In-situ preparation of TiO2/SnO2 nanocrystalline sol for photocatalysis

A novel preparation method to synthesize TiO₂/SnO₂ nanocrystalline sol under mild conditions was presented. Ti(OC₄H₉)₄ used as a precursor was hydrolyzed in the rutile SnO₂ nanocrystalline sol, and in-situ formed TiO₂/SnO₂ nanocrystalline sol. The crystal structure, morphology and photocatalysis performance of samples were investigated. The results show that the additional rutile SnO₂ nano grains serve as heterogeneous crystal nucleus and exhibite the inducing effect on TiO₂ grains growth, thus leading to the changes in crystalline phase and particle morphology. In addition, the photoluminescence (PL) spectra analysis indicates that TiO₂/SnO₂ composite structure induces a better charge separation, and thus the photocatalytic activity of TiO₂/SnO₂ sol is increased significantly compared with TiO₂ sol.     

Influence of silver doping on the phase transformation and crystallite growth of electrospun TiO2 nanofibers

Ag doped TiO₂ nanofibers were fabricated by electrospinning technique using polyvinyl pyrrolidone (PVP) and titanium isopropoxide (TiP) as precursor. The effects of silver and calcination temperature on the preparation of electrospun TiO₂ nanofibers were investigated. The calcination temperature determines the TiO₂ phases as ether anatase or rutile. When the calcination temperature increased, crystallite size of TiO₂ nanofiber increased. The crystallite size of Ag doped TiO₂ nanofiber is smaller than that of the pure TiO₂ nanofiber because silver is retrained in this phase transformation. Silver controlled the phase transformation as well as had an inhibition effect on the growth of anatase crystallite.     

A new method for surface modification of TiO2/Al2O3 nanocomposites with enhanced anti-friction properties

In this paper, the TiO₂/Al₂O₃ composite nanoparticles were prepared by a hydrothermal method and in situ modified with acrylic acid. It was found that the mean particle size of modified TiO₂/Al₂O₃ composite nanoparticles was about 80 nm with a uniform distribution by the particle size analysis. The modified TiO₂/Al₂O₃ composite nanoparticles can disperse in lubricating oil homogenously for several weeks. The dispersion stabilization of modified TiO₂/Al₂O₃ composite nanoparticles in lubricating oil was significantly improved in comparison with the as-prepared nanoparticles, which was due to the introduction of grafted polymers by surface modification. The formation of covalent bands was identified by Fourier transform infrared spectrum. Under an optimized concentration of 0.1 wt%, the averaged friction coefficient was reduced by 14.75%, when the modified TiO₂/Al₂O₃ composite nanoparticles were used as lubricating oil additivities.     

Fabrication of porous TiO2 film via hydrothermal method and its photocatalytic performances

Porous anatase (TiO₂) films were fabricated onto stainless steel substrates with Ti(OC₄H₉)₄ as a precursor via hydrothermal process. The crystallization and porous structure of TiO₂ film were dependent on the time and temperature of the hydrothermal reaction. A TiO₂ film with orderly porous structure and high crystallization was obtained upon treatment at 150 °C for 2 h. The grain size of TiO₂ is ca. 6 nm, and pore diameter is ca. 10 nm. Diffusion of Fe into the porous TiO₂ film occurred; Fe also diffused onto the surface of the film with the extension of hydrothermal reaction time or increase of the reaction temperature. The diffusion reaction has a large effect on the formation of porous TiO₂ film as well as its interface texture. However, it does not change the crystal phase of the TiO₂. The resultant TiO₂ film showed high photocatalytic activity towards degradation of gaseous formaldehyde.     

Investigation on solar photocatalytic activity of TiO2 loaded composite: TiO2/Eggshell, TiO2/Clamshell and TiO2/CaCO3

The TiO₂/Eggshell, TiO₂/Clamshell and TiO₂/CaCO₃ loaded composites were prepared by sol-gel method and characterized by XRD and SEM. Their photocatalytic activities were measured through the degradation of Acid Red B under solar light irradiation. The influences of TiO₂ loaded content, heat-treated temperature and time on the photocatalytic activities were reviewed. The effects of irradiation time and dye initial concentration on the photocatalytic degradation were also investigated. The results showed that the photocatalytic activity can be greatly enhanced by appropriate TiO₂ loaded content.     

Synthesis of nano-sized Al doped TiO2 powders using thermal plasma

High quality nano-sized Al doped TiO₂ powders were prepared using a DC plasma jet. Titanium tetrachloride (TiCl₄) and aluminum chloride (AlCl₃) were fed into the plasma flame as starting materials, and the ratio of Al to TiO₂ was varied from 1 to 8 wt.%. We investigated the effect of process parameters on phase composition, particle size, and optical property by using XRD, SEM/EDX, TEM, UV/Vis spectroscope. The powders collected at the reaction tube were dominated by anatase. The size of synthesized powder decreased by increasing the amount of Al because doped Al species inhibited the particle growth. For the optical property, the absorption band of synthesized powders shifted from the UV region to the visible region according to the increase of the amount of Al dopant.     

An investigation of super-hydrophilic properties of TiO2/SnO2 nano composite thin films

A sol-gel dip coating technique was used to fabricate TiO₂/SnO₂ nano composite thin films on soda-lime glass. The solutions of SnO₂ and TiO₂ were mixed with different molar ratios of SnO₂:TiO₂ as 0, 3, 4, 6, 8, 9, 10.5, 13, 15, 19.5, 25 and 28 mol.% then the films were prepared by dip coating of the glasses. The effects of SnO₂ concentration, number of coating cycles and annealing temperature on the hydrophilicity of films were studied using contact angle measurement. The films were characterized by means of scanning electron microscopy, X-ray diffraction and atomic force microscopy measurements. The nano composite thin films fabricated with 8 mol.% of SnO₂, four dip coating cycles and annealing temperature of 500 °C showed super-hydrophilicity.     

Photocatalytic properties of porous TiO2/Ag thin films

In this study, nanocrystalline TiO₂/Ag composite thin films were prepared by a sol-gel spin-coating technique. By introducing polystyrene (PS) spheres into the precursor solution, porous TiO₂/Ag thin films were prepared after calcination at a temperature of 500 °C for 4 h. Three different sizes (50, 200, and 400 nm) of PS spheres were used to prepare porous TiO₂ films. The as-prepared TiO₂ and TiO₂/Ag thin films were characterized by X-ray diffractometry (XRD) and by scanning electron microscopy to reveal structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methylene blue under UV irradiation.When PS spheres of different sizes were introduced after calcination, the as-prepared TiO₂ films exhibited different porous structures. XRD results showed that all TiO₂/Ag films exhibited a major anatase phase. The photodegradation of porous TiO₂ thin films prepared with 200 nm PS spheres and doped with 1 mol% Ag exhibited the best photocatalytic efficiency where ∼ 100% methylene blue was decomposed within 8 h under UV exposure.     

One-pot synthesis of intestine-like SnO2/TiO2 hollow nanostructures

In the present study the intestine-like binary SnO₂/TiO₂ hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO₂ spheres and Ti(SO₄)₂ are used as colloid seeds and Ti-source, respectively. The novel core (SnO₂ hollow sphere)-shell (TiO₂) nanostructures possess a large surface area of 122 m²/g (calcined at 350 °C) and a high exposure of TiO₂ surface. The structural change of TiO₂ shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO₂ could form even at room temperature due to the presence of SnO₂ core and the unique core-shell interaction.     

Phase transformation in semi-transparent TiO2 films irradiated with CO2 laser

Anatase (TiO₂) thin films were obtained by immersion of glass plates into a titanium sol-gel precursor followed by calcination at 450 °C for 3 h. The Raman results for the CO₂ laser irradiated TiO₂ films show that laser radiation is able to promote favorable changes of anatase phase in anatase/rutile mixtures. Nevertheless, the transformation process level depends on laser characteristics and scan speed of the radiation treatment.     

Structure and CO gas sensing properties of electrospun TiO2 nanofibers

Titanium dioxide (TiO₂) nanofibers were fabricated by electrospinning a hybrid solution, which is a mixture of the TiO₂ sol precursor, polymer, and solvent. The structure and gas sensing properties of TiO₂ nanofibers were investigated. By calcining at 600 °C, the polymeric components were decomposed and a multi-layered random network structure of TiO₂ nanofibers was obtained. Polycrystalline TiO₂ nanofibers consist of tetragonal anatase and rutile TiO₂ phases. The diameter ranged from 400 nm to 500 nm and the grain size was about 15 nm. The TiO₂ nanofibers-based sensor exhibited response to CO concentration as low as 1 ppm at 200 °C.     

Flame-made single phase Zn2TiO4 nanoparticles

Using zinc naphthenate and titanium tetra isopropoxide (1:1 mol.%) dissolved in ethanol as precursors, single phase Zn₂TiO₄ nanoparticles were synthesized by the flame spray pyrolysis technique. The Zn₂TiO₄ nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The BET surface area (SSA_BET) of the nanoparticles was measured by nitrogen adsorption. The average diameter of Zn₂TiO₄ spherical particles was in the range of 5 to 10 nm under 5/5 (precursor/oxygen) flame conditions. All peaks can be confirmed to correspond to the cubic structure of Zn₂TiO₄ (JCPDS No. 25-1164). The SEM result showed the presence of agglomerated nanospheres with an average diameter of 10-20 nm. The crystallite sizes of spherical particles were found to be in the range of 5-18 nm from the TEM image. An average BET equivalent particle diameter (d_BET) was calculated using the density of Zn₂TiO₄.     

碳纳米管修饰LaFeO3/TiO2复合材料的光催化性能与机理

采用超声辅助溶胶凝胶法制备了LaFeO₃颗粒,进一步以碳纳米管(CNTs)为基底和钛酸丁酯为前体,通过一步水热法煅烧合成CNTs/TiO₂/LaFeO₃(CTF)三元异质结光催化复合材料。通过扫描电子显微镜(SEM)、X射线衍射分析(XRD)、氮气吸附-解吸等温线(BET)、紫外-可见分光光度计(UV-Vis)、光致发光光谱(PL)等表征手段对材料的形貌与特征结构、比表面积和孔径结构以及光学特征进行了分析,并在紫外光下通过降解活性黑五(RB5)测试样品的光催化性能。结果表明,以CNTs作为载体,能够有效提升LaFeO₃/TiO₂复合材料的光催化性能。当CNTs在复合材料中的质量占比为5%时,150 W汞灯照射下RB5的50 min去除率可达99.5%。CNTs一方面通过增加复合材料的比较面积为催化反应的进行提供了更多的活性位点,更为重要的是,CNTs作为光生载流子传输的通道加快了电荷分离效率,提升了复合材料的降解能力和催化反应动力学进程。     

Synthesis of nanostructure rutile TiO2 in a carboxyl-containing ionic liquid

Nanostructure rutile TiO₂ was prepared in a carboxyl-containing ionic liquid, 1-methylimidazolium-3-acetate chlorine ([AcMIm]Cl), by using TiOCl₂ solution as a precursor at low temperature. The obtained nanostructure TiO₂ was analyzed with fourier transform infrared (FTIR), X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The as-prepared TiO₂ present only rutile crystal phase and a novel flower-like morphology. The as-prepared rutile TiO₂ shows better photocatalytic performance in the degradation of methyl orange. The template-directing performance of ionic liquid is due to the bidentate chelating complexation between the carboxylic functional group of ionic liquid and titania.     

Facile synthesis of rice-like anatase TiO2 nanocrystals

Rice-like anatase TiO₂ nanocrystals have been synthesized by hydrothermal treating Ti(OH)₃ precursor in deionized water, which is easy to form in-situ a stable TiO₂ aqueous dispersion and no post-synthetic purification process is required. The influences of synthetic parameters, such as reaction time and pH value, on the morphologies of the resulting nanocrystals have been investigated. It is found that the crystallinity and sizes of TiO₂ nanocrystals increase with the reaction time increased. The pH value is important for controlling the sizes and shapes of TiO₂ nanocrystals. As pH value increases from 2 to 11, spherical, rice-like, and rod-like TiO₂ nanocrystals are obtained, respectively. The formation mechanism of rice-like anatase TiO₂ nanocrystals is supposed to be a hydrothermal crystallization and Ostwald ripening process.     

Nanocrystalline anatase TiO2 prepared via a facile low temperature route

Nanocrystalline anatase TiO₂ was prepared by a facile sol-gel route at a temperature of 65 °C under mild conditions. Tetrabutyl titanate was used as a titanium precursor, glacial acetic acid was used as an inhibitor, and anhydrous ethanol was used as a solvent. XRD, TEM, FT-IR and XPS spectra were applied to characterize the crystal phase, microstructure, and other physicochemical properties of the nanoanatase TiO₂. The results showed that as prepared ellipse-shaped anatase TiO₂ with an average diameter of 7 nm, which is rich in surface hydroxyl groups, was found to exhibit high dispersibility.     

Solar photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) using TiO2/SiO2 aerogel composite photocatalysts

Silica aerogels and TiO₂/silica aerogel composite photocatalysts were synthesized by sol–gel technique at ambient pressure using orthosilioate and tetra-n-butyl titanate as precursors, respectively. The prepared composite photocatalysts were characterized by XRD, TEM, BET surface area, FT-IR and UV–vis absorption spectra. The results showed that the TiO₂/silica aerogel composite photocatalysts possess high surface area. The addition of silica aerogels inhibited the grain growth and phase transformation of anatase to rutile during calcination. The TiO₂/silica aerogel composite sample calcined at 500 °C with an optimal silica aerogel content of 7 wt.% afforded the highest photocatalytic activity. The photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) was investigated by using this novel TiO₂/silica aerogel composite photocatalyst under solar light irradiation. The effects of irradiation time, pH, catalyst concentration, temperature and initial DNBP concentration were examined as operational parameters. The optimal operational parameters were found as follows: pH as solution pH 4.82, 8 g L⁻¹ catalyst concentration, 20 °C, and 240 min irradiation time. The kinetics of DNBP degradation by TiO₂/silica aerogel composite fit well a pseudo-first-order kinetic model. The repeatability of photocatalytic activity was also tested. This study showed the feasible and potential use of TiO₂/silica aerogel composite photocatalysts in degradation of toxic organic contaminants.     

Preparation of Ni nanoparticle-TiO2 nanotube composite by pulse electrodeposition

A Ni/TiO₂ nanocomposite was successfully prepared by a pulse electrodeposition (PED) technique. Highly-ordered TiO₂ nanotube arrays fabricated by anodization were employed as a substrate and loaded with Ni nanoparticles by PED. The influence of pulse electrodeposition parameters was investigated on the morphology of nickel electrodeposits. The nanocomposite was characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicated that Ni nanoparticles with average size ranging from 19 to 84 nm were obtained by changing electrodeposition parameters. At constant current off-time (t_off) and pulse time of both negative and positive currents, the particle size decreased asymptotically with increasing amplitude of both negative and positive current. A progressive decrease of the particle size was observed with increasing current off-time at constant amplitude and pulse time of both negative and positive current. Increase in the deposition time at constant current off-time, amplitude and pulse time of both negative and positive current resulted in particle growth.     

等离子体电解氧化法制备多孔TiO2/V2O5复合物膜层及其增强光催化产氢活性

较差的光催化产氢效率极大地阻碍了TiO₂光催化剂的工业化应用。为此,本文在含有NH₄VO₃的磷酸盐溶液中,采用等离子体电解氧化(PEO)法制备了多孔TiO₂/V₂O₅复合膜光催化剂,通过扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)、X射线光电子谱(XPS)和紫外可见漫反射光谱(UV-Vis DRS)对其组成、结构及光吸收性质进行了表征,并采用气相色谱评价了薄膜催化剂的光催化产氢性能,研究了电解液中NH₄VO₃含量对膜的结构、组成和光催化产氢性能的影响。结果表明:复合膜催化剂主要由锐钛矿和金红石型TiO₂组成,具有微孔结构,V₂O₅主要以无定形形式存在于膜中,与TiO₂有很强的相互作用,影响TiO₂的晶面间距。研究发现,元素V抑制了TiO₂的结晶和金红石型TiO₂的形成,扩大了薄膜的光学吸收范围。针对Na₂S+ Na₂SO₃溶液中的光催化产氢性能的研究显示,在质量浓度为1 g/L NH₄VO₃的电解液中制备的TiO₂/V₂O₅薄膜的光催化活性最高,优于近年来报道的其他光催化剂。光催化重复实验表明,该复合膜催化剂具有较高的稳定性和较为恒定的光催化活性。     

Effect of porosity on the Seebeck coefficient of mesoporous TiO2 thin films

Mesoporous TiO₂ films were prepared by using titanium tetraisopropoxide as the titania precursor and triblock copolymer as the structure directing agent. The synthesized mesoporous TiO₂ film was confirmed to have the ordered pore structure with rutile phase by small angle and wide angle X-ray diffraction analyses. The mesoporous TiO₂ film has the porosity range from 21.6 to 35.6%, and its Seebeck coefficient was changed according to its porosity, up to −88.6 μV/K. From the obtained Seebeck coefficient, the ordered mesoporous TiO₂ film was found to be a good candidate of thermal sensing layer of thin film thermal sensor.