氧化钨介孔材料的制备与表征

以介孔二氧化硅(KIT-6)为硬模板, 硅钨酸为钨源, 用硬模板法制备WO3-SiO2复合材料, 再利用HF除去二氧化硅, 得到了介孔三氧化钨材料. 用X射线衍射(XRD)、能量扩散X射线(EDX)、高分辨透射电镜(HRTEM)、N2吸附-脱附等表征手段, 对制备复合材料的物料比、煅烧温度以及不同分散剂等条件进行了考察. 结果表明, 硅钨酸与硅介孔的物料比(m(WO3)/m(SiO2))在3:1到4:1之间, 在600-750 ℃下煅烧, 能制备结构较好的介孔氧化钨. 乙醇和蒸馏水为分散剂时, 用乙醇为分散剂所得的介孔WO3材料具有更高的比表面积和孔体积.     

Synthesis, amino-functionalization of mesoporous silica and its adsorption of Cr(VI)

Mesoporous silica materials with a centered rectangular symmetry (cmm) have been synthesized through a facile direct-templating method using tetraethylorthosilicate (TEOS) and amphiphilic block co-polymers Pluronic P123 under acidic conditions. The amino groups have been grafted to as-synthesized mesoporous silica by [1-(2-amino-ethyl)-3-aminopropyl]trimethoxysilane (AAPTS). Thus obtained amino-functionalized mesoporous silica (denoted as NN-silica) was used for sequestration of Cr(VI) from aqueous solution. After sequestration of Cr(VI), the sample was denoted as Cr(VI)-silica. The parent mesoporous silica, NN-silica and Cr(VI)-silica were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and N(2) adsorption-desorption isotherms. XRD and TEM results confirm that the structure of these samples is centered rectangular symmetry (cmm). N(2) adsorption-desorption isotherms show that there is a remarkable decrease in surface area and pore volume for NN-silica (S(BET)=54.5 m(2)g(-1), V(P)=0.09 cm(3)g(-1)) and Cr(VI)-silica (S(BET)=53.2 m(2)g(-1), V(P)=0.07 cm(3)g(-1)) compared to the parent mesoporous silica (S(BET)=444.0 m(2)g(-1), V(P)=0.71 cm(3)g(-1)). The BJH desorption average diameter of NN-silica, Cr(VI)-silica and the parent mesoporous silica is 4.40 nm, 4.07 nm and 5.11 nm, respectively. The results reveal the channels of as-synthesized mesoporous silica are essentially grafted with abundant amino groups and loaded with Cr(VI). The adsorption experiment results show that the functionalized mesoporous silica materials possess an increased Cr(VI) adsorption capacity and the maximum Cr(VI) loadings at 25, 35 and 45 degrees C can reach 2.28, 2.86 and 3.32 mmol/g, respectively.     

Preparation of ordered mesoporous SiC from preceramic polymer templated by nanoporous silica

Highly ordered mesoporous SiC materials were prepared by infiltrating viscous liquid preceramic polymer, allylhydridopolycarbosilane, into two types of surface modified nanoporous silica templates: mesoporous silica SBA-15 and mesocellular siliceous foam. The silica templates were subsequently etched off after pyrolysis at 1000 degrees C under nitrogen atmosphere with the resultant formation of ordered mesoporous structures. The mesoporous SiC materials, synthesized from both types of templates possessed high Brunauer-Emmett-Teller (BET) surface areas in the range of 250-260 m(2)/g with pore sizes of 3.4-3.6 nm. The ordered structures of mesoporous SiC were exact inverse replicas of their respective silica templates, as characterized by small angle X-ray diffraction (XRD), transmission electron microscope (TEM) images, and the adsorption-desorption isotherm of nitrogen.     

Electrorheological behavior of copper phthalocyanine-doped mesoporous TiO2 suspensions

A type of anhydrous electrorheological (ER) material of copper phthalocyanine (CuPC)-doped mesoporous TiO2 was synthesized by in situ micelle-assisted incorporation CuPC during mesoporous TiO2 synthesis. TEM, XRD and the nitrogen adsorption-desorption isotherms demonstrated that the material had mesoporous structure and an anatase framework. The ER behavior of the suspensions of CuPC-doped mesoporous TiO2 in silicone oil with the different volume fractions was investigated under an applied electric field. It is found that the suspensions showed visible electrorheological behavior which were compared with that of pure TiO2. The dopants of CuPC molecules within the mesochannel of TiO2 mesoporous sieve improved the conductivity of the particles and produced a proper conductivity of approximately 10(-7) S m(-1). Dielectric spectra of the ER fluid were measured to examine the peak of epsilon' should appear in the frequency range of 10(2)-10(5) Hz and have a large Deltaepsilon' in this frequency range. Therefore, the both properties may make a conjunct effect on electrorheological behavior.     

Synthesis of thermally stable zirconia-based mesoporous materials via a facile post-treatment

A novel method of preparing thermally stable zirconia-based mesoporous materials was developed. The zirconia-based mesoporous materials of 2D-hexagonal structure were prepared using zirconium sulfate as the zirconium precursor and cetyltrimethylammonium (CTMA) as the pore-directing agent with the aid of salt in the synthesis solution to reduce the sulfate content in the final product and significantly improve the crystallographic ordering. Post-treatment of the mesoporous material with NaCl solution and lowering the ramping rate to less than 0.2 degrees C/min during the calcination process, however, were the key steps to hinder the growth of the dense zirconia phase and to retain the ordered mesostructure up to 600 degrees C. It was found that a portion of the surfactant (8.9-17.4 wt %) and sulfate ions (0.5-1.2 wt %) were removed during the post-treatment, which prevented the remaining sulfate groups from being reduced by the hydrogen-rich surfactant during the calcination process as confirmed by sulfur K-edge X-ray absorption near edge structure (XANES) and infrared spectroscopy. The maintenance of sulfur in the sulfate state seemed to be important in stabilizing the mesoporous structure of zirconia materials. The mesoporous zirconia materials after extraction with NaCl solution three times and calcination at 550-600 degrees C had the composition ZrO(2-x)(SO4)x with x = 0.10-0.27. The material possesses high surface area (approximately 200 m2/g), large pore volume (approximately 0.10 cm3/g), and wormlike mesopores. In comparison with the mesoporous zirconia materials stabilized by chemical treatment, the present route was simpler and more environmentally friendly and resulted in mesoporous zirconia materials of better thermal stability.     

The formation of mesoporous TiO2 spheres via a facile chemical process

The mesoporous TiO(2) solid and hollow spheres have been synthesized via a controllable and simple chemical route. Structural characterization indicates that these TiO(2) mesoporous spheres after calcined at 500 degrees C have an obvious mesoporous structure with the diameters of 200-300 nm for solid spheres and 200-500 nm for hollow spheres. The average pore sizes and BET surface areas of the mesoporous TiO(2) solid and hollow spheres are 6.8, 7.0 nm and 162, 90 m(2)/g, respectively. Optical adsorption investigation shows that TiO(2) solid and hollow spheres possess a direct band gap structure with the optical band gap of 3.68 and 3.75 eV, respectively. A possible formation mechanism for TiO(2) solid and hollow spheres is discussed.     

Preparation of mesostructured barium sulfate with high surface area by dispersion method and its characterization

The spherical and cubic mesoporous BaSO(4) particles with high surface area were successfully produced via one-step process through precipitation reaction in aqueous solution of Ba(OH)(2) and H(2)SO(4) with ethylene glycol (n-HOCH(2)CH(2)OH) as a modifying agent. The BaSO(4) nanomaterial revealed that the high surface area and the mesoporous was stable up to 400 degrees C. Agglomerate mesoporous barium sulfate nanomaterials were obtained by the reaction of Ba(2+) and SO(2-)(4) with ethylene glycol aqueous solution. The ethylene glycol was used to control the BaSO(4) particle size and to modify the surface property of the particles produced from the precipitation. The dried and calcined mesoporous BaSO(4) nanomaterials were characterized by X-ray diffraction (XRD), BET surface area and N(2) adsorption-desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared resonance (FTIR) and thermogravimetric analysis (TGA). The as-prepared mesoporous dried BaSO(4) possesses a high BET surface area of 91.56 m(2) g(-1), pore volume of 0.188 cm(3) g(-1) (P/P(0)=0.9849) and pore size of 8.22 nm. The SEM indicates that the morphology of BaSO(4) nanomaterial shows shell like particles up to 400 degrees C, after that there is drastically change in the material due to agglomeration. Synthesis of mesoporous BaSO(4) nanomaterial is of significant importance for both sulphuric acid decomposition and oxidation of methane to methanol.     

Synthesis of mesoporous silica nanobamboo with highly dispersed tungsten carbide nanoparticles

By controlling the interaction between cationic surfactant micelles and ammonium metatungstate during the formation of mesoporous silica structure, highly dispersed tungsten carbide (WC) nanoparticles of 2.0 nm in diameter on mesoporous silica nanospheres were synthesized at lower concentration of ammonium metatungstate. With additional ammonium metatungstate, a novel mesoporous silica nanobamboo structure was formed with bimodal size-distributed WC nanoparticles, in which 2.0 nm WC was homogeneously distributed in nanobamboo's mesoporous silica wall and those with larger diameter (10.0-20.0 nm) were only formed on the nanobamboo's inner surface and at its internodes. The mesoporous silica nanobamboo also had a very high tensile strength due to its bamboo-like structure.     

High performance of phosphonate-functionalized mesoporous silica for U(VI) sorption from aqueous solution

The renaissance of nuclear energy promotes increasing basic research on the separation and enrichment of nuclear fuel associated radionuclides. Herein, we report the first study for developing mesoporous silica functionalized with phosphonate (NP10) as a sorbent for U(VI) sorption from aqueous solution. The mesoporous silica was synthesized by co-condensation of diethylphosphatoethyltriethoxysilane (DPTS) and tetraethoxysilane (TEOS), using cationic surfactant cetyltrimethylammonium bromide (CTAB) as the template. The synthesized silica nanoparticles were observed to possess a mesoporous structure with a uniform pore diameter of 2.7 nm, and to have good stability and high efficiency for U(VI) sorption from aqueous solution. A maximum sorption capacity of 303 mg g(-1) and fast equilibrium time of 30 min were achieved under near neutral conditions at room temperature. The adsorbed U(VI) can be easily desorbed by using 0.1 mol L(-1) HNO(3), and the reclaimed mesoporous silica can be reused with no decrease of sorption capacity. In addition, the preconcentration of U(VI) from a 100 mL aqueous solution using the functionalized mesoporous silica was also studied. The preconcentration factor was found to be as high as 100, suggesting the vast opportunities of this kind of mesoporous silica for the solid-phase extraction and enrichment of U(VI).     

Interface synthesis of mesoporous MnO2 and its electrochemical capacitive behaviors

Mesoporous MnO(2) has been synthesized by means of a novel, facile, and template-free method by virtue of a soft interface between CCl(4) and H(2)O without any surfactants or organometallic precursors or ligands. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy analysis, scanning electron microscopy, and an ASAP2010 autoadsorption analyzer were applied to investigate the composition and microstructure of the as-synthesized MnO(2). The structure characterizations indicated a good mesoporous structure for as-prepared MnO(2) with an adsorption average pore diameter of 9.7 nm, mesoporous volume of 0.58 cm(3) g(-1), and Brunauer-Emmett-Teller specific surface area of 239 m(2) g(-1). Electrochemical properties of the mesoporous MnO(2) were elucidated by cyclic voltammograms, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in 1 M Na(2)SO(4) electrolyte. Electrochemical data analysis demonstrated that as-synthesized MnO(2) had good capacitive behavior due to its unique mesoporous structure. A specific capacitance of ca. 220 F g(-1) could still be delivered for the mesoporous MnO(2) even at a scan rate of 100 mV s(-1).     

Preparation and characterization of unique inorganic-organic hybrid mesoporous materials incorporating arenetricarbonyl complexes [-C6H4M(CO)3-] (M = Cr, Mo)

Unique inorganic-organic hybrid mesoporous materials incorporating arenetricarbonyl complexes [-C6H4M(CO)3-] (M = Cr, Mo) within their mesoporous frameworks have been successfully prepared by a simple CVD treatment of the phenylene-bridged organosilica mesoporous materials with metal hexacarbonyls [M(CO)6] (M = Cr, Mo). FT-IR and UV-vis investigations revealed that the arenetricarbonyl complexes exist stably even at temperatures above 473 K under vacuum.     

Investigation on into the adsorption of Cu(II), Pb(II) and Cr(VI) on hollow mesoporous silica using microcalorimetry

Journal of Thermal Analysis and Calorimetry - Hollow mesoporous silica (SiO2) was synthesized by the modified self-template method, and the morphology and structural properties of mesoporous silica...     

The effect of interfacial microstructure on the lipid oxidation stability of oil-in-water emulsions

Novel rattle-type magnetic mesoporous carbon spheres are successfully prepared using composite spheres with Fe(3)O(4) as core and mesoporous SiO(2) as shell plus solid SiO(2) as a middle layer as templates. These rattle-type spheres possess the magnetization strength of as high as 37.5 emu/g, high and tunable specific surface areas (382-512.6 m(2)/g) due to mesoporous carbon shells. This magnetic rattle-type structure and the readily accessible mesoporous shell are very favoring for the fast adsorption and release of guest objects triggered by external stimulus, for example, the spheres showed very good adsorptive property to dye.     

Platinum/mesoporous WO3 as a carbon-free electrocatalyst with enhanced electrochemical activity for methanol oxidation

A new type of carbon-free electrode catalyst, Pt/mesoporous WO3 composite, has been prepared and its electrochemical activity for methanol oxidation has been investigated. The mesoporous tungsten trioxide support was synthesized by a replicating route and the mesoporous composties with Pt loaded were characterized by using X-ray diffraction (XRD), nitrogen sorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. Cyclic voltammetry (CV), line scan voltammetry (LSV) and chronoamperometry (CA) were adopted to characterize the electrochemical activities of the composites. The mesoporous WO3 showed high surface area, ordered pore structure, and nanosized wall thickness of about 6-7 nm. When a certain amount of Pt nanoparticles were dispersed in the pore structure of mesoporous WO3, the resultant mesostructured Pt/WO3 composites exhibit high electro-catalytic activity toward methanol oxidation. The overall electro-catalytic activities of 20 wt % Pt/WO3 composites are significantly higher than that of commercial 20 wt % Pt/C catalyst and are comparable to the 20 wt % PtRu/C catalyst in the potential region of 0.5-0.7 V. The enhanced electro-catalytic activity is attributed to be resulted from the assistant catalytic effect and the mesoporous structure of WO3 supports.     

Mesoporous silica spheres from colloids

A novel method has been developed to synthesize mesoporous silica spheres using commercial silica colloids (SNOWTEX) as precursors and electrolytes (ammonium nitrate and sodium chloride) as destabilizers. Crosslinked polyacrylamide hydrogel was used as a temporary barrier to obtain dispersible spherical mesoporous silica particles. The influences of synthesis conditions including solution composition and calcination temperature on the formation of the mesoporous silica particles were systematically investigated. The structure and morphology of the mesoporous silica particles were characterized via scanning electron microscopy (SEM) and N2 sorption technique. Mesoporous silica particles with particle diameters ranging from 0.5 to 1.6 microm were produced whilst the BET surface area was in the range of 31-123 m2 g-1. Their pore size could be adjusted from 14.1 to 28.8 nm by increasing the starting particle diameter from 20-30 nm up to 70-100 nm. A simple and cost effective method is reported that should open up new opportunities for the synthesis of scalable host materials with controllable structures.     

Synthesis of NiCo2O4/mesoporous carbon composites for supercapacitor electrodes

Journal of Solid State Electrochemistry - In this study, nickel cobaltite/mesoporous carbon composites are synthesized by reacting CoCl2, Ni (NO3)2 and nitric acid-treated biogas slurry mesoporous...     

One-step synthesis of mesoporous two-line ferrihydrite for effective elimination of arsenic contaminants from natural water

Mesoporous two-line (2-lines) ferrihydrite is successfully synthesized by a facile one-step method. The ferrihydrite is characterized by X-ray diffraction (XRD), Raman spectrum, N(2) adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The 2-lines ferrihydrite with mesoporous structure possesses excellent adsorption performance for arsenic (As(III)) contamination. Experimental results show that As(III) contamination can be effectively removed within 2 h by this 2-lines ferrihydrite, which is attributed to the special mesoporous structure and large surface area (133 m(2) g(-1)). The As(III) loading capacity of our obtained mesoporous 2-lines ferrihydrite is up to 128 mg(As) g(-1)(Fe). In addition, As(III) can be easily desorbed from 2-lines ferrihydrite by simple heat treatment in alkali solution. After reusage for 10 times, it still presents good adsorption performance, indicating the excellent stability of the 2-lines ferrihydrite. Furthermore, the mesoporous 2-lines ferrihydrite is also effective for As(III) removal when some natural water constituents are present. Therefore, the high adsorption capability of the mesoporous 2-lines ferrihydrite makes it a potentially attractive adsorbent for the removal of As(III) contamination from natural water.     

Preparation and characterization of polyimide/mesoporous silica hybrid nanocomposites based on water-soluble poly(amic acid) ammonium salt

Recently, mesoporous silica was blended with polyimide to develop low dielectric constant (k) materials with improving mechanical and thermal properties of polyimide by utilizing both the nanoporous structure and silica framework. However, even the use of mesoporous silica did not show a significant decrease of k due to the phase segregation in between polyimide and the mesoporous silica materials. In this work, we attempted to prepare polyimide/mesoporous silica hybrid nanocomposites having relatively good phase mixing behavior by utilizing polyimide synthesized from a water soluble poly(amic acid) ammonium salt, which lead to low k up to 2.45. The thermal properties of polyimide were improved by adding mesoporous silicas. For this work, we have fabricated mesoporous silicas through surfactant-templated condensation of tetraethyl orthosilicate (TEOS). Pyromellitic dianhydride (PMDA)-4,4′-oxydianiline (ODA) polyimide was prepared from poly(amic acid) ammonium salt, which had been obtained by incorporating triethylamine (TEA) into PMDA-ODA poly(amic acid) in dimethylacetamide (DMAc), followed by thermal imidization.     

Improved catalytic performance of lipase accommodated in the mesoporous silicas with polymer-modified microenvironment

The highly ordered mesoporous silicas with elaborately controlled microenvironment were synthesized via covalent incorporation of long-chain polymers (M(w) = 2000 g mol(-1)) bearing specific hydrophilic/hydrophobic balance. The microenvironment (hydrophilicity/hydrophobicity) of the mesoporous silicas was quantitatively determined by gas adsorption experiments and investigated by lysozyme (LYZ) adsorption. The relative activity of lipase from Pseudomonas cepacia (PCL) encapsulated in the mesoporous silica with moderate hydrophobic microenvironment (hereafter denoted as MHM) reaches up to 281% compared with the free PCL, notably higher than that of PCL accommodated in the mesoporous silicas with hydrophilic or strong hydrophobic microenvironment (20.7-26.2% relative to the free PCL). Moreover, PCL entrapped in the nanochannels with MHM affords the highest initial rate in the kinetic resolution of (R,S)-1-phenylethanol relative to other immobilized PCL. The above results suggest that the MHM could render the active center of PCL entirely exposed to the substrates without interrupting its native conformation in the "interfacial activation". In addition, the nanochannels with MHM could markedly improve the thermal stability of PCL (preserving nearly 60% of the initial activity after the incubation at 70 °C for 2 h) and facilitate the recycling of the immobilized PCL in both aqueous and organic media. Our work demonstrates that the subtle modulation of the microenvironment of mesoporous silicas for enzyme immobilization designates a very promising strategy to fabricate the highly active and stable heterogeneous biocatalysts for industrial application.     

Synergic effects of imidazolium ionic liquids on P123 mixed micelles for inducing micro/mesoporous materials

A series of micro/mesoporous silica composites were synthesized with P123 and imidazolium ILs ([C(n)mim]X) as the co-templates. [C(n)mim]X showed notable synergic interaction with P123. By changing the alkyl chain length n in methylimidazolium, ring-like micropores were observed in the wall of the mesoporous materials when n = 4. While increasing n to 10, micropores and mesopores were found in different separated regions. Various anions of Cl(-), Br(-), and BF(4)(-) of ILs have little effect on the aggregation behavior of P123/C4X mixed micelles. The strong hydrogen bonding effect of BF(4)(-) has resulted in the ordered mesoporous channels with numerous micropores in the wall at a low temperature of 313 K. Hydrophobic C4PF(6) can only be solubilized in the core of P123 micelles, which resulted in the swelling of P123/C4PF(6) mixed aggregates and the ordered hexagonal porous silica materials at 313 K. The fundamental understanding of the synergic interaction and formation mechanisms of various porous silica materials can provide a general convenient way toward a rational design and synthesis of the micro/mesoporous composites.