A New Family of Mesoporous Molecular Sieves
01 Jan 2002-pp 1-11
TL;DR: The M41S family of materials represent the first mesoporous molecular sieves as discussed by the authors, with high pore volumes and surface areas exhibiting an array of structures that are thermally stable inorganic analogs of organic, lyotropic liquid crystalline phases.
Abstract: The M41S family of materials represent the first mesoporous molecular sieves. This new family of materials with high pore volumes and surface areas exhibits an array of structures that are thermally stable inorganic analogs of organic, lyotropic liquid crystalline phases. The ability of the surfactant/aluminosilicate intermediate to assemble into stable extended structures results in mesoporous materials that are structurally diverse exhibiting hexagonal, cubic, and lamellar phases. The materials can be prepared with narrow pore size distributions at pore sizes ranging from 15 to greater than 100 A, varied elemental compositions and variable surface properties. This variability in physical properties has resulted in catalytic and sorption separation applications.
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TL;DR: The current approaches to create nanowires and nanocable structures are reviewed to critically evaluate their potential for developing unique nanostructure based sensors to improve recording and device performance to reduce noise and the detrimental effect of the interface on the tissue.
Abstract: Nanoscale structures have been at the core of research efforts dealing with integration of nanotechnology into novel electronic devices for the last decade. For instance, the unique electrical and optical properties of nanowires, nanotubes and nanocables with vertical orientation, assembled in nanoscale arrays, have been used in many device applications such as sensors that hold the potential to augment brain functions. However, the challenge in creating nanowires/nanotubes or nanocables arrays based sensors lies in making individual electrical connections fitting both the features of the brain and of the nanostructures. This review discusses two of the most important applications of nanostructures in neuroscience. First, the current approaches to create nanowires and nanocable structures are reviewed to critically evaluate their potential of developing unique nanostructure based sensors to improve recording and device performance to reduce noise and the detrimental effect of the interface on the tissue. Second, the implementation of nanomaterials in neurobiological and medical applications will be considered from the brain augmentation perspective. Because the size of nanomaterials is of the same order of magnitude with that of biomolecules, these materials are valuable tools for nanoscale manipulation in a broad range of neurobiological systems. Novel applications for diagnosis and treatment of brain diseases such as multiple sclerosis, meningitis, stroke, epilepsy, Alzheimer disease, schizophrenia, and autism will be considered. Because the blood brain barrier (BBB) has a defensive mechanism in preventing nanomaterials arrival to the brain, various strategies to help them to passing through the BBB will be discussed. The nanostructures at the interface between nanotechnology and neuroscience will play a pivotal role not only in addressing the multitude of brain disorders but also to repair/augment brain functions.
99 citations
TL;DR: In this paper, the authors describe the successful preparation of siliceous mesoporous materials MCM-41 with pores of ordered 2-dimensional hexagonal structure by condensation-polymerization using quaternary ammonium salt as structure directing agent and supernatant of the coal fly ash (CFA) as silica precursor.
96 citations
TL;DR: The adsorption capacity of the porous clay heterostructure from a Mexican clay suggests that the PCH has both hydrophobic and hydrophilic characteristics, as a result of the presence of silanol and siloxane groups formed during the pillaring and calcination of the P CH.
Abstract: A porous clay heterostructure (PCH) from a Mexican clay was prepared and characterized, and its aqueous phenol and dichlorophenols (DCPs) adsorption capacities were studied using a batch equilibrium technique. The PCH displayed a surface area of 305.5 m2/g, 37.2 A average porous diameter, and a basal space of 23.2 A. The adsorption capacity shown by the PCH for both phenol and DCPs from water (14.5 mg/g for phenol; 48.7 mg/g for 3,4-DCP; and 45.5 mg/g for 2,5-DCP) suggests that the PCH has both hydrophobic and hydrophilic characteristics, as a result of the presence of silanol and siloxane groups formed during the pillaring and calcination of the PCH. The values of maximal adsorption capacity for dichlorophenols were higher than those reported for aluminum pillared clays and some inorgano-organo clays and comparable with some ionic exchange resins.
20 citations
01 Sep 2003
TL;DR: In this paper, the results obtained from a Laboratory Directed Research & Development (LDRD) project entitled "Investigation of Potential Applications of Self-Assembled Nanostructured Materials in Nuclear Waste Management" are presented.
Abstract: This report summarizes the results obtained from a Laboratory Directed Research & Development (LDRD) project entitled 'Investigation of Potential Applications of Self-Assembled Nanostructured Materials in Nuclear Waste Management'. The objectives of this project are to (1) provide a mechanistic understanding of the control of nanometer-scale structures on the ion sorption capability of materials and (2) develop appropriate engineering approaches to improving material properties based on such an understanding.
12 citations
TL;DR: In this article, NaY zeolite was used to separate 1,2-BDO from EG, and its adsorption properties was then investigated, and the breakthrough curves of the binary mixture regressed from the empirical Dose-Response model in fixed-bed column showed that the adsorship selectivity of EG could reach to as high as 2.43.
11 citations
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TL;DR: In this paper, the synthesis of mesoporous inorganic solids from calcination of aluminosilicate gels in the presence of surfactants is described, in which the silicate material forms inorganic walls between ordered surfactant micelles.
Abstract: MICROPOROUS and mesoporous inorganic solids (with pore diameters of ≤20 A and ∼20–500 A respectively)1 have found great utility as catalysts and sorption media because of their large internal surface area. Typical microporous materials are the crystalline framework solids, such as zeolites2, but the largest pore dimensions found so far are ∼10–12 A for some metallophosphates3–5 and ∼14 A for the mineral cacoxenite6. Examples of mesoporous solids include silicas7 and modified layered materials8–11, but these are invariably amorphous or paracrystalline, with pores that are irregularly spaced and broadly distributed in size8,12. Pore size can be controlled by intercalation of layered silicates with a surfactant species9,13, but the final product retains, in part, the layered nature of the precursor material. Here we report the synthesis of mesoporous solids from the calcination of aluminosilicate gels in the presence of surfactants. The material14,15 possesses regular arrays of uniform channels, the dimensions of which can be tailored (in the range 16 A to 100 A or more) through the choice of surfactant, auxiliary chemicals and reaction conditions. We propose that the formation of these materials takes place by means of a liquid-crystal 'templating' mechanism, in which the silicate material forms inorganic walls between ordered surfactant micelles.
15,125 citations
TL;DR: In this paper, the synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described.
Abstract: The synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described. MCM-41, one member of this family, exhibits a hexagonal arrangement of uniform mesopores whose dimensions may be engineered in the range of - 15 A to greater than 100 A. Other members of this family, including a material exhibiting cubic symmetry, have ken synthesized. The larger pore M41S materials typically have surface areas above 700 m2/g and hydrocarbon sorption capacities of 0.7 cc/g and greater. A templating mechanism (liquid crystal templating-LCT) in which surfactant liquid crystal structures serve as organic templates is proposed for the formation of these materials. In support of this templating mechanism, it was demonstrated that the structure and pore dimensions of MCM-41 materials are intimately linked to the properties of the surfactant, including surfactant chain length and solution chemistry. The presence of variable pore size MCM-41, cubic material, and other phases indicates that M41S is an extensive family of materials.
10,349 citations
TL;DR: In this article, a generalized approach to the synthesis of periodic mesophases of metal oxides and cationic or anionic surfactants under a range of pH conditions is presented.
Abstract: THE recent synthesis of silica-based mesoporous materials1,2 by the cooperative assembly of periodic inorganic and surfactant-based structures has attracted great interest because it extends the range of molecular-sieve materials into the very-large-pore regime. If the synthetic approach can be generalized to transition-metal oxide mesostructures, the resulting nanocomposite materials might find applications in electrochromic or solid-electrolyte devices3,4, as high-surface-area redox catalysts5 and as substrates for biochemical separations. We have proposed recently6 that the matching of charge density at the surfactant/inorganic interfaces governs the assembly process; such co-organization of organic and inorganic phases is thought to be a key aspect of biomineralization7. Here we report a generalized approach to the synthesis of periodic mesophases of metal oxides and cationic or anionic surfactants under a range of pH conditions. We suggest that the assembly process is controlled by electrostatic complementarity between the inorganic ions in solution, the charged surfactant head groups and—when these charges both have the same sign—inorganic counterions. We identify a number of different general strategies for obtaining a variety of ordered composite materials.
1,996 citations
TL;DR: In this paper, a method for the calculation of effective pore size distribution from adsorption isotherms in molecular-sieve carbon is described, which is more exact theoretically as well as practically than previously described methods.
Abstract: A method for the calculation of effective pore size distribution from adsorption isotherms in molecular-sieve carbon is described. This method is more exact theoretically as well as practically than previously described methods. An average potential function has been determined inside the slit-like pores. With the help of this function the doubtful use of the Kelvin equation can be avoided at the scale of molecular dimensions. The method gives poor values for the larger pores but can be combined with the well-known Dollimore-Heal method at a pore size of 1.34 nm. Calculation is possible over a wide range of pore sizes. The calculation is shown through two examples from N2 isotherms at 77.4K. The model can be extended to other pore shapes as well as to other adsorbent-adsorbate pairs.
1,784 citations