Anatase-type Titanium Dioxide Research Articles

Porous TiO2 Electrodes Prepared By a Rapid Pyro-Synthesis for Advanced Lithium-Ion Batteries

In this study, anatase-type titanium dioxide (TiO2) anodes were prepared by a polyol-assisted pyro-synthetic process followed by mild annealing in the range of 300 to 600 °C. The XRD studies confirmed the formation of anatase-type TiO2 and the Scherrer formula aided in establishing the average crystallite size to be less than 50 nm for all of the prepared samples. Electron microscopy studies revealed the average particle-size to be in the range between 5 and 50 nm whereas the adsorption studies demonstrated the mesoporous characteristics of all the prepared samples and the 500 °C electrode, in particular, exhibited tri-porosity. This unique tri-porous feature in combination with the sufficiently high particle crystallinity appears to contribute to the impressive electrochemical lithium storage (154.7 and 116.4 mAh g-1 at 3.2 and 6.4 C, respectively) in the 500 °C electrode. Furthermore, the pyro-synthetic strategy aids in developing nanostructured battery electrodes with porous morphologies and appears promising to be developed as an energy saving process for large-scale applications.

Amorphous Carbon-Based Semiconductor Capable of Controlling Its Optical Gap and Conductivity by Incorporating Silicon and Nitrogen Atoms

Optical gap-selective amorphous carbon (a-C) based n-type semiconductor materials were fabricated by incorporating silicon and nitrogen atoms by radio frequency plasma enhanced chemical vapor deposition method using a mixed solution of tetramethylsilane and 1,1,1,3,3,3-hexamethyldisilazane as a source material. The optical gaps can be controlled from 1.25 to 2.76 eV when Si/C ratio at amorphous Si-C network and sizes and number of sp2 clusters in multi-phase structure of the resulting carbon-rich amorphous silicon-carbon alloys (C-rich a-SiC) are varied by regulating Si atom%. The resulting Si 24 atom%-added C-rich a-SiC shows the optical gap of 1.76 eV, while Si 44 and 18 atom%-added C-rich a-SiC show 2.76 and 1.25 eV, respectively. The films show n-type conduction with the carrier density of ca. 1014 cm−3 and the carrier mobility of ca. 1 cm2V−1s−1 by doping N atoms of 1 atom%. The results of photocurrent measurement under UV exposure are verified and showed that the films have a function of photon-to-electron conversion with the quantum yield of ca. 7%, approximately one-third of the value obtained at anatase-type titanium oxide prepared by the sol-gel method.

Photocatalytic properties of carbon nanotubes/titania nanoparticles composite layers deposited by electrophoresis

A large-scale use of nanotechnology for photocatalysis-based water purification requires to identify simple, reliable and low cost processes for the production of the photocatalytic materials.To this aim we have investigated the possibility to deposit, by electrophoresis, composite layers formed by multi-walled carbon nanotubes (MWCNTs) and anatase-type titanium dioxide nanoparticles (np-TiO2), with different weight ratios. This method allows one to obtain photocatalytic layers on any conductive substrates that in principle can be re-used several times. The photocatalytic efficiency for each C-nanostructure/np-TiO2 composite layer is evaluated by measuring the degradation of methylene blue (MB) dye induced by the light of a solar simulator or UVA/blue light irradiation. The morphology and the composition of the deposited layers are studied by scanning electron microscopy and energy dispersive X-ray analyses, respectively, while photoluminescence spectra were acquired in order to explain the different photocatalytic behaviors observed for each material.

High-frequency welding of glass–fibre-reinforced polypropylene with a thermoplastic adhesive layer: Effects of ceramic type and long-term exposure on lap shear strength

In this study, high-frequency (HF) welding of glass–fibre-reinforced polypropylene (GF/PP) with thermoplastic adhesive layers consisting of zinc oxide (ZnO), anatase-type titanium oxide or silicon carbide was investigated. Effects of the ceramic type and content on the dielectric and temperature characteristics of these adhesive layers were evaluated experimentally, and the ratio of the dielectric loss tangent to the relative dielectric permittivity (tanδ/ε′), which was the index of the HF heating efficiency, exhibited different tendencies by these parameters. This value increased rapidly with increasing temperature even at 10vol% ZnO, suggesting that the heating of the adhesive layer may be accelerated by combining temperature rise with a small amount of ZnO. During the HF welding process, the ZnO-containing adhesive layer bound to GF/PP in the shortest time (18s) with high bond strength (~14MPa). The effects of temperature (50°C) and moisture (80% relative humidity) on the mechanical strength of the HF-welded specimens after a long-term exposure were also examined.

A Porous TiO2 Electrode Prepared by an Energy Efficient Pyro-Synthesis for Advanced Lithium-Ion Batteries

Anatase-type titanium dioxide (TiO2) anodes were prepared by a polyol-assisted pyro-synthetic process followed by mild annealing at temperatures in the range of 300 to 600°C for 3 h. The XRD studies clearly revealed the formation of anatase-type TiO2 for all of the prepared samples. The average crystallite size, calculated using the Scherrer formula, was determined to be less than 50 nm in all samples. Electron microscopy studies revealed that the particle-size in all samples ranged from 5 to 50 nm. N2 adsorption studies confirmed that the samples show mesoporous characteristics and in particular the TiO2 anode prepared at 500°C demonstrated a unique tri-porous feature that appears to benefit its electrochemical performances vs. lithium. Although there is no order of variation in the particle-size of the samples prepared at temperatures under 600°C, the tri-porous feature in combination with the sufficiently high particle crystallinity in the TiO2 anode prepared at 500°C appears to contribute to its impressive electrochemical lithium storage properties among the prepared electrodes. The pyro-synthetic strategy aids in developing nanostructured battery electrodes with porous morphologies and appears to offer promise for being developed as an energy saving process for large-scale applications.

Effect of Mo6+ doping on electrochemical performance of anatase TiO2 as a high performance anode material for secondary lithium-ion batteries

The effects of molybdenum (Mo6+) doping on the electrochemical properties of anatase-type titanium dioxide (TiO2) were investigated. The Mo6+-doped TiO2 samples were prepared using a simple and cost-effective solvothermal method with the doping levels of 1, 3, and 5wt%, followed by annealing at a low temperature of 300°C for 5h. High-resolution synchrotron X-ray diffraction and electron microscopy were conducted to know the structural and morphological properties of doped TiO2 samples. The dopant significantly suppresses the growth of TiO2 grains and reduces the particles sizes, which can also improve markedly the performance and stability of charge/discharge cycles. The particles sizes are in the range of 115–250nm and 5–10nm for undoped and Mo-doped TiO2 nanoparticle samples, respectively. Electrochemical results show that the Mo6+-doped TiO2 nanoparticle samples display a significantly lower charge transfer resistance, higher rate capability and excellent reversibility. Author’s believed that the high rate performance offered by Mo-doped TiO2 nanoparticle electrodes may be attributed to the enhanced electronic and ionic conductivity, which are achieved by increasing the number of Ti4+ vacancies in the lattice via Mo6+ doping, which may lead to the generation of more free holes in the doped p-type semiconductor. The increased hole concentration in the valence band can contribute to the electrical conductivity of the doped sample.

Newly developed TiO2-2-HABT functional material for water treatment

In the present investigation, initially, 2-hydroxyacetophenone–biuret–trioxane (2-HABT) terpolymer was successfully synthesized, purified and characterized in the laboratory. Then, titanium oxide photocatalyst was anchored on 2-HABT terpolymer using molecular adsorption–deposition method. The titanium oxide particles, deposited on the 2-HABT terpolymeric molecules, formed a coating of about 100 nm in thickness. This newly modified functional photocatalytic material was characterized by means of infrared spectroscopy, X-ray diffraction and scanning electron studies. An anatase-type titanium oxide was uniquely developed. This new TiO2-2-HABT photocatalyst exhibited an excellent photocatalytic activity in the photodegradation of quite concentrated dyes. The dye molecules in bulk solution was supposed to be condensed around titanium oxide particles because of the adsorption phenomenon on 2-HABT polymer molecules, and, therefore, the photocatalytic process was enhanced due to the combined effect of adsorption by 2-HABT terpolymer macromolecules and photocatalytic activity on anatase-type titanium oxide. It was observed that the decolorization of contaminated water occurred within a short-time interval. Thus, it can be concluded that the functional photocatalytic material, reported in article, can be successfully used for water and wastewater treatments.

Development of Amorphous Carbon-Based Variable Optical Gap Semiconductor Materials

Amorphous carbon (a-C) based semiconductor materials with variable optical gap and high semiconductor properties could be successfully fabricated by radio frequency plasma enhanced chemical vapor deposition (RF-PeCVD) method using a mixed solution of tetramethylsilane (TES) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS) as a liquid source. The optical gap could be controlled by varying sizes and number of sp 2 clusters included in multi-phase structure of a-C by incorporating Si atoms. The resulting Si-doped a-C with 10 six-membered rings in sp 2 clusters shows 1.76 eV of optical gap and Si-doped a-C with 4 six-membered rings in sp 2 clusters shows 2.76 eV. From photocurrent measurement under UV exposure, it was clarified that these films functioned as high performance n-type semiconductors with ca. 4 % of quantum yield, which was on the same level as that obtained at anatase-type titanium oxide prepared by the sol-gel method.

Fabrication of silicon and carbon based wide-gap semiconductor thin films for high conversion efficiency

Nitrogen doped amorphous silicon carbide (N-doped a-SiC) thin films were fabricated by radio frequency plasma enhanced chemical vapor deposition (RF-PeCVD) method using mixed solution of tetramethylsilane (TES) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS) as a liquid source. Chemical composition of N-doped a-SiC thin film was Si:C = 1:4 and sp2-bonded carbon ratio was 0.75. N-doped DLC were multi-phase structure including a-SiC phase, sp2 clusters and a-Si clusters. Optical gap and resistivity of the film were 1.68 eV and 4.32×104 Ω cm, respectively. From photocurrent measurement under UV exposure, it was clarified that the film functioned as n-type semiconductor materials with 4.87 % of quantum yield, which was on the same level as that obtained at anatase-type titanium oxide prepared by sol-gel method. To apply these films to solar cells, further improvements of optical gap and conductivity are necessary.

Synthesis of spindle and square bipyramid-shaped anatase-type titanium dioxide crystals by a solvothermal method using ethylenediamine

Synthesis of spindle and square bipyramid-shaped anatase-type titanium dioxide crystals by a solvothermal method using ethylenediamine

A rapid and easy method for the qualitative detection of intracellular deposition of inhaled nanoparticles

In recent years, nanoparticle exposure risk has drawn increasing attention from the research community and the general public. However, analysis of nanoparticles is hindered by their small size, which prevents the development of methods for their detection in cells and tissues. For risk assessment of nanoparticle exposure, it is important to measure the exact amount of deposited material in pulmonary tissue. Using a nanoparticle exposure device, A/JJmsSlc mice were chronically exposed transtracheally to anatase-type titanium dioxide particles. A microscope-integrated laser Raman spectrometer was used to detect differentially stained macrophages in a pulmonary wash obtained from the mice exposed to the particles. This detection method allowed rapid and easy sample collection and qualitative analysis, and the method may be useful for conducting large-scale evaluations in workers exposed to environments heavily contaminated with nanoparticles. From the Clinical EditorThis paper discusses a microscope-integrated laser Raman spectrometer method to measure the exact amount of nanoparticles deposited in pulmonary tissue. This method allows rapid sample collection, qualitative analysis, and may be useful for large-scale evaluations.

Effect of co-dopant on the formation and properties of anatase-type titania solid solutions doped with niobium

The effect of co-dopant M (M=gallium (Ga), aluminum (Al), and scandium (Sc)) on the formation, crystallite growth, optical band gap, photocatalytic activity, and phase stability of anatase-type titanium dioxide solid solutions (Ti 1−2 X Nb X M X O 2) containing the same amount of dopant niobium (Nb) that were directly formed as nanoparticles under mild hydrothermal conditions at 180 °C for 5 h was investigated. The composition range X of the anatase-type solid solutions (Ti 1−2 X Nb X M X O 2) depended on the co-dopant M, i.e., X=0.15–0.20 for M=Ga and Al, and X=0.33 for M=Sc. A remarkable increase in the lattice parameter c 0 was detected in the solid solutions co-doped with M=Sc. The increase in the amount of co-dopant M=Ga and Al enhanced the crystallite growth of the anatase-type solid solutions under the hydrothermal conditions. The photocatalytic activity of the solid solutions (Ti 0.80Nb 0.10M 0.10O 2) co-doped with M=Sc, Ga, and Al increased in that order. The co-dopant M=Ga promoted the anatase-to-rutile phase transformation of the solid solutions at lower temperature.

Apatite-forming ability of titanium compound nanotube thin films formed on a titanium metal plate in a simulated body fluid

We compared the apatite-forming ability of a sodium titanate nanotube thin film, an anatase-type titanium dioxide nanotube thin film, and a silver nanoparticle/silver titanate nanotube nanocomposite thin film, in simulated body fluid. The ability of the silver nanoparticle/silver titanate nanotube nanocomposite thin film is slightly higher than that of the anatase-type titanium dioxide nanotube thin film and significantly higher than that of the sodium titanate nanotube thin film. The high ability of the silver nanoparticle/silver titanate nanotube nanocomposite thin film is a newly observed phenomenon, which is probably due to the crystal structure of silver titanate – specifically, to the surface atomic arrangement, the large amount of Ti–OH formed on the nanotube surface, or both. The anatase-type titanium dioxide nanotube thin film and the silver nanoparticle/silver titanate nanotube nanocomposite thin film may have bright prospects for future use in implant materials such as artificial joints. The silver nanoparticle/silver titanate nanotube nanocomposite thin film is particularly promising for its antibacterial properties.

UV-induced switching behavior of novel fluoroalkyl end-capped vinyltrimethoxysilane oligomer/titanium oxide nanocomposite between superhydrophobicity and superhydrophilicity with good oleophobicity

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer suffered the sol–gel reaction under alkaline conditions in the presence of titanium oxide nanoparticles in tetrahydrofuran to afford the corresponding fluorinated oligomer/titanium oxide nanocomposites[R F-(VM-SiO 2) n -R F/TiO 2] in excellent to moderate isolated yields. These fluorinated composites thus obtained were nanometer size-controlled fine particles, and exhibited good dispersibility and stability in traditional organic solvents except for water. These fluorinated nanocomposites were applied to the surface modification of glass to exhibit not only a completely superhydrophobic characteristic (a water contact angle: 180°) with a non-wetting property against water droplets but also a good oleophobicity imparted by fluoroalkyl segments in the composites on their surface. Of particular interest, we have found that the wettability for water can be switched between superhydrophobicity and superhydrophilicity by alternation of ultraviolet (UV) irradiation and dark storage with keeping a good oleophobicity on the modified surface treated with the anatase-type titanium oxide composite.

Preparation of Hollow Titanium Dioxide Shell Thin Films by Electrophoresis and Electrolysis for Dye-Sensitized Solar Cells

Titanium oxide (TiO x ) thin films were prepared by cathodic electrolysis of a solution of ammonium hexafluorotitanate and ammonium nitrate at 323 K on polystyrene (PS) spheres template adsorbed on a transparent conducting substrate [fluorine-doped tin oxide (FTO)] by electrophoresis. The calcination at 723 K converted the FTO/PS core/TiO x shell to a hollow anatase-type titanium dioxide (TiO 2 ) thin film. The energy-conversion efficiency of a dye-sensitized solar cell per TiO 2 weight using the hollow TiO 2 shell electrode was higher than that with a nanoparticle-sintered electrode.

Deposition of Metal Oxide Films at Liquid−Liquid Interface by the Liquid Phase Deposition Method

The liquid phase deposition (LPD) of metal oxide thin films at the liquid−liquid interface was investigated. Just after the start of the LPD reaction, depositions were observed continually at the liquid−liquid interface. The deposition grew two-dimensionally into a self-standing film with thickness of 1 μm and domain size of up to ca. 1 mm without any solid substrates. The self-standing film was formed with asymmetrical morphology, which consisted of flat surface on the side of the liquid−liquid interface and relatively rough surface on the side of the bulk solution. The structure was characterized by Raman spectroscopy, confirming that metastable ammonium titanium oxide fluoride (NH4TiOF3) was first deposited at the liquid−liquid interface, on which anatase-type titanium oxide (TiO2) was deposited second to forming the asymmetrical bilayer structure. It was suggested that the metal fluoride complex of the precursor was concentrated in the vicinity of the liquid−liquid interface compared with the solid−li...

Effect of UV irradiation on cellulase degradation of cellulose acetate containing TiO2

Cellulose acetate (CA) films containing anatase type titanium dioxide (TiO2) nanoparticles were prepared by solution casting. The film surface was modified by UV irradiation using a grid type UV irradiator. The UV irradiation caused slight increase in photodegradation of the CA films with TiO2 compared to the CA film alone. However, CA films irrespective of TiO2 content did not show a significant enzymatic degradation by a cellulase fromAspergillus niger without UV irradiation. Upon UV irradiation, the biodegradability remarkably improved even in the CA film without TiO2. The irradiation of CA films decreased both the water contact angle and the degree of substitution (DS) implying the decrease in acetyl groups of the CA film surface due to the photo-scission of the acetyl group and photooxidation, resulting in more facile biodegradation of the surface film layer. The substantial enhancement in biodegradation of the UV irradiated CA film containing TiO2 was attributed to the increased hydrophilicity, lowered DS and zeta potential due to the photoscission and the photooxidation effect of UV light. Also the increased surface area of the CA film due to the photocatalysis of TiO2 particles may encourage the facile biodegradation.

化成処理によるマグネシウム上への環境イノベーション皮膜の合成

Titanium dioxide (TiO2) coatings were prepared by chemical conversion treatment of magnesium in (NH4)2[TiO(C2O4)2] with H2O2, then, anatase type TiO2 coatings were prepared by sintering. To identify the coating structure, coating analysis was carried out using an infrared absorption spectrum analyzer. Based on the infrared absorption results, a component of the coating was found in the hydrolysis product of peroxo-titanium compound. Furthermore, the coating analysis was carried out using X-ray diffractometry (XRD), and non-sintered coating was amorphous; however, the coating sintered at more than 573 K was anatase-type titanium dioxide. In the forming process of the conversion treatment in (NH4)2[TiO(C2O4)2] with H2O2, first, the magnesium was dissolved to H+ in the bath and then, hydrogen ions on the magnesium surface were consumed to generated hydrogen gas. Thus, the pH of the interface became alkali. The hydrolysis of the peroxo-titanium compound was deposited on the magnesium because pH increased on the surface. From the XPS results and the TG-DTA results, a component of the coating is a hydrolyzation product of a peroxo-titanium compound and Mg(OH)2. Because Mg(OH)2 is generates in pH more than 11, it is considered that the pH on the magnesium surface is more than 11. The coating sintered at 573 K had the highest photocatalytic activity. The photocatalytic activity of the coating sintered at 623 K was lower than the coating heated at 573 K, which is attributed to growth of TiO2 particle. This forming process of the coating is low cost because of the useless electrolytic decomposition process and increasing the speed of the treatment. It is possible to treat complicated form of the substrate metal, so this method can be expected to use in various fields. Therefore this method is expected to practical use for environmental purification.

Photocatalytic Hydrogen Production from Gas-phase Methanol and Water with Nanocrystalline TiO2 Thin Films in High Vacuum

ABSTRACTPhotocatalytic hydrogen production with gas-phase reactions in high vacuum was examined for nanocrystalline anatase-type titanium dioxide (TiO2) thin films. The hydrogen generation process on platinized TiO2 specimens was investigated using a quadrupole mass spectrometer at a real-time scale under various partial pressures of gaseous methanol and water. As a result, hydrogen generation was successfully detected under ultraviolet ray (UV) illumination even in high vacuum (∼ 10−7 Torr). And the amount of produced H2 largely depends on the temperature of TiO2 samples, probably due to different surface states of TiO2. This study suggests the possibility of new high-speed H2 production system with gas-phase photocatalytic reactions.

Effects of Photocatalytic Agent on DS-Nh Mice, Developing Atopic Dermatitis-Like Eruption with an Increase of Staphylococcus aureus

Background:Staphylococcus aureus(S. aureus) is thought to play a significant role in the exacerbation of atopic dermatitis (AD). DS-Nh mice, a non-hair-bearing mouse model of AD, spontaneously develop dermatitis under conventional conditions. A remarkable increase in S. aureus is considered to strongly relate to the induction and aggravation of this dermatitis. A topical use of anatase-type titanium dioxide (TiO₂) followed by UV irradiation, acting as photocatalyst, is believed to have antibacterial activity. We investigated the bactericidal effect of TiO₂ with UV irradiation on DS-Nh mice to prevent the aggravation of the dermatitis. Methods: Ten-week-old DS-Nh mice were treated with TiO₂ in petrolatum on the back, followed by UVA irradiation, for 11 weeks. The severity of dermatitis was assessed by evaluating individual lesions using a 4-grade scale and expressed as the total skin score. S. aureus colonizing the mouse skin was counted after isolation and incubation with agar medium. The skin barrier dysfunction was evaluated by measuring transepidermal water loss (TEWL). Results:The mice treated with TiO₂ and UV irradiation showed a significant increase in total skin scores, the number of S. aureus and TEWL values, compared with non-treated mice. In contrast, these parameters were significantly lower in the mice treated with petrolatum and UV irradiation. Conclusions: A significant increase in S. aureus was recognized on the skin together with the aggravation of AD-like dermatitis in our mice model. Skin barrier dysfunction induced by TiO₂ and UV irradiation seems to facilitate the increase in S. aureus.