide some explanation for this fact.

Fe-Doped TiO2 Thin Films for CO Gas Sensing

Fe-doped TiO2 thin films were prepared by the sol–gel technique on silicon substrate. The thin films were evaluated for detection of carbon monoxide (CO) gas at room temperature. The TiO2 films were characterized by x-ray diffraction (XRD) analysis, field-emission scanning electron microscopy, and ultraviolet–visible (UV) spectroscopy. The characterization revealed that, as the doping concentration was increased, the grain size decreased. XRD patterns revealed the phase transition from rutile to anatase with addition of different percentages (weight/volume) of Fe. The bandgap determined from UV spectroscopy was found to decrease with increasing Fe doping concentration. Fe doping was observed to have a significant effect on the resistivity of the doped TiO2 thin films. The gas sensing behavior of the films was studied by exposure to different concentrations of CO gas with measurement of the electrical resistance. It was observed that Fe-doped (7% weight/volume) TiO2 exhibited high sensitivity and good response/recovery on exposure to CO gas in the concentration range from 100 ppm to 900 ppm in Ar.

Characteristics and anticorrosion performance of Fe-doped TiO 2 films by liquid phase deposition method

Fe-doped TiO2 thin films were fabricated by liquid phase deposition (LPD) method, using Fe(III) nitrate as both Fe element source and fluoride scavenger instead of commonly-used boric acid (H3BO3). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis spectrum were employed to examine the effects of Fe element on morphology, structure and optical characteristics of TiO2 films. The as-prepared films were served as photoanode applied to photogenerated cathodic protection of SUS304 stainless steel (304SS). It was observed that the photoelectrochemical properties of the as-prepared films were enhanced with the addition of Fe element compared to the undoped TiO2 film. The highest photoactivity was achieved for Ti13Fe (Fe/Ti = 3 molar ratio) film prepared in precursor bath containing 0.02 M TiF4 + 0.06 M Fe(NO3)3 under white-light illumination. The effective anticorrosion behaviors can be attributed to the Fe element incorporation which decreases the probability of photogenerated charge-carrier recombination and extends the light response range of Fe-doped TiO2 films appeared to visible-light region.

Optical and structural properties of highly porous shell structured Fe doped TiO2 thin films

TiO2 thin films with 0.2 wt%, 0.4 wt%, 0.6 wt%, and 0.8 wt% Fe were prepared on glass and silicon substrates using sol–gel spin coating technique. The optical cut-off points are increasingly red-shifted and the absorption edge is shifted over the higher wavelength region with Fe content increasing. As Fe content increases, the optical band gap decreases from 3.03 to 2.48 eV whereas the tail width increases from 0.26 to 1.43 eV. The X-ray diffraction (XRD) patterns for doped films at 0.2 wt% and 0.8 wt% Fe reveal no characteristic peaks, indicating that the film is amorphous whereas undoped TiO2 exhibits (101) orientation with anatase phase. Thin films of higher Fe content exhibit a homogeneous, uniform, and nano-structured highly porous shell morphology.

Degradation of Typical Indoor Air Pollutants Using Fe-Doped TiO2Thin Film under Daylight Illumination

A type of iron-doped titania thin film was prepared by means of sol-gel method to degrade indoor formaldehyde (HCHO), ammonia (NH3), and benzene (C6H6) under sunlight. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, and energy dispersive spetra (EDS). The results showed that the iron was doped in the TiO2photocatalyst successfully. The absorption edge of doped TiO2had red shifts and the doped TiO2had a stronger absorption than the pure TiO2in the visible region. Fe-doped TiO2thin film prepared with the optimal preparation condition could remove indoor HCHO, NH3and C6H6effectively under solar light irradiation. The removal percentage of HCHO, NH3or C6H6after 9 h photocatalytic reaction under solar light reached 55%, 53.1%, and 37.5%, respectively, when they existed in the air individually. When the three pollutants were mixed in the air, the removal percentage decreased to 33.3%, 28.3%, and 28%. The degradation reaction of the three pollutants followed the pseudo first-order kinetics, which reflects that the photocatalytic reaction was controlled by the surface chemical reaction and the reaction rate was controlled by concentration of reactants.

Structural, optical, photoluminescence and photocatalytic investigations on Fe doped Tio2 thin films

Pure and Fe doped TiO2 thin films were deposited onto quartz substrates maintained at room temperature by radio frequency magnetron sputtering. The films were annealed at 873K in air for 2h and characterized using X-ray diffraction (XRD), micro Raman spectroscopy, Scanning electron microscopy (SEM), Energy dispersive spectroscopy, ultraviolet-visible and photoluminescence (PL) spectroscopy. Pure TiO2 thin films were XRD-amorphous, but micro Raman spectra revealed the presence of anatase phase. Doping with Fe has influenced the transformation of films to anatase phase. Improved crystallinity was observed in the 0.1 at% Fe doped films, where the lattice constants approached the values for bulk anatase TiO2, and the films showed minimum strain. At higher Fe concentrations, micro Raman spectra revealed the presence of rutile phase also. SEM images revealed crack free surface and surface roughness was found to increase with increase in Fe concentration. Doping with Fe has resulted in a red shift of absorption edge. PL emission intensity was found to increase with Fe concentration, but at higher concentrations quenching of PL emission was observed. Fe doping resulted in enhancement of photocatalytic activity, evaluated by monitoring the degradation of methylene blue solution. 0.8 at% Fe doped TiO2 films exhibited the highest photocatalytic activity.

Optical Properties of Fe-Doped TiO<sub>2 </sub>Thin Film Prepared by Sol-Gel

Undoped and Fe-doped (Fe ions content was 0.1) TiO2 thin film prepared by Sol-gel method. X-ray diffraction (XRD) results showed that TiO2 gel annealed at 500°C was crystallized anatase phase. The contact angle for undoped and Fe-doped TiO2 thin film was 47.1° and 8.8°. The transparent spectra showed that the cutoff wavelength of was red shift. The band-gap of Fe-doped TiO2 film was 3.47 eV.

Degradation of Indoor Ammonia Using TiO<sub>2</sub> Thin Film Doped with Iron(III) under Visible Light Illumination

A type of titania thin film doped with iron(III) was prepared by means of sol-gel method to degrade indoor ammonia (NH3) under visible light irradiation. The photocatalysts was characterized by X-ray diffraction (XRD) and UV-vis spectroscopy. The results demonstrated that the adsorption edge of doped TiO2 thin film had red shifts and the doped TiO2 thin film had a stronger absorption than undoped TiO2 thin film in the visible region. Doping amount of Fe(III) effected the photocatalytic actitivity of Fe-doped TiO2 thin film significantly. The optimal doping amount of Fe(III) was 1%(mole fraction). Using the optimal Fe-doped TiO2 thin film, the removal percentage of NH3 after 9h phtocatalytic reaction under visible light reached 53.1%. The degradation reaction of NH3 was successfully described by the pseudo first-order kinetics. The reaction rate constant decreased with the increase of initial concentration of NH3, which reflected that there was oxidation competition between NH3 and its intermediate during the photocatalytic process.

Micro-arc oxidization fabrication and ethanol sensing performance of Fe-doped TiO2 thin films

In-situ pure TiO2 and Fe-doped TiO2 thin films were synthesized on Ti plates via the micro-arc oxidation (MAO) technique. The as-fabricated anatase TiO2 thin film-based conductometric sensors were employed to measure the gas sensitivity to ethanol. The results showed that Fe ions could be easily introduced into the MAO-TiO2 thin films by adding precursor K4(FeCN)6·3H2O into the Na3PO4 electrolyte. The amount of doped Fe ions increased almost linearly with the concentration of K4(FeCN)6·3H2O increasing, eventually affecting the ethanol sensing performances of TiO2 thin films. It was found that the enhanced sensor signals obtained had an optimal concentration of Fe dopant (1.28at%), by which the maximal gas sensor signal to 1000 ppm ethanol was estimated to be 7.91 at 275°C. The response time was generally reduced by doped Fe ions, which could be ascribed to the increase of oxygen vacancies caused by Fe3+ substituting for Ti4+.

Influence of structural phase transition on Ferromagnetism in Fe-doped TiO2 thin films

Fe doped TiO2 films are deposited on glass substrates using dc magnetron sputtering. The crystal structures and the magnetic properties of these films are studied. Room temperature ferromagnetism is observed in each of all the Fe doped TiO2 films. The source of magnetism is related to an exchange interaction between the transition-metal (Fe) ions and localized strapped holes. The maximal magnetization is observed in a TiO2 film with Fe concentration 7%. With the increase of Fe concentration, the crystal structure of TiO2 film transforms gradually from anatase phase to rutile phases, and magnetism in the film weakened. The changes of crystal structure and crystallization in TiO2 film resulting from Fe doping affect the change of ferromagnetism in the film.

A short literature survey on iron and cobalt ion doped TiO2 thin films and photocatalytic activity of these films against fungi

In this study, a short recent literature survey which concentrated on the usage of Fe3+ or Co2+ ion doped TiO2 thin films and suspensions were summarized. Additionally, a sol–gel method was used for preparation of the 2% Co or Fe doped TiO2 thin films. The surface of the prepared materials was characterised using scanning-electron microscopy (SEM) combined with energy dispersive X-ray (EDX) analysis and band gap of the films were calculated from the transmission measurements that were taken over the range of 190 and 1100nm. The Eg value was 3.40eV for the pure TiO2, 3.00eV for the Fe-doped TiO2 film and 3.25eV for Co-TiO2 thin film. Iron or cobalt doping at lower concentration produce more uniformed particles and doping greatly affected the size and shape of the TiO2 nanoparticles. Photocatalytic killing effect of the 2% Co doped TiO2 thin film on Candida albicans was significantly higher than Fe doped TiO2 thin film for short and long exposure periods. Doped thin films were more effective on Aspergillus niger for short exposure periods.

Structural properties of Fe doped TiO2 films on LaAlO3 and Si substrates

We have prepared 4 at.% Fe doped TiO2 thin films on LAO (001) and Si (111) substrates by pulsed laser deposition. X-ray diffraction (XRD) studies suggest different structural properties of the films on the different substrates. Raman measurements corroborate the XRD findings. The thicknesses of the films are also different on the two substrates, suggesting different nucleation process on the two substrates. Interestingly on both the substrates, Fe is not in metal clusters, suggesting their possible incorporation in TiO2 matrix.

Magnetic characterization of diluted magnetic semiconductor thin films

In studies of weak magnetism in diluted magnetic semiconductor thin films, there is often a significant difficulty in subtracting the background signal arising from the substrate. In the present work, an improved magnetic correction method is proposed. For Al doped ZnO and Fe doped TiO2 films, the magnetic moment and coercivity of the samples were corrected by the improved method, and the maximum fitting error due to the glass substrate was calculated. The accuracy and rationale of the improved method are discussed and compared with the traditional method. The results show that room temperature ferromagnetism is observed in Fe doped TiO2 thin films. The ferromagnetism is strongly correlated with the substitution of Ti by Fe in the TiO2 lattice, which results in a change in the crystal structure and the quality of the crystallization of the TiO2 films. The changes are responsible for altering ferromagnetism in the films.

Polaron transport in TiO2 thin films

Undoped and Fe-doped TiO2 thin films were obtained by rf-sputtering technique onto heated glass substrates (250 °C) covered with indium tin oxide. The temperature dependence of the electrical conductivity was investigated in the temperature range 13–320 K, and it shows that the conduction mechanism in the studied samples is described by small-polaron hopping (SPH) at temperatures higher than half of the Debye temperature (θD). It was found that the magnitude of the SPH coupling increases by Fe doping in TiO2 thin films. With decreasing temperature, the conduction behavior transited from SPH conduction to variable-range hopping (VRH) conduction. In the intermediate temperature domain (200 K<T<θD/2), the VRH conduction was found to be dominant, while a temperature-independent conductivity behavior was observed in the lower temperature range (T<200 K).

Preparation and Characterization of Nanocrystalline Fe-Doped TiO2 Film on Different Substrates and Its Application in Degrading Dyeing Water

TiO2 and Fe-doped TiO2 thin films were prepared on the substrates (glass plates and glass microballs) after dipped in colloid and calcined at 500°C. The films have been characterized by UV-absorption, x-ray diffraction and atomic force microscopy (AFM). The investigated Fe-doped TiO2 (A nominal 10 wt% Fe2O3 was impregnated) thin films were obtained by sol-gel method. The characterization results suggest that the calcined thin films primarily consist of TiO2 anatase. And the light absorption curve of the TiO2 films modified with Fe showed that red shift had happened by the dope of Fe. TiO2/beads as photocatalyst were used to degrade the simulated dyeing water which contains reactive deep-blue dye (K-R). Through the degradation experiment, we found that the dope of Fe promoted the photocatalytic activities. The results showed that the dyeing water can be decomposed more effectively by the photocatalytic oxidation of Fe/TiO2 film on glass micro-balls than glass plates.

A novel externally charged Fe-doped TiO2 thin film with extraordinary oxygen sensitivity

Different configurations of Fe-doped TiO2 thin films deposited on both quartz glass and heavily doped p-type silicon substrates were prepared by the sol–gel method. Oxygen-sensing properties of the TiO2 thin films were measured through the variations in resistivity under a low operating temperature of 300 °C using a micro-current instrument. Extraordinary oxygen sensitivity up to about 200 times of resistance ratio appeared only in the configuration of TiO2 thin film deposited on the heavy doped p-type silicon substrate with Fe doping of 4–6 mol %, in which the rutile phase content was maximum. The high oxygen sensitivity was induced by the extrinsic positive charge gained and was controlled by both the rutile phase content in the thin film and the positive charge transmitted from the heavily doped p-type single crystal silicon to the thin film.