Showing papers on "Mesoporous material published in 2003"
TL;DR: In this article, the pore size distributions derived from adsorption isotherms of micro- and mesoporous materials are identified and discussed based on new results and examples reported in the recent literature.
1,775 citations
TL;DR: An MCM-41 type mesoporous silica nanosphere-based controlled-release delivery system has been synthesized and characterized using surface-derivatized cadmium sulfide nanocrystals as chemically removable caps to encapsulate several pharmaceutical drug molecules and neurotransmitters inside the organically functionalized MSN Mesoporous framework.
Abstract: An MCM-41 type mesoporous silica nanosphere-based (MSN) controlled-release delivery system has been synthesized and characterized using surface-derivatized cadmium sulfide (CdS) nanocrystals as chemically removable caps to encapsulate several pharmaceutical drug molecules and neurotransmitters inside the organically functionalized MSN mesoporous framework. We studied the stimuli-responsive release profiles of vancomycin- and adenosine triphosphate (ATP)-loaded MSN delivery systems by using disulfide bond-reducing molecules, such as dithiothreitol (DTT) and mercaptoethanol (ME), as release triggers. The biocompatibility and delivery efficiency of the MSN system with neuroglial cells (astrocytes) in vitro were demonstrated. In contrast to many current delivery systems, the molecules of interest were encapsulated inside the porous framework of the MSN not by adsorption or sol−gel types of entrapment but by capping the openings of the mesoporous channels with size-defined CdS nanoparticles to physically block...
1,597 citations
TL;DR: In this article, a new synthesis route to high-quality large mesoporous cubic Ia3d silica is reported, utilizing a triblock copolymer (EO20PO70EO20) mixture for the structure direction in aqueous solution.
1,297 citations
TL;DR: It is shown that the uptake, storage and release of organic molecules in MCM-41 can be regulated through the photocontrolled and reversible intermolecular dimerization of coumarin derivatives attached to the pore outlets.
Abstract: Since the discovery of MCM-41 more than ten years ago, many investigations have explored the suitability of hexagonal mesoporous silicas for potential practical applications. These range from catalysis and optically active materials to polymerization science, separation technology and drug delivery, with recent successes in the fabrication of hybrid mesoporous organosilicas expected to open up further application possibilities. Because the pore voids of this class of materials exhibit relatively narrow pore size distributions in the range of 2-4 nm in diameter, mesoporous silicas can selectively include organic compounds and release them continuously at a later stage. The functionalization of MCM-41 pore voids with photoactive derivatives provides influence over the material's absorption behaviour, but full control over the release process remains difficult. Here we show that the uptake, storage and release of organic molecules in MCM-41 can be regulated through the photocontrolled and reversible intermolecular dimerization of coumarin derivatives attached to the pore outlets. Successful functionalization requires uncalcined MCM-41 still filled with the template molecules that directed the formation of its pores, to ensure that coumarin derivatives attach preferentially to the pore outlets, rather than their inside walls. We find that this feature and the one-dimensional, isolated nature of the individual pores allow for efficient and reversible photocontrol over guest access to the material's interior.
1,005 citations
TL;DR: The complete synthesis and characterization procedures to generate highly organized and oriented mesoporous titania thin films, using poly(ethylene oxide) (PEO)-based templates are reported.
Abstract: In this paper, we report the complete synthesis and characterization procedures to generate highly organized and oriented mesoporous titania thin films, using poly(ethylene oxide) (PEO)-based templates. Controlled conditions in the deposition, postsynthesis, and thermal treatment steps allow one to tailor the final mesostructure (2D hexagonal, p6m, or 3D cubic, Im3m). Various techniques were used to determine the time evolution of the mesostructure. Spectroscopic techniques (UV/vis, (17)O NMR) and EXAFS/XANES have been used to follow the chemical changes in the Ti(IV) environment. Crossing these techniques spanning all ranges permits a complete description of the chemistry all the way from solution to the mesostructured metal oxide. A critical discussion on all important chemical and processing parameters is provided; the understanding of these features is essential for a rational design and the reproducible construction of mesoporous materials.
851 citations
TL;DR: In this paper, a series of new mesoporous silica materials with MCM-41 type of structure containing a homogeneous layer of organic functional groups inside the pores was prepared using a co-condensation method under low surfactant concentration condition.
Abstract: A series of new mesoporous silica materials with MCM-41 type of structure containing a homogeneous layer of organic functional groups inside the pores was prepared using a co-condensation method under low surfactant concentration condition. This reproducible synthetic approach resulted in high surface coverage with several functional groups such as a primary amine, secondary amine, urea, isocyanate, vinyl, and nitrile. In addition, the presence of organoalkoxysilane precursors during the base catalyzed condensation greatly influenced the final particle shape. By changing the precursor or its concentration, the particle morphology was tuned to various shapes, including spheres, tubes, and rods of various dimensions. The synthetic procedures that gave rise to the specific particle morphologies were investigated and the mechanism responsible for shape control was postulated. The structure and functionality of these materials were characterized by field-emission scanning electron microscopy, transmission elec...
749 citations
TL;DR: In this paper, a mesoporous molecular sieve of MCM-41 type with polyethylenimine (PEI) was used for the preparation of CO2 adsorbents.
713 citations
TL;DR: A surfactant-templated approach was used to synthesize phosphated mesoporous titanium dioxide by incorporating phosphorus from phosphoric acid directly into the framework of TiO2 as discussed by the authors.
Abstract: A surfactant-templated approach was used to synthesize phosphated mesoporous titanium dioxide by incorporating phosphorus from phosphoric acid directly into the framework of TiO2. The resulting materials were characterized by XRD, nitrogen adsorption, TEM, XPS analysis, UV−vis spectroscopy, FT-IR spectroscopy, and isoelectric point measurements. The surface area of phosphated mesoporous TiO2 exceeded 300 m2/g after calcination at 400 °C. It was found that the incorporation of phosphorus could stabilize the TiO2 framework and increase the surface area significantly. This stabilization is attributed to two reasons: the more complete condensation of surface Ti−OH in the as-prepared sample and the inhibition of grain growth of the embedded anatase TiO2 by the interspersed amorphous titanium phosphate matrix during thermal treatment. Both pure and phosphated mesoporous TiO2 show significant activities on the oxidation of n-pentane. The higher photocatalytic activity of phosphated mesoporous TiO2 can be explai...
703 citations
TL;DR: In this paper, the authors highlight developments in the fields of microporous and mesoporous materials that were published mostly during the year 2002, and illustrate new zeolite structures, porous coordination materials, mesopore solids with new compositions, controlled morphologies, and increased hydrothermal and thermal stabilities.
Abstract: This report highlights developments in the fields of microporous and mesoporous materials that were published mostly during the year 2002. Selected examples are provided to illustrate new zeolite structures, porous coordination materials, mesoporous solids with new compositions, controlled morphologies, and increased hydrothermal and thermal stabilities, as well as porous solids with tunable pore openings or other structural features that can be dynamically modified. A number of applications are discussed, including stabilization of reactive guests, separations, electronic materials, and sensors.
701 citations
TL;DR: In this article, mesoporous SBA-15 was functionalized by co-condensation of tetraethoxysilane (TEOS) with APTES in a wide range of molar ratios of TEOS in the presence of triblock copolymer P123 under acidic synthetic conditions.
Abstract: The amine moiety is an important functionality for many applications such as enzyme immobilization on porous solid supports. In this study, mesoporous SBA-15 was functionalized by co-condensation of tetraethoxysilane (TEOS) with organosilane (aminopropyl)triethoxysilane (APTES) in a wide range of molar ratios of APTES:TEOS in the presence of triblock copolymer P123 under acidic synthetic conditions. The functionalized materials were characterized by physical adsorption, CHN elemental analysis, and various spectroscopic techniques. The data of FTIR, elemental analysis, XPS, and solid-state NMR demonstrated the incorporation of amine functional groups on the surface and inside the pore walls of the APTES-functionalized SBA-15 samples. The results of SAXS, N2 adsorption, and TEM showed the effect of APTES present in the initial synthesis mixtures on the formation of SBA-15 mesostructure such as structural ordering, pore size, and surface area. Reasons behind the observed strong adverse effect of APTES on SBA...
688 citations
TL;DR: The synthesis of 2-3 nm sized titania nanocrystals in a room-temperature ionic liquid under mild conditions and their self-assembly toward mesoporous TiO2 spheres are described and are expected to have potential in solar energy conversion, catalysis, and optoelectronic devices.
Abstract: In this Communication, we describe the synthesis of 2−3 nm sized titania nanocrystals in a room-temperature ionic liquid under mild conditions and their self-assembly toward mesoporous TiO2 spheres. The resulting structures combine the convenient handling of larger spheres with a considerable high surface area and narrow pore size distribution and are expected to have potential in solar energy conversion, catalysis, and optoelectronic devices.
TL;DR: The selectivities, sensitivities, and stabilities determined experimentally have demonstrated the potential of mesoporous platinum as a novel candidate for nonenzymatic glucose sensors.
Abstract: Roughness of nanoscopic dimensions can be used to selectively enhance the faradaic current of a sluggish reaction. Using this principle, we constructed mesoporous structures on the surfaces of pure platinum electrodes responding even more sensitively to glucose than to common interfering species, such as l-ascorbic acid and 4-acetamidophenol. Good sensitivities, as high as 9.6 μA cm-2 mM-1, were reproducibly observed in the presence of high concentration of chloride ion. The selectivities, sensitivities, and stabilities determined experimentally have demonstrated the potential of mesoporous platinum as a novel candidate for nonenzymatic glucose sensors.
TL;DR: In this article, the photocatalytic activity of titania powders with high photocatalysis was investigated by hydrolysis of titanium tetraisopropoxide in the presence of HNO3 or NH4OH under ultrasonic irradiation.
TL;DR: In this article, an image of the porous structure of SBA-15 and low-pressure argon adsorption was used to draw a coherent picture of the evolution of the precursor mesophase as a function of the synthesis temperature.
Abstract: Imaging of the platinum replica of the porous structure and low-pressure argon adsorption allowed us to elucidate the complicated porous structure of SBA-15. These techniques enabled us to draw a coherent picture of the evolution of the SBA-15 precursor mesophase as a function of the synthesis temperature. TEM of the platinum replicas has been unable to show bridges between the structural mesopores of SBA-15 synthesized at low temperature, whereas mesoporous bridges are clearly observed for samples formed at higher temperature. Argon adsorption has evidenced the ultramicroporosity of the materials formed at low temperature, as well as its evolution to secondary porosity with diameters greater than 1.5 nm under more severe hydrothermal treatment.
TL;DR: In this article, the synthesis of block copolymers (BC)-templated mesostructured oxides, stressing in the physical, chemical and processing parameters, which have to be thoroughly controlled to reproducibly obtain mesoporous materials.
Abstract: Block copolymers (BC) are indeed suitable and versatile templates for the creation of mesostructured and mesoporous materials. Great advances have been achieved in the last 3 years. Nowadays, it is possible to obtain highly controlled large-pore and highly stable mesostructured and mesoporous materials (silica, non-silica oxides, carbons,…) shaped as powders, films, monoliths or aerosols. This paper reviews mainly the synthesis of BC-templated mesostructured oxides, stressing in the physical, chemical and processing parameters, which have to be thoroughly controlled to reproducibly obtain mesoporous materials.
TL;DR: Mesoporous WO3 films with a lamellar structure have been synthesized by electrodeposition using sodium dodecyl sulfate (SDS) as a templating agent as mentioned in this paper.
Abstract: Mesoporous WO3 films with a lamellar structure (see Figure) have been synthesized by electrodeposition using sodium dodecyl sulfate (SDS) as a templating agent. Compared to non-porous WO3 prepared with isopropanol instead of SDS, lamellar phase mesoporous WO3 showed higher photocatalytic activity and greater current density for hydrogen intercalation, probably due to the larger surface area of mesoporous WO3 and more facile charge transport.
TL;DR: In this article, microwave-digested mesoporous materials are shown for the first time to be powerful hosts (templates) for the production of various crystalline metal oxide nanowire (the Figure shows a model) or nanosphere arrays via a simple impregnation and thermolysis synthesis.
Abstract: Microwave-digested (MWD) mesoporous materials are shown for the first time to be powerful hosts (templates) for the production of various crystalline metal oxide nanowire (the Figure shows a model) or nanosphere arrays via a simple impregnation and thermolysis synthesis. Some of the metal oxides (e.g., Co3O4) exhibit ordered structures on both meso- and atomic scales.
TL;DR: In this article, organosulfonic acid-functionalized mesoporous materials were synthesized in a one-step approach of co-condensing inorganic-organic reagents in the presence of different surfactant templates with in situ oxidation of the thiol groups to the sulfonic acid groups.
TL;DR: A new structure, mesoporous structured polyhedral drum and spherical cages and shells formed by textured self-assembly of ZnO nanocrystals, which are made by a novel self- assembly process during epitaxial surface oxidation are reported.
Abstract: We report a new structure, mesoporous structured polyhedral drum and spherical cages and shells formed by textured self-assembly of ZnO nanocrystals, which are made by a novel self-assembly process during epitaxial surface oxidation. The cages/shells exhibit unique geometrical shapes, and their walls are composed of mesoporous and textured ZnO nanocrystals. The structures of the cages and shells are studied, and a growth mechanism is proposed to be a process following solidification of the Zn liquid droplets, surface oxidation, and sublimation.
TL;DR: Organized mesoporous alumina represents a very interesting molecular sieve exhibiting a narrow pore size distribution with higher surface areas compared to conventional aluminas, used as a support for catalytically active species in numerous large-scale industrial processes as mentioned in this paper.
Abstract: Organized mesoporous alumina represents a very interesting molecular sieve exhibiting a narrow pore size distribution with higher surface areas compared to conventional aluminas, used as a support for catalytically active species in numerous large-scale industrial processes. This review encompasses various synthesis approaches to organized mesoporous aluminas, description of their structures and properties, and characterization by various experimental techniques. The potential of the mesoporous alumina with respect to use in catalysis is also outlined. Surface areas up to 800 m2/g and pore sizes ranging from 2.0 to more than 10 nm are characteristic for organized mesoporous aluminas prepared by neutral, anionic and cationic synthesis routes. Although utilization of mesoporous aluminas as a support in catalysis has not been reported frequently, they have a certain potential in hydrodesulfurization and metathesis reactions.
TL;DR: Mesoporous zeolite single-crystal catalysts combine the high acidity, shape-selectivity, and hydrothermal stability of zeolites with the efficient mass transport that is typically achieved in mesoporous materials.
Abstract: Mesoporous zeolite single-crystal catalysts are shown to be both more active and more selective than conventional zeolite catalysts in the alkylation of benzene with ethene. The superior catalytic properties are ascribed to improved mass transport in the mesoporous zeolite crystals. Thus, mesoporous zeolite single-crystal catalysts combine the high acidity, shape-selectivity, and hydrothermal stability of zeolites with the efficient mass transport that is typically achieved in mesoporous materials.
TL;DR: Convenient and commercially viable synthesis conditions are described, providing efficient and reproducible control of pore connectivity and pore wall thickness for the synthesis of high quality SBA-15 mesoporous silica.
TL;DR: In this article, the synthesis and precise structural characterization of highly ordered three-dimensional close-packed cage-type mesoporous silica is reported, which is proven to be commensurate with the face-centered-cubic Fm3m symmetry in high purity by a combination of experimental and simulated powder X-ray diffraction and transmission electron microscopy (TEM) analyses.
Abstract: The synthesis and precise structural characterization of highly ordered three-dimensional close-packed cage-type mesoporous silica is reported The siliceous mesoporous material is proven to be commensurate with the face-centered-cubic Fm3m symmetry in high purity by a combination of experimental and simulated powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses The cage-type calcined samples were additionally characterized by nitrogen physisorption The aqueous synthesis method to prepare large cage mesoporous silica with cubic Fm3m structure is based on the use of EO106PO70EO106 triblock copolymer (F127) at low HCl concentrations, with no additional salts or organic additives Here, emphasis is put on the low HCl concentration regime, allowing the facile thermodynamic control of the silica−triblock copolymer mesophase self-assembly Further, simple application of hydrothermal treatments at various temperatures ranging from 45 to 150 °C enables the tailoring of the mesopore
TL;DR: In this article, a hollow-structured and highly ordered mesoporous aluminosilicate with a 3D pore network and significantly improved hydrothermal stability has been successfully prepared.
Abstract: A hollow-structured and highly ordered mesoporous aluminosilicate with a 3D pore network and significantly improved hydrothermal stability has been successfully prepared by a simple method. To elucidate its novel structure and improved hydrothermal stability, a model for the formation of such a hollow spherical material has been proposed.
TL;DR: In this article, the accessibility and rate of access to the reactive sites were higher with ordered mesoporous solids than with amorphous material, and the results of batch experiments were obtained from batch experiments, by monitoring the reactant depletion in suspensions containing aminopropyl-grafted silica particles, and discussed with respect to the structure and porosity of organic−inorganic hybrids.
Abstract: Five different ordered mesoporous silica samples displaying various pore sizes and structures (two small-pore MCM-41, two large-pore MCM-41, and one small-pore MCM-48) and one amorphous silica gel have been grafted with either aminopropyl or mercaptopropyl groups. The resulting aminopropyl-grafted silicas (APS) and mercaptopropyl-grafted silicas (MPS) have been studied in solution via protonation of APS and metal ion binding on both APS and MPS. Special attention was given to characterize the accessibility to the binding sites and to the speed at which the reactants are reaching these reactive centers inside the mesoporous materials. Results have been obtained from batch experiments, by monitoring the reactant depletion in suspensions containing APS or MPS particles, and discussed with respect to the structure and porosity of the organic−inorganic hybrids. As a general trend, both accessibility and rate of access to the reactive sites were higher with ordered mesoporous solids than with amorphous material...
TL;DR: In this article, the internal pipe diameter was also adjustable by changing conditions of the deposition of the carbon film on the walls of the template, which was estimated as a difference between the pore radius.
Abstract: CMK-5 ordered mesoporous carbons that consist of two-dimensional (2-D) hexagonal arrays of pipes were synthesized using furfuryl alcohol as a carbon source and SBA-15 aluminosilicate of 2-D hexagonal structure as a template. External and internal pipe diameters were varied concomitantly by using SBA-15 templates with different pore diameters. The internal pipe diameter was also adjustable by changing conditions of the deposition of the carbon film on the walls of the template. It was shown that, under the typical synthesis conditions, furfuryl alcohol is fully polymerized inside SBA-15 pores. The internal pores of the pipes are generated during pyrolysis of the furfuryl alcohol under vacuum conditions. These pores are quite uniform in diameter, although there was evidence for the presence of constrictions in them, which may be related to the internal surface roughness or corrugation. The thickness of the carbon layer on the walls of the SBA-15 template was estimated as a difference between the pore radius...
TL;DR: A periodic mesoporous organosilica composed of interconnected three-ring [Si(CH2)]3 units built of three SiO2( CH2)2 tetrahedral subunits is reported, which represents the archetype of a previously unknown class of nanocomposite materials in which two bridging organic groups are bound to each silicon atom.
Abstract: A periodic mesoporous organosilica composed of interconnected three-ring [Si(CH2)]3 units built of three SiO2(CH2)2 tetrahedral subunits is reported. It represents the archetype of a previously unknown class of nanocomposite materials in which two bridging organic groups are bound to each silicon atom. It can be obtained with powder and oriented film morphologies. The nanocomposite is self-assembled from the cyclic three-ring silsesquioxane [(EtO)2Si(CH2)]3 precursor and a surfactant mesophase to give a well-ordered mesoporous framework. Low dielectric constants and good mechanical stability of the films were measured, making this material interesting for microelectronic applications. Methylene group reactivity of the three-ring precursor provides entry to a family of nanocomposites, exemplified by the synthesis and self-assembly of [(EtO)2Si(CHR)][(EtO)2Si(CH2)]2 (where R indicates iodine, bromine, or an ethyl group).
TL;DR: Very rapid and high capacity (up to 533 mg g−1) immobilization of enzymes within mesoporous silica has been achieved by finely tuning their morphologies as mentioned in this paper.