共查询到20条相似文献,搜索用时 31 毫秒
1.
Dr. Thanh‐Dinh Nguyen Dr. Kevin E. Shopsowitz Prof. Dr. Mark J. MacLachlan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15148-15154
Liquid crystalline phases can be used to impart order into inorganic solids, creating materials that mimic natural architectures. Herein, mesoporous silica and organosilica films with layered structures and high surface areas have been templated by nanocrystalline chitin. Aqueous suspensions of spindle‐shaped chitin nanocrystals were prepared by sequential deacetylation and hydrolysis of chitin fibrils isolated from king crab shells. The nanocrystalline chitin self‐assembles into a nematic liquid‐crystalline phase that has been used to template silica and organosilica composites. Removal of the chitin template by either calcination or sulfuric‐acid‐catalyzed hydrolysis gave mesoporous silica and ethylene‐bridged organosilica films. The large, crack‐free mesoporous films have layered structures with features that originate from the nematic organization of the nanocrystalline chitin. 相似文献
2.
Dr. Michael Giese Dr. Lina K. Blusch Dr. Mostofa K. Khan Dr. Wadood Y. Hamad Prof. Mark J. MacLachlan 《Angewandte Chemie (International ed. in English)》2014,53(34):8880-8884
Cellulose‐based materials have been and continue to be exceptionally important for humankind. Considering the bioavailability and societal relevance of cellulose, turning this renewable resource into an active material is a vital step towards sustainability. Herein we report a new form of cellulose‐derived material that combines tunable photonic properties with a unique mesoporous structure resulting from a new supramolecular cotemplating method. A composite of cellulose nanocrystals and a urea–formaldehyde resin organizes into a chiral nematic assembly, which yields a chiral nematic mesoporous continuum of desulfated cellulose nanocrystals after alkaline treatment. The mesoporous photonic cellulose (MPC) films undergo rapid and reversible changes in color upon swelling, and can be used for pressure sensing. These new active mesoporous cellulosic materials have potential applications in biosensing, optics, functional membranes, chiral separation, and tissue engineering. 相似文献
3.
A novel chiral mesoporous organosilica with L ‐tartardiamide moieties integrated in the backbone has been synthesized for the first time by a mild synthetic approach with block copolymer P123 as a template. The materials have highly ordered 2D hexagonal mesostructure and uniform pore size in the range of 7.6 to 5.5 nm. NMR, IR, and TG analyses confirm that the tartardiamide group was successfully incorporated into the framework. The intrinsic chirality of L ‐tartardiamide endows the materials with unique optical activities and chiral‐recognition properties. By dissolving the materials into NaOH, the solutions show rotation of polarized light by +8.42° to +15.53°, depending on the amount of the chiral moieties in the materials. Owing to the chirality of L ‐tartardiamide, the materials exhibited chiral‐induction ability in the epoxidation of allyl alcohol, thus further demonstrating the chirality of the materials. 相似文献
4.
Ling Gao Feng Wei Yu Zhou Xiao Xing Fan Ying Wang Prof. Dr. Jian Hua Zhu Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(33):8310-8318
A new series of carbamothioic acid‐containing periodic mesoporous organosilica (PMO) materials has been synthesized by a direct cocondensation method, in which an organosilica precursor N,S‐bis[3‐(triethoxysilyl)propyl]carbamothioic acid (MI) is treated with tetraethyl orthosilicate (TEOS), and the nonionic surfactant Pluronic 123 (P123) is used as a template under acidic conditions in the presence of inorganic additives. Moreover, the synthesis of the PMO material consisting of the MI precursor without TEOS has been realized. These novel PMO materials have large surface areas, well‐ordered mesoporous structures, hollow fiberlike morphologies, and thick walls. They are also structurally well‐ordered with a high organosilica precursor content, and the carbamothioic acid groups are thermally stable up to 250 °C. Furthermore, the organosilica materials exhibit hydrothermal stability in basic solution. 相似文献
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6.
Shopsowitz KE Stahl A Hamad WY MacLachlan MJ 《Angewandte Chemie (International ed. in English)》2012,51(28):6886-6890
Anatase TiO(2) nanocrystals have been organized into high-surface-area (150-230 m(2) g(-1)) mesoporous films with long-range chiral nematic ordering. The chiral structure of the anatase films causes them to selectively reflect circularly polarized light and appear iridescent. These materials show replication of structural features found in the silica template on nanometer to millimeter length scales. 相似文献
7.
Morell J Chatterjee S Klar PJ Mauder D Shenderovich I Hoffmann F Fröba M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(19):5935-5940
The first synthesis of a chiral periodic mesoporous organosilica (PMO) carrying benzylic ether bridging groups is reported. By hydrolysis and condensation of the new designed chiral organosilica precursor 1,4-bis(triethoxysilyl)-2-(1-methoxyethyl)benzene (BTEMEB) in the presence of the non-ionic oligomeric surfactant Brij 76 as supramolecular structure-directing agent under acidic conditions, an ordered mesoporous chiral benzylic ether-bridged hybrid material with a high specific surface area was obtained. The chiral PMO precursor was synthesized in a four-step reaction from 1,4-dibromobenzene as the starting compound. The evidence for the presence of the chiral units in the organosilica precursor as well as inside the PMO material is provided by optical activity measurements. 相似文献
8.
Pt µdisc electrodes have been modified by mesoporous organosilica thin films by electrochemically assisted self‐assembly (EASA) of mercaptopropyltrimethoxysilane (MPTMS), tetraethoxysilane (TEOS), and the surfactant cetyltrimethylammonium bromide (CTAB). The EASA process involves the generation of hydroxide ions at the electrode/solution interface, upon the application of a cathodic current density, leading to TEOS and MPTMS polycondensation around the CTAB template and concomitant growing of a thiol‐functionalized mesoporous film onto the electrode surface. The experimental conditions (current density, deposition time, silane concentration and molar ratio between surfactant template and silane) were optimised to form a thin and permeable film likely to be used in preconcentration electroanalysis. The morphology of the film electrodes were characterised by scanning electron microscopy. The permeability properties of the modified Pt µdisc electrodes have been evidenced by cyclic voltammetry using Ru(NH3)63+ as a redox probe. The best parameters identified for the film preparation are a current density of ? 8 mA cm?2 applied for 15 s in a solution containing 110 mM of hydrolysed silane precursors and 70.4 mM of CTAB. Pt µdisc electrodes modified in these conditions were used for the open‐circuit preconcentration of Hg(II) species prior to their detection by anodic stripping voltammetry in a mercury‐free solution. In the optimized conditions, a sensitivity of 14.3 mA cm?2 µM?1 was obtained for the 0.02–0.08 µM concentration range. The analytical performance of such organosilica films could decay by up to two orders of magnitude for the materials prepared in conditions other than the optimized ones, highlighting the need for a fine control of the deposition parameters to elaborate sensors based on such modified ultramicroelectrodes. 相似文献
9.
Norihiro Mizoshita Dr. Yasutomo Goto Dr. Mahendra P. Kapoor Dr. Toyoshi Shimada Prof. Dr. Takao Tani Dr. Shinji Inagaki Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(1):219-226
We report that 2,6‐naphthylene‐bridged periodic mesoporous organosilicas exhibit unique fluorescence behavior that reflects molecular‐scale periodicities in the framework. Periodic mesoporous organosilicas consisting of naphthalene–silica hybrid frameworks were synthesized by hydrolysis and condensation of a naphthalene‐derived organosilane precursor in the presence of a template surfactant. The morphologies and meso‐ and molecular‐scale periodicities of the organosilica materials strongly depend on the synthetic conditions. The naphthalene moieties embedded within the molecularly ordered framework exhibited a monomer‐band emission, whereas those embedded within the amorphous framework showed a broad emission attributed to an excimer band. These results suggest that the naphthalene moieties fixed within the crystal‐like framework are isolated in spite of their densely packed structure, different from conventional organosilica frameworks in which only excimer emission was observed for both the crystal‐like and amorphous frameworks at room temperature. This key finding suggests a potential to control interactions between organic groups and thus the optical properties of inorganic/organic hybrids. 相似文献
10.
苯官能化MCM-41的合成、表征、磺酰化及与二胺的反应 总被引:3,自引:0,他引:3
以三乙氧基硅基苯((C2H5O)3Si-Ph,((triethoxysilyl)benzene,TESB)以及正硅酸乙酯(TEOS)的混合液为硅源,以溴代十六烷基吡啶(CPBr)为模板剂,在HCl介质中合成了苯官能化的有机-无机杂化介孔分子筛MCM-41。对合成的分子筛用FT-IR、PXRD、TEM、N2吸附-脱附等手段进行了表征。结果表明,合成的苯官能化的有机-无机杂化介孔分子筛具有良好的介孔孔道结构。用三甲基氯硅烷对分子筛表面的Si-OH进行了封端处理,用氯磺酸对合成的苯官能化的有机-无机杂化介孔分子筛进行了磺酰化,并与各种二胺进行了反应。 相似文献
11.
Dr. Rui Liu Dr. Ronghua Jin Dr. Lingyu Kong Dr. Jinyu Wang Dr. Chen Chen Dr. Tanyu Cheng Prof. Guohua Liu 《化学:亚洲杂志》2013,8(12):3108-3115
Three organosilica‐bridged periodic mesoporous organosilicas were prepared by the immobilization of a chiral N‐sulfonylated diamine‐based organorhodium complex within their silicate network. Structural analysis and characterization confirmed their well‐defined single‐site active rhodium centers, whilst electron microscopy revealed their highly ordered hexagonal mesostructures. Among these three different organosilica‐bridged periodic mesoporous organosilicas, the ethylene‐bridged periodic mesoporous organosilica catalyst exhibited excellent heterogeneous catalytic activity and high enantioselectivity in the aqueous asymmetric transfer hydrogenation of aromatic ketones. This superior catalytic performance was attributed to its salient hydrophobicity, whilst its comparable enantioselectivity relative to the homogeneous catalyst was derived from the confined nature of the chiral organorhodium catalytic sites. Furthermore, this ethylene‐bridged periodic mesoporous organosilica could be conveniently recovered and reused at least 12 times without the loss of its catalytic activity. This feature makes this catalyst attractive for practical organic synthesis in an environmentally friendly manner. This study offers a general way of optimizing the bridged organosilica moiety in periodic mesoporous organosilicas, thereby enhancing its catalytic activity in heterogeneous catalysis. 相似文献
12.
Mondal J Modak A Dutta A Bhaumik A 《Dalton transactions (Cambridge, England : 2003)》2011,40(19):5228-5235
A new functionalized mesoporous organosilica has been designed via Schiff-base condensation of furfural and 3-aminopropyltriethoxy-silane (APTES) followed by its hydrothermal co-condensation with tetraethylorthosilicate (TEOS) in the presence of a cationic surfactant CTAB. Subsequent reaction of this mesoporous organosilica with Cu(OAc)(2) in absolute ethanol leads to the formation of a new Cu(II)-grafted mesoporous organosilica catalyst 1. Powder XRD, HR TEM, FE SEM, N(2) sorption and FT IR spectroscopic tools are used to characterize the materials. This Cu-anchored mesoporous material acts as an efficient, reusable catalyst in the aryl-sulfur coupling reaction between aryl iodide and thiophenol for the synthesis of value added diarylsulfides. 相似文献
13.
We report the synthesis and characterization of crystal-like structurally well-ordered ethylene-containing hybrid mesoporous organoaluminosilicate materials, which exhibit molecular-level periodicity in the pore walls and enhanced hydrothermal stability. Distilled 1,2-bis(triethoxysilyl)ethylene (BTEE) was used as the organosilica precursor, aluminum isopropoxide as aluminum source, and cetyltrimethylammonium bromide as template. The materials are structurally well-ordered and exhibit high surface area (>1300 m(2)/g) and pore volume (>1.10 cm(3)/g). The presence of molecularly ordered ethylene groups was confirmed by powder X-ray diffraction, (29)Si and (13)C MAS NMR, and Raman spectroscopy. The ethylene groups are thermally stable up to a temperature of 300 degrees C. The presence of ethylene groups enhances the hydrothermal stability in boiling water of both organosilica and organoaluminosilicate materials. The organoaluminosilicate materials possess a bifunctional character arising from the presence of both tetrahedrally coordinated Al and molecularly ordered ethylene groups in their frameworks. 相似文献
14.
Baleizão C Gigante B Das D Alvaro M Garcia H Corma A 《Chemical communications (Cambridge, England)》2003,(15):1860-1861
A chiral vanadyl salen complex having two peripheral trimethoxysilyl groups has been used to obtain a chiral periodic mesoporous organosilica having MCM-41 periodicity and the two Si-CH2 groups anchored on the framework; this solid induces 30% enantioselectivity in the cyanosilylation of benzaldehyde. 相似文献
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16.
Dr. Mostofa K. Khan Anas Bsoul Prof. Konrad Walus Dr. Wadood Y. Hamad Prof. Mark J. MacLachlan 《Angewandte Chemie (International ed. in English)》2015,54(14):4304-4308
Chiral nematic mesoporous phenol‐formaldehyde resins, which were prepared using cellulose nanocrystals as a template, can be used as a substrate to produce latent photonic images. These resins undergo swelling, which changes their reflected color. By writing on the films with chemical inks, the density of methylol groups in the resin changes, subsequently affecting their degree of swelling and, consequently, their color. Writing on the films gives latent images that are revealed only upon swelling of the films. Using inkjet printing, it is possible to make higher resolution photonic patterns both as text and images that can be visualized by swelling and erased by drying. This novel approach to printing photonic patterns in resin films may be applied to anti‐counterfeit tags, signage, and decorative applications. 相似文献
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18.
Qi Wei Li Liu Zuo-Ren Nie Hui-Qiao Chen Jing-Xia Zou 《Journal of Sol-Gel Science and Technology》2007,44(2):105-110
Fluorocarbon groups were used to modify the pore channels of ethane-bridged periodic mesoporous organosilica by the co-condensation
of 1,2-Bis(triethoxysilyl)ethane (BTESE) and trifluoropropyltrimethoxysilane (TFPTMS) in the presence of Poly(ethylene glycol)-B-Poly(propylene
glycol)-B-Poly(ethylene glycol) (P123) surfactants under acidic conditions. The functionalized materials were investigated
in detail by means of XRD, TEM, FT-IR, solid-state NMR, and N2 adsorption. The effect of fluorocarbon groups concentration on the mesoscopic order and pore structure of the functionalized
materials was also studied. The results show that bridging groups in the framework do not cleave and fluorocarbon groups are
attached covalently to the pore wall of periodic mesoporous organosilica after functionalization. The samples functionalized
with 20% TFPTMS remain desired mesoporous architecture, with a narrow pore size distribution centered at 4.1 nm, a large surface
of 834 m2/g and a pore volume of 0.91 cm3g−1, without pronounced change compared to the pure periodic mesoporous organosilica. Unfortunately the functionalized materials
become structurally disordered with increasing amount of fluorocarbon groups. 相似文献
19.
Lee B Im HJ Luo H Hagaman EW Dai S 《Langmuir : the ACS journal of surfaces and colloids》2005,21(12):5372-5376
A new methodology to immobilize ionic liquids through the use of a bridged silsesquioxane N-(3-triethoxysilylpropyl), N(3)-(3-trimethoxysilylpropyl-4,5-dihydroimidazolium iodide that incorporates an ionic functionality for the assembly of novel periodic mesoporous organosilica (PMO) materials has been developed. The resulting PMO materials were investigated for use as novel anion exchange resins for the separation of perrhenate anions in aqueous solution. As compared with cetyltrimethylammonium chloride, 1-hexadecane-3-methylimidazolium bromide has been demonstrated to be a more efficient surfactant template for the generation of mesopores and surface areas for such PMO materials. 相似文献
20.
Guo Y Mylonakis A Zhang Z Yang G Lelkes PI Che S Lu Q Wei Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(9):2909-2917
The synthesis and characterization of novel electroactive periodic mesoporous organosilica (PMO) are reported. The silsesquioxane precursor, N,N'-bis(4'-(3-triethoxysilylpropylureido)phenyl)-1,4-quinonene-diimine (TSUPQD), was prepared from the emeraldine base of amino-capped aniline trimer (EBAT) using a one-step coupling reaction and was used as an organic silicon source in the co-condensation with tetraethyl orthosilicate (TEOS) in proper ratios. By means of a hydrothermal sol-gel approach with the cationic surfactant cetyltrimethyl-ammonium bromide (CTAB) as the structure-directing template and acetone as the co-solvent for the dissolution of TSUPQD, a series of novel MCM-41 type siliceous materials (TSU-PMOs) were successfully prepared under mild alkaline conditions. The resultant mesoporous organosilica were characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry, X-ray diffraction, nitrogen sorption, and transmission electron microscopy (TEM) and showed that this series of TSU-PMOs exhibited hexagonally patterned mesostructures with pore diameters of 2.1-2.8 nm. Although the structural regularity and pore parameters gradually deteriorated with increasing loading of organic bridges, the electrochemical behavior of TSU-PMOs monitored by cyclic voltammetry demonstrated greater electroactivities for samples with higher concentration of the incorporated TSU units. 相似文献