Morphological and structural change of nano-pored alumina membrane above 1200 K

The transition and the change in pore morphology of a porous alumina membrane prepared by anodically oxidizing aluminum in sulfuric acid were studied mainly by TG-DTA, TMA, dilatometry and TEM. At ca. 1243 K, TMA showed an expansion followed by contraction; the CO₂ and SO₂ gases were quickly discharged, and the pore morphology of the as-prepared porous membrane (ca 150 mm-t, with pores ca 25 nm in diameter and containing ca 11% by mass of SO₂) showed an abrupt change, but the pores were retained to ca. 1573 K. Sulfur incorporated in the membrane was lost in two stages, i.e., at ca 1243 K and in a range up to 1373 K. Isothermal measurements revealed the complex crystallization of the amorphous phase into polycrystalline phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

Rigid nanoscopic containers for highly dispersed, stable metal and bimetal nanoparticles with both size and site control

We demonstrate a novel strategy for the preparation of mesoporous silica-supported, highly dispersed, stable metal and bimetal nanoparticles with both size and site control. The supporting mesoporous silica, functionalized by polyaminoamine (PAMAM) dendrimers, is prepared by repeated Michael addition with methyl acrylates (MA) and amidation reaction with ethylenediamine (EDA), by using aminopropyl-functionalized mesoporous silica as the starting material. The encapsulation of metal nanoparticles within the dendrimer-propagated mesoporous silica is achieved by the chemical reduction of metal-salt-impregnated dendrimer-mesoporous silica by using aqueous hydrazine. The site control of the metal or bimetal nanoparticles is accomplished by the localization of inter- or intradendrimeric nanoparticles within the mesoporous silica tunnels. The size of the encapsulated nanoparticles is controlled by their confinement to the nanocavity of the dendrimer and the mesopore. For Cu and Pd, particles locate at the lining of mesoporous tunnels, and have diameters of less than 2.0 nm. For Pd/Pt, particles locate at the middle of mesoporous tunnels and have diameters in the range of 2.0-4.2 nm. The Pd and Pd/Pt nanoparticles are very stable in air, whereas the Cu nanoparticles are stable only in an inert atmosphere.     

Nanostructured pure gamma-Fe2O3 via forced precipitation in an organic solvent

Pure maghemite, gamma-Fe(2)O(3), was prepared as ultra fine particles in the nanometer-sized range via the forced precipitation method in an organic solvent. The precipitation of iron(III) ions, from iron(III) chloride in 2-propanol led selectively to highly dispersed particles of ferrihydrite, which upon treatment with temperatures higher than 200 degrees C under dynamic vacuum resulted in high-surface-area particles of gamma-Fe(2)O(3). Precipitation in water also led to ferrihydrite, but the final product, after heating at 300 degrees C, contained a mixture of gamma-Fe(2)O(3) and alpha-Fe(2)O(3) (hematite). The precipitation from iron(III) nitrate in water resulted in goethite which was converted to hematite upon heating. On the other hand, the final product in 2-propanol was a mixture of maghemite and hematite. The products were characterized by FTIR, TGA, XRD, and gas sorption analysis. Nitrogen gas adsorption studies for the pure gamma-Fe(2)O(3) samples revealed mesoporous particles with high surface areas in the range of 70-120 m(2) g(-1) after heat treatment at 300 degrees C. The gamma-Fe(2)O(3) particles retained their gamma-phase as well as their mesoporous structure at relatively high temperatures, as high as 400 degrees C.     

金复合介孔SBA-15吸附血红蛋白在H2O2电催化反应中的应用

以P123嵌段共聚物表面活性剂为模板剂制备介孔氧化硅SBA-15,并用沉积-沉淀(DP)法在SBA-15介孔表面负载纳米Au颗粒制备得到金复合介孔SBA-15材料(Au-SBA-15).再以Au-SBA-15材料制备玻碳修饰电极,将血红蛋白固定于修饰电极上用循环伏安法考察其对不同浓度H2O2溶液的电催化反应.在固定了血红蛋白的Hb/Au-SBA-15/GC修饰电极上,H2O2在+0.95 V处出现了氧化峰,且随着H2O2浓度的增大峰电流不断增加,说明金复合介孔氧化硅材料具有良好的生物兼容性,有利于血红蛋白的固定,其修饰电极对H2O2溶液具有一定的电催化作用.     

杂原子HMS介孔分子筛的催化脱氢和加氢脱硫性能

ＭＣＭ４１［１］和ＨＭＳ［２］等介孔分子筛对大分子的扩散阻力较小且具有良好的热稳定性,特别是在合成中可以直接将各种杂原子引入骨架,从而调变其催化性能,因此目前介孔分子筛在催化中的应用引起了各国研究者的广泛兴趣．Ｔｉ,Ｚｒ,Ｖ,Ｃｒ,Ｍｎ,Ｃｕ和Ｆｅ...     

Nanorods of Various Oxides and Hierarchically Structured Mesoporous Silica by Sol-Gel Electrophoresis

In this paper, we report the template-based growth of nanorods of oxides and hierarchically structured mesoporous silica, formed by means of a combination of sol-gel processing and electrophoretic deposition. Both single metal oxides (TiO₂) and complex oxides (Pb(Zr_0.52Ti_0.48)O₃) have been grown by this method. This method has also been applied to the growth of nanorods of mesoporous silica having an ordered pore structure, where the pores are aligned parallel to the long axis of the nanorod. Uniformly sized nanorods of about 125–200 nm in diameter and 10 m in length were grown over large areas with near unidirectional alignment. Appropriate sol preparation yielded the desired stoichiometric chemical composition and crystal structure of the oxide nanorods, with a heat treatment (500–700°C for 15–30 min) for crystallization, densification and any necessary pyrolysis.     

Methyl methacrylate polymerization at samarium(II)-grafted MCM-41

Sm(II)-modified periodic mesoporous silica (PMS), Sm[N(SiHMe₂)₂]₂(THF)_x@MCM-41, was used for the synthesis of Sm(II) alkyl, alkoxide, and indenyl surface species via secondary ligand exchange. The performance of the novel Sm(II)-based organometallic–inorganic hybrid materials as initiators for the graft polymerization of methyl methacrylate (MMA) is reported. All of the Sm(II) hybrid materials including the new PMMA–PMS composites were characterized via N₂ physisorption, elemental analysis, FTIR spectroscopy, and scanning electron microscopy (SEM). The organic–inorganic composites revealed complete pore blockage as well as enrichment and strong adhesion of the polymer at the exterior of the porous silica material.     

Cobalt Ion Incorporation into Periodic Mesoporous Organosilica Materials Synthesized by Co-condensation of 1,2-Bistrimethoxysilylethane with 3-Glycidoxypropyltriethoxysilane

Bifunctional periodic mesoporous organosilica materials with and without cobalt ion incorporation were synthesized by co-condensation of 1,2-bistrimethoxysilylethane (BTME) with 3-glycidoxypropyltriethoxysilane (GPTS) in the presence of cetyltrimethylammonium bromide. Nitrogen gas adsorption on samples with varying ratios of BTME:GPTS revealed that increasing the amount of GPTS affects pore size, surface area and pore volume as well as shapes of the isotherms and hysteresis loops. The hysteresis loops of the Type IV isotherms obtained for GPTS-modified ethane silica materials (without cobalt ion) change from Type H3 to Type H4 with increasing GPTS content. There is a tendency for pore sizes to change from mesopore to micropore when the amount of GPTS is increased. Isotherms of cobalt ion incorporated GPTS-modified ethane silica materials change from Type IV to Type I with increasing GPTS content. The surface area, pore volume and pore diameter decrease with increasing loading of GPTS as well as after cobalt ion incorporation. Thermogravimetric analysis and differential thermal analysis show that the surfactant is removed by solvent extraction. Cobalt ion incorporation is confirmed by powder X-ray diffraction and Raman spectroscopy.     

A Transparent Thin Film with Hexagonal Mesostructure Containing Rhodamine 6G

A transparent this film was prepared by depositing the sol-gel mixture for the synthesis of MCM-41 mesoporous molecular sieve doped with rhodamine 6G(R6G) dye on glass substrates. The film of silica-surfactant-R6G materials, which was identified to possess hexagonally ordered mesostructure,was composed of nanocrystallites about 35 nm in diameter and 1-10μm in thickness. Cleanness of the substrates, concentration of the sol-gel mixture and rate of evaporation of the solvent were the key factors affecting transparency and homogeneity of the film. Moreover,optical change and lack in dye aggregation were observed to the R6G-functionalized MCM-41 thin film in contrast with that in ethanol solution.     

高比表面积介孔网状氧化镁的制备、表征及对废水中Pb(Ⅱ)的吸附性能和机理

以天然水菱镁矿为原料，通过"煅烧-水化-煅烧"的简单方法制备了高比表面积介孔网状MgO，且实验过程中无须加入任何试剂。系统性研究了氧化镁用量、吸附时间、吸附温度及pH对氧化镁吸附模拟废水中铅离子吸附性能的影响，揭示了吸附机理，并考察了氧化镁对多种离子的吸附效果。结果表明：该氧化镁吸附剂具有188 m²·g^-1的高比表面积和0.85 cm³·g^-1的高孔体积，平均孔径为12.33 nm，其吸附动力学和等温线数据与伪二级模型和Langmuir模型高度吻合，表明重金属离子在氧化镁上为单层化学吸附。MgO介孔网状结构表现出对Pb（Ⅱ）的高吸附性能，最大吸附量为7 431.5 mg·g^-1，该数值远高于其他报道的基于MgO吸附剂的数值，铅去除率高达99.8%以上。介孔网状MgO的吸附机理主要是羟基官能团以及Mg（Ⅱ）与MgO表面重金属离子之间的离子交换所致。另外，该氧化镁可同时吸附多种离子，对Cd、Cr、Ni、As、Co、P、Se、Be、Bi、Cu、Fe、Mn、V、Zn、Al离子均具有优异的吸附性能。