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Ramon K S Almeida - One of the best experts on this subject based on the ideXlab platform.
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synthesis of ferrierite by a new combination of co structure Directing Agents 1 6 bis n methylpyrrolidinium hexane and tetramethylammonium
Microporous and Mesoporous Materials, 2016Co-Authors: Ramon K S Almeida, Luis Gomezhortiguela, Ana B Pinar, Joaquin PerezparienteAbstract:Abstract Ferrierite zeolite was synthesized in fluoride medium using dicationic 1,6-bis(N-methylpyrrolidinium)hexane (MPH) as a bulky structure Directing Agent (SDA) in combination with tetramethylammonium (TMA) as a small Co-Structure-Directing Agent (co-SDA). When trimethylamine, pyrrole or tert-butylamine were used as co-SDA, amorphous and beta zeolite (BEA framework type) were obtained, suggesting that these amines do not play a strong role as co-SDA. Only when TMA was used as co-SDA in synthesis gels with moderate pH, ferrierite is obtained; in fact, we have found a dramatic influence of the pH of the synthesis gel on the ferrierite crystallization, since even using TMA as co-SDA, ferrierite was only obtained under moderate pH values. Interestingly, ICP and CHN chemical analyses suggest that the Al content is driven by the amount of SDAs able to be hosted within the ferrierite framework, more specifically, by the nitrogen (positive charge) content available to charge-balance the negative charge associated to the incorporation of Al. A computational study showed that the most stable configuration of the ferrierite system corresponds to the occupation of the FER cages by TMA, while MPH accommodates in the 10-membered ring channels of the FER structure; the packing arrangement of MPH determines the density of positive charges, and hence the Al incorporation. Moreover, the unit cell parameters of the as-made ferrierite samples indicate that the structure is slightly expanded along the [100] direction in order to accommodate the bulky MPH dication.
Takashi Tatsumi - One of the best experts on this subject based on the ideXlab platform.
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Amino-functionalized mesoporous silica as base catalyst and adsorbent
Applied Catalysis A-general, 2012Co-Authors: Toshiyuki Yokoi, Yoshihiro Kubota, Takashi TatsumiAbstract:Abstract Mesoporous molecular sieves with size-tunable mesopores have been well developed and have attracted a great deal of attention because of their controllable structures and compositions, which make them suitable for a wide range of applications in catalysis, adsorption, separation, chromatography, etc. The pore size of mesoporous silica is large enough to accommodate a variety of large molecules, and the high density of silanol groups on the pore wall is beneficial to the introduction of functional groups with a high coverage. Actually, various kinds of surface modifications have been conducted for providing new functions for the surfaces. Among various functional groups, the introduction of the amino groups onto the mesopores has enabled us to use amino-functionalized mesoporous materials as solid-base catalysts and adsorbents. Meanwhile, “anionic surfactant templated mesoporous silica (AMS)” has been synthesized via a novel templating route for preparing mesoporous silicas based on the self-assembly of anionic surfactants and inorganic precursors in the presence of aminosilane or quaternized aminosilane as a Co-Structure-Directing Agent. AMSs are synthetically interesting not only for their structural diversity, including chiral properties, but also for the chance of functionalizing the pore surface by removing the surfactant by solvent extraction, resulting in the formation of the mesoporous silica with aminopropyl groups intact. Thus obtained amino-functionalized AMS can be applied to solid-base catalysis, adsorption, drug delivery, etc. This review gives an overview on the recent development of amino-functionalized mesoporous silica. In particular, the difference in the state and catalytic activity of amino groups between the functionalized mesoporous silicas synthesized via anionic and cationic surfactants templating routes is featured. Interesting applications of amino-functionalized mesoporous silica besides solid-base catalyst are also described.
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amino functionalized mesoporous silica synthesized by an anionic surfactant templating route
Journal of Materials Chemistry, 2006Co-Authors: Toshiyuki Yokoi, Yoshihiro Kubota, Hideaki Yoshitake, Takashi Yamada, Takashi TatsumiAbstract:A “S−N+∼I− pathway” (S−: anionic surfactant, N+: cationic amino group and I: inorganic species) for the synthesis of mesoporous silica has been developed by using 3-aminopropyltriethoxysilane (APS) as a Co-Structure Directing Agent (CSDA), which can interact with the anionic head group in the surfactant (SDA). Thus synthesized mesoporous silica has been designated as AMS (Anionic-surfactant-templated Mesoporous Silica). Removal of the anionic surfactant by extraction led to the functionalized AMS containing amino groups on the silica surface. Amino-functionalized AMS using 3-aminopropyltriethoxysilane (APS) and lauric acid sodium salt (LAS) as CSDA and SDA, respectively, was synthesized with varying proportions of APS in the silica sources (x-APS-AMS, where x is the proportion of APS in the silica sources, x = 0.1–0.6). In 0.4-APS-AMS, the content of amino groups derived from APS estimated by CHN elemental analysis and the argentometric titration was 2.36 and 2.24 mmol g−1, respectively, suggesting that almost all the aminopropyl moieties were on the surfaces in contrast to the MCM-41 type materials synthesized with a cationic surfactant. Thus obtained amino-functionalized AMS via the anionic surfactant templating route shows a higher adsorption capacity for Co2+ cations than amino-functionalized MCM-41 prepared by the direct co-condensation method via a conventional cationic templating route. There was also a marked difference in the activity for the Knoevenagel reaction between amino-functionalized AMS and MCM-41, indicating a significant difference in the state of aminopropyl moieties exposed to the surfaces.
Joaquin Perezpariente - One of the best experts on this subject based on the ideXlab platform.
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synthesis of ferrierite by a new combination of co structure Directing Agents 1 6 bis n methylpyrrolidinium hexane and tetramethylammonium
Microporous and Mesoporous Materials, 2016Co-Authors: Ramon K S Almeida, Luis Gomezhortiguela, Ana B Pinar, Joaquin PerezparienteAbstract:Abstract Ferrierite zeolite was synthesized in fluoride medium using dicationic 1,6-bis(N-methylpyrrolidinium)hexane (MPH) as a bulky structure Directing Agent (SDA) in combination with tetramethylammonium (TMA) as a small Co-Structure-Directing Agent (co-SDA). When trimethylamine, pyrrole or tert-butylamine were used as co-SDA, amorphous and beta zeolite (BEA framework type) were obtained, suggesting that these amines do not play a strong role as co-SDA. Only when TMA was used as co-SDA in synthesis gels with moderate pH, ferrierite is obtained; in fact, we have found a dramatic influence of the pH of the synthesis gel on the ferrierite crystallization, since even using TMA as co-SDA, ferrierite was only obtained under moderate pH values. Interestingly, ICP and CHN chemical analyses suggest that the Al content is driven by the amount of SDAs able to be hosted within the ferrierite framework, more specifically, by the nitrogen (positive charge) content available to charge-balance the negative charge associated to the incorporation of Al. A computational study showed that the most stable configuration of the ferrierite system corresponds to the occupation of the FER cages by TMA, while MPH accommodates in the 10-membered ring channels of the FER structure; the packing arrangement of MPH determines the density of positive charges, and hence the Al incorporation. Moreover, the unit cell parameters of the as-made ferrierite samples indicate that the structure is slightly expanded along the [100] direction in order to accommodate the bulky MPH dication.
Mohamed Ibrahim - One of the best experts on this subject based on the ideXlab platform.
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simple and facile synthesis of amino functionalized hollow core mesoporous shell silica spheres using anionic surfactant for pb ii cd ii and zn ii adsorption and recovery
Chemical Engineering Journal, 2014Co-Authors: Ahmed Mohamed Eltoni, Mohamed Ibrahim, Joselito P Labis, Mohamed A Habila, Zeid A AlothmanAbstract:Abstract In this work, amino functionalized hollow core–mesoporous shell silica spheres (NH 2 -HCMSSs), which are expected to have a significant tendency for heavy metal removal, are synthesized by ultrasonic assisted soft-templating method using anionic surfactant. Ultrasonic waves, have produced bubbles on which the anionic surfactant micelles have assembled and thereafter the silica nuclei have precipitated to form hollow core structure. Co-Structure Directing Agent, 3-aminopropyltrimethoxysilane (APMS), was used to assist the electrostatic interaction between the partially negatively charged silica particles and the negatively charged surfactant molecules through S − N + I − pathway. Upon the surfactant removal by solvent extraction, amino groups of APMS have then functionalized the mesoporous shell of hollow core structure. Various synthesis parameters, such as sonication time, solvent type, and acid concentration, have been investigated to synthesize HCMSSs spheres with superior textural properties (e.g., total pore volume and surface area). Furthermore, the impact of these parameters on the removal of heavy metal cations from polluted water was evaluated accordingly. HCMSSs were characterized by low-angle X-ray diffraction (Lo-XRD), transmission electron microscopy (TEM), and N 2 sorption analysis. In this study, the variation of synthetic parameters have led to a considerable increment of the surface area and pore volume from 319.44 to 718.024 m 2 /g and 3.309 × 10 −1 to 1.190 cm 3 /g, respectively. HCMSSs samples have shown heavy metal adsorption capacity of 194.4, 190.5 and 193 mg/g for Pb(II), Cd(II), and Zn(II) metal cations, respectively.
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synthesis of double mesoporous core shell silica spheres with tunable core porosity and their drug release and cancer cell apoptosis properties
Joint International Conference on Information Sciences, 2012Co-Authors: Ahmed Mohamed Eltoni, Aslam Khan, Mohamed Ibrahim, Joselito P Labis, Gamal Badr, Mansour Alhoshan, Shu Yin, Tsugio SatoAbstract:In this work, we demonstrate a simple two-pot approach to double mesoporous core-shell silica spheres (DMCSSs) with uniform size of 245-790 nm, shell thickness of 41-80 nm and surface area and total pore volume of 141-618 m(2) g(-1) and 0.14-0.585 cc g(-1), respectively. First, solid silica spherical particles were synthesized by the Stober method and used as a core. Second, a mesoporous shell could be formed around the silica cores by using an anionic surfactant and a Co-Structure Directing Agent. It was found that mesopores can be anchored within dense silica cores during mesoporous silica shell formation, synchronously the base group with surfactant assistant can etch the dense silica cores to re-organize new mesostructure, so that double mesoporous core-shell silica sphere (DMCSS) structure can be obtained by a single surfactant-templating step. The spherical size and porosity of the silica cores of DMCSS together with shell thickness can be tuned by controlling Stober parameters, including the concentrations of ammonia, solvent and tetraethoxysilane and the reaction time. DMCSS were loaded with ketoprofen and thymoquinone, which are an anti-inflammatory and a potential novel anti-cancer drug, respectively. Both drugs showed controlled release behavior from the pores of DMCSS. Drug uptakes within DMCSS were ~27 and 81 wt.% for ketoprofen and thymoquinone, respectively. Furthermore, DMCSS loaded with thymoquinone was more effective in inducing cancer cell apoptosis than uncontained thymoquinone, because of the slow release of the drug from the mesoporous structure.
Lu Han - One of the best experts on this subject based on the ideXlab platform.
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anionic surfactant templated mesoporous silicas amss
ChemInform, 2013Co-Authors: Lu Han, Shunai CheAbstract:This tutorial review highlights the research on anionic surfactant templated mesoporous silica (AMS), which employs a Co-Structure Directing Agent (CSDA) to establish the critical interaction between the surfactant head group and silica species. As the geometry of anionic surfactants can be readily tuned via the ionisation of the surfactant head group, AMS materials possess a variety of mesostructures and morphologies. Chiral mesoporous silica (CMS) and helical ribbons can be formed via the chiral packing of the surfactant. Due to the pairing effect between the CSDA and the surfactant, a regular array of the organic groups is formed based on the stoichiometry and geometric arrangement of the surfactant, which produces functionalised materials with a uniform distribution of their organic groups. Furthermore, a brief introduction to the applications and future requirements of AMS is also included. This review is addressed to researchers and students interested in diverse areas of chemistry, particularly inorganic, physical, supramolecular and materials chemistry (63 references).
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anionic surfactants templating route for synthesizing silica hollow spheres with different shell porosity
Solid State Sciences, 2011Co-Authors: Lu Han, Chuanbo Gao, Qianru Chen, Peng Shu, Zhiguang Ding, Shunai CheAbstract:Abstract Silica hollow spheres with different shell porosity were simply synthesized with micelle and emulsion dual templating route. Various anionic surfactants, such as palmitic acid (C16AA), N-acyl- l -phenylalanine (C18Phe), N-palmitoyl- l -alanine (C16AlaA) and oleic acid (OA) have been used as templates, and 3-aminopropyl-triethoxysilane (APES) and tetraethyl orthosilicate (TEOS) have been used as Co-Structure Directing Agent (CSDA) and silica source, respectively. The circle lamellar layer structure and mesopores vertical to the silica hollow spheres surface are believed to originate from the initial formation of amphiphilic carboxylic acid oil drop, which afterwards self-assemble to form the shell of hollow spheres and its mesostructure upon addition of CSDA and silica source. The mesoporous silica hollow spheres with high porosity could be achieved by adding a moderate amount of ethanol in the OA synthesis system, depending on the co-surfactant effect of ethanol that changes the curvature of micelles. The particle diameter and the hollow structure have been controlled by choosing different templates and by manipulating synthesis gel composition. The average particle diameter of the mesoporous silica hollow spheres were controlled in the range of 80–220 nm with constant shell thickness of ∼20 nm and constant mesopore size of ∼4 nm. Besides, the formation of the silica hollow spheres has been investigated in detail with reaction time. These mesoporous silica hollow spheres would have potential applications on catalysis, bimolecular encapsulation, adsorption, drug release, etc.
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synthesis of amino group functionalized monodispersed mesoporous silica nanospheres using anionic surfactant
Microporous and Mesoporous Materials, 2011Co-Authors: Lu Han, Chuanbo Gao, Qianru Chen, Yu Wang, Shunai CheAbstract:Abstract A series of anionic surfactant templated mesoporous silica (AMS) monodispersed nanospheres were synthesized by anionic surfactant, Co-Structure-Directing Agent (CSDA) bearing amino group, and silica source in the presence of nonionic surfactant. The amino group functionalized well-ordered cubic Fd-3m, bi-continuous cubic Ia-3d and disordered structures with tunable pore size from 2.2 to 9.2 nm and the particle size from 30 to 320 nm, have been synthesized by changing the type of the surfactant, the concentration of the nonionic and anionic surfactant and the reaction temperature. Loadings of the amino groups were determined in the range of 2.7–3.4 mmol/g. It has been found that, the higher concentration of the nonionic and the anionic surfactant, the shorter chain length of the anionic surfactant and the higher reaction temperature favor the formation of mesoporous silica nanospheres with larger particle size. These functional AMS nanospheres may find potential use in catalysis, sensor devices and bio-applications, etc.
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insight into the defects of cage type silica mesoporous crystals with fd3m symmetry tem observations and a new proposal of polyhedron packing for the crystals
Chemistry: A European Journal, 2009Co-Authors: Lu Han, Shunai Che, Yasuhiro Sakamoto, Osamu TerasakiAbstract:The many faces of crystals: Silica mesoporous crystals were synthesized by using a Co-Structure Directing method. Structural defects in the crystals with Fdm symmetry—described as tetrahedrally close-packed and consisting of 512 and 51264 polyhedra—were found (see figure). These defects were explained through the use of simulated TEM images. The defect formation is also discussed. Silica mesoporous crystals were synthesized by using a gemini cationic surfactant (C18-3-1) as the Directing Agent, carboxyethylsilanetriol sodium salt as the Co-Structure Directing Agent (CSDA), and varying amounts of HCl. By using transmission electron microscopy (TEM) we observed 1) a structural change from the close-packed structures of spherical micelles—face-centered cubic (Fmm) and hexagonal close-packed (P63/mmc)—to Fdm structures with an increase of HCl and 2) a few structural defects in the crystals with Fdm symmetry. The structure of a crystal with Fdm symmetry is described as one of the tetrahedrally close-packed (tcp) structures consisting of 512 and 51264 polyhedra. The observed TEM images of the structural defects were explained well through use of simulated TEM images by introducing new 13–15 polyhedra comprising 51262, 51263, 4151062, 425865, and 4151064, which have been observed in bubbles by Matzke. The mesostructural changes and defect formation are discussed in terms of the hardness of micelles composed of surfactant/CSDA/silica species that have formed through a change of the interaction between the surfactant and CSDA, which causes the micelles to change from a regime of close-packing to one of minimum-area packing.