Showing papers on "Mesoporous material published in 2006"
TL;DR: An overview of the preparation, properties, and potential applications of mesoporous organic-inorganic hybrid materials in the areas of catalysis, sorption, chromatography, and the construction of systems for controlled release of active compounds, as well as molecular switches, are given.
Abstract: Mesoporous organic-inorganic hybrid materials, a new class of materials characterized by large specific surface areas and pore sizes between 2 and 15 nm, have been obtained through the coupling of inorganic and organic components by template synthesis. The incorporation of functionalities can be achieved in three ways: by subsequent attachment of organic components onto a pure silica matrix (grafting), by simultaneous reaction of condensable inorganic silica species and silylated organic compounds (co-condensation, one-pot synthesis), and by the use of bissilylated organic precursors that lead to periodic mesoporous organosilicas (PMOs). This Review gives an overview of the preparation, properties, and potential applications of these materials in the areas of catalysis, sorption, chromatography, and the construction of systems for controlled release of active compounds, as well as molecular switches, with the main focus being on PMOs.
2,765 citations
TL;DR: A review of the progress made in the last ten years concerning the synthesis of porous carbon materials is summarized in this paper, where several different routes have been used to synthesize mesoporous carbon materials.
Abstract: In this review, the progress made in the last ten years concerning the synthesis of porous carbon materials is summarized. Porous carbon materials with various pore sizes and pore structures have been synthesized using several different routes. Microporous activated carbons have been synthesized through the activation process. Ordered microporous carbon materials have been synthesized using zeolites as templates. Mesoporous carbons with a disordered pore structure have been synthesized using various methods, including catalytic activation using metal species, carbonization of polymer/polymer blends, carbonization of organic aerogels, and template synthesis using silica nanoparticles. Ordered mesoporous carbons with various pore structures have been synthesized using mesoporous silica materials such as MCM-48, HMS, SBA-15, MCF, and MSU-X as templates. Ordered mesoporous carbons with graphitic pore walls have been synthesized using soft-carbon sources that can be converted to highly ordered graphite at high temperature. Hierarchically ordered mesoporous carbon materials have been synthesized using various designed silica templates. Some of these mesoporous carbon materials have successfully been used as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for enzyme immobilization. Ordered macroporous carbon materials have been synthesized using colloidal crystals as templates. One-dimensional carbon nanostructured materials have been fabricated using anodic aluminum oxide (AAO) as a template.
1,904 citations
TL;DR: The synthesis of the crystalline aluminosilicate materials with tunable mesoporosity and strong acidity has potentially important technological implications for catalytic reactions of large molecules, whereas conventional mesoporous materials lack hydrothermal stability and acidity.
Abstract: Zeolites are a family of crystalline aluminosilicate materials widely used as shape-selective catalysts, ion exchange materials, and adsorbents for organic compounds. In the present work, zeolites were synthesized by adding a rationally designed amphiphilic organosilane surfactant to conventional alkaline zeolite synthesis mixtures. The zeolite products were characterized by a complementary combination of X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analyses show that the present method is suitable as a direct synthesis route to highly mesoporous zeolites. The mesopore diameters could be uniformly tailored, similar to ordered mesoporous silica with amorphous frameworks. The mesoporous zeolite exhibited a narrow, small-angle XRD peak, which is characteristic of the short-range correlation between mesopores, similar to disordered wormhole-like mesoporous materials. The XRD patterns and electron micrographs of the samples taken during crystallization clearly showed the evolution of the mesoporous structure concomitantly to the crystallization of zeolite frameworks. The synthesis of the crystalline aluminosilicate materials with tunable mesoporosity and strong acidity has potentially important technological implications for catalytic reactions of large molecules, whereas conventional mesoporous materials lack hydrothermal stability and acidity.
1,043 citations
TL;DR: In this paper, the synthesis of mesoporous polymers and carbon frameworks from organic−organic assembly of triblock copolymers with soluble, low-molecular-weight phenolic resin precursors (resols) by an evaporation induced self-assembly strategy has been reported.
Abstract: The syntheses of a family of highly ordered mesoporous polymers and carbon frameworks from organic−organic assembly of triblock copolymers with soluble, low-molecular-weight phenolic resin precursors (resols) by an evaporation induced self-assembly strategy have been reported in detail. The family members include two-dimensional hexagonal (space group, p6m), three-dimensional bicontinuous (Ia3d), body-centered cubic (Im3m), and lamellar mesostructures, which are controlled by simply adjusting the ratio of phenol/template or poly(ethylene oxide)/poly(propylene oxide) in the templates. A five-step mechanism from organic−organic assembly has been demonstrated. Cubic FDU-14 with a gyroidal mesostructure of polymer resin or carbon has been synthesized for the first time by using the copolymer Pluronic P123 as a template in a relatively narrow range. Upon calcination at 350 °C, the templates should be removed to obtain mesoporous polymers, and further heating at above a critical temperature of 600 °C transfor...
1,013 citations
TL;DR: A general method based on two-phase polymerization has been described to synthesize mesoporous carbons via self-assembly through two phase polymerization, with obvious advantages over the techniques previously reported.
Abstract: A general method based on two-phase polymerization has been described to synthesize mesoporous carbons via self-assembly. Mild reacting conditions and wide composition ranges are the obvious advantages of this method over the techniques previously reported.
728 citations
TL;DR: In this paper, the authors report superior electric double layer capacitive properties of ordered mesoporous carbon (OMCs) with varying ordered pore symmetries and mesopore structure.
677 citations
TL;DR: It is proposed for the first time that ordered mesoporous nanocomposites have "reinforced concrete"-structured frameworks.
Abstract: Highly ordered mesoporous polymer−silica and carbon−silica nanocomposites with interpenetrating networks have been successfully synthesized by the evaporation-induced triconstituent co-assembly method, wherein soluble resol polymer is used as an organic precursor, prehydrolyzed TEOS is used as an inorganic precursor, and triblock copolymer F127 is used as a template. It is proposed for the first time that ordered mesoporous nanocomposites have “reinforced concrete”-structured frameworks. By adjusting the initial mass ratios of TEOS to resol, we determined the obtained nanocomposites possess continuous composition with the ratios ranging from zero to infinity for the two constituents that are “homogeneously” dispersed inside the pore walls. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon−silica nanocomposites. Combustion in air or etching in HF solution can remove carbon or silica from the...
578 citations
TL;DR: In this paper, the state of the art for hierarchical meso-macroporous inorganic materials and their carbon replicas is reviewed from the viewpoint of synthesis strategies and emerging applications.
Abstract: A great deal of progress has recently been made in the field of ordered porous materials having uniform channel dimensions which can be adjusted over a wide range of length scales. Incorporation of macropores in mesoporous materials combines benefits from both the mesoporous and macroporous structures. Hierarchical materials containing both interconnected macroporous and mesoporous structures have enhanced properties compared with single-sized pore materials due to increased mass transport through the material and maintainance of a specific surface area on the level of fine pore systems. Bimodal mesoporous–macroporous inorganic materials can be prepared by using a self-assembling surfactant or amphiphilic block copolymer species in conjunction with macrotemplates such as colloidal crystals, polymer foams, bio-celluloses, emulsions, inorganic salts and ice crystals, or by macroscopic phase separations. Here, we review the state of the art for hierarchical meso–macroporous inorganic materials and their carbon replicas from the viewpoint of synthesis strategies and emerging applications. Detailed synthetic processes are described, in which the very recently developed spontaneous formation of meso–macroporous (single and binary) metal oxides, metal phosphates and aluminosilicates is specifically addressed. These novel meso–macroporous materials have found a number of applications, including HPLC separation, catalysis, fuel cell electrode materials, biomaterials engineering, controlled drug delivery devices, and membrane reactors, and these are discussed illustratively.
524 citations
TL;DR: In this paper, an optimal molar Si/Al ratio in the range of 25-50 has been identified for mesoporous ZSM-5 zeolites with preserved structural integrity, and a successive combination of post-treatments, in which desilication is followed by dealumination, enables a decoupled modification of the mesopore and acidic properties.
Abstract: Recent studies have shown that desilication by treatment in alkaline medium is, with respect to other methods, a very suitable and reproducible methodology to obtain mesoporous ZSM-5 zeolites with preserved structural integrity. This feature article analyzes mechanistic and kinetic aspects associated with this post-synthesis treatment. Framework aluminium controls the process of framework silicon extraction and makes desilication selective towards intracrystalline mesopore formation. An optimal molar Si/Al ratio in the range of 25–50 has been identified. At higher Si/Al ratios non-selective and excessive extraction of framework silicon occurs, while minor extraction and limited mesopore formation occurs at lower ratios. The presence of non-framework aluminium species, for example obtained by steam treatment, inhibits mesopore formation by alkaline treatment due to reinsertion of these species into the zeolite framework. Additional kinetic optimization of the physicochemical properties of the hierarchical porous zeolite structures is achieved by variation of time and temperature of the alkaline treatment. A successive combination of post-treatments, in which desilication is followed by dealumination, enables a decoupled modification of the mesoporous and acidic properties, being interesting in catalyst design and optimization. Preliminary work on other zeolite framework types has shown a promising outlook of the alkaline treatment. Development of mesoporous zeolites via desilication should induce a more efficient usage of the zeolite crystal due to an improved accessibility and a facilitated transport to and from the active sites.
518 citations
TL;DR: Mesoporous zeolites from nanosized carbon templates have been successfully synthesized, but their industrial applications are still limited by the complexity of the synthetic procedure involved and the hydrophobicity of the carbon templates.
Abstract: Crystals of zeolites with intricate micropores have been widely used in industry as heterogeneous catalysts, in particular as solid acid catalysts in the fields of oil refining and petrochemistry. However, relatively small individual micropores in zeolites such as Beta, ZSM-5, and Y strongly influence mass transport to and from the active sites located within them, severely limiting the performance of industrial catalysts.[1,2] To overcome this problem, various strategies have been successfully pursued, such as the synthesis of nanosized zeolites,[3] ultralarge-pore zeolites and zeolite analogues (VPI-5,[4] JDF-20,[5] UTD-1,[6, 7] CIT-5,[8] SSZ-53,[9] ECR-34,[10] UCSB,[11] ITQ-21,[12] IM-12,[13] and SU-M,[14, 15] among others), and ordered mesoporous materials (e.g. MCM-41,[17] SBA-15,[18] and FSM-16,[19]). However, the use of these materials is rather limited owing to the difficult separation of nanosized zeolite crystals from the reaction mixture,[3] the complexity of the templates used for the synthesis of ultralarge-pore zeolites,[6–9] and the relatively low thermal and hydrothermal stability of ordered mesoporous materials.[17–28] More recently, mesoporous zeolites from nanosized carbon templates have also been successfully synthesized,[29–32] but their industrial applications are still limited by the complexity of the synthetic procedure involved and the hydrophobicity of the carbon templates.
512 citations
TL;DR: It is shown that the type of hysteresis loop formed by adsorption/desorption isotherms is determined by different mechanisms of condensation and evaporation and depends upon the shape and size of pores, and a novel hybrid nonlocal density functional theory (NLDFT) method is elaborate for calculations of pore size distributions from advertisers in the entire range of micro- and mesopores.
Abstract: We report results of nitrogen and argon adsorption experiments performed at 77.4 and 87.3 K on novel micro/mesoporous silica materials with morphologically different networks of mesopores embedded into microporous matrixes: SE3030 silica with worm-like cylindrical channels of mode diameter of approximately 95 angstroms, KLE silica with cage-like spheroidal pores of ca. 140 angstroms, KLE/IL silica with spheroidal pores of approximately 140 angstroms connected by cylindrical channels of approximately 26 angstroms, and, also for a comparison, on Vycor glass with a disordered network of pores of mode diameter of approximately 70 angstroms. We show that the type of hysteresis loop formed by adsorption/desorption isotherms is determined by different mechanisms of condensation and evaporation and depends upon the shape and size of pores. We demonstrate that adsorption experiments performed with different adsorptives allow for detecting and separating the effects of pore blocking/percolation and cavitation in the course of evaporation. The results confirm that cavitation-controlled evaporation occurs in ink-bottle pores with the neck size smaller than a certain critical value. In this case, the pressure of evaporation does not depend upon the neck size. In pores with larger necks, percolation-controlled evaporation occurs, as observed for nitrogen (at 77.4 K) and argon (at 87.3 K) on porous Vycor glass. We elaborate a novel hybrid nonlocal density functional theory (NLDFT) method for calculations of pore size distributions from adsorption isotherms in the entire range of micro- and mesopores. The NLDFT method, applied to the adsorption branch of the isotherm, takes into account the effect of delayed capillary condensation in pores of different geometries. The pore size data obtained by the NLDFT method for SE3030, KLE, and KLE/IL silicas agree with the data of SANS/SAXS techniques.
TL;DR: A novel high surface area heterogeneous catalyst based on solution phase colloidal nanoparticle chemistry has been developed and characterization of the Pt/SBA-15 catalysts suggests that Pt particles are located within the surfactant micelles during silica formation leading to their dispersion throughout the silica structure.
Abstract: A novel high surface area heterogeneous catalyst based on solution phase colloidal nanoparticle chemistry has been developed. Monodisperse platinum nanoparticles of 1.7−7.1 nm have been synthesized by alcohol reduction methods and incorporated into mesoporous SBA-15 silica during hydrothermal synthesis. Characterization of the Pt/SBA-15 catalysts suggests that Pt particles are located within the surfactant micelles during silica formation leading to their dispersion throughout the silica structure. After removal of the templating polymer from the nanoparticle surface, Pt particle sizes were determined from monolayer gas adsorption measurements. Infrared studies of CO adsorption revealed that CO exclusively adsorbs to atop sites and red-shifts as the particle size decreases suggesting surface roughness increases with decreasing particle size. Ethylene hydrogenation rates were invariant with particle size and consistent with a clean Pt surface. Ethane hydrogenolysis displayed significant structure sensitivi...
TL;DR: In this paper, the authors describe the application of novel chemistry methods for the fabrication of robust nanostructured titanium oxide (TiO2) photocatalysts, which can be applied in the development of efficient photocATalytic systems for the treatment of water.
Abstract: This study describes the application of novel chemistry methods for the fabrication of robust nanostructured titanium oxide (TiO2) photocatalysts. Such materials can be applied in the development of efficient photocatalytic systems for the treatment of water. Mesoporous photocatalytic TiO2 films and membranes were synthesized via a simple synthesis method that involves dip-coating of appropriate substrates into an organic/inorganic sol composed of isopropanol, acetic acid, titanium tetraisopropoxide, and polyoxyethylenesorbitan monooleate surfactant (Tween 80) followed by calcination of the coating at 500 8C. Controlled hydrolysis and condensation reactions were achieved through in-taking of water molecules released from the esterification reaction of acetic acid with isopropanol. The subsequent stable incorporation of Ti–O–Ti network onto self-assembled surfactants resulted in TiO2 photocatalysts with enhanced structural and catalytic properties. The properties included high surface area (147 m 2 /g) and porosity (46%), narrow pore size distribution ranging from 2 to 8 nm, homogeneity without cracks and pinholes, active anatase crystal phase, and small crystallite size (9 nm). These TiO2 photocatalysts were highly efficient for the destruction of methylene blue and creatinine in water. High water permeability and sharp polyethylene glycol retention of the prepared photocatalytic TiO2/Al2O3 composite membranes evidenced the good structural properties of TiO2 films. In addition, the multi-coating procedure made it possible to effectively control the physical properties of TiO2 layer such as the coating thickness, amount of TiO2, photocatalytic activity, water permeability and organic retention. # 2005 Elsevier B.V. All rights reserved.
TL;DR: Graphitic porous carbons with a wide variety of textural properties were obtained by using a silica xerogel as template and a phenolic resin as carbon precursor.
TL;DR: The photocatalytic activity of Fe-doped TiO(2) powders prepared by this method and calcined at 400 degrees C exceeded that of Degussa P25 (P25) by a factor of more than two times at an optimal atomic ratio of Fe to Ti of 0.25.
TL;DR: In this paper, the authors summarized recent advances in the immobilization of homogeneous and enzyme catalysts on ordered mesoporous materials (OMMs) for the purpose of catalyzing catalysts.
TL;DR: The bisphosphonate adsorption rate has been increased from 1% in oral administration to around 40% locally delivered, and the use of these drug delivery systems opens new fields with new possibilities for tissue engineering.
Abstract: Bisphosphonates have been confined in siliceous ordered mesoporous materials, and the drug release rate of these systems has been investigated. The bisphosphonate adsorption rate has been increased from 1% in oral administration to around 40% locally delivered. Drug dosage can be modulated through amine modification of the material surface, leading to a bisphosphonate adsorption in the ordered mesoporous matrices 3 times larger than that for unmodified materials. The use of these drug delivery systems opens new fields with new possibilities for tissue engineering.
TL;DR: In this paper, a novel CO 2 capture phenomenon is observed by modifying as-prepared mesoporous silica SBA-15 (SBA-P) with tetraethylenepentamine (TEPA), not only conserving the energy and time required for removing the template, but also opening the way to utilizing the micelle for dispersing guest species.
Abstract: A novel CO 2 capture phenomenon is observed by modifying as-prepared mesoporous silica SBA-15 (SBA(P)) with tetraethylenepentamine (TEPA), not only conserving the energy and time required for removing the template, but also opening the way to utilizing the micelle for dispersing guest species. The TEPA species dispersed within the channels of SBA(P) are highly accessible to CO 2 molecules; moreover, the hydroxyl group of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (Pluronic P123) template is able to modify the interactions between CO 2 and the amine to enhance the adsorptive capacity of this system. The remarkably high adsorption capacity (173 mg g -1 ) of this mesoporous silica-amine composite suggests potential CO 2 trapping applications, especially at low CO 2 concentrations during prolonged cyclic operations.
TL;DR: It is shown by TEM, PXRD, and EXAFS that alpha-Fe(2)O(3) with the same ordered mesoporous structure but disordered walls contains small crystalline domains, and Mössbauer and magnetic susceptibility data demonstrate that this material exhibits no long-range magnetic order but superparamagnetic behavior.
Abstract: α-Fe2O3 has been synthesized with an ordered mesoporous structure and crystalline walls that exhibit a near-single crystal-like order. The unique magnetic behavior of the material, distinct from bulk nanoparticles of α-Fe2O3 or mesoporous Fe2O3 with disordered walls, has been established. Magnetic susceptibility, Mossbauer, and neutron diffraction data show that the material possesses the same long-range magnetic order as bulk α-Fe2O3, despite the wall thickness being less than the 8 nm limit below which magnetic ordering breaks down in nanoparticulate α-Fe2O3, yet the Morin transition of bulk α-Fe2O3 is absent. It is also shown by TEM, PXRD, and EXAFS that α-Fe2O3 with the same ordered mesoporous structure but disordered walls contains small crystalline domains. Mossbauer and magnetic susceptibility data demonstrate that this material exhibits no long-range magnetic order but superparamagnetic behavior.
TL;DR: In this article, the effects of the quantity of triamine silane added to the grafting mixture on the CO2 adsorption capacity and the apparent adorption rate have been examined.
Abstract: Conventional MCM-41 and pore-expanded MCM-41 (PE-MCM-41) silicas have been used as supports for grafting 3-[2-(2-aminoethylamino)ethylamino]propyl trimethoxysilane (TRI) and tested for CO2 adsorption. The effects of the quantity of triamine silane added to the grafting mixture on the CO2 adsorption capacity and apparent adsorption rate have been examined. The results showed that when both supports were grafted under the same conditions, PE-MCM-41 was grafted with slightly larger quantities of amine than MCM-41, for all controlled silane additions. Based on the adsorption performance of the materials using a dry 5% CO2/N2 feed mixture, the optimal quantity of triamine silane added to the grafting mixture was determined to be ca. 3.0 cm3/g(SiO2), for both MCM-41 and PE-MCM-41. The CO2 adsorption capacity of TRI−PE-MCM-41 was significantly higher than that of TRI−MCM-41. Furthermore, the dynamic adsorption performance of TRI−PE-MCM-41 was far superior to TRI−MCM-41. In comparison to 13X zeolite, TRI−PE-MCM-4...
TL;DR: On the basis of the consideration of "host-guest" chemistry, the interactions between guest molecules are highlighted in the synthesis of nonsiliceous mesoporous materials by the "soft-template" and "hard- template" approaches.
Abstract: On the basis of the consideration of "host-guest" chemistry, the interactions between guest molecules are highlighted in the synthesis of nonsiliceous mesoporous materials by the "soft-template" and "hard-template" approaches. A generalized "acid-base pair" concept is utilized in selecting appropriate guest molecules to prepare highly ordered mesoporous metal oxides, phosphates, and borates with diversified structures. Mesoscopically ordered polymer and carbon frameworks with uniformly large pore sizes are derived from the self-assembly of an organic surfactant with an organic guest. Properly building the guest unit and decorating the host are important in replicating ordered nonsiliceous single-crystal nanoarrays. Outlooks on the potential possibilities for synthesizing ordered mesoporous nonsiliceous materials are presented as well.
TL;DR: By combining the multiplexing capability of QDs with the superparamagnetic properties of iron oxide nanocrystals, this class of encoded beads is expected to find broad applications in high-throughput and multiplexed biomolecular assays.
Abstract: Mesoporous beads are promising materials for embedding functional nanoparticles because of their nanometer-sized pores and large surface areas. Here we report the development of silica microbeads embedded with both semiconductor quantum dots (QD) and iron oxide (Fe3O4) nanocrystals as a new class of dual-function carriers for optical encoding and magnetic separation. The embedding (doping) process is carried out by either simultaneous or sequential addition of quantum dots and iron oxide (Fe3O4) nanocrystals in solution. The doping process is fast and quantitative, but the incorporated iron oxide strongly attenuates the signal intensity of QD fluorescence. We find that this attenuation is not due to conventional fluorescence quenching but is caused by the broad optical absorption spectrum of mixed-valence Fe3O4. For improved biocompatibility and reduced nonspecific binding, the encoded beads are further coated with amphiphilic polymers such as octylamine poly(acrylic acid). The results indicate that the polymer-coated beads are well suited for target capturing and enrichment, yielding magnetic separation efficiencies higher than 99%. By combining the multiplexing capability of QDs with the superparamagnetic properties of iron oxide nanocrystals, this class of encoded beads is expected to find broad applications in high-throughput and multiplexed biomolecular assays.
TL;DR: In this article, a strategy for the synthesis of multifunctional mesoporous silica nanoparticles is presented, which simultaneously possess magnetic, luminescent, and porous properties.
Abstract: We demonstrate a strategy for the synthesis of multifunctional mesoporous silica nanoparticles. These uniform tumblerlike nanocomposites, which simultaneously possess magnetic, luminescent, and porous properties, have great potential in biomedical applications.
TL;DR: In this article, a series of ordered mesoporous SiO2−CaO−P2O5 sol−gel glasses which are highly bioactive has been synthesized through evaporation-induced self-assembly in the presence of a nonionic triblock copolymer, EO20PO70EO20 (P123), template.
Abstract: A series of ordered mesoporous SiO2−CaO−P2O5 sol−gel glasses which are highly bioactive has been synthesized through evaporation-induced self-assembly in the presence of a nonionic triblock copolymer, EO20PO70EO20 (P123), template. By keeping constant the SiO2 + P2O5/P123 ratio, the influence of the CaO precursor, Ca(NO3)2·4H2O, on the mesostructure has been determined. After calcination at 700 °C, ordered mesoporous glasses are obtained, showing structures that evolve from 3D-cubic to 2D-hexagonal when the CaO content increases. The mesoporous glasses are highly bioactive compared with conventional ones, due to the increased textural characteristics supplied by the template. The bioactivity tests point out that the surface area, porosity, and 3D-structure become more important than chemical composition during the apatite crystallization stage in these materials, due to the very high textural parameters obtained.
TL;DR: Mesoporous silica SBA-15 was prepared to evaluate its effectiveness as a matrix for the controlled delivery of macrolide-type antibiotics, and two types of material were used to evaluate the delivery.
Abstract: Mesoporous silica SBA-15 was prepared to evaluate its effectiveness as a matrix for the controlled delivery of macrolide-type antibiotics. Two types of material were used to evaluate the delivery: calcined samples and samples functionalized with octyltrimethoxysilane and octadecyltrimethoxysilane. The samples were charged with the macrolide antibiotic erythromycin and the release assays were carried out in vitro. It has been observed that the release rate decreases as the population of hydrophobic –CH2 moieties in the host increases.
TL;DR: A novel quenched solid density functional theory (QSDFT) model of adsorption on heterogeneous surfaces and porous solids, which accounts for the effects of surface roughness and microporosity is presented.
Abstract: We present a novel quenched solid density functional theory (QSDFT) model of adsorption on heterogeneous surfaces and porous solids, which accounts for the effects of surface roughness and microporosity. Within QSDFT, solid atoms are considered as quenched component(s) of the solid−fluid system with given density distribution(s). Solid−fluid intermolecular interactions are split into hard-sphere repulsive and mean-field attractive parts. The former are treated with the multicomponent fundamental measure density functional. Capabilities of QSDFT are demonstrated by drawing on the example of adsorption on amorphous silica materials. We show that, using established intermolecular potentials and a realistic model for silica surfaces, QSDFT quantitatively describes adsorption/desorption isotherms of Ar and Kr on reference MCM-41, SBA-15, and LiChrosphere materials in a wide range of relative pressures. QSDFT offers a systematic approach to the practical problems of characterization of microporous, mesoporous, ...
TL;DR: In this paper, the bioactivity behavior of mesoporous materials is revisited and strategies to modify their kinetics are proven and discussed, on the basis of the experimental data showing the feasibility of control of their bioactivity kinetics, together with their controlled drug release abilities.
Abstract: The bioactivity behaviour of SBA-15, MCM-48, MCM-41 mesoporous materials, is revisited in this paper. The influence of their different textural and structural properties on apatite formation is outlined and strategies to modify their kinetics are proven and discussed. On the basis of the experimental data showing the feasibility of control of the bioactivity kinetics on mesoporous materials, together with their controlled drug release abilities, new possibilities for tissue engineering developments are proposed.
TL;DR: In this paper, the pore structure of fly-ash-based geopolymers was studied using electron microscopy and porosimetry, showing that higher curing temperature increases the extent and rate of reaction, shown through an increase in mesopore volume, surface area, and an accelerated setting time.
Abstract: The development of the pore structure of geopolymers synthesized from class F fly ash was studied using electron microscopy and porosimetry. Fly-ash-based geopolymer can be classified as a mesoporous aluminosilicate material, with a Si/Al composition varying from 1.51 to 2.24. The Si/Al composition and pore structure of fly-ash-based geopolymer vary depending on the curing temperature and the silicate ratio of the activating solutions (SiO2/M2O, M = Na or K). A higher Si/Al ratio and finer pores are obtained in geopolymers synthesized at higher temperature and silicate ratios. Elevating the curing temperature increases the extent and rate of reaction, shown through an increase in mesopore volume, surface area, and an accelerated setting time. The kinetics appears to be temperature-controlled only before the material is hardened. Very high silicate ratios (SiO2/M2O ≥ 2.0) are also believed to slow the reactions. The pore structure of K-based geopolymer is more susceptible to change in temperature than that...
TL;DR: Preliminary magnetic measurements reveal that the spins in both Fe(3)O(4) and gamma-Fe(2)O-3) are frozen at 295 K, despite the wall thickness being less than the lower limit for such freezing in corresponding nanoparticles (>8 nm).
Abstract: Ordered mesoporous Fe3O4 with crystalline walls (inverse spinel structure) has been synthesized for the first time, representing to the best of our knowledge, the first synthesis of a reduced mesoporous iron oxide. Synthesis was achieved by reducing ordered mesoporous α-Fe2O3 (corundum structure) to Fe3O4 spinel then to γ-Fe2O3 by oxidation, while preserving the ordered mesostructure and crystalline walls throughout. Such solid/solid transformations demonstrate the stability of the mesostructure to structural phase transitions from the hexagonal close packed oxide subarray of α-Fe2O3 (corundum structure) to the cubic close packed subarray of Fe3O4 spinel and γ-Fe2O3. Preliminary magnetic measurements reveal that the spins in both Fe3O4 and γ-Fe2O3 are frozen at 295 K, despite the wall thickness (7 nm) being less than the lower limit for such freezing in corresponding nanoparticles (>8 nm).
TL;DR: In this article, a novel sol-gel dip-coating process to fabricate nanocrystalline TiO2 photocatalytic membranes with a robust hierarchical mesoporous multilayer and improved performance has been studied.
Abstract: A novel sol–gel dip-coating process to fabricate nanocrystalline TiO2 photocatalytic membranes with a robust hierarchical mesoporous multilayer and improved performance has been studied. Various titania sols containing poly(oxyethylenesorbitan monooleate) (Tween 80) surfactant as a pore-directing agent to tailor-design the porous structure of TiO2 materials at different molar ratios of Tween 80/isopropyl alcohol/acetic acid/titanium tetraisopropoxide = R:45:6:1 have been synthesized. The sols are dip-coated on top of a homemade porous alumina substrate to fabricate TiO2/Al2O3 composite membranes, dried, and calcined, and this procedure is repeated with varying sols in succession. The resulting asymmetric mesoporous TiO2 membrane with a thickness of 0.9 μm exhibits a hierarchical change in pore diameter from 2–6, through 3–8, to 5–11 nm from the top to the bottom layer. Moreover, the corresponding porosity is incremented from 46.2, through 56.7, to 69.3 %. Compared to a repeated-coating process using a single sol, the hierarchical multilayer process improves water permeability significantly without sacrificing the organic retention and photocatalytic activity of the TiO2 membranes. The prepared TiO2 photocatalytic membrane has great potential in developing highly efficient water treatment and reuse systems, for example, decomposition of organic pollutants, inactivation of pathogenic microorganisms, physical separation of contaminants, and self-antifouling action because of its multifunctional capability.