Dual latex/surfactant templating of hollow spherical silica particles with ordered mesoporous shells

Hollow spherical silica particles with hexagonally ordered mesoporous shells are synthesized with the dual use of cetyltrimethylammonium bromide (CTAB) and unmodified polystyrene latex microspheres as templates in concentrated aqueous ammonia. In most of the hollow mesoporous particles, cylindrical pores run parallel to the hollow core due to interactions of CTAB/silica aggregates with the latices. Effects on the product structure of the CTAB:latex ratio, the amount of aqueous ammonia, and the latex size are studied. Hollow particles with hexagonally patterned mesoporous shells are obtained at moderate CTAB:latex ratios. Too little CTAB causes silica shell growth without surfactant templating, and too much induces nucleation of new mesoporous silica particles without latex cores. The concentration of ammonia must be large to induce co-assembly of CTAB, silica, and latex into dispersed particles. The results are consistent with the formation of particles by addition of CTAB/silica aggregates to the surface of latex microspheres. When the size and number density of the latex microspheres are changed, the size of the hollow core and the shell thickness can be controlled. However, if the microspheres are too small (50 nm in this case), agglomerated particles with many hollow voids are obtained, most likely due to colloidal instability.     

Fabrication of spindle Fe(2)O(3)@polypyrrole core/shell particles by surface-modified hematite templating and conversion to spindle polypyrrole capsules and carbon capsules

By using a surface-modified templating method, Fe(2)O(3)@polypyrrole (PPy) core/shell spindles have been successfully prepared in this paper. The Fe(2)O(3) particles with spindle morphology were initially fabricated as core materials. After the PVP modification, the Fe(2)O(3) spindles were subsequently coated with a tunable thickness layer of PPy by in situ deposition of the conducting polymer from aqueous solution. Hollow PPy spindles were produced by dissolution of the Fe(2)O(3) core from the core/shell particles. High-temperature treatment under vacuum condition covert the hollow PPy spindles into carbon capsules by carbonization of the PPy shell. Transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of the Fe(2)O(3)@PPy core/shell particles, PPy and carbon capsules with spindle morphology.     

CMC和CTAB双模板法合成具有稳定结构的MCM-41中孔分子筛

以羧甲基纤维素和十六烷基三甲基溴化铵为双模板,制备出了具有更高稳定性并且具有高度有序二维六方结构的MCM-41介孔分子筛.透射电镜和X射线衍射结果表明,以双模板制备的MCM-41介孔分子筛具有高度有序的二维六方(p6mm)孔道结构.此外,以双模板制备的MCM-41介孔分子筛焙烧前后的X射线衍射结果表明,在焙烧过程中其晶胞收缩比例为3.1%.与以纯表面活性剂为模版制备的MCM-41介孔分子筛(晶胞收缩比例为9.7%)相比,双模板制备的MCM-41介孔分子筛具有更高的稳定性能. MCM-41介孔分子筛稳定性能的提高可能是由于在硅物种、表面活性剂以及羧甲基纤维素在自组装过程中,羧甲基纤维素表面丰富的羟基与硅物种Si-(OH)x的相互作用促进了Si-(OH)x的缩聚.     

Mesoporous Fe2O3 microspheres: rapid and effective enrichment of phosphopeptides for MALDI-TOF MS analysis

Mesoporous Fe(2)O(3) microspheres have been successfully synthesized by the polymerization (urea and formaldehyde)-induced ferric hydroxide colloid aggregation. The urea-formaldehyde resin was removed by calcination in air. The obtained mesoporous Fe(2)O(3) materials have spherical morphology with uniform particle size of approximately 3.0 microm and porous surface with large inter-particle pores of approximately 48.0 nm. The surface area is as large as approximately 33.3 m(2)/g and the pore volume is 0.31 cm(3)/g. The mesoporous Fe(2)O(3) microspheres were used for the enrichment of phosphopeptides for the first time, in which high sensitivity, selectivity and capacity of specifically enriched phosphopeptides were achieved under a mild condition in a relative short time. After enriched from tryptic digest products of beta-casein by the novel mesoporous Fe(2)O(3) microspheres, phosphopeptides can be selectively detected with high intensity in MALDI-TOF mass spectrometry. Elimination of "shadow effect" was observed by using mesoporous Fe(2)O(3) microspheres, and the detectable limitation is 5x10(-10) M. This material is also effective for enrichment of phosphopeptides from the complex tryptic digests of commercial phosphoprotein casein, with much more phosphorylated sites (26 in 27 of total) and higher signal/noise ratio in the MALDI-TOF mass spectrometry, compared to commercial Fe(2)O(3) nanoparticles. It shows a great potential application in the field of rapid and effective isolation of phosphopeptides.     

Fabrication and characterization of mesoporous Co3O4 core/mesoporous silica shell nanocomposites

A mesoporous Co(3)O(4) core/mesoporous silica shell composite with a variable shell thickness of 10-35 nm was fabricated by depositing silica on Co(3)O(4) superlatticed particles. The Brunauer-Emmett-Teller (BET) surface area of the composite with a shell thickness of ca. 2.0 nm was 238.6 m(2)/g, which varied with the shell thickness, and the most frequent pore size of the shell was ca. 2.0 nm. After the shell was eroded with hydrofluoric acid, mesoporous Co(3)O(4) particles with a pore size of ca. 8.7 nm could be obtained, whose BET surface area was 86.4 m(2)/g. It is proposed that in the formation of the composite the electropositive cetyltrimethylammonium bromide (CTAB) micelles were first adsorbed on the electronegative Co(3)O(4) particle surface, which directed the formation of the mesoporous silica on the Co(3)O(4) particle surface. Electrochemical measurements showed that the core/shell composites exhibited a higher discharge capacity compared with that of the bare Co(3)O(4) particles.     

Electrodeposition of mesoporous V2O5 with enhanced lithium-ion intercalation property

Mesoporous vanadium oxide (V₂O₅) thin films were deposited electrochemically onto indium tin oxide-coated glass substrates from an aqueous solution of vanadyl sulfate using CTAB (hexadecyltrimethylammonium bromide) as a templating agent. For comparison, a control sample was electrodeposited without CTAB templating. Transmission electron microscopy and small angle X-ray diffraction indicated the presence of mesoporosity with a well-ordered lamellar phase in the electrodeposited films. The crystallinity of the V₂O₅ thin films was confirmed by X-ray diffraction. Cyclicvoltammetry and chronoamperometry were used to measure electrochemical properties of synthesized films. The mesoporous films prepared with CTAB templating had a much higher capacity and lithium-ion diffusion rate than the non-porous electrode prepared without CTAB templating.     

介孔TiO2的水热法制备及其光催化性能

以二钛酸钾(K2Ti2O5)经离子交换得到的无定形水合二钛酸(H2Ti2O5·xH2O)为原料, 与葡萄糖溶液在220 ℃下进行水热反应, 再在空气中520 ℃焙烧, 制备出介孔TiO2. 用扫描电子显微镜(SEM)、X射线衍射(XRD)、N2吸附、透射电子显微镜(TEM)等技术对样品进行了表征. 结果表明, 该介孔TiO2具有微米级棒状或针状形貌, 晶粒大小为12.3 nm, 比表面积为106 m2·g-1, 孔容为0.31 cm3·g-1, 孔径为8.06 nm, 焙烧处理后晶型仍是锐钛矿相. 水热生成的碳抑制了晶粒的团聚生长和晶型的转变, 提高了介孔TiO2的热稳定性. 甲基橙降解实验评价了介孔TiO2的光催化性能, 结果发现其活性与商用TiO2催化剂P25相当, 而其较大的粒径更容易回收再利用. 以碘化钾为探针反应, 表明介孔TiO2的光催化机制以光生空穴氧化为主.     

Use of the ternary phase diagram of a mixed cationic/glucopyranoside surfactant system to predict mesostructured silica synthesis

Mixed surfactant systems have the potential to impart controlled combinations of functionality and pore structure to mesoporous metal oxides. Here, we combine a functional glucopyranoside surfactant with a cationic surfactant that readily forms liquid crystalline mesophases. The phase diagram for the ternary system CTAB/H(2)O/n-octyl-beta-D-glucopyranoside (C(8)G(1)) at 50 degrees C is measured using polarized optical microscopy. At this temperature, the binary C(8)G(1)/H(2)O system forms disordered micellar solutions up to 72 wt% C(8)G(1), and there is no hexagonal phase. With the addition of CTAB, we identify a large area of hexagonal phase, as well as cubic, lamellar and solid surfactant phases. The ternary phase diagram is used to predict the synthesis of thick mesoporous silica films via a direct liquid crystal templating technique. By changing the relative concentration of mixed surfactants as well as inorganic precursor species, surfactant/silica mesostructured thick films can be synthesized with variable glucopyranoside content, and with 2D hexagonal, cubic and lamellar structures. The domains over which different mesophases are prepared correspond well with those of the ternary phase diagram if the hydrophilic inorganic species is assumed to act as an equivalent volume of water.     

Effect of calcination temperature on the structure of a Pt/TiO2 (B) nanofiber and its photocatalytic activity in generating H2

Hydrogen trititanate (H 2Ti 3O 7) nanofibers were prepared by a hydrothermal method in 10 M NaOH at 403 K, followed by acidic rinsing and drying at 383 K. Calcining H 2Ti 3O 7 nanofibers at 573 K led to the formation of TiO 2 (B) nanofibers. Calcination at 673 K improved the crystallinity of the TiO 2 (B) nanofibers and did not cause any change in the morphology and dimensions of the nanofibers. TiO 2 (B) and H 2Ti 3O 7 nanofibers are 10-20 nm in diameter and several micrometers long, but FE-SEM reveals that several of these nanofibers tend to bind tightly to each other, forming a fiber bundle. Calcination at 773 K transformed TiO 2 (B) nanofibers into a TiO 2 (B)/anatase bicrystalline mixture with their fibrous morphology remaining intact. Upon increasing the calcination temperature to 873 K, most of the TiO 2 (B) nanofibers were converted into anatase nanofibers and small anatase particles with smoother surfaces. In the photocatalytic dehydrogenation of neat ethanol, 1% Pt/TiO 2 (B) nanofiber calcined at 673 K was the most active catalyst and generated about the same amount of H 2 as did 1% Pt/P-25. TPR indicated that the calcination of 1% Pt/TiO 2 (B) nanofiber at 573 K produced a poor Pt dispersion and poor activity. Calcination at a temperature higher than 773 K (in ambient air) resulted in an SMSI effect similar to that observed over TiO 2 in the reductive atmosphere. As suggested by XPS, such an SMSI effect decreased the surface concentration of Pt metal and created Pt (delta) sites, preventing Pt particles from functioning as a Schottky barrier and leading to a lower activity. Because of the synergetic effect between TiO 2 (B) and anatase phases, the bicrystalline mixture, produced by calcining at 773 K, was able to counter negative effects such as the reduction in surface area and the SMSI effect and maintained its photocatalytic activity.     

由钛铁矿制备Fe3O4/TiO2复合物的研究进展

归纳了从钛铁矿中分离铁和二氧化钛的方法,包括亚熔盐法、预氧化法、还原锈蚀法;其次,初步总结了目前国内外制备Fe_3O_4磁性纳米颗粒和TiO_2纳米粒子的方法。最后,对Fe_3O_4/TiO_2复合材料的制备方法包括溶胶-凝胶法、微乳液法、均匀沉淀法作了梳理。Fe_3O_4/TiO_2复合纳米材料很好地解决了单独使用TiO_2作为废水处理催化剂,在实际应用过程中易随水流失,难以回收利用的问题,具有一定的实用性。     

“Noodle-like” Mesoporous Silica Templated by Polyelectrolyte／Surfactant Complex

“Noodle-like” mesoporous silica with a diameter of about 180 nm and a length of ca. 10μm was prepared through sol-gel process by using poly(sodium 4-styrenesulfonate) (PSS)/cetyltrimethylammonium bromide (CTAB) complex as template. Parallel oriented regular mesopores with a diameter of around 2-4 nm are distributed along the wall of the particles, while the “worm-like” disordered mesopores can be found in the fringe part. This approach provides a new series of templates and a novel route to prepare inorganic mesoporous materials with special morphology.     

Application of tetrahydrofuran dispersant in microemulsion for fabricating titania mesoporous thin film

A new strategy was used to fabricate titania mesoporous thin film by incorporating tetrahydrofuran (THF) into the CTAB/n-butyl alcohol/cyclohexane/water reverse microemulsion as a micelle disperser. Highly dispersed and congregated TiO(2) particles in the microemulsion with and without THF were observed by transmission electron microscopy (TEM), respectively. The photographs observed by field-emission scanning electron microscopy (FE-SEM) show that a uniform titania mesoporous thin film with monodisperse TiO(2) spherical nanoparticles of ca. 20 nm was obtained using the microemulsion with THF.     

A general templated method to homogeneous and composition-tunable hybrid TiO2 nanocomposite fibers

Sequential impregnations of metal ions and titanium tetraisopropoxide (TTIP) into activated carbon fibers (ACF) followed by a solvothermal treatment has been found to be a general method in the preparations of homogeneous and composition-tunable hybrid TiO(2) hierarchical nanocomposite fibers like WO(3)/TiO(2), Fe(2)O(3)/TiO(2) and SnO(2)/TiO(2).     

Beneficial role of cetyltrimethylammonium bromide in the enhancement of photovoltaic properties of dye-sensitized rutile TiO2 solar cells

A new approach involving the introduction of the common cationic surfactant cetyltrimethylammonium bromide (CTAB) for modifying a rutile TiO2 film during its formation from hydrolyzed TiCl4 solution has been adopted, intending to improve the photoelectrochemical properties of the pertinent dye-sensitized solar cell. CTAB-routed films were found to consist of smaller clusters of near-spherical TiO2 particles, compared with larger clusters of long rod-shaped particles in the absence of CTAB. As a consequence, the photocurrent and photovoltage of the cell fabricated by using CTAB have increased significantly, leading to a conversion efficiency increase, compared with those of the cell prepared without CTAB. On the basis of FE-SEM, BET, and XRD analyses, the increases are attributed to decreased particle size, improved interparticle connectivity, and enhanced crystallinity of the CTAB-promoted TiO2 particles and decreased void volume in the film. Faster growth of the TiO2 film was another beneficial effect of CTAB. A mechanism is proposed for the beneficial role of CTAB during the film formation.     

F127辅助制备介孔Fe/TiO2催化剂用于中温NH3选择性催化还原反应

NOx是大气污染物的重要组成部分,能够造成酸雨、光化学烟雾和臭氧层破坏等一系列环境问题,严重危害人类健康.选择性催化还原(SCR)是控制NOx排放的主要技术,当前工业上普遍采用的是钒钛催化剂,然而该催化剂活性温度窗口较窄(300-400oC),N2选择性较低,而且钒物种本身有毒.因此开发新型SCR催化剂成为研究热点.Fe/TiO2催化剂具有稳定的化学性质,环境污染少且价格低廉,近年来受到广泛关注.为了提高Fe/TiO2催化活性,人们采用了各种不同的制备方法.本文以F127作为结构导向剂,结合溶胶-凝胶法原位合成了具有介孔结构、工作温度在150-300 oC的Fe/TiO2脱硝催化剂,并与普通浸渍法和共沉淀法制备的催化剂进行了对比.利用N2吸附脱附、紫外-可见光谱、X射线电子能谱、NH3程序升温脱附和原位红外光谱等技术研究了制备方法对Fe/TiO2催化剂物理结构及脱硝性能的影响.结果表明,相较于浸渍法和共沉淀法,模板法制备的催化剂具有较高的脱硝效率和抗H2O和SO2性能.作为结构导向剂,F127能够诱导催化剂形成均匀的介孔结构,有利于提高催化剂比表面积,促进反应物分子的扩散和转移,从而提高催化剂脱硝效率.进一步研究发现,模板法能够明显促进活性组分Fe物种的分散和NH3吸附,载体与活性组分具有较强的相互作用,因而有利于催化剂产生较多的活性位.结合XPS结果,较多的活性位点有利于表面吸附氧(Oα)在催化剂表面的吸附.Oα有利于NO到NO2的转化,从而促进快速SCR反应:NO+NO2+2NH3→2N2+3H2O.通过原位红外机理分析证明,吸附在模板法制备的催化剂表面的NO物种具有较强的稳定性,当温度超过200 oC时,仍然保持一定的吸附强度;吸附NH3红外结果表明,Lewis酸性位比Br?nsted酸性位具有更强的稳定性,当温度超过150oC仍然具有较强的Lewis酸吸附.催化剂表面稳定的NO物种和Lewis酸位上强的NH3吸附是催化剂催化活性增加的重要原因.     

Fe-MSU-1介孔分子筛的合成及其催化苯酚羟基化性能

以月桂醇聚氧乙烯醚为模板剂,在中性条件下成功合成了Fe-MSU-1介孔分子筛.采用X射线衍射、傅里叶变换红外光谱、紫外-可见吸收光谱、电子自旋共振谱、透射电镜、低温N2吸附和电感耦合等离子体原子发射光谱对样品进行了表征.考察了Fe-MSU-1分子筛在苯酚羟基化反应中的催化性能以及工艺条件对苯酚羟基化反应的影响.结果表明,Fe3 离子进入了分子筛骨架,Fe-MSU-1分子筛具有均一的蠕虫状介孔结构,平均孔径约为2.9nm.在焙烧后的Fe-MSU-1样品中,Fe3 主要以四配位的形式存在,无骨架外Fe2O3物种形成.以水为溶剂,在苯酚/H2O2摩尔比为3,反应温度353K,反应时间7h的条件下,苯酚和H2O2的转化率以及苯二酚的选择性分别达到20.4%,96.9%和99.6%.     

A new dual immunoassay for tumor markers based on chemiluminescence signal amplification by magnetic mesoporous silica and enzyme modified gold nanoparticles

A sensitive dual immunoassay was proposed for the determination of carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) based on signal amplification. Monoclonal antibodies immobilized on magnetic mesoporous silica particles (Fe(3)O(4)/SiO(2)) were prepared as the primary probe. Horseradish peroxidase (HRP) labeled antibodies co-coated with HRP on gold nanoparticles (AuNPs) were used as the secondary probe to achieve signal amplification. HRP tags were retained in the flow cells after a sandwich immunoassay. By controlling two switches on the two channels, chemiluminescent substrates were injected orderly man way, and then signals for CEA and AFP were sequentially detected by HRP-luminol-H(2)O(2). Due to the increased amount of HRP on AuNPs and the increased amount of monoclonal antibodies on Fe(3)O(4)/SiO(2), the signals were largely amplified. Under the optimal conditions, CEA and AFP could be detected in the linear ranges of 1.0 - 80 and 1.0 - 75 ng mL(-1) with detection limits of 0.25 and 0.5 ng mL(-1), respectively.     

Rapid Fabrication of Mesoporous Titania Films with Controlled Macroporosity to Improve Photocatalytic Property

Hierarchically porous titania films were fabricated by dual templating using a triblock copolymer such as Pluronic F127 and polystyrene (PS) beads, affording mesoporous films with controlled macroporosity. The presence of the triblock copolymer in the precursor solutions suppressed a regular accumulation of spherical PS beads, and PS‐derived macropores could be dispersed over the whole mesoporous titania film through rapid fabrication by spin‐coating. Some of the macropores were clustered, but the presence of the large spaces was important for keeping the mesostructure after calcination. Photodegradation of methylene blue (MB) was investigated by using the photoactive anatase films. The photodegradation of MB over the porous anatase films was accelerated by effective diffusion of MB molecules in the PS‐derived macropores, but it was important for improving photocatalytic performance to regulate the balance between the effectiveness of the diffusion in the macropores and the decrease of the surface area from the embedded macropores, as well as the reduction in the transparency of the porous films.     

Mesoporous Fe2O3-doped TiO2 nanostructured fibers with higher photocatalytic activity

Mesoporous Fe(2)O(3)-doped TiO(2) nanostructured fibers were fabricated through electrospinning the relevant gel precursor. The prepared fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and surface analysis, respectively. The photocatalytic activity of these mesoporous composite fibers was evaluated by photocatalytic degradation of methylene blue (MB) in water under UV irradiation. Compared with different types of photocatalysts, the 1% Fe(2)O(3)-doped TiO(2) fibers exhibited super photocatalytic activity.     

Heterometal alkoxides as precursors for the preparation of porous Fe- and Mn-TiO2 photocatalysts with high efficiencies

Transition-metal-doped titanium glycolates (M-TG, with M=Fe, Mn), which are the first non-stoichiometric heterometal alkoxides, have been synthesised through a solvothermal doping approach. X-ray diffraction, UV/Vis diffuse reflectance and ESR spectroscopy revealed that the dopant ion (Fe(3+) or Mn(2+)) is substituted for Ti(4+) in the TG lattice. Fe(3+) prolongs the crystallisation time of Fe-TG, whereas Mn(2+) has a smaller effect on the crystallisation time in comparison with Fe(3+). The as-synthesised M-TG materials were used directly as single-source precursors for the preparation of metal-doped titania (M-TiO(2)) through a simple thermal treatment process. The as-prepared M-TiO(2) materials maintain the rod-like morphology of the precursors and possess a mesoporous structure with high crystallinity. It has been proved that the dopant ions are incorporated into the TiO(2) lattice at the Ti(4+) positions. The photocatalytic activities of the M-TiO(2) materials obtained were evaluated by testing the degradation of phenol under UV irradiation. From the photocatalytic results, it was concluded that high crystallinity, a large surface area and appropriate transition-metal-doping are all beneficial to the enhancement of the photocatalytic performance of the doped TiO(2) material. In addition, it was noted that in comparison with Mn-TiO(2), Fe-TiO(2) shows higher photocatalytic activity due to the better inhibition effect of Fe(3+) on recombination of photogenerated electron-hole pairs. In contrast to the conventional nanosized TiO(2) photocatalyst, the micrometre-sized M-TiO(2) particles we obtained can be easily separated and recovered after the photocatalytic reactions.