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Mesoporous silica nanoparticles as controlled release …

In general alcohol with appropriate carbon chain length such as n -butanol and hexanol could act as the co-surfactant in the synthesis of mesoporous silica templated by anionic surfactant.">

Well-ordered mesoporous materials 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, environmental clean-up, and development of advanced materials. In general, the mesoporous materials can be synthesized based on the self-assembly of surfactants and inorganic precursors. In addition to the use of the surfactants including cationic and nonionic surfactants, a synthesis route for preparing mesoporous silicas using anionic surfactants has been developed by using aminosilane or quaternized aminosilane as a co-structure-directing agent. Thus obtained “anionic surfactant templating mesoporous silica” (AMS) is synthetically interesting not only for their structural diversity but also for the opportunity to functionalize the pore surface. The removal of the surfactant from the so-called “as-synthesized” AMS by solvent extraction results in the mesoporous silica with aminopropyl groups intact. Thus obtained amino-functionalized AMS can be applied to solid-base catalysis, adsorption, drug delivery, etc. Besides well-known surfactant-templating route, a silica material having three-dimensionally ordered mesopores can be also obtained a hard-sphere packing (HSP) route based on the formation of a colloidal array of uniform-sized silica spheres. A novel and simple liquid-phase method for forming uniform-sized silica nanospheres (SNSs) has been developed by using basic amino acid as a base catalyst for hydrolysis of tetraethyl orthosilicate Si(OC2H5)4. The size of SNSs can be tuned ranging from 8 to 550 nm by employing the seed regrowth method. Interestingly, the arrangement of SNSs into the cubic closed packed (ccp) structure was achieved simply by solvent evaporation. The thus-formed colloidal array of SNSs has three-dimensional interparticle voids with high uniformity in size, and can be categorized into well-ordered mesoporous silicas.

Syntheses and Applications of Well-ordered Porous Silicas by Using Anionic Surfactants ..

Methods of Synthesis of Nano- and Micrometric ..

The cationic polymer connected the anionic surfactant micelle to the anionic polysilicate species to induce the synthesis of the mesoporous silica materials.

Without the addition of extra alcohols, spherical mesoporous silica with radially oriented mesopores could be obtained through the anionic surfactant templating route.

Superparamagnetic Iron Oxide Nanoparticles as MRI …

In general alcohol with appropriate carbon chain length such as n -butanol and hexanol could act as the co-surfactant in the synthesis of mesoporous silica templated by anionic surfactant.

Dr. Takashi Tatsumi has carried out basic research on the synthesis of zeolites to be applied to petrochemical reactions and developed new methods for preparing catalysts having much improved functions. Shape-selective and regio-selective catalysis controlled by the pore structure of zeolites and microenvironment of the active center of catalysts has been also attained. These zeolites can be applied to a variety of chemical transformations without wastes and by-products, thus making them ecologically more acceptable and environmentally safer.

TS-1 is a titanosilicate zeolite where Ti is introduced into the framework of zeolites of the MFI structure. Titanosilicates demonstrate redox catalysis, quite distinct from conventional aluminosilicate zeolites. Dr. Tatsumi has discovered that TS-1 zeolite can catalyze the oxidation of chemically inactive simple alkanes at low temperature using H2O2 as oxidant. This discovery highlighted a special feature of TS-1 as a unique oxidation catalyst, attracting attention of a large number of researchers in the area of zeolites catalysis. He has succeeded in synthesizing new types of zeolites containing Ti in the framework such as Ti-SAPO-37, Ti-MWW, and Ti-YNU-1 and also Ti-containing mesoporous molecular sieves. He has also carried out the solid-state synthesis of Ti-beta, which could be an improved synthesis method. It is particularly noteworthy that Ti-MWW zeolite showed an alkene epoxidation activity several times as high as TS-1 that is a current industrial catalyst. Ti-YNU-1 has a new type of zeolite topology with 12-membered ring large pore; therefore it showed a very high activity in the epoxidation of bulky cyclic alkenes. It has been made clear that in this type of liquid phase oxidation using aqueous H2O2 as oxidant the hydrophobicity of the catalyst surface is critically important. Thus it has been revealed that the introduction of organic moieties resulted in the enhancement of the catalytic activity of Ti-containing mesoporous materials. Furthermore, he has synthesized a novel inorganic-organic hybrid zeolite ZOL, in which a methylene group is incorporated as a lattice. This hybrid zeolite material is synthesized from an organosilane with a bridging methylene group between two silicon atoms (Si-CH2-Si) to be substituted for a siloxane bridge (Si-O-Si) and has changed the concept of "zeolites" that has been considered as silica-based porous crystalline materials. ZOL materials have high hydrophobicity and demonstrate the shape-selectivity in hydrocarbon adsorption. He has also succeeded in expanding interlayer pore of zeolites of a layered type by silylating layered precursors of zeolites followed by calcination. This is a new methodology of building a variety of zeolites structures, those with large pores in particular, starting from layered sheets of zeolites as nanoparts.

Mesoporous molecular sieves have attracted much attention of chemists and materials scientists because of emerging applications in catalysis, adsorption, sensors, and separations. They are analogous to zeolites, but their pore size is extremely large compared to zeolites pores, accommodating large reactants and products and mitigating the problem with their diffusion. Dr. Tatsumi has succeeded in the synthesis of a cubic 3-dimensional mesoporous molecular sieve Ti-MCM-48, which proved to be an active oxidation catalyst for bulky reactants impossible to be oxidized by zeolites. Although mesoporous molecular sieves had been reported to be unstable to water and mechanical impact, he has discovered that the mesostructure can be greatly stabilized by silylating the surface silanol groups on mesoporous materials. He has also found that in acidic synthesis using cationic surfactants as a structure directing agent (SDA) the mesostructures are transformed in the solid-solid manner and highly dependent of the counter anion as well as the cation, thus establishing the fundamental principles of control of the mesostructures. Although the use of anionic surfactants as a SDA for the synthesis of the mesoporous silica had been strongly desired, the synthesis of mesoporous silica by using an anionic surfactant had been unsuccessful for long time. He has developed a method of synthesizing the anionic surfactant templated mesoporous silica, AMS. The use of anionic surfactant as a SDA for the formation of the mesostructured silica-micelle composite has been presented as the "S- N+∼I- pathway" that is promoted by the use of an organoalkoxysilane containing an amino group. Some of the AMS materials have mesostructures that have never been synthesized by using either cationic or nonionic surfactants; their structures have long-range periodical modulations. By using amino acid derived anionic surfactants, a new type of enantioenriched mesoporous material in the shape of helical rod, in which helical channels are running through. This is a purely inorganic chiral material, which could be utilized for the synthesis of and the separation of racemic mixtures into enantiomerically pure chemicals.

Dr. Tatsumi has also conducted researches into acid catalysis by zeolites; he found the effect of diluents in the Beckmann rearrangement, and achieved shape-selective control over alkene hydration. He has also discovered the unique features of metal nanoparticles and clusters incorporated into zeolite pores and led to the development of advanced catalysts active in alkane aromatization, selective synthesis of gasoline-range hydrocarbons from synthesis gas, and deep hydrodesulfurization of light oil.

In summary Dr. Takashi Tatsumi has achieved magnificent results through close coordination of the syntheses of novel porous materials with their application to useful catalytic reactions. He would deserve to receive the Chemical Society of Japan (CSJ) Award.

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PDF Downloads : Oriental Journal of Chemistry


Program | 6th World Congress and Expo on …

Abstract:
This work focuses on the synthesis and the modification of mesoporous silica SBA-15 using in-situ polymerization of polypyrrole. In order to study the effect of polypyrrole contents on the structural, textural and dye adsorption properties, several polypyrrole contents were dispersed and analyzed by various techniques such as X-ray diffraction (XRD), nitrogen sorption at 77 K, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and scanning electronic microscopy (SEM). The obtained materials were tested for the removal of cationic and anionic dyes. The effect of pH, contact time, adsorbent dose, and initial dye concentration were investigated and discussed in terms of adsorption efficiency. The obtained results show that the adsorption efficiency of MO dye is preferably carried out by the nanocomposites PPY/SBA-15(50%) containing higher polypyrrole content. Whereas, the adsorption of MB is oriented by the parent material SBA-15 and the nanocomposite PPY/SBA-15(1%) containing lower content of polypyrrole. The experimental data were verified by the Langmuir and Freundlich isotherms, and the kinetic data were fitted by pseudo-first-order and pseudo-second-order models. The obtained results showed that the adsorption of the both dye by nanocomposite PPY/SBA-15 followed Langmuir adsorption isotherm models and pseudo-second-order kinetics. The adsorbed amounts recorded for MO and MB dyes are 41.66 mg/g and 58.82 mg/g, respectively.

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