Synthesis of multifunctional metal- and metal oxide core@mesoporous silica shell structures by using a wet chemical approach

We demonstrate a facile wet chemical approach for fabricating spherical metal/metal-oxide core@mesoporous silica shell hybrid nanoparticles with different core and shell thicknesses. Vertically aligned mesoporous silica (mSiO(2) ) shells were fabricated over the pre-synthesized spherical SiO(2) nanoparticles through a three-step strategy: 1)?synthesis of core materials, 2)?covering the core with an organic-inorganic composite layer, and 3)?removing the organic template through calcinations in air. The mechanisms of hybrid structure formation are proposed. The multifunctional nature of the hybrid structures could be induced by incorporating guest ions/molecules, such as Ag, Mn, and TiO(2) , into the pores of an mSiO(2) shell. Mn and TiO(2) cluster- incorporated composite structures have been tested to be antioxidizing agents and effective photocatalysts through electron spin resonance, radical scavenging tests, and the photocatalytic degradation of rhodamine B. The possibility of incorporating several hetero-element guest clusters in these mesoporous composite particles makes them highly attractive for multifunctional applications.     

Molecular selective photocatalysis by TiO2/nanoporous silica core/shell particulates

The coating of TiO(2) particles (P25) by a nanoporous silica layer was conducted to impart molecular recognitive photocatalytic ability. TiO(2)/nanoporous silica core/shell particles with varied pore diameters of the shell were synthesized by the reaction of P25 with an aqueous mixture of tetraethoxysilane and alkyltrimethylammonium chloride with varied alkyl chain lengths, followed by calcination. The TEM and nitrogen adsorption/desorption isotherms of the products showed that a nanoporous silica shell with a thickness of ca. 2nm and controlled pore diameter (1.2, 1.6, and 2.7 nm) was deposited on the titania particle when surfactants with different alkyl chain lengths (C12, C16 and C22) were used. The water vapor adsorption/desorption isotherms of the core/shell particles revealed that a larger amount of water adsorbed on the core/shell particles when the pore diameter is larger. The (29)Si MAS NMR spectra of the core/shell particles showed that the amount of surface silanol groups was independent of the water vapor adsorption capacity of the products. The possible molecular recognitive photocatalysis on the products was investigated under UV irradiation using two kinds of aqueous mixtures containing different organic compounds with varied sizes and functional groups: a 4-butylphenol, 4-hexylphenol, and 4-nonylphenol mixture and a 2-nitrophenol, 2-nitro-4-phenylphenol, and 4-nitro-2,6-diphenylphenol mixture. It was found that the core/shell particles exhibited selective adsorption-driven molecular recognitive photocatalytic decomposition of 4-nonylphenol and 2-nitrophenol in the two mixtures.     

Encapsulation of titanium(IV) oxide particles in hollow silica for size-selective photocatalytic reactions

A core-shell composite of TiO2 particles encapsulated in a hollow silica was fabricated, and the core-shell composite showed size-selective photocatalytic activity for decomposition of organics without reducing the intrinsic activity of the naked TiO2 core.     

Fabrication of hydroxyl group modified monodispersed hybrid silica particles and the h-SiO(2)/TiO(2) core/shell microspheres as high performance photocatalyst for dye degradation

The monodisperse hybrid silica particles (h-SiO(2)) were firstly prepared by a modified sol-gel process and the surface was modified in situ with double bonds, then abundant carboxyl moieties were introduced onto the surface of the silica core via thiol-ene click reaction. Afterward, the h-SiO(2)/TiO(2) core/shell microspheres were prepared by hydrolysis of titanium tetrabutoxide (TBOT) via sol-gel process in mixed ethanol/acetonitrile solvent, in which the activity of TBOT could be easily controlled. The carboxyl groups on the surface of silica particles promote the formation of a dense and smooth titania layer under well control, and the layer thickness of titania could be tuned from 12 to 100nm. The well-defined h-SiO(2)/TiO(2) core/shell structures have been confirmed by electron microscopy and X-ray photoelectron spectroscopy studies. After calcination at 500°C for 2h, the amorphous TiO(2) layer turned into anatase titania. These anatase titania-coated silica particles showed good photocatalytic performance in degradation of methyl orange aqueous solution under UV light.     

Mesoporous TiO2/SiO2 composite nanofibers with selective photocatalytic properties

Mesoporous TiO2/SiO2 composite nanofibers with a diameter of 100-200 nm and silica shell thickness of 5-50 nm have been fabricated by a sol-gel combined two-capillary co-electrospinning method; the composite nanofibers exhibited selective photocatalytic activity based on the decomposition of Methylene Blue, Active Yellow and Disperse Red.     

Effects of thermal treatments on the recovery of adsorbed water and photocatalytic activities of TiO2 photocatalytic systems

The effects of thermal treatments on the rehydration process and photocatalytic activity were investigated by 1H NMR spectroscopy for six anatase abundant TiO2 photocatalysts with different properties. Acetic acid and benzoic acid were employed for photodecomposition in aqueous suspension. After the calcinations at 973 K, physisorbed water layers recovered relatively fast for P25, F4, and AMT-600 (shorter than 24 h) with no significant enhancement of the photocatalytic decomposition. On the other hand, for ST-01, UV-100, and AMT-100, the recovery was very slow (longer than 1 week) and only partially reversible, and the photocatalytic decomposition was considerably enhanced but retarded with rehydration. In the presence of adsorbed water, the binding of a carboxyl group of the molecules with adsorbed water is considered to compete with the direct adsorption on the surface, which reduces the amount of the direct adsorption and results in the reduction in the photocatalytic efficiency. In addition, the photocatalytic decomposition of benzoic acid with an aromatic ring was much faster in all of the TiO2 aqueous suspensions and more enhanced for the fully dehydroxylated TiO2 than that of acetic acid. These results suggest that the most efficient photocatalytic sites should be the hydrophobic sites on the TiO2 surface. The difference among the rehydration rates of different TiO2 is discussed in terms of thermally induced changes of surface morphology.     

掺硼纳米TiO2的制备及光催化性能研究

采用改进的Sol-gel方法,制备了单分散椭球形微孔结构的掺B纳米TiO₂光催化剂,并用TG-DTA、XRD、XPS、UV-Vis、TEM、BET等手段进行表征.以难生化降解的染料罗丹明B为目标降解物,采用HPLC检测,通过不同光照时间下染料降解率考察了产物的光催化活性.结果表明,改进的Sol-gel法制得的光催化剂具有明显的孔结构,而且比表面积大、孔径分布窄、粒径小、分散性好;适量B的掺杂能够有效促进TiO₂纳米粒子的光催化活性.最佳催化剂制备条件:B掺杂的摩尔分数为20%、450℃煅烧2 h,此时所制得的B-TiO₂光催化剂活性比纯TiO₂有显著提高.     

乙酸修饰Ag/TiO2复合光催化剂的制备及协同催化性能

利用光化学还原法制备了Ag/TiO₂,然后通过乙酸浸渍制备了HAc-Ag/TiO₂复合光催化剂.利用X射线衍射（XRD）、透射电子显微镜（TEM）、傅里叶变换红外光谱（FTIR）、X射线光电子能谱（XPS）和紫外-可见漫反射光谱（UV-Vis DRS）等手段表征了催化剂的性质.以降解水溶液中的甲基橙（MO）为探针反应,考察了催化剂在可见光下的光催化性能.结果表明,乙酸对TiO₂的修饰在TiO₂禁带中产生了"带尾",使TiO₂的禁带宽度发生了显著的缩减;Ag纳米粒子和乙酸共同修饰的HAc-Ag/TiO₂样品具有更窄的禁带宽度和更正的价带顶位置;Ag和乙酸的协同作用使HAc-Ag/TiO₂具有良好的可见光催化活性：可见光照射2 h后,甲基橙在HAc-Ag/TiO₂上的降解率接近100%.     

Synthesis and Characterization of Magnetic TiO2/SiO2/NiFe2O4 Composite Photocatalysts

Magnetic TiO2/SiO2/NiFe2O4 composite photocatalytic particles with high crystalline TiO2 shell were synthesized via a mild solution route.The prepared composite particles were characterized with X-ray diffraction(XRD),transmission electron microscopy(TEM),high resolution transmission electron microscopy(HRTEM),scanning electron microscopy(SEM),ultraviolet-visible(UV-Vis) spectroscopy and vibrating sample magnetometer(VSM).The results show that the obtained TiO2/SiO2/NiFe2O4 composite particles were composed...     

Fabrication and photocatalytic characterizations of ordered nanoporous X-doped (X = N, C, S, Ru, Te, and Si) TiO2/Al2O3 films on ITO/glass

Transparent, ordered nanoporous TiO2/Al2O3 composite films doped with metal elements (Ru, Si, and Te) and nonmetal elements (N, C, and S) were fabricated by successive anodization and sol-gel process directly on glass substrates covered with a tin-doped indium oxide (ITO) film. The doping of ruthenium, nitrogen, carbon, and sulfur in TiO2 exhibited an enhanced effect on the absorbance, while the doping of silicon and tellurium showed little effect. Particularly, the N- and Ru-doped TiO2/Al2O3 films on ITO/glass developed an enhanced absorption red shift of 580 nm (-N) and 500 nm (-Ru). The nanoporous TiO2/Al2O3 composite film exhibited the highest photocatalytic activity in decomposing acetaldehyde under ultraviolet-light irradiation, with a value of 13 times in initial reaction rate or 7.8 times in quantum yield higher than a commercially available TiO2 material, Degussa P25. The ultraviolet-light photocatalytic activities of nanoporous TiO2/Al2O3 films were enhanced by the doping of nitrogen, carbon, and sulfur but slightly weakened by the doping of ruthenium, silicon, and tellurium. Particularly, the nanoporous N-doped TiO2/Al2O3 films exhibited effective photocatalytic activity on ultraviolet light decomposition of a highly toxic dioxin, HpCDD, and gave the highest decomposition rate of approximately 95% (via 7 h of irradiation) for the specimen with a dopant content of 1.7 wt % nitrogen.     

Absorption and action spectra analysis of ammonium fluoride-doped titania photocatalysts

The photocatalytic behaviour of a series of ammonium fluoride (NH(4)F)-doped titania (TiO(2)) photocatalysts was investigated in the decomposition of acetic acid in aqueous suspensions and in the gas phase mineralization of acetaldehyde. Very similar photocatalytic activity trends, usually increasing with increasing the calcination temperature for a given nominal dopant amount, were obtained for the two test reactions. Moderately doped TiO(2) calcined at 700 °C, consisting of pure anatase, was the best performing photocatalyst in both reactions. The photocatalytic oxidation of acetic acid was investigated systematically as a function of irradiation wavelength, by collecting so-called action spectra. By comparing the shapes of the action spectra with those of the absorption spectra of the investigated photocatalysts a model is proposed, based on spectral features deconvolution, which allows a clear distinction between inactive light absorption and effective photoactivity in acetic acid decomposition.     

Photocatalytic Characterization of TiO_2 Supported on Active Carbon

Photocatalysis on TiO2, with a promising application to the elimination of organic contaminants from air and water, has been a particularly active area1. For such application, it is important to improve the efficiency of TiO_2 photocatalysts. In the most cases, the concentration of organic contaminants in water is extremely dilute (ppm level or below) and TiO_2 itself has low adsorbabilities for them, it usually takes a long time to complete their decomposition. One of the effective ways to …     

类蛋结构的可磁分离光催化剂纳米球的制备及催化性能

通过反胶束和静电自组装方法制备了一种类蛋结构的可磁分离光催化剂纳米材料SiO₂@NiFe₂O₄@TiO₂(TSN), 这种光催化剂对甲基橙废水有较好的降解效果, 并显示出了超顺磁性, 通过外加磁场方便地实现催化剂在水中的分离与回收. 该光催化剂纳米球的X射线衍射, TEM和FTIR结果表明, 铁酸镍纳米粒子被包裹在SiO₂内, 形成SiO₂@NiFe₂O₄(SN)纳米球载体, 纳米TiO₂颗粒组装在SN表面, 形成TiO₂光催化壳层. 利用甲基橙的降解考察了光催化剂纳米球的活性, 结果表明, 在NiFe₂O₄和TiO₂之间包覆一层无定形的SiO₂可以显著提高光催化剂纳米球TSN的催化活性.     

氮和碳共掺杂TiO2纳米晶的制备及可见光催化性能

以钛酸四丁酯为钛源, 冰醋酸为抑制剂, 超细铵盐为固体载体, 采用新型溶胶-凝胶法制备了氮和碳共掺杂TiO2纳米晶(N-C-TiO2) 光催化剂. 透射电子显微镜(TEM)结果表明, N-C-TiO2样品颗粒均匀, 尺寸细小, 且分散性好; 热失重分析(TGA)、 X射线粉末衍射(XRD)和X射线光电子能谱(XPS)研究结果表明, 复合干凝胶经低温热处理, 使铵盐载体分解、 挥发去除, 样品为单一的锐钛矿相, N和C原子扩散进入晶格结点或间隙位置, 与TiO2化学键结合; 氮气等温吸附-脱附结果表明, 样品比表面积高达356 m2/g, 孔体积为0.27 mL/g. 以氙灯为可见光光源, 罗丹明B水溶液为模拟污染物, P25为参比催化剂, 在辐射强度为100 mW/cm2的可见光照射条件下, N-C-TiO2具有很高的光催化活性, 其可见光催化活性明显高于P25.     

Synthesis of Multifunctional Metal‐ and Metal Oxide Core@Mesoporous Silica Shell Structures by Using a Wet Chemical Approach

We demonstrate a facile wet chemical approach for fabricating spherical metal/metal‐oxide core@mesoporous silica shell hybrid nanoparticles with different core and shell thicknesses. Vertically aligned mesoporous silica (mSiO₂) shells were fabricated over the pre‐synthesized spherical SiO₂ nanoparticles through a three‐step strategy: 1) synthesis of core materials, 2) covering the core with an organic–inorganic composite layer, and 3) removing the organic template through calcinations in air. The mechanisms of hybrid structure formation are proposed. The multifunctional nature of the hybrid structures could be induced by incorporating guest ions/molecules, such as Ag, Mn, and TiO₂, into the pores of an mSiO₂ shell. Mn and TiO₂ cluster‐ incorporated composite structures have been tested to be antioxidizing agents and effective photocatalysts through electron spin resonance, radical scavenging tests, and the photocatalytic degradation of rhodamine B. The possibility of incorporating several hetero‐element guest clusters in these mesoporous composite particles makes them highly attractive for multifunctional applications.     

Ag／TiO2复合纳米催化剂的制备和表征及其光催化活性

 采用光还原沉积贵金属法，制备了Ag／TiO2复合纳米催化剂．通过调节溶液的pH值控制TiO2表面负载银的形貌，利用AAS，XRD，TEM和XPS等手段对样品进行了表征．以苯胺氧化为模型反应，考察了Ag／TiO2复合纳米催化剂样品的光催化活性以及银沉积量和沉积形貌对催化剂活性的影响．结果表明，通过调控光还原沉积条件，可在平均粒径为24nm左右的TiO2颗粒上获得3nm左右均匀分散的银粒子；在TiO2上沉积适量的具有较高分散度的金属Ag，能有效提高TiO2对苯胺氧化反应的光催化活性．     

Direct nanocomposite of crystalline TiO2 particles and mesoporous silica as a molecular selective and highly active photocatalyst

Well-crystallised TiO2 particles (P-25, 20-30 nm in diameter) were directly incorporated into surfactant-templated mesoporous silica particles (pore diameter: 2.7 nm), and the composite material with a high TiO2 content (60 wt%) showed molecular selective and enhanced photocatalysis for decomposition of 4-nonylphenol.     

超临界流体干燥法制备TiO2／C纳米粒子及光催化性能

以TiCl4为原料,采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO2/C复合光催化剂.以苯酚的光催化降解对所得催化剂的催化活性进行了评价.结果表明,纳米TiO2/C复合粒子与单组分TiO2比较,复合粒子光催化活性高于单组分的TiO2,h苯酚降解率高达975 ％,COD为957%.并用XRD、TEM、 UV-Vis和XPS等手段进行了表征,iO2以锐钛矿型形式存在.比较了不同制备方法制得的TiO2/C复合催化剂,得出超临界干燥法制备的光催化剂具有粒径小,比表面积大,分散性好,光催化活性高等特点.     

A new patterning method using photocatalytic lithography and selective atomic layer deposition

We report a new patterning method using photocatalytic lithography of alkylsiloxane self-assembled monolayers and selective atomic layer deposition of thin films. The photocatalytic lithography is based on the fact that the decomposition rate of the alkylsiloxane monolayers in contact with TiO2 is much faster than that with SiO2 under UV irradiation in air. The photocatalytic lithography, using a quartz plate coated with patterned TiO2 thin films, was done to prepare patterned monolayers of the alkylsiloxane on Si substrates. A ZrO2 thin film was selectively deposited onto the monolayer-patterned Si substrate by atomic layer deposition.     

A plasmonic photocatalyst consisting of silver nanoparticles embedded in titanium dioxide

Titanium dioxide (TiO2) displays photocatalytic behavior under near-ultraviolet (UV) illumination. In another scientific field, it is well understood that the excitation of localized plasmon polaritons on the surface of silver (Ag) nanoparticles (NPs) causes a tremendous increase of the near-field amplitude at well-defined wavelengths in the near UV. The exact resonance wavelength depends on the shape and the dielectric environment of the NPs. We expected that the photocatalytic behavior of TiO2 would be greatly boosted if it gets assisted by the enhanced near-field amplitudes of localized surface plasmon (LSP). Here we show that this is true indeed. We named this new phenomenon "plasmonic photocatalysis". The key to enable plasmonic photocatalysis is to deposit TiO2 on a NP comprising an Ag core covered with a silica (SiO2) shell to prevent oxidation of Ag by direct contact with TiO2. The most appropriate diameter for Ag NPs and thickness for the SiO2 shell giving rise to LSP in the near UV were estimated from Mie scattering theory. Upon implementing a device that took these design considerations into account, the measured photocatalytic activity under near UV illumination of such a plasmonic photocatalyst, monitored by decomposition of methylene blue, was enhanced by a factor of 7. The enhancement of the photocatalytic activity increases with a decreased thickness of the SiO2 shell. The plasmonic photocatalysis will be of use as a high performance photocatalyst in nearly all current applications but will be of particular importance for applications in locations of minimal light exposure.