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Dialkoxydichlorosilanes ((RO)2SiCl2, R = alkyl) react almost completely with interlayer silanol groups in a layered silicate octosilicate to create a new crystalline silicate structure consisting of new five-membered rings arranged regularly on both sides of the silicate layers. The introduction of dialkoxysilyl groups to the interlamellar region of layered silicates with regular reaction sites provides a new methodology for the design and construction of novel crystalline silicate frameworks by a soft chemical route. 相似文献
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Naoto Sato Taiki Hayashi Kazuma Tochigi Prof. Hiroaki Wada Prof. Atsushi Shimojima Prof. Kazuyuki Kuroda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7860-7865
Eight corners of a double-four ring cage-type germanoxane, containing a fluoride ion, were successfully silylated by the combination of chlorosilanes and silazanes. Three different silyl groups, trimethylsilyl, dimethylsilyl, and dimethylvinylsilyl, were attached on the corners of germanoxane cage. The solubility and reactivity of the cage modified with dimethylvinylsilyl groups were significantly increased, allowing for further reaction. Hydrosilylation reaction between dimethylvinylsilylated cage geramanoxanes and dimethylsilylated cage siloxanes afforded porous solids. Functionalization of the corners of germanoxanes with silyl groups should provide valuable building blocks in various functional materials. 相似文献
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Oligomeric Alkoxysilanes with Cagelike Hybrids as Cores: Designed Precursors of Nanohybrid Materials
Hideki Kuge Yoshiaki Hagiwara Atsushi Shimojima Dr. Kazuyuki Kuroda Prof. 《化学:亚洲杂志》2008,3(3):600-606
Well‐defined alkoxysilane oligomers containing a cagelike carbosiloxane core were synthesized and used as novel building blocks for the formation of siloxane‐based hybrid networks. These oligomers were synthesized from the cagelike trimer derived from bis(triethoxysilyl)methane by silylation with mono‐, di‐, and triethoxychlorosilanes ((EtO)nMe3?nSiCl, n=1, 2, and 3). Hybrid xerogels were prepared by hydrolysis and polycondensation of these oligomers under acidic conditions. The structures of the products varied depending on the number of alkoxy groups (n). When n=2 and 3, microporous xerogels (BET surface areas of 820 and 510 m2 g?1, respectively) were obtained, whereas a nonporous xerogel was obtained when n=1. 29Si NMR spectroscopic analysis suggested that partial rearrangement of the siloxane networks, which accompanied the cleavage of the Si–O–Si linkages, occurred during the polycondensation processes. By using an amphiphilic triblock copolymer surfactant as a structure‐directing agent, hybrid thin films with a 2D hexagonal mesostructure were obtained when n=2 and 3. These results provide important insight into the rational synthesis of molecularly designed hybrid materials by sol–gel chemistry. 相似文献
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The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single‐Crystalline Ordered Mesoporous Nb‐TiO2 and Plate‐like Nb‐TiO2 with Ordered Mesoscale Dimples 下载免费PDF全文
Takamichi Matsuno Dr. Yoshiyuki Kuroda Prof.Dr. Atsushi Shimojima Prof.Dr. Hiroaki Wada Prof.Dr. Kazuyuki Kuroda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):13073-13079
Highly ordered mesoporous niobium‐doped TiO2 with a single‐crystalline framework was prepared by using silica colloidal crystals with ca. 30 nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb‐doped TiO2. The XPS measurements of Nb‐doped TiO2 showed the presence of Nb5+ and correspondingly Ti3+. With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate‐like TiO2 with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals. 相似文献
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Yukiji Shimojima Hiroshi Hayashi Tadaaki Ooka Mitsuru Shibukawa Yoichi Iitaka 《Tetrahedron letters》1982,23(51):5435-5438
The structures of a novel gastroprotective substance AI-77-B and its analogues AI-77-C, D, F and G, which are produced by Bacillus pumilus, are described. Five of the asymmetric centers of AI-77-B have S absolute stereochemistry confirmed by X-ray in combination with chemical studies. 相似文献
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Wang J Sugawara A Shimojima A Okubo T 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18491-18498
A facile solution process for the preparation of anisotropic silica nanoparticles (ASNPs) is presented. ASNPs are prepared via controlled self-assembly of spherical silica seeds (22 nm) in alcohol-water mixed media, followed by their in situ fixation and overgrowth with tetraethoxysilane (TEOS). Ethanol and L-arginine (Arg) are used to modify the dielectric constant and ionic strength of the reaction media, by which seed assembly is controlled through the adjustment of electrostatic interaction. Ethanol and Arg also serve as a cosolvent and a catalyst for hydrolysis and condensation of TEOS, respectively, which enables us to produce ASNPs in a simple one-pot process. In addition to ASNPs with wormlike structures, different kinds of NPs (bimodal spherical NPs, monodisperse spherical NPs, and spherical aggregates) have also been obtained by changing the concentrations of ethanol and Arg. The length, thickness, or both of ASNPs are controlled systematically by varying the concentrations of Arg, seed NPs, and TEOS. Other alcoholic cosolvents, such as methanol, 1-propanol, 2-propanol, and t-butanol, are also effective to give ASNPs when the dielectric constant of the alcohol-water mixed media is properly adjusted, showing the versatility of the present method. 相似文献
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Molecularly Designed Nanoparticles by Dispersion of Self‐Assembled Organosiloxane‐Based Mesophases 下载免费PDF全文
Shigeru Sakamoto Yasuhiro Tamura Dr. Hideo Hata Dr. Yasuhiro Sakamoto Prof. Atsushi Shimojima Prof. Kazuyuki Kuroda 《Angewandte Chemie (International ed. in English)》2014,53(35):9173-9177
The design of siloxane‐based nanoparticles is important for many applications. Here we show a novel approach to form core–shell silica nanoparticles of a few nanometers in size through the principle of “dispersion of ordered mesostructures into single nanocomponents”. Self‐assembled siloxane–organic hybrids derived from amphiphilic alkyl‐oligosiloxanes were postsynthetically dispersed in organic solvent to yield uniform nanoparticles consisting of dense lipophilic shells and hydrophilic siloxane cores. In situ encapsulation of fluorescent dyes into the nanoparticles demonstrated their ability to function as nanocarriers. 相似文献
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Moteki T Chaikittisilp W Shimojima A Okubo T 《Journal of the American Chemical Society》2008,130(47):15780-15781
Novel pure silica sodalite with hollow sodalite-cages has been synthesized for the first time by topotactic conversion of layered silicate (RUB-15) precursor. This success has been achieved by stepwise syntheses from silicate monomers, through clusters and layers, to microporous crystals. The pretreatment of layered silicate with small carboxylic acids before conversion is a crucial step. The obtained sodalite possesses accessible micropores, as confirmed by physical adsorption of hydrogen molecules. This plate-like silica sodalite would be very promising as fillers in mixed-matrix membranes for hydrogen separation. 相似文献