Study on the photocatalytic activity of TiN/TiO2 nanoparticle formed by ball milling

TiN/TiO₂ nanoparticle photocatalyst was prepared by ball milling of TiO₂ in H₂O solution doped with TiN. The photocatalyst was characterized by UV–Vis diffuse reflection spectroscopy, X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Based on the results of the characterization, the mechanism of the increase in photocatalytic activity was investigated. The results show that when the amount of doped TiN is 0.15 wt%, the photocatalytic activity of the TiN/TiO₂ is at its peak. Compared with TiO₂, the photoabsorption wavelength range of the TiN/TiO₂ photocatalyst red-shifts about 30 nm, and the photoabsorption intensity increases as well. The photocatalytic activities of the photocatalyst are higher than that of TiO₂ under UV and visible light irradiation. The increase of surface Ti³⁺ reactive center and the extension of the photoabsorption wavelength are the main factors for the increase in the photocatalytic activity of the TiN/TiO₂. Doped TiN neither changes the TiO₂ crystal phase nor creates new crystal phase by ball milling.     

Resonant infrared matrix-assisted pulsed laser evaporation of TiO2 nanoparticle films

The successful development of flexible, high performance thin films that are competitive with silicon-based technology will likely require fabricating films of hybrid materials that incorporate nanomaterials, glasses, ceramics, polymers, and thin films. Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is an ideal method for depositing organic materials and nanoparticles with minimal photochemical or photothermal damage to the deposited material. Furthermore, there are many nonhazardous solvents containing chemical functional groups with infrared absorption bands that are accessible using IR lasers. We report here results of recent work in which RIR-MAPLE has been employed successfully to deposit thin films of TiO₂ nanoparticles on Si substrates. Using an Er:YAG laser (λ=2.94 μm), we investigated a variety of MAPLE matrices containing –OH moieties, including water and all four isomers of butyl alcohol. The alcohol isomers are shown to provide effective and relatively nontoxic solvents for use in the RIR-MAPLE process. In addition, we examine the effects of varying concentration and laser fluence on film roughness and surface coverage.     

Preparation and photocatalytic activity of bicrystal phase TiO2 nanotubes containing TiO2-B and anatase

Bicrystal phase TiO₂ nanotubes (NTS) containing monoclinic TiO₂-B and anatase were prepared by the hydrothermal reaction of anatase nanoparticles with NaOH aqueous solution and a heat treatment. Their structure was characterized by XRD, TEM and Raman spectra. The results showed that the bicrystal phase TiO₂ NTS were formed after calcining H₂Ti₄O₉·H₂O NTS at 573 K. The bicrystal phase TiO₂ NTS exhibit significantly higher photocatalytic activity than the single phase anatase NTS and Dessuga P-25 nanoparticles in the degradation of Methyl Orange aqueous solution under ultraviolet light irradiation, which is attributed to the large surface and interface areas of the bicrystal phase TiO₂ NTS.     

Preparation and characterization of polyphosphotungstate/ZrO2 nanocomposite and their sonocatalytic and photocatalytic activity under UV light illumination

Polyoxometalates (POM) supported on zirconia, H₃PW₁₂O₄₀/ZrO_2, were prepared by incorporating polyphosphotungstate into a zirconia matrix via sol-gel technique that involving the hydrolysis of zirconium (IV) n-butoxide, Zr (n-OBu)₄, as the ZrO₂ source. This insoluble and readily separable catalyst was characterized by using XRD, FT-IR, SEM, and UV diffuse reflectance spectroscopy (UV-DRS), indicating that the polyphosphotungstate was chemically attached to the zirconia supports, and primary Keggin structure remained intact. The photocatalytic and sonocatalytic activity of the supported polyphosphotungstate was tested via degradation of different dyes in aqueous solutions. The POM-ZrO₂ nanocomposite showed higher photocatalytic and sonocatalytic activity than pure polyoxometalate or pure ZrO₂.     

Enhanced photocatalytic activity of In2O3-decorated TiO2

Titania (TiO₂)-based photocatalysts decorated with different amounts of indium oxide (In₂O₃) were prepared by a pore impregnating method and characterized by the Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The separation efficiency of photogenerated charges was investigated using benzoquinone (BQ) as scavenger. The activities of the photocatalysts were evaluated by decolorization of methyl orange (MO) aqueous solution under ultraviolet-light irradiation. Compared to TiO₂, In₂O₃/TiO₂ composites show improved photocatalytic performance due to the coupling effect of TiO₂ and In₂O₃, which greatly improves the separation of photogenerated electrons and holes.     

Optical constants and their dispersion of Ag-MgF2 nanoparticle composite films

Ag-MgF2 composite films with different Ag fractions were prepared through a co-evaporation method.Microstructure analysis shows that the films are composed of amorphous MgF2 matrix and embedded fcc-Ag nanoparticles. The optical constants and their dispersion of the films, within the wavelength range of 250 - 650 nm, were measured by reflecting spectroscopic ellipsometry. The maximum of the imaginary part ε" of the complex dielectric permittivity attributing to the surface plasmon resonance polarization of the Ag nanoparticles in an Ag-MgF2 film, and the tangent of the phase-shift angle δ resulting from the dielectric loss of the film, occur at λ = 435 nm and λ = 420 nm, respectively. Based on Maxwell-Garnett effective medium theory, the experimentally observed dispersion spectra were reasonably described.     

Preparation and characterization of SiO2/TiO2/methylcellulose hybrid thick films for optical waveguides

SiO2/TiO2/methylcellulose composite materials processed by the sol-gel technique were studied for optical waveguide applications.     

Triblock copolymer-templated synthesis of porous TiO2 and its photocatalytic activity

Mixed amorphous and anatase-type titania particles were synthesized using non-ionic triblock copolymer as surfactant template and TiOSO₄ as inorganic precursor through sol–gel process. The as-prepared materials were characterized by X-ray diffraction spectroscopy, scanning and transmission electron microscopy, specific surface area, Fourier-transformed infrared spectroscopy, and diffuse reflectance ultraviolet–visible spectroscopy. The template material could be easily removed by extracting with dichloromethane and was confirmed by infrared spectroscopy. X-ray diffraction pattern reveals the crystalline part of as-prepared product as a framework of anatase phase. From the N₂ adsorption–desorption analysis, the as-prepared sample has a surface area of 301 m²/g with pore size distribution narrowly centered around 6 nm. The photodegradation of indigo carmine including kinetics, effect of pH, and recyclability of the product were investigated. The photocatalytic results showed that the as-synthesized titania could efficiently degrade indigo carmine under ultraviolet irradiation and showed higher photocatalytic activity than the commercial Degussa P25–TiO₂.     

Preparation and characterization of polyaniline+TiO2 composite films

In this work, we have prepared electrochemically and studied a composite materials based on an organic conducting polymer, polyaniline (PANI), in which inorganic semiconductor titanium dioxide (TiO₂) particles were incorporated with different concentrations. The polyaniline/titanium dioxide composite material which had been deposited by cyclic voltammetry on substrates of indium tin oxide was then characterized. The cyclic voltammogram showed one redox couple characteristic of the oxidation and reduction states of the produced composite material. The impedance spectroscopy study showed that the resistance of the film increases with the TiO₂ cocntent incorporated in the polymer. The incorporation of TiO₂ in PANI covering the surfaces was confirmed by the scanning electron microscopy and the energy dispersive X-ray analysis. The morphological analysis of the film surfaces showed that the TiO₂ nanoparticle increased the roughness. These observations allow to consider a new approach to improve the physicochemical properties of the interface between the organic and inorganic material. The I–V characteristics of PANI+TiO₂ heterostructure diode showed the nonlinear nature of the I–V curve of PANI+TiO₂ heterostructure device.     

The influence of TiO2 nanoparticle incorporation on surface potential decay of corona-resistant polyimide nanocomposite films

PI nanocomposite films containing surface modified nanoparticles by employing silane coupling agent were prepared using in-situ dispersion polymerization process. The surface potential decay measurements on films were investigated over the different negative corona-charged voltages and times in a controlled environment where temperature and relative humidity were kept at 21 °C and 45%, respectively. There is a significant change in the surface potential decay characteristics after nano-fillers were introduced into polyimide. The surface potential decay pattern depends also on the amount of nano-fillers. The possible surface potential decay and corona resistance mechanisms responsible for the observed phenomena were discussed.     

SERS activity of Au nanoparticle films

The core-shell gold nanoparticle film is fabricated by using nanolithography and self-assembly monolayer technology. The film exhibits unique optical properties and has strong surface enhanced Raman scattering （SERS） activity. The relationship between nanostructure and surface electrical field is studied by employing pyridine as the SERS probe. It is found that particle size and inter-particle space are important factors. The enhancement ratio is measured to be more than 10^4.     

One-step solvothermal preparation of TiO2/C composites and their visible-light photocatalytic activities

Preparation of anatase type titania nanoparticles and their carbon modification were synchronously achieved by the solvothermal method with glycerol as the carbon source. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectra (DRS). It was found that the glycerol/ethanol ratio affected significantly the morphology and properties of TiO₂/C composites. The TiO₂/C composite which was obtained in the solution with the glycerol/ethanol ratio of 5/75, contained 1.2 mass% carbon and exhibited both superior adsorption capability and visible-light photocatalytic activity. Contrary to this, samples prepared in the solution with higher glycerol/ethanol ratio, exhibited lower photocatalytic activity similar to that of the titania without carbon modification. It was suggested that excess addition of glycerol might contribute to large amounts of carbonaceous species and severe aggregation of the as-prepared samples, and thus reduced the surface area. As a result, the adsorption capability and visible-light photocatalytic activity increased at first and then decreased with the increase of glycerol addition. Present study provided a facile one-step method to obtain TiO₂/C composites with a controllable carbon content and photocatalytic performance under mild temperature.     

P/Si-TiO2 transparent films with high anatase stability and photocatalytic activity

The anatase-TiO₂ transparent films, containing 3 mol% of Si and P elements (as dopants), were synthesized using a process combining the sol-gel method and spin-coating technique. Effects of relative ratio of dopants and calcination temperature on phase transformation, grain growth, surface morphology, light transmittance, band-gap energy and photocatalytic activity of the P/Si-TiO₂ films were examined and their results were compared with those of the undoped-TiO₂ and Si-TiO₂ films. The P/Si-TiO₂ films calcined at temperature between 600 and 900 °C adhered strongly to the surface of fused-silica substrate and were composed of anatase-TiO₂ monophase. The photocatalytic activities of the films were measured and represented using a characteristic time constant (τ) for the methylene blue (MB) photodegradation. The small τ stands for high photocatalytic ability of the film. The P/Si-TiO₂ film, containing equalmolar Si and P dopants, calcined at 800 °C gave the best performance in photocatalysis; this film had τ=5.7 h and decomposed about 90 mole% of MB in the water after 12 h of the 365-nm UV light irradiation.     

Synthesis of Zr-doped TiO2 templated from cloth and its photocatalytic activity

Biomorphic Zr-doped TiO₂ (Zr _x Ti_{1 ? x} O₂) with hierarchical micro- and nanostructures was successfully fabricated using cloth as the host template. We found that the resulting Zr _x Ti_{1 ? x} O₂ faithfully duplicated the morphologic microstructures of the initial cloth with grain size of about 10–50 nm. The photocatalytic activity of the as-prepared Zr _x Ti_{1 ? x} O₂ was examined by the degradation of rhodamine B in aqueous solution under simulated solar light, which showed that templates pretreated with NaOH solution followed by mixed acid and an appropriate amount of doped Zr (3 mol%) could significantly enhance the photocatalytic activities of Zr _x Ti_{1 ? x} O₂. This simple template method provides a cost-effective and ecofriendly route to synthesize other metal-doped semiconductor materials of predicted morphology.     

The structure and photocatalytic activity of TiO2 thin films deposited by dc magnetron sputtering

This paper seeks to determine the optimal settings for the deposition parameters, for TiO₂ thin film, prepared on non-alkali glass substrates, by direct current (dc) sputtering, using a ceramic TiO₂ target in an argon gas environment. An orthogonal array, the signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. Using the Taguchi method for design of a robust experiment, the interactions between factors are also investigated. The main deposition parameters, such as dc power (W), sputtering pressure (Pa), substrate temperature (°C) and deposition time (min), were optimized, with reference to the structure and photocatalytic characteristics of TiO₂. The results of this study show that substrate temperature and deposition time have the most significant effect on photocatalytic performance. For the optimal combination of deposition parameters, the (1 1 0) and (2 0 0) peaks of the rutile structure and the (2 0 0) peak of the anatase structure were observed, at 2θ ∼ 27.4°, 39.2° and 48°, respectively. The experimental results illustrate that the Taguchi method allowed a suitable solution to the problem, with the minimum number of trials, compared to a full factorial design. The adhesion of the coatings was also measured and evaluated, via a scratch test. Superior wear behavior was observed, for the TiO₂ film, because of the increased strength of the interface of micro-blasted tools.     

Preparation, characterization and visible-light photocatalytic activity of AgI/AgCl/TiO2

In this paper, a novel composite photocatalyst AgI/AgCl/TiO₂ was prepared by ion exchange method and characterized by XRD, SEM and UV-Vis spectrometry. The as-prepared AgI/AgCl/TiO₂ composites show much higher photocatalytic activity than AgCl/TiO₂ and AgI/TiO₂ under visible-light irradiation (λ > 400 nm) in the process of methyl orange (MO) degradation. When the molar percentage of AgI to initial AgCl is 20% (sample SE-20%), the maximal degradation efficiency of MO has reached 85.8% after irradiation for 120 min. The enhancement of photocatalytic activity of the composite photocatalyst AgI/AgCl/TiO₂ will be attributed to its good absorption in the visible-light region, especially low recombination rate of the electron-hole pairs based on the photoluminescence (PL) spectra investigation of AgI/AgCl/TiO₂ and the matching band structures of AgI, AgCl and TiO₂. The detection of reactive species by radical scavengers displays that O₂⁻ and H₂O₂ are the main reactive species for the degradation of MO under visible-light irradiation. Moreover, PL analysis by using terephthalic acid (TA) as a probe molecule further reveals that OH can be negligible for the degradation of MO.     

Synthesis and characterization of nitrogen-doped TiO2 coatings on reduced graphene oxide for enhancing the visible light photocatalytic activity

Nitrogen-doped TiO₂ coatings on reduced graphene oxide were prepared via a sonochemical synthesis and hydrothermal process. The nanocomposites showed improved photocatalytic activity due to their large specific surface areas (185–447 m²/g), the presence of TiO₂ in the anatase phase, and a quenched photoluminescence peak. In particular, GN3-TiO₂ (nitrogen-doped TiO₂ coatings on rGO with 3 ml of titanium (IV) isopropoxide) exhibited the best photocatalytic efficiency and degradation rate among the materials prepared. With nitrogen-doped on the reduced graphene oxide surface, the photocatalytic activity is enhanced approximately 17.8 times compared to that of the pristine TiO₂. The dramatic enhancement of activity is attributed to the nitrogen contents and rGO effectively promoting charge-separation efficiency and providing abundant catalytically active sites to enhance the reactivity. The composites also showed improved pollutant adsorption capacity, electron–hole pair lifetime, light absorption capability, and absorbance of visible light.     

Physicochemical properties of core/shell structured pyrite FeS2/anatase TiO2 composites and their photocatalytic hydrogen production performances

A new photocatalytic system using anatase TiO₂ loaded onto pyrite FeS₂ (FeS₂/TiO₂) was developed to enhance the production of hydrogen. The FeS₂ (3.0, 5.0, 10.0, and 15.0 wt-%)/TiO₂ particles in SEM photos showed a core/shell structure composed of pyrite FeS₂ with a grape-like morphology of length of ～1.0 μm and anatase TiO₂ of diameter <50 nm. The evolution of H₂ by methanol/water (1:1) photo splitting over FeS₂/TiO₂ in a liquid system was enhanced as compared with that obtained using pure TiO₂ and FeS₂. In particular, 9.8 mmol of H₂ gas was produced in 10 h when 0.5 g of a 10.0 wt-% FeS₂/TiO₂ core/shell composite was used. Hydrogen production was increased by adding KOH electrolyte to 11.2 mmol. On the basis of cyclic voltammetry (CV) and UV–visible spectra results, this photoactivity of the FeS₂/TiO₂ composite was attributed to a shorter band gap than those of pure TiO₂ and FeS₂.     

TiO2/Al2O3薄膜的原子层沉积和光学性能分析

采用原子层沉积技术在熔石英和BK7玻璃基片上镀制了TiO2/Al2O3薄膜,沉积温度分别为110℃和280℃。利用X射线粉末衍射仪对膜层微观结构进行了分析研究,并在激光损伤平台上进行了抗激光损伤阈值测量。采用Nomarski微分干涉差显微镜和原子力显微镜对激光损伤后的形貌进行了观察分析。结果表明,采用原子层沉积技术镀制的TiO2/Al2O3增透膜的厚度均匀性较好,Φ50 mm样品的膜层厚度均匀性优于99%;光谱增透效果显著,在1 064 nm处的透过率〉99.8%;在熔石英和BK7基片上,TiO2/Al2O3薄膜在110℃时的激光损伤阈值分别为（6.73±0.47）J/cm2和（6.5±0.46）J/cm2,明显高于在280℃时的损伤阈值。     

Anatase TiO2 films fabricated by pulsed laser deposition using Ti target

TiO₂ films were prepared by pulsed laser deposition using a metallic Ti target in an O₂ gas ambient. The microstructure along with optical and photocatalytic properties of the deposited films were systematically studied by changing the deposition parameters and substrates. It was found that TiO₂ films having nearly pure anatase phase grew effectively in O₂ atmosphere. When the films were fabricated at a substrate temperature of 400°C, their phase structures were greatly affected by the O₂ gas pressure, and nearly pure anatase phase with typical (101) and (004) peaks can be obtained under an O₂ pressure of 15 Pa. For the deposition at 700°C, the crystal structure of the TiO₂ films exhibited a strong anatase (004) peak and was inert to the oxygen pressures. Two modes, namely a substrate-temperature-controlled mode and an oxygen-pressure-controlled mode, were considered for the growth of the anatase TiO₂ films under different substrate temperatures. In addition, the optical and photocatalytic properties were found to be sensitive to both the microstructure and grain size of the TiO₂ films.