Fabrication of Gold-Doped Titanium Dioxide (Tio2:Au) Nanofibers Photocatalyst by Vacuum Ion Sputter Coating

Gold-doped titanium dioxide (TiO₂:Au) nanofibers were prepared by a combination of an electrospinning method and sputtering technology and characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The results show that the morphologies of Au-deposited TiO₂ nanofibers can be well controlled by the sputtering time. The photocatalytic decomposition of acetaldehyde on TiO₂:Au nanofibers was investigated at room temperature. The photocatalytic effect of the TiO₂ nanofiber was improved by using the Au-doped titania nanofibers catalyst and increased as the Au depositing time was increased from 40 s to 3 min. The photocatalytic removal rate of acetaldehyde remained above 94% on the TiO₂:Au nanofibers (2 min) catalyst under ultraviolet (UV) irradiation for 70 min, 1.7 times that of pure TiO₂ fibers.     

低成本溶胶-凝胶法制备SiO2/TiO2双层膜的减反射与自清洁性能

将玻璃基底依次在低成本的SiO₂溶胶和TiO₂溶胶中浸渍后,在500 oC下煅烧制备了同时具备减反射与自清洁性能的SiO₂/TiO₂双层膜．该膜的光学性能与结构特征分别通过紫外-可见分光光度计和场发射扫描电镜进行了表征．同时,源于超亲水性和光催化作用的自清洁性能也凸显出来．实验结果表明制备SiO₂/TiO₂双层膜对光的透射率最高可达到95%,同时具备自清洁性能．     

Photosensitization of nanocrystalline TiO2 film electrode with cadmium sulphoselenide

Nanocrystalline titanium dioxide (TiO₂) thin films composed of densely packed nanometer-sized grains have been successfully deposited onto an indium-doped-tin oxide (ITO) substrate. Then cadmium sulphoselenide (CdSSe) thin film was deposited onto pre-deposited TiO₂ to form a TiO₂/CdSSe film, at low temperature using a simple and inexpensive chemical method. The X-ray diffraction, selected area electron diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and water contact angle techniques were used for film characterization. Purely rutile phase of TiO₂ with super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 30-40 (±2) nm was observed. The increase in optical absorption was observed after CdSSe film deposition. Nest like surface morphology of CdSSe on TiO₂ surface results in air trapping in the crevices which prevents water from adhering to the film with increase in water contact angle. Photosensitization of TiO₂ with CdSSe was confirmed with light illumination intensity of 80 mW/cm².     

Titanium dioxide-coated nanofibers for advanced filters

This article reports on titanium dioxide (TiO₂)-coated nanofibers deposited on a filter surface by the electrospinning process. After depositing a micrometer-thick film of polyamide 11 nanofibers on polypropylene fabric, TiO₂ nanoparticles can be directly electrosprayed onto the nanofibers. X-ray diffraction and Raman spectroscopy showed minimal change in the phase composition (anatase and rutile) and no change in the particle size of nanocrystalline TiO₂ after coating. Scanning electron microscopy demonstrated that nanofibers were uniformly coated by titanium dioxide nanoparticles without agglomeration. TiO₂-coated filters showed excellent photocatalytic-bactericidal activity and photo-induced hydrophilicity.     

Enhanced photocatalytic degradation of Safranin-O by heterogeneous nanoparticles for environmental applications

Nanostructure titanium dioxide (TiO₂) has been synthesized by hydrolysis of titanium tetrachloride in aqueous solution and Ag-TiO₂ nanoparticles were synthesized by photoreduction method. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier-transform infrared (FT-IR) and UV-vis absorption spectroscopy. The experimental results showed that the sizes of the synthesized TiO₂ and Ag-TiO₂ particles are in the range of 1.9-3.2 nm and 2-10 nm, respectively. Moreover, Ag-TiO₂ nanoparticles exhibit enhanced photocatalytic activity on photodegradation of Safranin-O (SO) dye as compared to pure TiO₂. The positive effect of silver on the photocatalytic activity of TiO₂ may be explained by its ability to trap electrons. This process reduces the recombination of light generated electron-hole pairs at TiO₂ surface and therefore enhances the photocatalytic activity of the synthesized TiO₂ nanoparticles. The effects of initial dye and nanoparticle concentrations on the photocatalytic activity have been studied and the results demonstrate that the dye photodegradation follows pseudo-first-order kinetics. The observed maximum degradation efficiency of SO is about 60% for TiO₂ and 96% for Ag-TiO₂.     

Influence of deposition atmosphere on photocatalytic activity of TiO2/SiOx double-layers prepared by RF magnetron sputtering

TiO₂/SiO_x double-layers have been prepared at room temperature by RF magnetron sputtering. The TiO₂ top-layer was deposited in an Ar atmosphere, while the SiO_x bottom-layer was deposited in an Ar/O₂ atmosphere. Samples were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and photoluminescence techniques. The photocatalytic activity of the samples was evaluated by the photodegradation of methylene blue; the results showed that the photocatalytic activity of the TiO₂/SiO_x double-layers was superior to that of the TiO₂ single-layers. The presence of the SiO_x bottom-layer improved the photocatalytic activity of the TiO₂ layer because it may act as a trap for electrons generated in the TiO₂ layer thus preventing electron-hole recombinations.     

Investigation of Ag-TiO2 nanostructures photocatalytic properties prepared by modified dip coating method

In this article, titanium dioxide and silver nanostructures were deposited on glass substrates using modified sol–gel methods and dip-coating technique. The films were characterised chemically and physically using different techniques (TLC, UV–Vis and XRD) and tested for environmental applications regarding degradation of aromatic hydrocarbons. The photocatalytic activity of the TiO₂ nanostructures is tested with different small concentrations of phenol in water and reaction mechanisms discussed. Considerable enhancement is observed in the photodegradation activity of Ag-modified (3 wt.%) TiO₂ compared to unmodified TiO₂ nanostructures for phenol concentrations within the pseudo-first-order Langmuir–Hinshelwood (LH) model for reaction kinetics. The pseudo-first-order global degradation rate constant increased from <0.005 min^?1 for TiO₂ to 0.013 min^?1 for 3 mol% Ag-modified TiO₂. The enhancement is attributed to the incorporation of Ag which promotes the generation of reactive oxygen species and increases the carrier recombination life-time. In addition, Ag has been observed to extend the absorption to the visible region by its surface plasmon resonances and to suppress the anatase–rutile phase transformation. Moreover, TiO₂ grain size prepared was found to be 10 nm which maximises the active surface area. For phenol initial concentrations as low as 0.0002 M, saturation trend in the degradation process occurred at 0.00014 M and the reaction rate can be fitted with half-order LH kinetics.     

Enhanced photocatalytic activity and stability of nano-scaled TiO2 co-doped with N and Fe

Titanium dioxide (TiO₂) nanoparticles co-doped with N and Fe were prepared via modified sol-gel process. The products were characterized by transmission electron microscopy (TEM), N₂ adsorption, X-ray diffraction (XRD), Raman spectroscopy, UV-vis spectroscopy, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). It is shown that the prepared TiO₂ particles were less than 10 nm with narrow particle size distribution. The addition of MCM-41 caused the formation of Ti-O-Si bond which fixed the TiO₂ on MCM-41 surface, thus restricted the agglomeration and growth of TiO₂ particles. The photocatalytic performance in the degradation of methylene blue showed that N, Fe co-doped TiO₂ exhibited much higher photocatalytic activity than doped sample with nitrogen or Fe³⁺ alone under both UV and visible light. N, Fe co-doping decreased the loss of doping N during the degradation reaction, thus increased the photocatalytic stability. It was also found that the nitridation time had significant influence on the photocatalytic activity of prepared TiO₂ catalysts.     

Highly Active TiO2/Polyelectrolytes Hybrid Multilayered Hollow Nanofibrous Photocatalyst Prepared from Electrouspun Fibers Using Electrostatic Layer-by-Layer Technique

Compared to conventional film photocatalysts, fiber photocatalyst has a greater surface-to-volume ratio and a 3-D open structure that allows its surface active sites to be accessible for reactants more easily and effectively. However, TiO ₂ powder (Degussa P25), by itself, cannot be prepared in the form of fibers, but with the help of a polymer nanofiber, TiO ₂ particles can be immobilized in a fibrous network of polyelectrolyte. Here, hybrid multilayered hollow nanofibers (HMHNFs) composed of TiO ₂ /polyelectrolyte (PE) have been prepared by a combination of a electrospinning method and layer-by-layer (LBL) technology. The results show that both the average diameter and the wall thickness of the HMHNFs can be well controlled by the template, as well as the number of coating layers. The dried morphology of the obtained HMHNFs is dependent on the inner deposited numbers of the polyelectrolyte layers. When compared with other nanostructured TiO ₂ materials, such as commercial TiO ₂ nanoparticles (P25, Degussa) and TiO ₂ films, the hollow TiO ₂ /PE hybrid nanofibers exhibited higher photocatalytic activities.     

Fabrication of titanium dioxide nanofibers containing hydroxyapatite nanoparticles

In the present study, we introduce titanium dioxide (TiO₂) nanofibers that contain hydroxyapatite (HAp) nanoparticles (NPs) as a result of an electrospinning process. A simple method that does not depend on additional foreign chemicals has been employed to synthesize HAp NPs through calcination of bovine bones. Typically, a colloidal gel consisting of titanium isopropoxide/HAp was prepared to produce nanofibers embedded with solid NPs by electrospinning process. The SEM results confirmed well oriented nanofibers and good dispersion of HAp NPs over the nanofibers. XRD results demonstrated well crystalline feature of both TiO₂ and HAp. Physiochemical aspects of prepared nanofibers were characterized for TEM and TEM-EDS which confirmed nanofibers were well oriented and had good dispersion of HAp NPs. Accordingly, these results strongly recommend the use of obtained nanofiber mats as a future candidate for hard tissue engineering applications.     

A new method to characterizing surface roughness of TiO2 thin films

Titanium dioxide (TiO₂) thin films have been widely coated in the self-cleaning glass for facade application. The benefit of these glasses is its ability to actively decompose organic compounds with the help of ultraviolet light. Understanding the surface roughness of TiO₂ thin films is important before manufacturing of self-cleaning glasses using TiO₂ thin films because surface roughness of TiO₂ thin films has highly significant influence on the photocatalytic performance. Traditional approach for measuring surface roughness of TiO₂ thin films is atomic force microscopy. The disadvantage of this approach include long lead-time and slow measurement speed. To solve this problem, an optical inspection system for rapidly measuring the surface roughness of TiO₂ thin films is developed in this study. It is found that the incident angle of 60° is a good candidate for measuring surface roughness of TiO₂ thin films and y=90.391x+0.5123 is a trend equation for predicting the surface roughness of TiO₂ thin films. Roughness average (Ra) of TiO₂ thin films (y) can be directly determined from the peak power density (x) using the optical inspection system developed. The results were verified by white-light interferometer. The measurement error rate of the optical inspection system developed can be controlled by about 8.8%. The saving in inspection time of the surface roughness of TiO₂ thin films is up to 83%.     

Characterization and photocatalytic activity of Zn–TiO2/AC composite photocatalyst

Activated carbon (AC) supported Zn²⁺–TiO₂ photocatalyst was prepared by sol–gel method. The prepared samples were characterized by X-ray diffraction, scanning electron micrograph, nitrogen absorption, diffuse reflectance UV/VIS and X-ray photoelectron spectroscopy. Using toluene as a pollution target, the photocatalytic activity of photocatalyst was evaluated. The results showed that prepared photocatalyst was obviously helpful for the removal of toluene in air. The photocatalytic degradation of toluene by Zn²⁺–TiO₂/AC reached 100% for 40 min and remained 75% after 160 min, while degradation by TiO₂ was only 30%. It indicated that the photocatalytic activity of prepared photocatalyst was enhanced. It is due to Zn²⁺-doping increased the oxidation and reduction of hole–electron pairs, which was the important factor in heterogeneous photocatalysis.     

Photocatalytic Activities of Boron Doped Titanium Dioxide Nanoparticles and its Composite with Polyaniline

Abstract

Titanium dioxide (TiO₂) was doped with a nonmetalic element, boron (B), and the boron doped TiO₂ (B-TiO₂) was combined with polyaniline (Pani) through an in-situ polymerization technique. The photocatalytic activity of the prepared samples was monitored by the degradation of methylene blue under UV light irradiation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to reveal the effect of boron doping on the crystalline and chemical structure of the photocatalyst, respectively. The morphological and elemental compositional characteristics of the samples were evaluated using field emission scaning electron microscopy (FE-SEM) and energy dispersive x-ray analysis. The optical band gap energy of the prepared samples was obtained by UV-Visible (UV-Vis) spectroscopy. B-TiO₂ exhibited enhanced photocatalytic performance compared to the undoped photocatalyst. Furthermore, compared with TiO₂ and B-TiO₂, Pani/B-TiO₂ displayed superior photocatalytic activity. The composite achieved almost 26% methylene blue degradation within 150?minutes. Although the boron doping enhanced the crystallinity of TiO₂ slightly, it did not affect the morphology. FTIR confirmed the presence of tri-coordinated interstitial boron in the Ti–O–B bonds. The UV-Vis spectra displayed a red shift with the incorporation of the boron atoms. The incorporation of the boron atoms in the TiO₂ crystal structure are suggested to promote the separation of the photoinduced electron-hole pairs, a possible reason for the enhanced photocatalytic activity. B-TiO₂ and its composite with polyaniline could be considered as a promising photocatalyst to remove organic dyes from the wastewater.     

Preparation and Properties of Antimicrobial Poly(butylene adipate-co-terephthalate)/TiO2 Nanocomposites Films

Abstract

Poly(butylene adipate-co-terephthalate) (PBAT) nanocomposite films with various contents of nano-titanium dioxide (TiO₂) and titanium dioxide doped silver (Ag-TiO₂) were prepared by a solvent casting method. The TiO₂ and Ag-TiO₂ nanoparticles were surface-modified with silane coupling agents to improve their compatibility and dispersibility in the PBAT matrix. They were denoted as mTiO₂ and mAg-TiO₂, and were characrterized by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The morphology of the PBAT nanocomposite films was studied by field emission scanning electron microscopy (FE-SEM). The crystallinity of the PBAT film increased upon the introduction of the nano-TiO₂/Ag-TiO₂. Its mechanical properties and gas barrier properties were also significantly improved. In addition, the PBAT/mTiO₂ and PBAT/mAg-TiO₂ nanocomposite films showed a strong antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) food-borne pathogenic bacteria.     

Fabrication of titanium dioxide nanofibers via anodic oxidation

In this work, titanium dioxide (TiO₂) nanofibers were obtained from anodic oxidation process. A piece of titanium sheet was anodized in 1.0 M sodium chloride (NaCl) solution, at 30 V. The as-anodized sample was calcinated at 400 °C for one hour. Subsequently the sample was characterized using field-emission scanning electron microscopy (FE-SEM), high resolution X-ray diffraction (HR-XRD), and Raman spectroscopy. Interestingly, results showed rutile phase dominates over anatase phase, which is rarely reported. In addition, the possible chemical reactions that lead to the formation of nanofibers were proposed. It was found that the nanofibers having an average length of 3 μm, also diameter of 83 nm.     

The synthesis and kinetic growth of anisotropic silver particles loaded on TiO2 surface by photoelectrochemical reduction method

Silver nanorods with average diameters of 120-230 nm and aspect ratio of 1.7-5.0 were deposited on the surface of TiO₂ films by photoelectrochemical reduction of Ag⁺ to Ag under UV light. The composite films prepared on soda-lime glass substrates were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the TiO₂ film after UV irradiation in AgNO₃ solution is composed of anatase phase TiO₂ and metallic silver with face centered cubic structure. Other compounds cannot be found in the final films. The maximum deposition content of silver particles on the surface of TiO₂ film was obtained with the AgNO₃ concentration of 0.1 M. The kinetic growth rates of silver particles can be controlled by photocatalytic activity of TiO₂ films. The studies suggest that the growth rates of silver particles increase with the enhancement of photocatalytic activity of TiO₂ films. The maximum growth rate of silver particles loaded on TiO₂ films can be up to 0.353 nm min⁻¹ among samples 1#, 2# and 3#, while the corresponding apparent rate constant of TiO₂ is 1.751 × 10⁻³ min⁻¹.     

Antibacterial effect of silver modified TiO<Subscript>2</Subscript>/PECVD films

This paper deals with photocatalytic activity of silver treated TiO₂ films. The TiO₂ films were deposited on glass substrates by plasma enhanced chemical vapor deposition (PECVD) in a vacuum reactor with radio frequency (RF) low temperature plasma discharge in the mixture of oxygen and titanium isopropoxide vapors (TTIP). The depositions were performed under different deposition conditions. Subsequently, the surface of TiO₂ films was modified by deposition of silver nanoparticles. Photocatalytic activity of both silver modified and unmodified TiO₂ films was determined by decomposition of the model organic matter (acid orange 7). Selected TiO₂ samples were used for tests of antibacterial activity. These tests were performed on Gram-negative bacteria Escherichia coli. The results clearly proved that presence of silver clusters resulted in enhancement of the photocatalytic activity, which was up to four times higher than that for pure TiO₂ films.     

Synthesis, characterization and application of iodine modified titanium dioxide in phototcatalytical reactions under visible light irradiation

Iodine doped titanium dioxide has been successfully prepared by simple hydrolysis of tetrabutyl titanate in the presence of iodic acid. The adopted method allowed for the production of spherical iodine doped titaniun dioxide nanoparticles with varied amount of iodine content. Analysis by X-ray diffraction, Raman, transmission electron microscopy as well as UV-vis DRS revealed that titanium dioxide nanostructures were doped with iodine which existed in two different valence states I⁵⁺ and I⁻. The iodine in the form of I⁵⁺ is believed to have doped into the lattice whereas I⁻ was well dispersed on the surface of TiO₂ probably as iodine adducts hence rendering it to be highly absorbing in visible light region. The I-TiO₂ exhibited improved photocatalytic activity toward degradation of acid orange 7 (AO7), methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP) under visible light over the pristine TiO₂ prepared by the same method. High catalytic properties are attributed to iodine doping which led to high specific surface area, absorption in visible region as well as alleviation of charge carrier recombination. The most probable route undertaken in the degradation of AO7 is through indirect oxidation by the hydroxyl radicals.     

Preparation of nanosized crystalline TiO2 particles at low temperature for photocatalysis

Nanocrystalline titanium dioxide (TiO₂) particles were prepared by a modified alkoxide method under acidic conditions at temperatures ranging from 60°C to 90°C. The reaction temperature was used to control the crystalline phase of the TiO₂ particles. At 60°C and 75°C rutile was formed whilst at 90°C anatase and brookite were formed.The photocatalytic activity of the prepared particles was tested for the degradation of sucrose. The photocatalytic activities of the prepared nanosized TiO₂ were compared to those obtained from Degussa P-25 TiO₂ as well as TiO₂ crystalline samples prepared using the conventional sol–gel/heat treatment method. At low organic concentrations, Degussa P-25 exhibited higher photocatalytic behaviour than all the prepared particles while, at high organic concentrations, the nanosized TiO₂ particles prepared at low temperature displayed an activity comparable to Degussa P-25 but much higher than the heat treated sample. The formation of excess intermediates during the degradation of higher sucrose loadings is believed to hinder the photoactivity of Degussa P-25, while the prepared TiO₂ particles are able to maintain their activity for the degradation of the intermediates of sucrose.     

Cotton fabric coated with nano TiO2-acrylate copolymer for photocatalytic self-cleaning by in-situ suspension polymerization

Two kinds of nano TiO₂-polyacrylate hybrid dispersions, TBM-w and TBM-e were synthesized by in-situ suspension polymerization and solution polymerization respectively, in order to fix the nano TiO₂ on fabrics. The photocatalytic self-cleaning fabrics have received much attention in recent years for its water-saving and environment-protection advantages. However, the fixation of the photocatalyst on fabrics is still a key problem that inhibits industrialization of these eco-friendly fabrics. The cotton fabric was treated by the two hybrid dispersions. The photocatalytic self-cleaning property was characterized. Infrared spectroscopy, burning loss test and thermogravimetry showed that some copolymer chains entangled with the nano TiO₂. Transmission electron microscope illustrated that there was a polymeric layer on the surface of nano TiO₂. The average diameter of TBM-w was smaller than that of TBM-e based on size analysis. The photocatalytic decoloration of the grape syrup indicated that the fabric with TiO₂-polymer hybrid had excellent self-cleaning property.