Size control synthesis of sulfur doped titanium dioxide (anatase) nanoparticles,its optical property and its photo catalytic reactivity for CO_2 + H_2O conversion and phenol degradation

Sulfur doped anatase TiO2 nanoparticles （3 nm- 12 nm） were synthesized by the reaction of titanium tetrachloride, water and sulfuric acid with addition of 3 M NaOH at room temperature. The electro-optical and photocatalytic properties of the synthesized sulfur doped TiO2 nanoparticles were studied along with Degussa commercial TiO2 particles （24 nm）. The results show that band gap of TiO2 particles decreases from 3.31 to 3.25 eV and for that of commercial TiO2 to 3.2 eV when the particle sizes increased from 3 nm to 12 nm with increase in sulfur doping. The results of the photocatalytic activity under UV and sun radiation show maximum phenol conversion at the particle size of 4 nm at 4.80% S-doping. Similar results are obtained using UV energy for both phenol conversion and conversion of CO2＋H2O in which formation of methanol, ethanol and proponal is observed. Production of methanol is also achieved on samples with a particle size of 8 and 12 nm and sulfur doping of 4.80% and 5.26%. For TiO2 particle of 4 nm without S doping, the production of methanol, ethanol and proponal was lower as compared to the S-doped particles. This is attributed to the combined electronic effect and band gap change, S dopant, specific surface area and the light source used.

Characterization and photoelectrochemical performance of Zn-doped TiO_2 films by sol-gel method

Zn-doped TiO2 (Zn?TiO2) thin films were prepared by the sol?gel method on titanium substrates with heat treatment at different temperatures. The effects of heat treatment temperatures and Zn doping on the structure, photocathodic protection and photoelectrochemical properties of TiO2 thin films were investigated. It is indicated that the photoelectrical performance of the Zn?TiO2 films is enhanced with the addition of Zn element compared with the pure-TiO2 film and the largest decline by 897 mV in the electrode potential is achieved under 300 °C heat treatment. SEM?EDS analyses show that Zn element is unevenly distributed in Zn?TiO2 films; XRD patterns reveal that the grain size of Zn?TiO2 is smaller than that of pure-TiO2; FTIR results indicate that Zn - O bond forms on Zn?TiO2 surface. Ultraviolet visible absorption spectra prove that Zn?TiO2 shifts to visible light region.Mott?Shottky curves show that the flat-band potential of Zn?TiO2 is more negative and charge carrier density is bigger than that ofpure-TiO2, implying that under the synergy of the width of the space-charge layer, carrier density and flat-band potential, Zn?TiO2 with 300 °C heat treatment displays the best photocathodic protection performance.

Photocatalysts of Cr Doped TiO2 Film Prepared by Micro Arc Oxidation

A series of Cr doped TiO2 films were prepared by micro arc oxidation （MAO） using an electrolyte of Na3PO4＋K2Cr2O7. X-ray diffraction and scanning electron microscopy revealed that the films mainly consisted of anatase phase with a porous surface morphology. The films have an excellent photocatalytic effect for degradation of methylene blue and decomposition of water under visible light illumination. This arises from the formation of Cr3＋/Cr4＋ and oxygen vacancy energy levels owing to Cr doping. The former reduces the electron-hole recombination chance, while the latter generates a new gap between the conduction band （CB） and valence band （VB） of TiO2, which lowers the photo energy of the excited electron in the VB to the oxygen vacancy states. The mechanisms for film synthesis during the MAO process are also presented.

STUDY ON PHOTOCATALYTIC MECHANISM OF SOL-GEL-DERIVED Pb-DOPED TiO_2 THIN FILMS

Pb-doped TiO2 photocatalytic thin films were prepared on a soda-lime glass substrate via sol-gel method using TiO2 sol solution containing lead and characterized by X-ray photoelectron spectroscopy (XPS). The results showed that besides oxides of Ti(IV) there is a certain amount of oxides of To(?) and Ti(?) and Pb exists in the forms of PbTiO3 and PbO. The photocatalytic activity of the Pb-doped TiO2 films was evaluated by the photocatalytic decolorization of aqueous methyl orange and photocatalytic mechanism mas also analyzed.

Degradation of Pollutant and Antibacterial Activity of Waterborne Polyurethane/Doped TiO_2 Nanoparticle Hybrid Films

The waterborne polyurethane/doped Ti O2 nanoparticle hybrid films were prepared. Nd, I doped Ti O2 was prepared with a 50 nm particle size firstly. The hybrid film was prepared by mixing doped Ti O2 with waterborne polyurethane, followed by heat treatment. The presence and nanometric distribution of doped Ti O2 nanoparticles in prepared membranes is evident according to SEM images. The photocatalytic activities of doped Ti O2 were signifi cantly enhanced compared with pure Ti O2 powders. After the hybrid fi lm fabrication, the photocatalytic activities were almost the same as the pure catalysts with kMB of 0.046. In the antibacterial testing, the hybrid fi lms can inhibit E. coli growth. A signifi cant decrease in membrane fl uidity and increase of permeability of E. coli were observed.

Improved carrier transport in Mn:ZnSe quantum dots sensitized La-doped nano-TiO2 thin film

Mn:ZnSe/ZnS/L-Cys core-shell quantum dots(QDs)sensitized La-doped nano-TiO2 thin film(QDSTF)was prepared.X-ray photoelectron spectroscopy(XPS),nanosecond transient photovoltaic(TPV),and steady state surface photovoltaic(SPV)technologies were used for probing the photoelectron behaviors in the Mn-doped QDSTF.The results revealed that the Mn-doped QDSTF had a p-type TPV characteristic.The bottom of the conduction band of the QDs as a sensitizer was just 0.86 eV above that of the La-doped nano-TiO2 thin film,while the acceptor level of the doped Mn2+ions was located at about 0.39 eV below and near the bottom of the conduction band of the QDs.The intensity of the SPV response of the Mn-doped QDSTF at a specific wavelength was ~2.1 times higher than that of the undoped QDSTF.The region of the SPV response of the Mn-doped QDSTF was extended by 191 nm to almost the whole visible region as compared with the undoped QDSTF one.And the region of the TPV response of the Mn-doped QDSTF was also obviously wider than that of the undoped QDSTF.These PV characteristics of the Mn-doped QDSTF may be due to the prolonged lifetime and extended diffusion length of photogenerated free charge carriers injected into the sensitized La-doped nano-TiO2 thin film.

Doped-TiO_2 Photocatalysts and Synthesis Methods to Prepare TiO_2 Films

TiO2 is a promising photocatalyst. However, the low photocatalytic efficiency calls for the modification of TiO2. Metal- and nonmetal-doping of TiO2 have been proved to be effective ways to enhance photocatalytic properties. This review provides a deep insight into the understanding of the metal- and nonmetal-doped TiO2 photocatalysts. This article begins with the introduction of the crystal structures of TiO2 and applications of TiO2 materials. We then reviewed the doped-TiO2 system in two categories： （1） metal-doped TiO2 photocatalysts system, and （2） nonmetal-doped TiO2 photocatalysts system. Both experimental results and theoretical analyses are elaborated in this section. In the following part, for the advantages of TiO2 thin films over particles, various preparation methods to obtain TiO2 thin films are briefly discussed. Finally, this review ends with a concise conclusion and outlook of new trends in the development of TiO2-based photocatalysts.

Preparation and Enhanced Daylight-Induced Photo-Catalytic Activity of Transparent C-Doped TiO_2 Thin Films

The transparent C-doped TiO2 nanostructure films were fabricated on the silicate glass substrates by sol-gel spin-coated method. The as-prepared films were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, UV-visible absorption spectra （UV-vis） and X-ray photoelectron spectroscopy （XPS）. The photocatalytic activity was evaluated via the photocatalytic oxidation of methylene blue in aqueous under daylight irradiation at room temperature. The results show that the daylight-induced photocatalytic activities of the as-prepared films are improved by the C-doping. The calcination temperatures significantly affect the morphology, microstructure and photocatalytic activity of the as-prepared samples. At 723 K, the C-doped TiO2 films exhibit the highest photocatalytic activity due to the synergetic effects of good crystallization, appropriate oxygen vacancies and strong absorption in the near UV and visible-light region.

Humidity sensing properties of spray deposited Fe doped TiO_(2)thin film

In the present work,ferrite(Fe)doped TiO_(2)thin films with different volume percentage(vol%)were synthesized using a spray pyrolysis technique.The effect of Fe doping on structural properties such as crystallite size,texture coefficient,microstrain,dislocation densities etc.were evaluated from the X ray diffratometry(XRD)data.XRD data revealed a polycrystalline anatase TiO_(2)phase for sample synthesized up to 2 vol%and mixed anatase and rutile crystalline phase for sample synthesized at 4 vol%Fe doped TiO_(2).The crystalline size was observed to decrease with increase in Fe dopant vol%and also other structural parameters changes with Fe dopant percentage.In the present work,electrical resistance was observed to decrease with a rise in Fe dopant vol%and temperature of the sample.Thermal properties like temperature coefficient of resistance and activation energy also showed strong correlation with Fe dopant vol%.Humidity sensing properties of the synthesized sample altered with a change in Fe dopant vol%.In the present paper,maximum sensitivity of about 88.7%for the sample synthesized with 2 vol%Fe doped TiO_(2)and also the lowest response and recovery time of about 52 and 3 s were reported for the same sample.

Photoelectric properties of thin Eu^(3+)-doped TiO_2 films sensitized by cis-RuL_2(SCN)_2·2H_2O

Thin nanocrystalline TiO2 films doped by europium ions (Eu3+) were obtained by the sol-gel method. The photoelectric properties of Eu3+-doped TiO2 film electrode sensitized by cis-RuL2(SCN)2·2H2O (L=cis-2,2′-bipyridine-4,4′-dicarboxlic acid) ruthenium complex were studied. The thin films were characterized by X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. Effect of doping Eu3+ on microscopic structure and photoelectrical properties were discussed. The result shows that doping europium ions makes specific surface area of these films larger, which contributes to improving the photoelectric properties. It is found that an optimal composition doped with 0.2 mol.% Eu3+ exhibits the highest photoelectric properties. Isc is 0.37 mA·cm-2, which is 0.17 mA·cm-2 bigger than that of un-doped films; Voc is 405 mV, which is 50 mV bigger than that of un-doped films.

Enhanced Photoelectric Property of Mo-C Codoped TiO2 Films Deposited by RF Magnetron Cosputtering

Mo-C codoped TiO2 films were prepared by RF magnetron cosputtering. Ultraviolet-visible spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray Analysis and X-Ray Diffraction were used to study the influences of codoping on energy gap, surface morphology, valence states of elements, ions content and crystal structure, respectively. The concentration of photogenerated carriers was measured by studying photocurrent density, while catalytic property was evaluated by observing degradation rate of methylene blue under visible light. A Mo-doped TiO2 film, whose content of Mo had been optimized in advance, was prepared and later used for subsequent comparisons with codoped samples. The result indicates that Mo-C codoping could curtail the energy gap and shift the absorption edge toward visible range. Under the illumination of visible light, codoped TiO2 films give rise to stronger photocurrent due to smaller band gaps. It is also found that Mo, C codoping results in a porous surface, whose area declines gradually with increasing carbon content. Carbon and Molybdenum doses were delicately optimized. Under the illumination of visible light, sample doped with 9.78at% carbon and 0.36at% Mo presents the strongest photocurrent which is about 8 times larger than undoped TiO2 films, and about 6 times larger than samples doped with Mo only.

Photoelectrocatalytic reduction of CO_2 into formic acid using WO_(3-x)/TiO_2 film as novel photoanode

A novel WO3-x/TiO2 film as photoanode was synthesized for photoelectrocatalytic（PEC） reduction of CO2 into formic acid（HCOOH）. The films prepared by doctor blade method were characterized with X-ray diffractometer（XRD）, scanning electron microscope（SEM） and transmission electron microscope（TEM）. The existence of oxygen vacancies in the WO3-x was confirmed with an X-ray photoelectron spectroscopy（XPS）, and the accurate oxygen index was determined by a modified potentiometric titrimetry method. After 3h of photoelectrocatalytic reduction, the formic acid yield of the WO3-x/TiO2 film is 872 nmol/cm^2, which is 1.83 times that of the WO3/TiO2 film. The results of PEC performance demonstrate that the introduction of WO3-x nanoparticles can improve the charge transfer performance so as to enhance the performance of PEC reduction of CO2 into formic acid.

Self-Cleaning Properties of Vanadium Doped TiO₂Sol-Gel Derived Thin Films

In this study, vanadium doped TiO2 thin films were deposited on glass substrates using a sol-gel dip-coating process. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectrophotometer were used to characterize the structural, chemical and the optical properties of the thin films. The photo-catalytic activities of films were investigated by methylene blue degradation. Water contact angle on the film surfaces was measured by a water contact angle analyzer. The results indicated that vanadium doping had a significant effect on the self-cleaning properties of TiO2 thin films.

Inverted organic solar cells with solvothermal synthesized vanadium-doped TiO2 thin films as efficient electron transport layer

We investigated the effects of using different thicknesses of pure and vanadium-doped thin films of TiO2 as the electron transport layer in the inverted configuration of organic photovoltaic cells based on poly（3-hexylthiophene） P3HT：[6-6] phenyl-（6） butyric acid methyl ester（PCBM）. 1% vanadium-doped TiO2nanoparticles were synthesized via the solvothermal method. Crystalline structure, morphology, and optical properties of pure and vanadium-doped TiO2 thin films were studied by different techniques such as x-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and UV–visible transmission spectrum. The doctor blade method which is compatible with roll-2-roll printing was used for deposition of pure and vanadium-doped TiO2 thin films with thicknesses of 30 nm and 60 nm. The final results revealed that the best thickness of TiO2 thin films for our fabricated cells was 30 nm. The cell with vanadium-doped TiO2 thin film showed slightly higher power conversion efficiency and great Jsc of 10.7 mA/cm^2 compared with its pure counterpart. In the cells using 60 nm pure and vanadium-doped TiO2 layers, the cell using the doped layer showed much higher efficiency. It is remarkable that the external quantum efficiency of vanadium-doped TiO2 thin film was better in all wavelengths.

Fabrication and Luminescence Properties of Eu^(3+) Doped SiO_2 Thin Films

Rare earth doped silica films were prepared by sol-gel method accompanied with the spin-coating process. It was found that the photoluminescence (PL) property of the thin films was dependent strongly on the doping amount of Eu3+. For thin films annealed at 700 ℃, the PL intensity increased constantly as elevating the doping amount up to 10% without any evident concentration quench, which indicated the good doping property of the SiOmatrix. In order to further improve the PL efficiency, co-doping of Tb3+ into SiO∶Eu3+ thin films were also investigated. It was found that the luminescence intensity was obviously enhanced by co-doping which could be explained in terms of the effective energy transfer from Tb3+ to Eu3+.

Effects of Substrate Temperature on Properties of Transparent Conductive Ta-Doped TiO_2 Films Deposited by Radio-Frequency Magnetron Sputtering

Ta-doped titanium dioxide films are deposited on fused quartz substrates using the rf magnetron sputtering technique at different substrate temperatures. After post-annealing at 550℃ in a vacuum, all the films are crystallized into the polycrystalline anatase TiO2 structure. The effects of substrate temperature from room temperature up to 350℃ on the structure, morphology, and photoelectric properties of Ta-doped titanium dioxide films are analyzed. The average transmittance in the visible region（400-800 nm） of all films is more than 73%.The resistivity decreases firstly and then increases moderately with the increasing substrate temperature. The polycrystalline film deposited at 150℃ exhibits a lowest resistivity of 7.7 × 10^-4Ω·cm with the highest carrier density of 1.1×10^21 cm^-3 and the Hall mobility of 7.4 cm^2·V^-1s^-1.

Carbon Doped Nano-Crystalline TiO₂Photo-Active Thin Film for Solid State Photochemical Solar Cells

Carbon doped titanium dioxide (C-TiO2) is considered as a promising photocatalytic material due to its optical absorption extended in the visible region compared to pure TiO2. However, in the field of photovoltaic’s, use of C-doped nano-crystalline titanium dioxide (C-TiO2) electrodes for light absorption has been considered to be unnecessary so far. In this context, we report here on the use of C-TiO2 nano-crystalline electrodes in photochemical solar cells devices (PCSC). Carbon doping has reduced the band gap of TiO2 to 2.41 eV and 2.25 eV with increase in the doping extent for the 9 mM C-TiO2 and 45 mM C-TiO2 respectively. The C-TiO2 electrodes were first used as photo electrodes for solar cells, exhibiting JSC of 1.34651 mA/cm2, VOC 0.683 V, FF 50.23% and η 0.46%. for the 9 mM C-TiO2 and exhibiting JSC of 1.34651 mA/cm2, VOC 0.815 V, FF 54.3% and η 0.59% for the 45 mM C-TiO2. The fabricated solar cell devices have shown an increase in VOC of up to 0.815 V, which is higher than that of 0.7 V for dye sensitized solar cells. The doping of carbon in TiO2 lattice was closely studied by SEM, XRD, RS and UV-Vis spectroscopy.

Preparation and photocatalytic performance of Cu-doped TiO_2 nanoparticles

Cu-doped TiO2 nanoparticles with different doping contents from 0 to 2.0% （mole fraction） were synthesized through sol-gel method. X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and field emission scanning electron microscope （FE-SEM） were used to characterize the crystalline structure, chemical valence states and morphology of TiO2 nanoparticles. UV-Vis absorption spectrum was used to measure the optical absorption property of the samples. The photocatalytic performance of the samples was characterized by degrading 20 mg/L methyl orange under UV-Vis irradiation. The results show that the Cu-doped TiO2 nanoparticles exhibit a significant increase in photocatalytic performance over the pure TiO2 nanoparticles, and the TiO2 nanoparticles doped with 1.0% Cu show the best photocatalytic performance. The improvement in photocatalytic performance is attributed to the enhanced light adsorption in UV-Vis range and the decrease of the recombination rate of photoinduced electron-hole oair of the Cu-doped TiO2 nanoparticles.

Preparation of Nano-TiO_2 Doped with Cerium and Its Photocatalytic Activity

Cerium-doped titanium dioxide nano-powders were prepared through the sol-gel method and the compound sampies were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and UV/Vis diffuse reflectance spectra （DRS）. The photocatalytic activity was evaluated by photocatalytic degradation of phenol in water. The results of XRD, TEM, and DRS show that pure TiO2 and Ce-doped TiO2 powder crystallines are a mixture of anatase and rutile ; the doping can retard the development of the grain size of TiO2 and decrease the diameter of TiO2 from more than 20 nm of pure TiO2 to about 10 nm; the doped TiO2 can improve the light absorption of TiO2 and suitable doping content tends to move the DRS spectrum of TiO2 towards visible light, but too much doping is not good for the light absorption ability. The results of the photocatalytic experiments show that doping with Ce content of 0.08% -0.4% can increase the photocatalytic activity of TiO2; however, doping with Ce content of 0.5% -2.5% can significantly decrease the photocatalytic activity of TiO2. The favorite doping content is 0.4% in the range of our experiments.

Synthesis of iron(Ⅲ)-doped nanostructure TiO_2/SiO_2 and their photocatalytic activity

Iron（Ⅲ）-doped nanostructure TiO2-coated SiO2 （TiO2/SiO2） particles were prepared using the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized employing the sol-gel method with TiChas a precursor. The samples were characterized by Fourier transform infrared spectroscopy （FTIR）, SEM, EDS, XPS, and XRD. The experimental results show that TiO2 nanopowders on the surface of SiO2 particles are well distributed, the amount of TiO2 is increased with the adding of coating layers, the pure anatase-TiO2 coating layers are synthesized at 500℃, and the photocatalytic activity of Fe^3＋-doped TiO2/SiO2 is higher than that of undoped TiO2/SiO2.