Preparation and visible light photocatalytic activity of mesoporous N, S-codoped TiO2(B) nanobelts

The mesoporous N, S-codoped TiO₂(B) nanobelts are synthesized via hydrothermal synthesis and post-treatment, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption-desorption measurements (BET), X-ray photoelectron spectra (XPS), and UV-vis diffuse reflectance spectra (DRS). The results show that the prepared samples are mesoporous structured and exhibit stronger absorption in the visible light region with red shift in the absorption edge. The photocatalytic activity of N, S-codoped mesoporous TiO₂(B) nanobelts is evaluated by the photocatalytic photodegradation of potassium ethyl xanthate (KEX) under visible light irradiation. It is found that the photocatalytic activity of the prepared samples increases with increasing the molar ratio of thiourea to Ti (R). At R = 3, the photocatalytic activity of the N, S-codoped TiO₂(B) sample TBLTS-3 reaches a maximum value. With further increasing R, the photocatalytic activity of the sample decreases. The high photocatalytic activity of N, S-codoped TiO₂(B) nanobelts can be attributed to the balance between strong absorption in visible light region and low recombination rate of electron/hole pairs.     

Fabrication of Ag/TiO2 nanotube array with enhanced photo-catalytic degradation of aqueous organic pollutant

In this paper, the fabrication of Ag/TiO₂ nanotube arrays and their photo-catalytic activity have been studied. The SEM, TEM and XRD were performed to characterize the morphology and crystalline phase of the TiO₂ nanotube array and Ag/TiO₂ nanotube array. Ag nanoparticles with different loadings, which are aimed to suppress the electron–hole recombination so as to enhance the photo-catalytic oxidation efficiency, were systematically coated onto TiO₂ nanotubes. The photo-catalytic activity of these nano-materials was evaluated by the degradation of two different pollutants: methyl orange and glyphosate. The effects of various parameters, such as the amount of the photo-catalyst, the illumination time, and pH value on the photo-catalytic oxidation activity, were studied.     

铈和磷钨酸共掺杂纳米二氧化钛中空纤维的制备及其光催化活性

以棉花纤维为模板,以钛酸四正丁酯、硝酸铈铵和磷钨酸为原料采用模板法制备了一系列铈和磷钨酸共掺杂的、具有中空纤维结构的TiO₂光催化材料, 利用扫描电子显微镜、X射线衍射、BET和紫外-可见光谱等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以苯酚溶液的光催化降解为模型反应,考察了不同掺杂量的样品在紫外和可见光下的光催化性能. 结果表明,用模板法制备的TiO₂纤维材料具有中空结构,共掺杂的TiO₂纤维在紫外和可见光条件下较纯TiO₂纤维和单掺杂TiO₂纤维对苯酚溶液具有更好的光催化降解效果, 且铈和磷钨酸的掺杂量显著影响该纤维材料的催化性能;当铈掺杂量为0.3mol%和磷钨酸掺杂量为2mol%,在500 oC焙烧2 h所得中空纤维材料的催化性能最佳,4 h即可使苯酚溶液的降解率达98.5%;重复使用4次仍可使苯酚溶液的降解率保持在87%以上,且该催化剂材料易于离心分离去除.     

Optimized monolayer grafting of 3-aminopropyltriethoxysilane onto amorphous,anatase and rutile TiO2

Experimental conditions were studied for optimized attachment of 3-aminopropyltriethoxysilane (APTES) onto amorphous, anatase and rutile titanium dioxide (TiO₂) surfaces. The attachment process and extent was characterized using X-ray photoelectron spectroscopy (XPS). In particular, the effect of attachment time, silane concentration, reaction temperature and the TiO₂ crystalline structure on the growth kinetics of the silane layers was studied. The measurements reveal that typically monolayers are more dense on amorphous than on crystalline TiO₂. The results show that critical experimental conditions exist where APTES attachment to the TiO₂ surface changes from a monolayer to a multilayer growth mode. The obtained results and parameters to produce optimized APTES layers are of a high practical relevance as APTES attachment often constitutes the initial step for organic modification of TiO₂ surface with biorelevant molecules such as proteins, enzymes or growth factors.     

Enhancing the crystallinity and surface roughness of sputtered TiO2 thin film by ZnO underlayer

TiO₂ and TiO₂/ZnO double layer films were sputtered on glass substrates. It was found that a thin ZnO underlayer is helpful for tailoring the microstructure and surface morphology of the TiO₂ film. By applying a 70-nm-thick ZnO underlayer, a TiO₂ thin film of 100 nm in thickness with well crystallized anatase phase and rough surface was successfully fabricated without heating the substrate. Relatively high photo-catalytic activity and good hydrophilic properties were observed in such TiO₂/ZnO double layer films.     

Optimal levels of oxygen deficiency in the visible light photocatalyst TiO2−x and long-term stability of catalytic performance

The dependence of the visible light-responsive photocatalytic activity of oxygen deficient TiO₂ (TiO_2−x) prepared by Ar/H₂ plasma surface treatment on the degree of oxygen deficiency (x) was assessed to determine the deficiency region associated with highest performance. The highest activity was obtained at x=0.06 (TiO_1.94). The maximum visible light activity for this material, estimated from the formaldehyde (HCHO) removal rate, was three times higher than that exhibited by nitrogen-doped TiO₂ (TiO_2−xN_x). The catalytic ability was found to decrease over the first week after fabrication of the material, after which it became stable, and the performance of TiO_2−x at this point was found to be nearly equal to that of TiO_2−xN_x. The results of ab initio calculations of density of states for TiO_2−x suggest that new oxygen deficiency states emerge at almost the exact center between the valence and conduction bands when x>0.06, which increases the recombination rate between electrons and holes. Therefore the declining performance of TiO_2−x at larger x values is attributed to the emergence of new oxygen deficient states.     

N-doped TiO2 photo-catalyst for the degradation of 1,2-dichloroethane under fluorescent light

The photo-catalytic degradation of 1,2-dichloroethane (1, 2-DCE) using nitrogen-doped TiO₂ photo-catalysts under fluorescent light irradiation was investigated. Highly pure TiO₂ and nitrogen-doped TiO₂ were prepared by a sol-gel method and characterized by thermo-gravimetric/differential-thermal analysis (TG/DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the photo-catalysts were mainly nano-size with an anatase-phase structure. The degradation reaction of 1,2-DCE was operated under visible-light irradiation, and the photo-catalytic oxidation was conducted in a batch photo-reactor with various nitrogen doping ratios (N/Ti = 0-25 mol%). The relative humidity (RH) was controlled at 0-20% and the oxygen concentration was controlled at 0-21%. The photo-degradation with nitrogen-doped TiO₂ showed superior photo-catalytic activity compared to that for pure TiO₂. TiO₂ doped with 15 mol% nitrogen exhibited the best photo-catalytic efficiency under the tested conditions. The products from the 1,2-DCE photo-catalytic oxidation were CO₂ and water; the by-products included dichloromethane, methyl chloride, ethyl chloride, carbon monoxide, and hydrogen chloride. The reaction pathway of 1,2-DCE indicates that oxygen molecules are the major factor that causes the degradation of 1,2-DCE in the gas phase.     

Effect of surface ethoxy groups on photoactivity of TiO2 nanocrystals

TiO₂ nanocrystals modified by ethoxy groups were prepared by a facile nonhydrolytic solvothermal method and characterized by XRD, TEM, TG-DTA and XPS, which showed an enhanced visible-light photocatalytic activity on the degradation of Rhodamine B compared with TiO₂ modified by benzyloxy groups and the “naked” TiO₂. The adsorption and degradation pathway of Rhodamine B on TiO₂ modified by ethoxy groups were also investigated. The zeta-potential (ζ) results showed that the TiO₂ modified by ethoxy groups had high negative surface charge, which incited the positive -N(Et)₂ group of RhB absorbing on the TiO₂ surface and preferably led the N-dealkylation pathway under visible light irradiation.     

电场热处理条件下TiO2薄膜的晶化行为研究

利用溶胶-凝胶法和电场热处理工艺在玻璃表面制备出一层TiO₂薄膜，采用DTA ，Raman光 谱，XRD和AFM等测试手段分析了TiO₂薄膜在电场热处理过程中的晶化行为.然后 在理论上 分析了外电场对TiO₂薄膜热处理过程的影响，提出了通过引入外电场促进TiO2薄膜从无 定形到锐钛矿的相转变的方法.通过甲基橙水溶液的光催化降解实验表明：在520℃电场热处 理条件下的TiO₂薄膜的光催化效率高于未引入电场热处理的TiO₂薄 膜. 关键词： 薄膜 晶化 电场 2')" href="#">TiO₂     

Understanding the solar photo-catalytic activity of TiO2-ITO nanocomposite deposited on low cost substrates

In this work, we report on the photo-catalytic properties of TiO₂-ITO nanocomposite deposited on low cost conventional clay ceramic substrates. The nanocomposite was formed by spraying a solution prepared from the P25 TiO₂ powder (Degussa) mixed with an organometallic paste of a dissolved combination of indium and tin. A TiO₂-ITO powder-like nanocomposite was prepared for X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization. The mean particle size of the TiO₂-ITO nanocomposite was found to be larger than that of pure TiO₂. The optical features of TiO₂-ITO-based layers (deposited on glass substrates) were investigated using UV-vis spectroscopy. The TiO₂-ITO nanocomposite deposited layers were found to have higher light absorption than the P25 TiO₂ powder. The photo-catalytic properties of the TiO₂-ITO nanocomposite (deposited on low cost clay ceramic substrates) were tested under solar irradiation using a well-known polluting dye. It was shown that the TiO₂-ITO nanocomposite exhibits higher degradation rates towards the pollutant dye than the P25 TiO₂ powder. The optical band gap of the TiO₂-ITO nanocomposite (2.79 eV) was found to be lower than that of pure TiO₂ (3.1 eV), while ITO (indium tin oxide) has a band gap of about 4.2 eV. ITO was found to be entirely transparent to sun light, while it exhibits a slight photo-catalytic activity, signifying the possible existence of an indirect photo-catalysis phenomenon (sensitized semiconductor photocalysis) and potential degradation (oxidation) of the pollutant through electron transfer from the dye to conduction band of the semiconductor. All photo-catalytic activity results were discussed in light of the optical band gap of the various compounds.     

Preparation of PS/TiO2 as a white pigment for electrophoretic displays

PS (polystyrene)/TiO₂, TiO₂ coated onto PS by a hydrolysis reaction, was prepared as a white pigment for electronic paper (e-paper). Two key parameters, density and zetapotential, were precisely controlled for use as a white pigment. The density was manipulated by changing the mixture ratio of EtOH to H₂O, and the concentration of titanium tetrabutoxide (TBO) in the hydrolysis reaction. The modification of PS/TiO₂ with (3-aminopropyl)triethoxy silane (APTES) and acetic acid showed positive zetapotential originated from the mutual effects between an amino functional group in APTES, and a proton from acetic acid. The mutual effect was studied, and PS/TiO₂ with density of 1.6 g/cm² and zetapotential of 75 mV was prepared using the results.     

Correlation between bioactivity and structural properties of titanium dioxide coatings grown by atomic layer deposition

TiO₂ coatings were grown on Ti and Si by Atomic Layer Deposition (ALD) from titanium ethoxide and water at 300 °C in a wide range of the reaction cycles number N = 100-2000. TiO₂ coatings were found to be amorphous at low value of N < 300 while the coatings grown at N ≥ 300 revealed anatase polycrystalline structure. The TiO₂ coatings bioactivity was evaluated by hydroxyapatite forming ability by the technique of soaking in Simulated Body Fluid (SBF). Correlation between bioactivity and structural properties of TiO₂ was determined. X-ray diffraction and scanning electron microscopy with electron probe microanalysis showed that amorphous TiO₂ coating did not induce the hydroxyapatite growth whereas anatase resulted in the hydroxyapatite forming on the samples surfaces which confirmed TiO₂ anatase bioactivity.     

The preparation of nitrogen-doped TiO2−xNx photocatalyst coated on hollow glass microbeads

In this paper, the effective method for nitrogen-doped TiO_2−xN_x photocatalyst coated on hollow glass microbeads is described, which uses titanium tetraisopropoxide [Ti(iso-OC₃H₇)₄] as the raw materials and gaseous ammonia as a heat treatment atmosphere. The effects of heat treatment temperature and time on the photocatalytic activity of TiO_2−xN_x/beads are studied. The photocatalyst is characterized by the UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM). The results show that when the TiO_2−xN_x/beads is heated at 650 °C for 5 h, the photocatalytic activity of the TiO_2−xN_x/beads is the best. Compared with TiO₂, the photoabsorption wavelength range of nitrogen-doped TiO_2−xN_x red shifts of about 60 nm, and the photoabsorption intensity increases as well. The photocatalytic activity of the TiO_2−xN_x/beads is higher than that of the TiO₂/beads under visible light irradiation. The presence of nitrogen neither influences on the transformation of anatase to rutile, nor creates new crystal phases. When the TiO_2−xN_x/beads is heated at 650 °C for 5 h, the amount of nitrogen-doped is 0.53 wt.% in the TiO_2−xN_x. As the density of TiO_2−xN_x/beads prepared is lower than 1.0 g/cm³, it may float on water surface and use broader sunlight spectrum directly.     

Effect of N2 ion flux on the photocatalysis of nitrogen-doped titanium oxide films by electron-beam evaporation

Nitrogen-doped titanium oxide (TiO_xN_y) films were prepared with ion-assisted electron-beam evaporation. The nitrogen (N) incorporated in the film is influenced by the N₂ flux modulated by the N₂ flow rate through an ion gun. The TiO_xN_y films have the absorption edge of TiO₂ red-shifted to 500 nm and exhibit visible light-induced photocatalytic properties in the surface hydrophilicity and the degradation of methylene blue. The structures and states of nitrogen in the films are investigated by X-ray diffraction patterns (XRD), and X-ray photoelectron spectroscopy (XPS) and related to their visible light-induced photocatalytic properties. The results indicate that the substitutional N in anatase TiO₂ can induce visible light photocatalysis. The substitutional N is readily doped by the energetic nitrogen ions from the ion gun. The best photocatalytic activity is obtained at the largest N loading about 5.6 at.%, corresponding to the most substitutional N in anatase TiO₂. The film exhibits the degradation of methylene blue with a rate-constant (k) about 0.065 h⁻¹ and retaining 7° water contact angle on the surface under visible light illumination.     

Structure and properties of (TiVCrZrY)N coatings prepared by energetic bombardment sputtering with different nitrogen flow ratios

(TiVCrZrY)N coatings were deposited onto Si substrate by the radio-frequency (RF) magnetron sputtering of a TiVCrZrY alloy target in an N₂/Ar atmosphere. The crystal, microstructural, mechanical, and electrical properties at different N₂-to-total (N₂+Ar) flow-rate ratio (R _N) values were investigated. The coating produced in pure Ar had an equiaxed structure with a hexagonal-close-packed phase. With increased R _N, the crystallinity and grain size markedly decreased. The microstructure of (TiVCrZrY)N coatings transformed from V-shaped columnar with a rough-domed surface into fine fibrous with a smooth surface. The amorphous transition layer above the substrate was also significantly thickened. The hardness of (TiVCrZrY)N decreased from 20.9 GPa to 18.9 GPa, and the electrical resistivity increased from 398.2 μΩ?cm to 21870 μΩ?cm.     

Preparation of hybrid bimodal mesoporous silicas loaded with various capacity of 1,8-naphthalic anhydride and their luminescent properties

The novel luminescent hybrid bimodal mesoporous silicas (LHMS) modified with different amount of (3-aminopropyl)triethoxysilane (APTES) on the mesoporous surface and then loaded with various capacity of 1,8-naphthalic anhydride (NA) were synthesized through two-step route. The relative hybrid materials were characterized by XRD, N₂ adsorption-desorption isotherms, ²⁹Si NMR, TG and PL, and the results show that the bimodal pore system is a suitable host matrix for the fluorescent materials. After modification by using propylamine group as a linker, the surface area and the pore volume of resultant samples decreased with the increasing concentration of APTES in tetrahydrofuran solution and the amount of the NA, respectively. The luminescent behaviors of LHMS indicated that the fluorescence intensity and position of emission spectra depended on the various preparation parameters, especially including the concentration of APTES in the tetrahydrofuran solution during the modification process and mass ratio of NA with the modified mesoporous silicas. Particularly, their blue-shift effectiveness of the position of the emission peak was remarkable with the loading NA amount decreased. The detailed mechanism was also discussed.     

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.     

Modified g-C3N4/TiO2 nanosheets/ZnO ternary facet coupled heterojunction for photocatalytic degradation of p-toluenesulfonic acid (p-TSA) under visible light

Novel ternary nanocomposites with facet coupled structure were synthesized by using modified g-C₃N₄, TiO₂ nanosheets and nano-ZnO. Nanosheet/nanosheet heterojunction structure was investigated by TEM, XPS and XRD. FT–IR and Nitrogen adsorption were illustrated for chemical/physical structure analyses. Solution of p-Toluenesulfonic acid (p-TSA) was chosen as target pollutant for visible light photodegradation and the excellent removal efficiency was achieved by this structurally modified g-C₃N₄/TiO₂/ZnO hybrid. The visible light absorption improvement and quantum efficiency enhancement, which were testified by UV–vis DRS, PL and p-TSA photodegradation measurements, due to the facet coupled structure and appropriate quantity of modified g-C₃N₄ in the nanocomposites.     

IR and XPS investigation of visible-light photocatalysis—Nitrogen-carbon-doped TiO2 film

To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Nitrogen and carbon doping TiO_2−x−yN_xC_y films were obtained by heating the TiO₂ gel in an ionized N₂ gas and then were calcined at 500 °C. The TiO_2−x−yN_xC_y films have revealed an improvement over the TiO₂ films under visible light (wavelength, 500 nm) in optical absorption and photocatalytic activity such as photodegradation of methyl orange. X-ray photoemission spectroscopy, infrared spectrum and UV-visible (UV-vis) spectroscopy were used to find the difference of two kinds of films. Nitrogen and carbon doped into substitutional sites of TiO₂ has been proven to be indispensable for band-gap narrowing and photocatalytic activity.     

A novel approach towards high-performance composite photocatalyst of TiO2 deposited on activated carbon

TiO₂ photocatalysts deposited on activated carbon (TiO₂/AC) were prepared by dip-hydrothermal method at 180 °C using peroxotitanate as a precursor, then calcinated at 300-800 °C. The samples were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and the nitrogen absorption. Their photocatalytic activity was evaluated by degradation of methyl orange (MO). The results showed that TiO₂ particles of anatase type were well deposited on the activated carbon surface. TiO₂/AC calcinated at 600 °C exhibited the best photocatalytic performance. For the comparison, the same photocatalysis experiment was carried out for two mixtures of commercial TiO₂ (Degussa P25) with AC and synthetic TiO₂ with AC. It was found that the composite catalyst TiO₂/AC was better than the two mixtures. Besides, different from fine powdered TiO₂, the granular TiO₂/AC photocatalysts could be easily separated from the bulk solution and reused; indeed, its photocatalytic ability was hardly decreased after a five-cycle for MO degradation. The kinetics of the MO degradation fitted well the Langmuir-Hinshelwood model.