弱酸性条件下SBA-16型二氧化硅介孔材料的合成与表征

引言 有序介孔材料由于具有较大的比表面积、均一可调的孔径(2～50 nm)、规则可控的形貌、较高的热稳定性和耐水解性等性能,在分离、吸附、催化、生物材料、信息材料、碳纳米管制备等领域有着广泛应用[1-3].     

介孔二氧化硅KIT-6介观单晶微球的合成

以非离子表面活性剂［聚环氧乙烷（PEO）-聚环氧丙烷（PPO）-聚环氧乙烷三嵌段共聚物,P123］和阳离子聚电解质（聚二甲基二烯丙基氯化铵,PAC）形成的复合物胶束为模板,合成了具有球形形貌的介孔二氧化硅KIT-6介观单晶微球。通过扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、氮气物理吸附和热重分析（TGA）等手段对合成材料的形貌及孔结构进行了表征分析。结果表明,以有机复合物胶束为模板合成出的介孔KIT-6二氧化硅材料具有较规整的球形形貌,颗粒直径为2~3 μm,具有较大的比表面积和孔体积（747 m²/g和1.3 cm³/g）,介孔孔径为8.5 nm,且在整个颗粒内部介孔保持高度的有序排列。由于长链聚电解质PAC与硅源有着较强相互作用,样品可以在较高水热温度下（160 ℃）合成,有利于提升介观结构的稳定性。该合成方法对于介孔二氧化硅KIT-6单晶微球的合成及其在催化及吸附分离等领域的应用具有一定的启发意义。     

Trypsin immobilization on mesoporous silica with or without thiol functionalization

The effects of pore size, structure, and surface functionalization of mesoporous silica on the catalytic activity of the supported enzyme, trypsin, were investigated. For this purpose, SBA-15 with 1-dimensional pore arrangement and cubic Ia3d mesoporous silica with 3-dimensional pores were prepared and tested as a support. Materials with varying pore diameters in the range 5–10 nm were synthesized using a non-ionic block copolymer by controlling the synthesis temperature. Thiol-group was introduced to the porous materials via siloxypropane tethering either by post synthesis grafting or by direct synthesis. These materials were characterized using XRD, SEM, TEM, N₂ adsorption, and elemental analysis. Trypsin-supported on the solids prepared was active and stable for hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). Without applying thiol-functionalization, cubic Ia3d mesoporous silica with ca. 5.4 nm average pore diameter was found to be superior to SBA-15 for trypsin immobilization and showed a better catalytic performance. However, enzyme immobilized on the 5% thiol-functionalized SBA-15 prepared by directly synthesis was found to be the most promising and was also found recyclable.     

Trypsin immobilization on mesoporous silica with or without thiol functionalization

The effects of pore size, structure, and surface functionalization of mesoporous silica on the catalytic activity of the supported enzyme, trypsin, were investigated. For this purpose, SBA-15 with 1-dimensional pore arrangement and cubic Ia3d mesoporous silica with 3-dimensional pores were prepared and tested as a support. Materials with varying pore diameters in the range 5–10 nm were synthesized using a non-ionic block copolymer by controlling the synthesis temperature. Thiol-group was introduced to the porous materials via siloxypropane tethering either by post synthesis grafting or by direct synthesis. These materials were characterized using XRD, SEM, TEM, N₂ adsorption, and elemental analysis. Trypsin-supported on the solids prepared was active and stable for hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). Without applying thiol-functionalization, cubic Ia3d mesoporous silica with ca. 5.4 nm average pore diameter was found to be superior to SBA-15 for trypsin immobilization and showed a better catalytic performance. However, enzyme immobilized on the 5% thiol-functionalized SBA-15 prepared by directly synthesis was found to be the most promising and was also found recyclable.     

共聚物为模板制备草莓状二氧化硅空心球

成功地通过三嵌段共聚物聚乙二醇-聚丙二醇-聚乙二醇(PEG-PPG-PEG)为模板,正辛烷为壳材料来制备介孔外壳的草莓状二氧化硅空心球。其中正硅酸乙酯(TEOS)作为二氧化硅的前驱体。通过改变反应参数,我们发现当将反应最终溶液先室温下静置24h然后加热到较高温度12h可以获得草莓状结构。产物的表面形貌通过扫描电子显微镜(SEM)来分析;透射电子显微镜(TEM)表明空心球的平均直径为800nm,外壳为20nm;多孔性分析通过氮气吸附-解附法来测量,同时用Brunauer-Emmett-Tell-er(BET)的方法来测孔径大小。另外我们提出了二氧化硅的形成机理。     

PICA法合成介孔二氧化硅研究

以硅酸钠为硅源,在酸性条件下,通过尿素和甲醛的缩聚反应,用诱导聚合胶体团聚法(PICA)制备出单分散脲醛/SiO2复合微球,并经高温煅烧制得介孔二氯化硅。通过X射线衍射(XRD)、氮气脱吸附、透射电镜(TEM)和高分辨透射电镜(HRTEM)等手段对介孔二氧化硅进行了表征。结果表明,通过PICA法制得的介孔二氧化硅有序性好,孔径较大、孔壁较厚、孔径分布均匀。     

An organic/inorganic hybrid mesoporous silica membrane: preparation and characterization

An organic/inorganic hybrid mesoporous silica membrane composed of mesoporous silica materials inside the channels of polycarbonate filtration membrane (PC) was synthesized by using aspiration-induced infiltration method, and the surfactant in as-prepared membrane was removed by employing template-extraction method. The obtained materials were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD),transmission electron microscopy (TEM) and N₂ adsorption–desorption measurement. The SEM images and EDS elemental analyses show that as-synthesized materials in PC are one-dimensional silica rods estimated as 200 nm in diameter and 9 μm in length. Moreover, the results of XRD, TEM and N₂ adsorption–desorption analysis clearly demonstrate that such silica rods are mesoporous materials with two-dimensional hexagonal mesostructure and the average mesopore diameter is about 3.0 nm. In addition, the porosity of organic/inorganic hybrid mesoporous silica membrane was further examined by molecule permeation. It is found that small molecule, such as rhodamine B, can transport across the membrane, but relatively large molecule, such as horse radish peroxidase, can not transport across the membrane, indicating that it is size-selectivity of such a membrane for molecule permeation, which has the potential application in the molecule filters to separate bio-macromolecule from small molecule.     

Quantitative Electron Microscopic Investigation of the Pore Structure in 10:90 Colloidal Silica/Potassium Silicate Sol-Gels

Transmission electron microscopy (TEM), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and nitrogen sorption technique (BET) were utilized to characterize the microstructure of a 10:90 wt% colloidal silica/potassium silicate gel as first described by Shoup. Gels in the unsintered state (15% theoretical density) were prepared for microscopy by the techniques of ultramicrotomy, Pt/C replication, and pore casting. Electron microscopic images of the ultramicrotomed thin sections (70 nm) show that the unfired gel possesses three distinct species of pores which are referred to as the micropores, mesopores, and macropores. The average micropore diameter was found to be 4 nm as determined by nitrogen desorption. Quantitative stereological analysis of the ultramicrotomed sections indicated that the average circular and lengthwise dimensions of the cylindrical mesopores were 0.15 and 0.39 μm, respectively. Similarly, this same analysis determined the average spherical macropore diameter to be 0.83 μm. In contrast, MIP results suggested that these gels possessed a unimodal pore size distribution centered around the 0.2-μm pore size. The discrepancy between MIP and microscopy can be explained by viewing the void space as a pore-throat network. Experimental evidence for this type of pore geometry was obtained from stereo pairs of Pt/C replicas and thick microtomed sections (0.5 μm) which gave information about particle connectivity and pore casts which depicted the pore connectivity in three dimensions.     

Preparation and characterization of CuO nanoparticles encapsulated in mesoporous Silica

CuO nanoparticles supported in mesoporous silica MCM-41 (or CuO-nano-MCM-41 nanocomposites) were prepared via an in situ method. A 2.10 wt.% Cu loading was achieved without the loss of pore ordering. Highly dispersed and uniform CuO nanoparticles could be detected using transmission electron microscopy (TEM) confirming also the absence of large particles outside the mesopore silica. The bandgaps of the resulting CuO particles are widened from 1.7 to 3.15 eV for an indirect allowed bandgap and from 3.25 to 4.43 eV for a direct allowed interband transition owing to the quantum size effect.     

Pd/CMK-3的合成及其在Suzuki-Miyaura碳-碳偶联反应中的应用

利用介孔二氧化硅（SBA-15）为模板、蔗糖为碳源,制备了有序介孔碳材料CMK-3,然后以CMK-3为载体,利用浸渍还原法得到介孔碳负载Pd纳米粒子的复合催化剂（Pd/CMK-3）,通过XRD、TEM以及氮气吸附-脱附等手段对催化剂的微结构和组分进行分析,结果表明CMK-3为有序介孔结构,孔径约为5nm,Pd/CMK-3保留了介孔结构,且孔道中负载有不同尺寸的Pd粒子。应用于无配体催化的Suzuki-Miyaura相似文献   

微乳液法制备CdTe纳米颗粒的表征

CdTe纳米晶作为一种重要的Ⅱ-Ⅵ族半导体材料,在LEDs、光子学材料和生物标记等方面已被应用。本实验利用CTAB／环己烷／异丁醇／水作为反应介质,氮气保护下在微乳液体系中制备了CdTe纳米颗粒。利用X射线衍射（XRD）、透射电子显微镜（TEM）、扫描电子电镜（SEM）表征了CdTe纳米颗粒的形貌和粒径尺寸,研究水与表面活性剂摩尔比以及陈化时间对CdTe纳米颗粒的影响,结果表明当水与表面活性剂摩尔比为40,陈化时间为24h时制备出了产量高,稳定性好的直径为40-50nm的CdTe纳米颗粒。     

Preparation of structured meso–macroporous silica materials: influence of composition variables on material characteristics

Meso–macroporous silica materials with a well-ordered array of mesopores were prepared from oil-in-water emulsions. The influence of the following three composition variables on material characteristics was studied: the dispersed phase fraction of the emulsion, the concentration of silica used and the concentration of surfactant. The obtained materials were characterized via small-angle X-ray diffraction scattering, scanning electron microscopy, transmission electron microscopy, Hg intrusion porosimetry and nitrogen adsorption–desorption isotherms. A network of structured mesopores was obtained even when using a highly concentrated emulsion (volume of the disperse phase, ? ≥ 0.75). The mesopores network presented a hexagonal arrangement, with mesopore diameters between 4 and 7 nm. Non-ordered macropores, with diameters between 50 nm and 10–15 μm were also present, depending on composition variables. The isotherms were of type IV, typical of mesoporous materials, but at high p/p₀ they were the usual shape for the macroporous materials. The possibility of tailoring mesopore and macropore structures by altering in composition variables could extend the application of these materials.     

Novel Two-Step Synthesis of Controlled Size and Shape Platinum Nanoparticles Encapsulated in Mesoporous Silica

Uniform shape and size platinum nanoparticles encapsulated in mesoporous silica (SBA-15) were prepared in the same solution by a novel two-step method. Platinum nanoparticles were prepared in aqueous solution of K₂PtCl₄, the reduction was carried out by bubbling hydrogen, the capping material was tri-block poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer. The mesoporous silica was synthesized using the same copolymer as template from tetraethyl orthosilicate by hydrolysis in acidic conditions. The Pt-nanoparticles-in-mesoporous-silica system was characterized by a combination of low-angle powder X-ray diffraction, transmission electron microscopy and N₂ porosimetry. The platinum nanoparticles are encapsulated in the mesopores and retained their size and morphology. It appears that this hybrid material should be a superior three-dimensional high-surface-area catalyst for selective platinum-catalyzed reactions.     

Controlling the textural parameters of mesoporous carbon materials

The mesoporous carbon materials prepared by inorganic templating technique using mesoporous silica, SBA-15 as a template and sucrose as a carbon source, have been systematically investigated as a function of sucrose to mesoporous silica composition, with a special focus on controlling the mesoporous structure, surface morphology and the textural parameters such as specific surface area, specific pore volume and pore size distribution. All the materials have been unambiguously characterized by XRD, N₂ adsorption–desorption isotherms, high-resolution transmission electron microscopy, high-resolution field emission scanning electron microscopy, and Raman spectroscopy. It has been found that the porous structure, morphology and the textural parameters of the mesoporous carbons materials, CMK-3-x where x represent the sucrose to silica weight ratio, can be easily controlled by the simple adjustment of concentration of sucrose molecules. It has also been found that the specific surface area of the mesoporous carbon materials systematically increases with decreasing the sucrose to silica weight ratio. Moreover, the specific pore volume of the materials increases from 0.57 to 1.31 cm³/g with decreasing the sucrose to silica weight ratio from 5 to 1.25 and then decreases to 1.23 cm³/g for CMK-3-0.8. HRTEM and HR-FESEM also show a highly ordered pore structure and better surface morphology for CMK-3-1.25 as compared to other materials prepared in this study. Thus, it can be concluded that the sucrose to silica weight ratio of 1.25 is the best condition to prepare well ordered mesoporous carbon materials with good textural parameters, pore structure and narrow pore size distribution.     

Mesoporous silica–magnetite nanocomposites: Fabrication, characterisation and applications in biosciences

Template assisted fabrication of magnetic mesoporous silica–magnetite nanocomposites and their performance in binding and elution of Salmon sperm DNA has been reported. The effect of reaction pH (10–2) during the fabrication of nanocomposites has been studied. All materials fabricated at various pH were characterised by XRD, TEM, FT-IR, nitrogen adsorption and magnetic susceptibility measurements. Fabrication at neutral pH (7) in the presence of a cationic surfactant (cetyl trimethyl ammonium bromide; CTAB) produced core–shell nanocomposites of quasi spherical and rod shaped morphologies with mesoporous (pore size 3.5 nm) silica shell and rhombic magnetite core. Fabrication at alkaline pH (10) produced monolithic mesoporous silica composites with embedded magnetite nanoparticles. Fabrication at acidic pH (4 and 2) produced a biphasic mixture of rhombic magnetite and amorphous silica rods. A similar fabrication at acidic pH (2) in the absence of CTAB produced a biphasic mixture of rhombic magnetite and spherical silica nanoparticles. All materials exhibited a high value of Salmon sperm DNA binding at physiological pH whereas elution value of DNA was observed to be dependent on the extent of silica coating on magnetite nanoparticles.     

Polyurethaneurea–silica nanocomposites: Preparation and investigation of the structure–property behavior

Nanocomposites consisting of thermoplastic polyurethane–urea (TPU) and silica nanoparticles of various size and filler loadings were prepared by solution blending and extensively characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermal analysis, tensile tests, and nanoindentation. TPU copolymer was based on a cycloaliphatic diisocyanate and poly(tetramethylene oxide) (PTMO-2000) soft segments and had urea hard segment content of 20% by weight. TPU/silica nanocomposites using silica particles of different size (29, 74 and 215 nm) and at different loadings (1, 5, 10, 20 and 40 wt. %) were prepared and characterized. Solution blending using isopropyl alcohol resulted in even distribution of silica nanoparticles in the polyurethane–urea matrix. FTIR spectroscopy indicated strong interactions between silica particles and polyether segments. Incorporation of silica nanoparticles of smaller size led to higher modulus and tensile strength of the nanocomposites, and elastomeric properties were retained. Increased filler content of up to about 20 wt. % resulted in materials with higher elastic moduli and tensile strength while the glass transition temperature remained the same. The fracture toughness increased relative to neat TPU regardless of the silica particle size. Improvements in tensile properties of the nanocomposites, particularly at intermediate silica loading levels and smaller particle size, are attributed to the interactions between the surface of silica nanoparticles and ether linkages of the polyether segments of the copolymers.     

介孔SiO2薄膜的制备与表征

采用浸涂法,以载玻片为基底,十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,丙三醇为成膜干燥控制剂,制备出有序的介孔SiO2薄膜.利用X射线衍射仪(XRD)、红外光谱(IR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对其结构进行表征.XRD测试结果表明,合成的薄膜具有MCM-41介孔结...     

Synthesis of mesoporous silica with cationic-anionic surfactants

Ordered mesoporous silica was successfully synthesized by using mixed surfactants, cetyltrimethylammonium bromide and sodium dodecylsulfate, proceeded with the hydrolysis and condensation of tetraethyl orthosilicate in a mixture of TritonX-100 as a cosolvent. The synthesized products were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen sorption analysis. It was found with increasing the anionic surfactant sodium dodecylsulfate to cetyltrimethylammonium bromide molar ratio, the morphologies of mesoporous silica changed from spherical shape to ellipsoidal shape, at last became rod-like and lamellar shape. Correspondingly the pore diameter and surface area of mesoporous silica all decreased according to nitrogen sorption analysis. The TEM analysis illustrated the product with ordered hexagon mesostructure and homogeneous pore arranged can be obtained, when the molar ratio of cetyltrimethylammonium bromide/sodium dodecylsulfate is 15: 1. It also demonstrated the less the molar ratio of sodium dodecylsulfate was used, the more ordered pore structure the products exhibited. Furthermore, prolonging the crystal time was beneficial to improve the stability of the product.     

CTAB assisted microwave synthesis of ordered mesoporous carbon supported Pt nanoparticles for hydrogen electro-oxidation

Mesoporous carbon with ordered hexagonal structure derived from the co-assembly of triblock copolymer F127 and resol was employed as the carbon support of Pt catalysts for hydrogen electro-oxidation. Structural characterizations revealed that the mesoporous carbon exhibited large surface area and uniform mesopores. The Pt nanoparticles supported on the novel mesoporous carbon were fabricated by a facile CTAB assisted microwave synthesis process, wherein CTAB was expected to improve the wettability of carbon support as well as the dispersion of Pt nanoparticles. X-ray diffraction and transmission electron microscopy were applied to characterize the Pt catalysts. It was found that the Pt nanoparticles were uniform in size and highly dispersed on the mesoporous carbon supports. The cyclic voltammograms in sulfuric acid demonstrated that the electrochemical active surface area of Pt catalysts prepared with CTAB was two times than that without CTAB.     

Nano Composite from Coal Modified Novolac Resin

Coal-modified novolac/clay nanocomposites were synthesized using clay as reinforcing materials. It was found that coal-modified novolac resin based silica nano-composites showed improved tensile strength compared to that of neat novolac resin. The structure of the nanocomposites was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Scanning electron microscopy (SEM) studies have also been undertaken to see the morphology of the nanocomposites prepared. The results obtained are being reported.