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Mesoporous Silica (mesoporou + silica)
Kinds of Mesoporous Silica Terms modified by Mesoporous Silica Selected AbstractsDifferent Morphological Organic,Inorganic Hybrid Nanomaterials as Fluorescent Chemosensors and Adsorbents for CuII IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2008Soo Jin Lee Abstract Functionalized silica nanotubes (FSNT), functionalized mesoporous silica (FMS), and functionalized silica nanoparticles (FSNP-15) with an immobilized phenanthroline moiety as a fluorescent receptor were fabricated by a sol,gel reaction, and their binding abilities with metal ions were evaluated by fluorophotometry in water/acetonitrile (8:2, v/v) at pH 7. They selectively recognized Cu2+ ions among other metal cations such as Co2+, Cd2+, Hg2+, Ni2+, Fe3+, Ag+, Pb2+, and Zn2+, because the Cu2+ ion selectively binds to the nitrogen atoms of the phenanthroline moiety. Among the three silica nanomaterials with the immobilized receptor 1, the sensitivity of FSNT for Cu2+ ions is better than those of FMS and FSNP-15, indicating that the adsorption capacity for metal ions is dependent on the shape and surface area of the supporting nanomaterials. FSNT (10 mg) adsorb 75,% of the Cu2+ ions (2.0,×,10,4 mM) while FSNP-15 (10 mg) adsorb only 36,%. The detection limit of FSNT for Cu2+ ions was ca. 3.0,×,10,8M. FSNT and FMS can be easily renewed by treatment with a solution of HCl and tetrabutylammonium hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Monodisperse Mesoporous Silica Spheres Inside a Bioactive Macroporous Glass,Ceramic Scaffold,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Renato Mortera In the field of bone tissue engineering, monosized MCM-41 spheres have been incorporated inside a bioactive glass,ceramic macroporous scaffold belonging to the SiO2CaOK2O (SCK) system so obtaining a multiscale hierarchical composite. The MCM-41-SCK system was prepared by dipping the glass,ceramic scaffold into the MCM-41 synthesis solution and was characterized by means of XRD, micro-XRD, N2 sorption and scanning electron microscopy. The MCM-41 spheres inside the scaffold are highly uniform in diameter, as those synthesized in powder form. The adsorption capacity of the composite toward ibuprofen is three times higher than that of the MCM-41-free scaffold, because of the presence of the ordered mesoporous silica. Also the release behavior in SBF at 37,°C is strongly affected by the presence of MCM-41 inside the scaffold macropores. [source] Interfacial Polar-Bonding-Induced Multifunctionality of Nano-Silicon in Mesoporous SilicaADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Jung Y. Huang Abstract The optoelectronic response of a material governs its suitability for a wide range of applications, from photon detection to photovoltaic conversion. To conquer the material limitations and achieve improved optoelectronic responses, nanotechnology has been employed to arrange subunits with specific size-dependent quantum mechanical properties in a hierarchically organized structure. However, building a functional optoelectronic system from nano-objects remains a formidable challenge. In this paper, the fabrication of a new artificially engineered optoelectronic material by the preferential growth of silicon nanocrystals on the bottom of the pore-channels of mesoporous silica is reported. The nanocrystals form highly stable interface structures bonded on one side; these structure show strong electron,phonon coupling and a ferroelectric-like hysteretic switching property. A new class of multifunctional materials is realized by invoking a concept that employs semiconductor nanocrystals for optical sensing and utilizes interfacial polar layers to facilitate carrier transport and emulate ferroelectric-like switching. [source] Ordered Mesoporous Silica Derived from Layered SilicatesADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Tatsuo Kimura Abstract Here, the development of ordered mesoporous silica prepared by the reaction of layered silicates with organoammonium surfactants is reviewed. The specific features of mesoporous silica are discussed with relation to the probable formation mechanisms. The recent understanding of the unusual structural changes from the 2D structure to periodic 3D mesostructures is presented. The formation of mesophase silicates from layered silicates with single silicate sheets depends on combined factors including the reactivity of layered silicates, the presence of layered intermediates, the variation of the silicate sheets, and the assemblies of surfactant molecules in the interlayer spaces. FSM-16-type (p6mm) mesoporous silica is formed via layered intermediates composed of fragmented silicate sheets and alkyltrimethylammonium (CnTMA) cations. KSW-2-type (c2mm) mesoporous silica can be prepared through the bending of the individual silicate sheets with intralayer and interlayer condensation. Although the structure of the silicate sheets changes during the reactions with CnTMA cations in a complex manner, the structural units caused by kanemite in the frameworks are retained. Recent development of the structural design in the silicate framework is very important for obtaining KSW-2-based mesoporous silica with molecularly ordered frameworks. The structural units originating from layered silicates are chemically designed and structurally stabilized by direct silylation of as-synthesized KSW-2. Some proposed applications using these mesoporous silica are also summarized with some remarks on the uniqueness of the use of layered silicates by comparison with MCM-type mesoporous silica. [source] Multiple Functionalization of Mesoporous Silica in One-Pot: Direct Synthesis of Aluminum-Containing Plugged SBA-15 from Aqueous Nitrate Solutions,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2008Y. Wu Abstract Aluminum-containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X-ray diffraction, transmission electron microscopy, and N2 sorption measurements show that the Al-containing plugged silicas possess well-ordered hexagonal mesostructures with high surface areas (700,860 m2,g,1), large pore volume (0.77,1.05 cm3,g,1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma,atomic emission spectrometry results show that 0.7,3.0 wt,% aluminum can be introduced into the final samples. 27Al MAS NMR results display that about 43,60% aluminum species are incorporated into the skeleton of the Al-containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al-containing plugged silica has a similar morphology to that of traditional SBA-15. Furthermore, the Al-containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities. [source] Encapsulation of Water-Insoluble Drugs in Polymer Capsules Prepared Using Mesoporous Silica Templates for Intracellular Drug DeliveryADVANCED MATERIALS, Issue 38 2010Yajun Wang Water-insoluble compounds were encapsulated in polymer capsules through mesoporous silica nanoparticle-mediated layer-by-layer assembly. The drug-loaded capsules exhibit excellent colloidal stability and high potency to colorectal cancer cells in vitro with similar cytotoxicity to the free drug dissolved in organic solvent. [source] Control of Morphology and Helicity of Chiral Mesoporous Silica,ADVANCED MATERIALS, Issue 5 2006H. Jin Chiral ordered mesoporous silica has been synthesized by using a chiral surfactant (N -myristoyl- L -alanine sodium salt) as a template, 3-aminopropyltriethoxysilane as a co-structure directing agent, and tetraethoxylsilane as an inorganic source. The helicity and the morphology of the mesoporous silica are determined by the stirring rate during the chiral surfactant self-assembly (see Figure), providing new insight into the chiral self-assembly of molecules. [source] Probing of Functionalized Mesoporous Silica Nanoparticles Using Transition Metal Clusters,ADVANCED MATERIALS, Issue 21 2003S. Hermans Molecular clusters (homo- and bi-metallic) have been used to gain structural information on nanoparticles of mesoporous silica (see Figure). Using scanning transmission electron microscopy, the spatial distribution of clusters has been imaged to determine the accessibility of the mesopores. The clusters are also used as "stains" to determine the exact location and number of functional sites within the substrates. [source] Control of Molecular Transport Through Stimuli-Responsive Ordered Mesoporous Materials,ADVANCED MATERIALS, Issue 15 2003Q. Fu External and reversible control of the size and surface energy of the pores in mesoporous architectures has been achieved. The method involves modification of mesoporous silica by atom transfer radical polymerization of N -isopropyl acrylamide (the precursor to a stimuli- responsive polymer). The resulting polymer-grafted particles allow the adsorption and transport of molecular species to be dynamically controlled as illustrated in the Figure for the release of rhodamine 6G from the particles at 50,°C. [source] In-situ small-angle neutron scattering study of pore filling and pore emptying in ordered mesoporous silicaJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2010M. Erko The capillary condensation and capillary emptying of water and perfluoropentane in ordered mesoporous SBA-15 silica is studied by in-situ small-angle neutron scattering (SANS). The SANS data can be perfectly described by a simple analytical model for spatially random pore filling (Laue scattering) for the entire range of pore-filling fractions. From this it is concluded that recently proposed pore correlations due to elastic interactions between neighbouring pores upon capillary condensation do not play a role in this system. The pores fill randomly according to their size distribution, in perfect agreement with the classical Kelvin equation. The relation between the overall pore-filling fraction as determined from the volumetric sorption isotherm, and the fraction of completely filled pores as obtained from the fit of the SANS data, allows conclusions to be drawn about the thermodynamic metastability of the adsorption process. [source] Inclusion and release of fenbufen in mesoporous silicaJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2010Daniel Carriazo Abstract This work reports the immobilization of Fenbufen, a nonsteroidal anti-inflamatory drug, into two different hexagonal mesoporous silicas (MCM-41) which exhibit some differences in terms of morphology and pore size, and their behavior as systems for sustained release at pH 7.5. The drug/mesoporous silica systems have been characterized by powder X-ray diffractometry (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption,desorption, and transmission electron microscopy (TEM). The results show that the drug is mainly incorporated inside the pores, and its loading is dependent on both the pore size and the impregnation temperature. The Fenbufen/mesoporous-silica systems give a well-sustained release profile, releasing 100% of the initially loaded drug at the end of the in vitro assays. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3372,3380, 2010 [source] Functionalized HMS mesoporous silica as solid phase extractant for Pb(II) prior to its determination by flame atomic absorption spectrometryJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2007Damián Pérez-Quintanilla Abstract In this work, a mesoporous silica has been chemically modified with 5-mercapto-1-methyl-1-H-tetrazol using the homogeneous route (MTTZ-HMS). This synthetic route involved the reaction of 5-mercapto-1-methyl-1-H-tetrazol with 3-chloropropyltriethoxysilane, prior to immobilization on the support. The resulting material has been characterized and employed as solid phase extractant for Pb(II). The effect of several variables (stirring time, pH, temperature, metal concentration, presence of other metals) has been studied using batch and column techniques. In batch experiments, 15 min stirring time, 55°C and pH 8 were the optimal conditions for Pb(II) adsorption. In column experiments, sorption was quantitative for 1000 mL of 2.41×10,4 mM of Pb(II) solution and adsorbed ions were eluted out by 5 mL of 1 M HCl (preconcentration factor of 200). Spiked tap water was used for the preconcentration and determination of Pb(II) by flame atomic absorption spectrometry, and a 100% recovery was obtained. The LOD and LOQ values of the proposed method were found to be 3.52×10,3 and 4.20×10,3 mM, respectively. The RSD for three preconcentration experiments was found to be ,2%. The linear working range for measurements was between 2×10,3 and 0.14 mM (y = 0.0136x + 0.0007, R2 = 0.9999). [source] A Study on the Effect of Template Chain Length on the Synthesis of Mesoporous Silica in An Acidic ConditionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Yang Yu-Xiang Hexagonal mesoporous silica materials were synthesized in an acidic medium using different chain length of the quaternary ammonium surfactants as a template. The effects of chain length on the physical property, morphology of mesoporous materials, and the temperature on synthesis of materials in CnTMBr,TEOS,HNO3,H2O (n=12,14,16,18) system were systematically studied. The synthesized products were characterized by X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption analysis. It was found that degree of ordering, the d spacing values, and pore size all increase with an increase in the chain length of the template. The optimum synthesis temperature for mesoporous silica using C18TMBr,TEOS,HNO3,H2O system is slightly higher than the Krafft point. The temperature and pH can all affect the expandability of micelles, and so an increase in temperature and decrease in pH all lead to an increase in the pore size. It is also found that the shear flow and chain length are two key factors inducing the formation of millimeter-scaled silica ropes and micrometer-scaled rope fibers. [source] Palladium supported on polyether-functionalized mesoporous silica.APPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010Synthesis, application as catalyst for Heck coupling reaction Abstract A new catalytic system based on Pd supported on polyether-functionalized mesoporous silica was prepared. This material was obtained by co-hydrolysis and polycondensation of tetraethylorthosilicate and a bis-silylated triblock copolymer P123 (Mw = 5800) followed by the decomposition of Pd(OAc)2 salt. We have shown that this material can be applied as powerful heterogeneous catalyst for the Heck coupling reaction. Copyright © 2009 John Wiley & Sons, Ltd. [source] Correlating the surface area and synthesis conditions of block co-polymer templated mesoporous silicaASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010A. T. Harris Abstract In this work we investigate the influence of (1) temperature, (2) curing (post reaction ageing) technique, (3) curing time, (4) surfactant (block co-polymer) concentration, and (5) the addition of secondary (pore swelling) reagents on the surface area and structure of ordered hexagonal mesoporous silica (SBA-15). We also investigate the use of microwave preparation and curing techniques, as a precursor to the development of large-scale synthesis processes for mesoporous silica. Samples were analyzed using transmission electron microscopy and nitrogen pore size analysis. The results of the study show that it is possible to optimize the surface area of the final material in a reproducible way, by using higher hydrolysis temperatures or lower surfactant concentrations. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Influence of the OMCs pore structures on the capacitive performances of supercapacitorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Gu-Zhen Nong Abstract In the present study, two mesoporous carbons OMC-KIT-6 and OMC-SBA-16 were nanocasted using mesoporous silica of KIT-6 and SBA-16 as templates and furfuryl alcohol as carbon precursor. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations confirmed that the resultant samples are mesoporous carbons, and the as-prepared OMC-KIT-6 has an Ia3d ordered structure, whereas OMC-SBA-16 belongs to Im3m space group. The surface area and the average pore size are (1658 m2 g,1 and 3.4 nm) for OMC-KIT-6 and (1638 m2 g,1 and 2.9 nm) for OMC-SBA-16, respectively. The results of cyclic voltammograms and galvanostatic charge-discharge tests show that these two mesoporous carbons have excellent capacitive performances. But the difference of capacitive behavior between OMC-KIT-6 and OMC-SBA-16 may be a result of the difference of pore geometries of these two carbons. In order to find out the function of mesopore in a supercapacitor, we compared the capacitive properties of mesoporous and microporous carbons; the experiment results indicated that these two kinds of carbon exhibit nearly ideal capacitive behavior at low scan rate. When the scan rate is enhanced up to 50 mV s,1 the performance of mesoporous carbon is more stable than microporous carbon. This outcome demonstrated that mesopore plays an important role in forming double layers in the electrode materials. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Mesoporous Silicas by Self-Assembly of Lipid Molecules: Ribbon, Hollow Sphere, and Chiral MaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2008Haiying Jin Abstract Using lipids (N -acyl amino acids) and 3-aminopropyltriethoxysilane as structure- and co-structure-directing agents, mesoporous silicas with four different morphologies, that is, helical ribbon (HR), hollow sphere, circular disk, and helical hexagonal rod, were synthesized just by changing the synthesis temperature from 0,°C to 10, 15, or 20,°C. The structures were studied by electron microscopy. It was found that 1),the structures have double-layer disordered mesopores in the HR, radially oriented mesopores in the hollow sphere, and highly ordered straight and chiral 2D-hexagonal mesopores in the disklike structure and helical rod, respectively; 2),these four types of mesoporous silica were transformed from the flat bilayered lipid ribbon with a chain-interdigitated layer phase through a solid,solid transformation for HR formation and a dissolving procedure transformation for the synthesis of the hollow sphere, circular disk, and twisted morphologies; 3),the mesoporous silica helical ribbon was exclusively right-handed and the 2D-hexagonal chiral mesoporous silica was excessively left-handed when the L -form N -acyl amino acid was used as the lipid template; 4),the HR was formed only by the chiral lipid molecules, whereas the 2D-hexagonal chiral mesoporous silicas were formed by chiral, achiral, and racemic lipids. Our findings give important information for the understanding of the formation of chiral materials at the molecular level and will facilitate a more efficient and systematic approach to the generation of rationalized chiral libraries. [source] Catalysis of a Peptidic Micellar Assembly Covalently Immobilized within Mesoporous Silica Channels: Importance of Amphiphilic Spatial DesignCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2007Wataru Otani Abstract A mesostructured silica/organic composite 1-MS, constructed from a rodlike micelle of amino acid amphiphile 1 that has a condensable head group and that can be used as a template, was found to be able to catalyze the acetalization of cyclohexanone, in ethanol at 25,°C (50,% in 12,h), whereas no reaction took place with unfunctionalized mesoporous silica. In sharp contrast, hydrolytic removal of the C16 alkyl tail of immobilized 1 resulted in the complete disappearance of the catalytic activity, which suggests the importance of a hydrophobic inner domain for the admission of cyclohexanone. Unsupported peptide amphiphile 2, under identical conditions to those above, was inefficient for acetalization regardless of the absence (2,% in 24,h) or presence of mesoporous silica (7,% in 24,h). Reference composite 2-MS, which is a noncovalently immobilized peptidic micelle, was virtually inactive (1,% in 24,h). These observations indicate the importance of covalent immobilization of the peptidic rod micelle for catalysis. Mesostructured silicate 3-MS hybridized with a nonpeptidic, ammonium ion amphiphile (3) showed a certain catalytic activity, but the yield (12,% in 24,h) of the acetal was much lower than that achieved by using 1-MS as the catalyst. Amorphous silica with immobilized 1 on its surface was much less active than 1-MS for acetalization (5,% in 24,h). [source] Photovoltaic activity of Ti/MCM-41CHEMPHYSCHEM, Issue 1 2009Pedro Atienzar Dr. Abstract Ti/MCM-41 is a well-known heterogeneous catalyst for alkene epoxidation with organic peroxides. This titanosilicate contains isolated titanium atoms forming part of a framework of mesoporous silica whose structure is formed by parallel hexagonal channels 3.2 nm in diameter. The surface area and porosity of Ti/MCM-41 are about 880 m2,g,1 and 0.70 cm3,g,1, respectively. These values are among the highest for any material. Herein, we show that Ti/MCM-41 exhibits photovoltaic activity. Dye-sensitized solar cells using mesoporous Ti/MCM-41 (2.8,5.7,% Ti content) as active layer, black dye N3 as photosensitizer and I3,/I, in methoxyacetonitrile as electrolyte exhibit a VOC, JSC and FF of 0.44 V, 0.045 mA,cm,2 and 0.33, respectively. These values compare well against 0.75 V, 4.1 mA,cm,2 and 0.64, respectively, measured for analogous solar cells using conventional P-25 TiO2. However, the specific current density (JSC/Ti atom) for the Ti/MCM-41 is very similar to that of P25 TiO2. [source] Control of Drug Release through the In Situ Assembly of Stimuli-Responsive Ordered Mesoporous Silica with Magnetic ParticlesCHEMPHYSCHEM, Issue 17 2007Shenmin Zhu Dr. Abstract A site-selective controlled delivery system for controlled drug release is fabricated through the in situ assembly of stimuli-responsive ordered SBA-15 and magnetic particles. This approach is based on the formation of ordered mesoporous silica with magnetic particles formed from Fe(CO)5 via the surfactant-template sol-gel method and control of transport through polymerization of N-isopropyl acrylamide inside the pores. Hydrophobic Fe(CO)5 acts as a swelling agent as well as being the source of the magnetic particles. The obtained system demonstrates a high pore diameter (7.1 nm) and pore volume (0.41 cm3,g,1), which improves drug storage for relatively large molecules. Controlled drug release through the porous network is demonstrated by measuring the uptake and release of ibuprofen (IBU). The delivery system displays a high IBU storage capacity of 71.5 wt,%, which is almost twice as large as the highest value based on SBA-15 ever reported. In vitro testing of IBU loading and release exhibits a pronounced transition at around 32,°C, indicating a typical thermosensitive controlled release. [source] A Mesoporous ErIII -MCM-41 Catalyst for the Cyanosilylation of Aldehydes and Ketones under Solvent-free ConditionsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 11 2008Antonio Procopio Prof. EvEr green: A simple synthetic protocol has been developed for the solvent-free cyanosilylation reaction of aldehydes and ketones with trimethylsilylcyanide (TMSCN) catalysed by a new mesoporous silica supported ErIII catalyst. The catalyst can be recovered and reused in subsequent reactions without showing any loss of activity (three uses). [source] Organically Functionalized Mesoporous Silica by Co-structure-Directing RouteADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Chuanbo Gao Abstract This article provides a brief overview of functional mesoporous silica materials synthesized by the co-structure-directing route, which is distinct from conventional synthesis strategies. In these systems, organosilane serves as the co-structure-directing agent (CSDA), which provides critical interactions between the template and organic part of the organosilane to form mesostructures, thus retaining the organic groups on the pore surface after removal of the template by extraction. i) The formation of anionic-surfactant-templated mesoporous silicas (AMSs) has been achieved by the co-structure-directing route, which leads to a variety of mesostructures, porous properties and morphologies. ii) Other co-structure-directing systems for synthesizing mesoporous silicas have also been achieved, including systems using cationic surfactants and non-surfactants, and systems using DNA for constructing nanofibers and DNA,silica liquid crystalline complexes. iii) Evidence for the regular arrangement of functional groups on the pore surface resulted from the co-structure-directing effect has been discussed. Also included is a brief description of the application, future requirements, and trends in the development of mesoporous materials by the co-structure-directing route. [source] Multiple Functionalization of Mesoporous Silica in One-Pot: Direct Synthesis of Aluminum-Containing Plugged SBA-15 from Aqueous Nitrate Solutions,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2008Y. Wu Abstract Aluminum-containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X-ray diffraction, transmission electron microscopy, and N2 sorption measurements show that the Al-containing plugged silicas possess well-ordered hexagonal mesostructures with high surface areas (700,860 m2,g,1), large pore volume (0.77,1.05 cm3,g,1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma,atomic emission spectrometry results show that 0.7,3.0 wt,% aluminum can be introduced into the final samples. 27Al MAS NMR results display that about 43,60% aluminum species are incorporated into the skeleton of the Al-containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al-containing plugged silica has a similar morphology to that of traditional SBA-15. Furthermore, the Al-containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities. [source] Inclusion and release of fenbufen in mesoporous silicaJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2010Daniel Carriazo Abstract This work reports the immobilization of Fenbufen, a nonsteroidal anti-inflamatory drug, into two different hexagonal mesoporous silicas (MCM-41) which exhibit some differences in terms of morphology and pore size, and their behavior as systems for sustained release at pH 7.5. The drug/mesoporous silica systems have been characterized by powder X-ray diffractometry (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption,desorption, and transmission electron microscopy (TEM). The results show that the drug is mainly incorporated inside the pores, and its loading is dependent on both the pore size and the impregnation temperature. The Fenbufen/mesoporous-silica systems give a well-sustained release profile, releasing 100% of the initially loaded drug at the end of the in vitro assays. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3372,3380, 2010 [source] Spherical ordered mesoporous silicas and silica monoliths as stationary phases for liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2006Anne Galarneau Abstract Ordered mesoporous silicas such as micelle-templated silicas (MTS) feature unique textural properties in addition to their high surface area (,1000 m2/g): narrow mesopore size distributions and controlled pore connectivity. These characteristics are highly relevant to chromatographic applications for resistance to mass transfer, which has never been studied in chromatography because of the absence of model materials such as MTS. Their synthesis is based on unique self-assembly processes between surfactants and silica. In order to take advantage of the perfectly adjustable texture of MTS in chromatographic applications, their particle morphology has to be tailored at the micrometer scale. We developed a synthesis strategy to control the particle morphology of MTS using the concept of pseudomorphic transformation. Pseudomorphism was recognized in the mineral world to gain a mineral that presents a morphology not related to its crystallographic symmetry group. Pseudomorphic transformations have been applied to amorphous spherical silica particles usually used in chromatography as stationary phases to produce MTS with the same morphology, using alkaline solution to dissolve progressively and locally silica and reprecipitate it around surfactant micelles into ordered MTS structures. Spherical beads of MTS with hexagonal and cubic symmetries have been synthesized and successfully used in HPLC in fast separation processes. MTS with a highly connected structure (cubic symmetry), uniform pores with a diameter larger than 6 nm in the form of particles of 5 ,m could compete with monolithic silica columns. Monolithic columns are receiving strong interest and represent a milestone in the area of fast separation. Their synthesis is a sol-gel process based on phase separation between silica and water, which is assisted by the presence of polymers. The control of the synthesis of monolithic silica has been systematically explored. Because of unresolved yet cladding problems to evaluate the resulting macromonoliths in HPLC, micromonoliths were synthesized into fused-silica capillaries and evaluated by nano-LC and CEC. Only CEC allows to gain high column efficiencies in fast separation processes. Capillary silica monolithic columns represent attractive alternatives for miniaturization processes (lab-on-a chip) using CEC. [source] Organic,inorganic hybrid mesoporous silicas: functionalization, pore size, and morphology controlTHE CHEMICAL RECORD, Issue 1 2006Sung Soo Park Abstract Topological design of mesoporous silica materials, pore architecture, pore size, and morphology are currently major issues in areas such as catalytic conversion of bulky molecules, adsorption, host,guest chemistry, etc. In this sense, we discuss the pore size-controlled mesostructure, framework functionalization, and morphology control of organic,inorganic hybrid mesoporous silicas by which we can improve the applicability of mesoporous materials. First, we explain that the sizes of hexagonal- and cubic-type pores in organic,inorganic hybrid mesoporous silicas are well controlled from 24.3 to 98.0,Å by the direct micelle-control method using an organosilica precursor and surfactants with different alkyl chain lengths or triblock copolymers as templates and swelling agents incorporated in the formed micelles. Second, we describe that organic,inorganic hybrid mesoporous materials with various functional groups form various external morphologies such as rod, cauliflower, film, rope, spheroid, monolith, and fiber shapes. Third, we discuss that transition metals (Ti and Ru) and rare-earth ions (Eu3+ and Tb3+) are used to modify organic,inorganic hybrid mesoporous silica materials. Such hybrid mesoporous silica materials are expected to be applied as excellent catalysts for organic reactions, photocatalysis, optical devices, etc. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 32,42; 2006: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20070 [source] Mesoporous Silicas by Self-Assembly of Lipid Molecules: Ribbon, Hollow Sphere, and Chiral MaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2008Haiying Jin Abstract Using lipids (N -acyl amino acids) and 3-aminopropyltriethoxysilane as structure- and co-structure-directing agents, mesoporous silicas with four different morphologies, that is, helical ribbon (HR), hollow sphere, circular disk, and helical hexagonal rod, were synthesized just by changing the synthesis temperature from 0,°C to 10, 15, or 20,°C. The structures were studied by electron microscopy. It was found that 1),the structures have double-layer disordered mesopores in the HR, radially oriented mesopores in the hollow sphere, and highly ordered straight and chiral 2D-hexagonal mesopores in the disklike structure and helical rod, respectively; 2),these four types of mesoporous silica were transformed from the flat bilayered lipid ribbon with a chain-interdigitated layer phase through a solid,solid transformation for HR formation and a dissolving procedure transformation for the synthesis of the hollow sphere, circular disk, and twisted morphologies; 3),the mesoporous silica helical ribbon was exclusively right-handed and the 2D-hexagonal chiral mesoporous silica was excessively left-handed when the L -form N -acyl amino acid was used as the lipid template; 4),the HR was formed only by the chiral lipid molecules, whereas the 2D-hexagonal chiral mesoporous silicas were formed by chiral, achiral, and racemic lipids. Our findings give important information for the understanding of the formation of chiral materials at the molecular level and will facilitate a more efficient and systematic approach to the generation of rationalized chiral libraries. [source] | |||||||||||||