Synthesis of nano titania particles embedded in mesoporous SBA-15: characterization and photocatalytic activity

Supported nanocrystalline titanium dioxide (TiO2) has been prepared by a post-synthesis step via Ti-alkoxide hydrolysis through the use of mesoporous SBA-15 silica. TiO2/SBA-15 composites with various TiO2 loading have been prepared and characterized by X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy and diffusive reflective UV-vis spectroscopy. The addition of mesoporous SBA-15 prevents the anatase to rutile phase transformation and the growth of crystal grain. TiO2 did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of the composites up to 800 degrees C did not change the nanocrystal phase and slightly increased the domain size from 5.0 to 7.5 nm, indicating that the anatase TiO2 grains in the mesostructures have a relatively high thermal stability and proper pore diameter allows controlling the size of obtained titania particles. The TiO2/SBA-15 composites prepared by this study showed much higher photodegradation ability for methylene blue (MB) than commercial pure TiO2 nanoparticles P-25. Experimental results indicate that the photocatalytic activity of titania/silica mixed materials depends on the adsorption ability of composite and the photocatalytic activity of the titania, and there is an optimal ratio of Ti:Si, too high or low Ti:Si ratio will lower the photodegradation ability of the composites.     

Low-temperature selective catalytic reduction of NO on MnO(x)/TiO(2) prepared by different methods

Catalysts based on MnO(x)/TiO(2) were prepared by sol-gel, impregnation, and coprecipitation methods for low-temperature selective catalytic reduction (SCR) of NO with NH(3). Among the catalysts, the sample prepared by sol-gel method had the best performance on both activity and SO(2) resistance. From the results of thermo gravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectrum (XPS), it was known that manganese oxides and titania existed in different phase in the samples prepared by three methods. Strong interaction, large surface area, high concentration of hydroxyl groups, high concentration of amorphous Mn on the surface might be the main reasons for the excellent performance of the catalysts.     

Synthesis and photo-degradation application of WO3/TiO2 hollow spheres

A WO(3)/TiO(2) composite, hollow-sphere photocatalyst with average diameter of 320 nm and shell thickness of 50 nm was successfully prepared using a template method. UV-vis diffuse reflectance spectra illustrated that the main absorption edges of the WO(3)/TiO(2) hollow spheres were red-shifted compared to the TiO(2) hollow spheres, indicating an extension of light absorption into the visible region of the composite photocatalyst. The WO(3) and TiO(2) phases were confirmed by X-ray diffraction analysis. BET isotherms revealed that the specific surface area and average pore diameter of the hollow spheres were 40.95 m(2)/g and 19 nm, respectively. Photocatalytic experiments indicate that 78% MB was degraded by WO(3)/TiO(2) hollow spheres under visible light within 80 min. Under the same conditions, only 24% MB can be photodegraded by TiO(2). The photocatalytic mineralization of MB, catalyzed by TiO(2) and WO(3)/TiO(2), proceeded at a significantly higher rate under UV irradiation than that under visible light, and more significant was the increase in the apparent rate constant with the WO(3)/TiO(2) composite semiconductor material which was 3.2- and 3.5-fold higher than with the TiO(2) material under both UV and visible light irradiation. The increased photocatalytic activity of the coupled nanocomposites was attributed to photoelectron/hole separation efficiency and the extension of the wavelength range of photoexcitation.     

Preparation of TiO2/Al-MCM-41 mesoporous materials from coal-series kaolin and photodegradation of methyl orange

TiO₂/Al-MCM-41 mesoporous materials were prepared via sol-gel method by loading titania onto Al-MCM-41 mesoporous molecular sieve by hydrothermal treatment from coal-series kaolin as raw material. The TiO₂/Al-MCM-41 mesoporous materials were characterized by XRD, FT-IR, HRTEM, N₂ adsorption-desorption and the photocatalytic degradation of methyl orange solution under visible light irradiation. The results showed that the TiO₂/Al-MCM-41 mesoporous materials possessed a high surface area of 369.9–751.3 m²/g and a homogeneous pore diameters of 2.3–2.8 nm. The titania crystalline phase was anatase, and the particles size of TiO₂ increased with TiO₂ content. The Al-MCM-41 mesoporous materials exhibited excellent photodegradation activity under visible-light irradiation for methyl orange.     

介孔TiO2微球水热法合成及在染料敏化太阳能电池中的应用

以Ti(SO4)2为钛源,采用尿素辅助水热法合成了介孔TiO2微球,利用XRD、FESEM和比表面积分析仪对样品的晶型、形貌和比表面积进行分析,探讨了尿素加入量对TiO2微球的颗粒尺寸、比表面积、孔径和孔容的影响。采用刮涂法,用所合成的介孔TiO2微球制备了染料敏化太阳能电池(DSSC)的光阳极,结果表明,尿素用量为1.2g合成的介孔TiO2微球所组装的电池在模拟太阳光的照射下(100mW/cm2,AM1.5),光电转换效率为6.2%,明显高于商用P25纳晶所组装的电池光电转换效率(4.24%)。     

H(2)O(2)-sensitized TiO(2)/SiO(2) composites with high photocatalytic activity under visible irradiation

TiO(2)/SiO(2) composite photocatalysts were prepared by depositing of TiO(2) onto nano-SiO(2) particles. X-ray diffraction (XRD), transmission electron micrograph (TEM), Raman spectrometer, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the properties of the synthesized TiO(2)/SiO(2) composites. These results indicated that the products without calcination were amorphous, and calcination could enhance the crystallinity of TiO(2). Increases in the amount of TiO(2) would decrease the dispersion in the composites. H(2)O(2)-sensitized TiO(2)/SiO(2) composite photocatalysts could absorb visible light at wavelength below 550 nm. The photocatalytic activity of as-prepared catalysts was characterized by methyl-orange degradation. The results showed the uncalcined composite photocatalysts with amorphous TiO(2) exhibited higher photocatalytic activity under visible light, and the activity of catalysts with TiO(2) content over 30% decreased with increasing of TiO(2) content. Increases in the calcination temperature and TiO(2) content promote the formation of bulk TiO(2) and result in a decrease in activity.     

Low temperature synthesis and visible light driven photocatalytic activity of highly crystalline mesoporous TiO2 particles

Mesoporous TiO2 powder materials with a high crystallinity have been prepared by evaporation induced self assembly (EISA) process using titanium tetraisopropoxide (TTIP) and pluronic P123 surfactant (EO20PO70EO20) as titanium source and structure-directing reagent, respectively. The prepared materials were characterized by low and wide-angle X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical absorption, and N2 adsorption-desorption experiments. The crystallinity of the materials was controlled by varying the calcination temperature. The resulting TiO2 materials showed highly crystalline structure with uniform particle size which increases from 11.8 to 23.8 nm with increasing the calcination temperature from 400 to 600 degrees C, respectively, whereas the specific surface area decreases from 125 to 40 m2/g. TEM and XRD results revealed that the calcination temperature of 600 degrees C is the best condition to obtain highly crystalline mesoporous TiO2. The photocatalytic activity of the TiO2 mesoporous materials with different crystallinity and textural parameters has been studied in the decomposition of methylene blue (MB) dye molecules under visible light irradiation. Among the mesoporous TiO2 materials studied, the material with the highest crystallinity, prepared at 600 degrees C, showed the best photocatalytic performance in the decomposition of MB under visible light in a short time.     

Effect of Microstructure on Electrorheological Property for Pure TiO2 Particle Material

Pure titanium dioxide （TiO2） particle materials were prepared by hydrolyzing titanium tetrachloride （TiCl4）. The microstructures of these materials were determined by X-ray diffraction （XRD）, accelerated surface area and porosimetry apparatus （BET）, and transmission electron microscopy （TEM）. The TiO2 materials obtained by calcinations under different temperatures distinctly revealed different microstructures in crystal structure type, surface area, pore size, pore volume and grain size. The relationship between the microstructure of the TiO2 materials and their electrorheological （ER） activity was investigated. Anatase titania particles have better ER performance than rutile titania particles. Amorphous TiO2 materials display higher ER activity than the crystalline titania materials. A large pore volume can be more advantageous in improving the ER effect of a particle material.     

合成条件对晶态介孔TiO2结构和性能的影响

采用sol-gel法合成了锐钛矿相介孔氧化钛，利用XRD、BET、TEM和PL对介孔TiO2的结构和光致发光性能进行了表征及分析。结果表明，采用预制TiO2溶胶为钛源，所得介孔氧化钛具有良好的锐钛矿晶型、较大的孔径和比表面积，具有高的光致发光活性。     

A two-step sol-gel method for synthesis of nanoporous TiO2

This article reports a study of the effects of synthesis parameters on the preparation and formation of mesoporous titania nanopowders by employing a two-step sol-gel method. These materials displayed crystalline domains characteristic of anatase. The first step of the process involved the hydrolysis of titanium isopropoxide in a basic aqueous solution mediated by neutral surfactant. The solid product obtained from step 1 was then treated in an acidified ethanol solution containing the same titanium precursor to thicken the pore walls. Low pH and higher loading of the Ti precursor in step 2 produced better mesoporosity and crystallinity of titanium dioxide polymorphs. The resultant powder exhibited a high surface area (73.8 m2/g) and large pore volume (0.17 cm3/g) with uniform mesopores. These materials are envisaged to be used as precursors for mesoporous titania films as a wide band gap semiconductor in dye-sensitized nanocrystalline TiO2 solar cells.     

Visible light active photocatalytic degradation of bisphenol-A using nitrogen doped TiO2

Nitrogen doped titania was prepared by low temperature sol-gel method using titanium precursor and nitrogen containing bases like triethylamine and tetramethyl ammonium hydroxide compounds. The materials were characterized by XRD, BET, SEM, XPS, DRS-UV, and FT-IR techniques. DRS-UV study substantially indicates shift of the absorption edge of TiO2 to lower energy region. The phase composition, crystallinity, specific surface area, and visible light activity of nitrogen doped titania depend upon the preparation conditions. Photocatalytic degradation of bisphenol-A in aqueous medium was investigated by TiO2 and nitrogen doped TiO2 under visible light irradiation in a batch photocatalytic reactor. The results indicate higher visible light activity for nitrogen doped TiO2 than commercial TiO2 (Degussa P25) for bisphenol-A degradation. The influence of various parameters such as initial concentration of bisphenol-A, catalyst loading and pH was examined for maximum degradation efficiency.     

A CdS-modified TiO(2) nanocrystalline photoanode for efficient hydrogen generation by visible light

Cadmium sulfide (CdS) was in situ synthesized onto mesoporous TiO(2) films and used as a sensitizer to fabricate a photoelectrode for hydrogen generation in visible light. The incorporation of CdS extends the optical absorption threshold of a TiO(2) electrode to visible light, enhancing the visible-light-induced photocurrent. A maximum photoconversion efficiency of 3.67% was achieved for this CdS-sensitized TiO(2) electrode under visible light illumination of 100?mW?cm(-2). The hydrogen generation rate obtained at conditions of maximum efficiency is 95.5?μmol?cm(-2)?h(-1). To the best of our knowledge, the hydrogen generation rate is the highest among those reported for a photoelectrochemical cell under the illumination of visible light.     

TiO2/聚酰胺反渗透复合膜的制备及表征

以钛酸四丁酯为原料,在水/丁醇界面区进行水解,制备了锐钛矿型TiO2。分别将不同量的TiO2分散在水相或油相中,以界面聚合方法制备了TiO2/聚酰胺反渗透复合膜,研究了TiO2含量对所制备复合膜结构和分离性能的影响。SEM图谱结果表明,当TiO2添加到水相中时,其同时存在于聚酰胺复合膜皮层的底层以及聚砜基膜的指状孔道中;当TiO2添加到油相中时,复合膜表面结构致密,峰谷结构明显,可看到在膜皮层的表面有TiO2存在。膜分离性能的研究结果表明,与TiO2添加在水相中相比,TiO2添加在油相中能更好地提高膜分离性能。膜抑菌性能研究表明TiO2/聚酰胺反渗透膜在紫外光照下对大肠杆菌表现出良好的杀灭性能。     

Synthesis, characterization and photocatalytic evaluation of visible light activated C-doped TiO2 nanoparticles

We have demonstrated heterogeneous photocatalytic degradation of microcystin-LR (MC-LR) by visible light activated carbon doped TiO(2) (C-TiO(2)) nanoparticles, synthesized by a modified sol-gel route based on the self-assembly technique exploiting oleic acid as a pore directing agent and carbon source. The C-TiO(2) nanoparticles crystallize in anatase phase despite the low calcination temperature of 350 °C and exhibit a highly porous structure that can be optimized by tuning the concentration of the oleic acid surfactant. The carbon modified nanomaterials exhibited enhanced absorption in the broad visible light region together with an apparent red shift in the optical absorption edge by 0.5 eV (2.69 eV), compared to the 3.18 eV of reference anatase TiO(2). Carbon species were identified by x-ray photoelectron spectroscopy analysis through the formation of both Ti-C and C-O bonds, indicative of substitution of carbon for oxygen atoms and the formation of carbonates, respectively. Electron paramagnetic resonance spectroscopy revealed the formation of two carbon related paramagnetic centers in C-TiO(2), whose intensity was markedly enhanced under visible light illumination, pointing to the formation of localized states within the anatase band gap, following carbon doping. The photocatalytic activity of C-TiO(2) nanomaterials was evaluated for the degradation of MC-LR at pH 3.0 under visible light (λ > 420 nm) irradiation. The doped materials showed a higher MC-LR degradation rate than reference TiO(2), behavior that is attributed to the incorporation of carbon into the titania lattice.     

掺碳二氧化钛的制备和其电流变性质

采用十二烷基胺 (DDA)作模板合成了二氧化钛颗粒 ,并在氮气流中以不同温度碳化制出了掺碳的二氧化钛。掺碳的二氧化钛的结构由透射电子显微镜 (TEM )、氮气吸附 -解吸等温线、XPS等表征。掺碳二氧化钛颗粒的电镜照片显示有不规则孔 ,粒径大小为 130～ 2 0 0nm。氮气吸附 -解吸等温线表明 :这些有着IV型等温线的颗粒存在介孔。XPS分析显示碳主要分布在粒子的表面。掺碳的二氧化钛粉末分散在石蜡油中形成无水电流变液 ,表现出很强的电流变效应。DDA和二氧化钛的物质的量比在 0 .0 5～ 0 .10并在 6 73K碳化的掺碳二氧化钛表现出很强的电流变效应 ,主要是因为在粒子表面的碳有合适的电导率     

Graft copolymer-templated mesoporous TiO(2) films micropatterned with poly(ethylene glycol) hydrogel: novel platform for highly sensitive protein microarrays

In this study, we describe the use of organized mesoporous titanium oxide (TiO(2)) films as three-dimensional templates for protein microarrays with enhanced protein loading capacity and detection sensitivity. Multilayered mesoporous TiO(2) films with high porosity and good connectivity were synthesized using a graft copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly(oxyethylene methacrylate) (POEM) side chains as a structure-directing template. The average pore size and thickness of the TiO(2) films were 50-70 nm and 1.5 μm, respectively. Proteins were covalently immobilized onto mesoporous TiO(2) film via 3-aminopropyltriethoxysilane (APTES), and protein loading onto TiO(2) films was about four times greater than on planar glass substrates, which consequently improved the protein activity. Micropatterned mesoporous TiO(2) substrates were prepared by fabricating poly(ethylene glycol) (PEG) hydrogel microstructures on TiO(2) films using photolithography. Because of non-adhesiveness of PEG hydrogel towards proteins, proteins were selectively immobilized onto surface-modified mesoporous TiO(2) region, creating protein microarray. Specific binding assay between streptavidin/biotin and between PSA/anti-PSA demonstrated that the mesoporous TiO(2)-based protein microarrays yielded higher fluorescence signals and were more sensitive with lower detection limits than microarrays based on planar glass slides.     

Preparation and characterization of sulfur-doped TiO(2)/Ti photoelectrodes and their photoelectrocatalytic performance

Sulfur-doped TiO(2)/Ti photoelectrodes were prepared by anodization and characterized by SEM, AFM, XRD, XPS, UV-vis and SPS. The results of investigation indicated that S(4+) and S(6+) were dispersed on the surface of TiO(2) nanoparticles. The doping with an appropriate amount of sulfur expanded the response range of TiO(2)/Ti photoelectrodes to visible light, and enhanced the separation of photoinduced electrons from cavities. The photoelectrocatalytic performance test run with sulfur-doped TiO(2)/Ti photoelectrodes under Xenon light indicated that Na(2)SO(3) concentration of 750 mg/L and voltage of 160 V were the optimal conditions for preparation of sulfur-doped TiO(2)/Ti photoelectrodes.     

Synthesis and characterization of visible light driven mesoporous nano-photocatalyst MoO3/TiO2

A novel mesoporous-structured photocatalyst MoO3/TiO2 was synthesized through a modified sol-gel method by using P123 as the template, and the resulting nano-photocatalysts were characterized by X-ray diffraction (XRD), N2 adsorption measurements, transmission electron microscope (TEM), UV-vis spectroscopy, XPS and Raman techniques. Low-angle XRD and TEM images show the lack of long-range order in the as-prepared MoO3/TiO2, but the Mo species are homogenously dispersed on the anatase matrix. According to the results of N2 ads-desorption, the calcined products possess the high surface area and the pore size distribution centered between 4-7 nm. The calcined meso-MoO3/TiO2 materials exhibit the high photocatalytic activity for the degradation of MB (methylene blue) under visible light radiation.     

3D Bi12TiO20/TiO2 hierarchical heterostructure: synthesis and enhanced visible-light photocatalytic activities

A three-dimensional (3D) multicomponent oxide, Bi(12)TiO(20)/TiO(2) hierarchical heterostructure was successfully synthesized via a one-step and template-free hydrothermal route. X-ray diffraction and X-ray photoelectron spectroscopy measurements confirm that the composition of the as-fabricated sample is Bi(12)TiO(20)/TiO(2) composite. Scanning and transmission electron microscopy observation reveals that the as-synthesized sample is microsized flower-like hierarchical networks consisted of Bi(12)TiO(20) nanorods decorated with the primary TiO(2) nanoparticles. Extension of the light absorption from the ultraviolet region to the visible-light region was confirmed by UV-vis absorption spectra. Due to the structure-property relationships, the 3D Bi(12)TiO(20)/TiO(2) heterostructure exhibited enhanced visible photocatalytic activity over that of Bi(12)TiO(20) and TiO(2) samples in the decomposition of Rhodamine B in water which is a typical model pollutant. The enhanced photocatalytic activity can be attributed to the extended absorption in the visible light region resulting from the 3D Bi(12)TiO(20)/TiO(2) heterostructures, and the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the Bi(12)TiO(20)/TiO(2) junction interface, demonstrating that the Bi(12)TiO(20)/TiO(2) heterostructure is a promising candidate as a visible light photocatalyst.     

模板法制备介孔TiO2及其光催化性能研究

以十六烷基三甲基溴化铵(CTAB)作为模板剂,钛酸正四丁酯(TBOT)为钛源,异丙醇为溶剂,通过溶胶-凝胶过程合成出介孔TiO2前驱体凝胶后,经老化、焙烧得到了TiO2介孔材料.利用XRD、HR-TEM、TGA、N2的吸附-脱附、BET等方法对材料的结构、形貌、比表面积、孔径分布进行表征.以亚甲基蓝的降解为模型反应,对其催化性能进行评价并与商品DegussaP-25进行比较.实验结果表明,比表面积为137.5m2/g、孔径为8.62nm的锐钛型介孔TiO2具有很高的催化活性.