Microwave-induced synthesis of highly dispersed gold nanoparticles within the pore channels of mesoporous silica

Highly dispersed gold nanoparticles have been incorporated into the pore channels of SBA-15 mesoporous silica through a newly developed strategy assisted by microwave radiation (MR). The sizes of gold are effectively controlled attributed to the rapid and homogeneous nucleation, simultaneous propagation and termination of gold precursor by MR. Diol moieties with high dielectric and dielectric loss constants, and hence a high microwave activation, were firstly introduced to the pore channels of SBA-15 by a simple addition reaction between amino group and glycidiol and subsequently served as the reduction centers for gold nanoparticles. Extraction of the entrapped gold from the nanocomposite resulted in milligram quantities of gold nanoparticles with low dispersity. The successful assembly process of diol groups and formation of gold nanoparticles were monitored and tracked by solid-state NMR and UV-vis measurements. Characterization by small angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the incorporation of gold nanoparticles would not breakup the structural integrity and long-range periodicity of SBA-15. The gold nanoparticles had a narrow size distribution with diameters in the size range of 5-10 nm through TEM observation. The average particles size is 7.9 nm via calculation by the Scherrer formula and TEM measurements. Nitrogen adsorption and desorption isotherms gave further evidence that the employed method was efficient and gold nanoparticles were successfully incorporated into the pore channels of SBA-15.     

Synthesis of novel mesoporous silica spheres with starburst pore canal structure

Novel spherical mesoporous silica materials with uniform diameters and starburst mesopore structures were synthesized by a simple one-step procedure with ethanol as the co-solvent in dilute aqueous solution and their formation mechanism was proposed. The arrangement of the pore canal and the diameter of the sphere could be tailored by altering the concentration of ethanol.     

功能化含钨介孔硅材料的直接合成表征及其在多相氧化脱硫中的应用

温和条件下,燃油深度脱硫一直是非常重要的研究课题.目前,加氢脱硫(HDS)是石油工业上广泛采用的脱硫技术,它能够有效脱除燃油中的硫醚、硫醇和等无机硫化物,但对于芳香族硫化物(如二苯并噻吩、4,6-二甲基二苯并噻吩等),则效果较差.对于上述有机硫化物的深度脱除,现有的加氢脱硫技术需要更为苛刻的反应条件,如高温、高压、高活性贵金属催化剂等,这势必导致燃油成本的大幅上升.因此,世界各国科学家都加强了高效非加氢脱硫方法的研究,主要包括氧化脱硫法、吸附脱硫法、萃取脱硫法和生物脱硫法等,其中氧化脱硫法是一种公认的具有应用前景的高效脱硫技术,该技术只需在常温常压下进行,可将含硫化合物氧化成其相应的砜类物质后,再用溶剂萃取法或吸附法除去.氧化脱硫反应中所涉及氧化剂有过氧化氢、有机过氧化物和氧气等.在这些氧化剂中,过氧化氢由于其活性高,在氧化反应后的副产物只有水,而被广泛研究.
　　离子液体作为一种低温熔融盐,因其独特的理化性质,如无蒸气压、低毒性、良好的溶解性以及结构可调等,受到了广泛的关注.其中,功能化多酸基离子液体不仅具备离子液体的特点,还具备多金属氧酸盐的优势,已被用于燃油的均相氧化脱硫过程中.但是,此过程中离子液体往往用量较大,催化剂难于回收和循环利用,氧化剂用量较大,阻碍其在工业中的应用.为了克服上述缺点,本课题组以多酸基离子液体[C16mim]3PW12O40和正硅酸四乙酯为原料通过溶胶-凝胶法直接合成了一系列含钨功能化介孔复合材料 W-SiO2,其中咪唑型阳离子作为介孔模板剂,而多酸阴离子作为金属源.采用 XRD, IR, Raman, BET, DRS, TEM等测试手段对所合成的材料进行了表征.结果表明,钨活性物种是以氧化钨的形式存在,并且能够均匀地分散在载体二氧化硅上,所合成的材料比表面积为513–743 m2/g,孔体积为0.37–0.50 cm3/g,孔径为2.91–3.20 nm.将所合成的材料 W-SiO2-20应用于燃油氧化脱硫反应(过程中无需有机溶剂),结果表明,所合成的复合材料既能作为吸附剂来吸附有机硫化物,又能作为催化剂来活化过氧化氢以氧化有机硫化物.在最优条件(反应温度60oC, O/S摩尔比为2.5,反应时间40 min)下,二苯并噻吩脱除率可100%,而且反应体系易于循环使用,7次循环后脱硫率无明显降低.此外,还考察了复合材料在相同条件下对于不同硫化物的脱除效果,结果表明,反应活性顺序为4,6-DMDBT＞ DBT＞ BT＞ DT.     

Preparation and characterization of helical carbon/silica nanofibers with lamellar mesopores on the surfaces

Helical 1,2-ethylene-silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like mesopores inside were prepared according to literature procedures. After carbonization, helical carbon/ silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were obtained. The morphologies and pore architectures of the carbon]silica nanofibers were characterized using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction and N2 sorptions. Although the mesopores inside shrank into micropores, the helical nanostructure remained. Moreover, several carbon/silica nanofibers with lamellar mesopores on the surfaces and concentric circular micropores inside were also obtained. After being calcined in air, helical silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were produced as well.     

Enzyme-functionalized mesoporous silica for bioanalytical applications

The unique properties of mesoporous silica materials (MPs) have attracted substantial interest for use as enzyme-immobilization matrices. These features include high surface area, chemical, thermal, and mechanical stability, highly uniform pore distribution and tunable pore size, high adsorption capacity, and an ordered porous network for free diffusion of substrates and reaction products. Research demonstrated that enzymes encapsulated or entrapped in MPs retain their biocatalytic activity and are more stable than enzymes in solution. This review discusses recent advances in the study and use of mesoporous silica for enzyme immobilization and application in biosensor technology. Different types of MPs, their morphological and structural characteristics, and strategies used for their functionalization with enzymes are discussed. Finally, prospective and potential benefits of these materials for bioanalytical applications and biosensor technology are also presented. Figure Enzyme-functionalized mesoporous silica fibers and their integration in a biosensor design. The immobilization process takes place essentially in the silica micropores.     

Luminophore-immobilized mesoporous silica for selective Hg sensing

Novel mesoporous silica-immobilized rhodamine (MSIR) and silica particle-immobilized rhodamine (SPIR) anchored by a tren (N(CH₂CH₂NH₂)₃) were synthesized. The binding and adsorption abilities of both MSIR and SPIR for metal cations were investigated with fluorophotometry and ion chromatography, respectively. Both MSIR and SPIR show selectivity for Hg²⁺ ion over other metal cations because the Hg²⁺ ion selectively induces a ring opening of the rhodamine fluorophores. The sensitivity of the MSIR for Hg²⁺ ion is greater than that of the SPIR and the MSIR adsorbs 70% of Hg²⁺ ion while the SPIR does only 40%. The MSIR can be also easily recovered by treatment of a solution of TBA⁺OH⁻. For the application of Hg²⁺ detection in the environmental field, the MSIR-coated glass plate is also developed and exhibits an excellent function in visual and fluorescence changes with Hg²⁺ ion.     

Aminopyrene functionalized mesoporous silica for the selective determination of resorcinol

Aminopyrene was convalently anchored onto the surface of mesoporous MCM-41 silica by post-grafting. This organic-inorganic hybrid has been applied as sensing material to phenols determination. Experimental results reveal that the functionalized material presents good sensitivity and selectivity towards resorcinol and can be used for resorcinol determination in water at pH 6.0. The fluorescence intensity of aminopyrene functionalized mesoporous silica decreases proportionally to the logarithm of resorcinol concentration in water. The linear range for resorcinol detection lies in 4.79-163 μM with a detection limit of 2.86 μM (S/N = 3).     

Evaluation of microstructures and properties of bulk mesoporous silica

Synthesis of mesoporous MCM-type bulks prepared by hydrothermal hot-pressing (HHP) method using MCM-type mesoporous powder was attempted. Scanning electron microscopy (SEM), bulk density measurement, N₂ adsorption-desorption isotherms and formaldehyde adsorption test have been employed to characterize the bulky products. As a result, we succeeded in preparing a dense and strong mesoporous bulks with high BET over 1000 m²/g through the hydrothermal hot-pressing method under appropriate conditions.     

Sequestration of CO2 using Cu nanoparticles supported on spherical and rod-shape mesoporous silica

The CO₂ sequestration is one of the most promising solutions to tackle global warming. In this study, spherical mesoporous silica particles (MPS-S) and rod-shaped mesoporous silica particles (MPS-R) loaded with Cu nanoparticles were selectively prepared and employed for CO₂ adsorption. For the first time uniform Cu nanoparticles were incorporated into the rod-shaped mesoporous silica particles by post-synthesis modification using both N-[3-(trimethoxysilyl)propyl]ethylenediamine (PEDA) and ethylenediamine (EDA) as coupling agents. The physiochemical properties of the mesoporous and copper grifted silica composites were investigated by CHN elemental analysis, FTIR spectroscopy, thermogravimetric analysis, X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), surface area analysis, scanning, transmission electron microscopy and gas analysis system (GSD 320, TERMO). The mesoporous silica shows highly ordered mesoporous structures, with the rod-shaped particles having a higher surface area than the spherical ones. Copper nanoparticles with an average diameter of 6.0 nm were uniformly incorporated into the MPS-S and MPS-R. Moreover, Cu-loaded mesoporous silica exhibits up to 40% higher CO₂ adsorption capacity than the bare MPS. The MPS-R modified with Cu nanoparticles showed a maximum CO₂ adsorption capacity of 0.62 mmol/g and the humidity showed a slight negative effect on CO₂ uptake process. The enhancement of CO₂ adsorption onto transition metal/mesoporous substrates provides basis for imminent CO₂ sequestration.     

Synthesis of anionic gemini surfactant-templated mesoporous silica nanoparticles and its adsorption application for Pb2+

Abstract

Amino-functionalized mesoporous silica nanoparticles (AFMSN) were prepared based on the self-assembly process of the pre-fabricated template of anionic gemini surfactant. The perfect mass ration of the reactants for the synthesis of the AFMSN with high surface area and amino loading was optimized by orthogonal experiments. Adsorption capability of the optimized product for lead ion (Pb²⁺) was investigated in detail. Specially, the effects of the amino content, solution pH, adsorbent dosage, temperature, and interference of other metal ions on the removal efficiency of Pb²⁺ were studied. It is found that these factors can greatly affect the removal efficiency of Pb²⁺ and the prepared adsorbent exhibits the high adsorption selectivity for Pb²⁺. At an optimal condition, the AFMSN adsorbent presents an excellent adsorption capacity for Pb²⁺ up to 211.42?mg/g. The adsorption kinetics study revealed that the pseudo-second-order model could well describe the Pb²⁺ adsorption process, and the adsorption isotherm was fitted well with the Langmuir model. More importantly, the AFMSN adsorbent could be recycled 8 times and a high adsorption efficiency of Pb²⁺ could still be maintained. Therefore, the prepared AFMSN adsorbent may find practical application in removing Pb²⁺ from the polluted water.     

Synthesis of mesoporous silica materials with ascorbic acid as template via sol-gel process

Mesoporous silica materials with pore diameters of 2-5 nm have been prepared using ascorbic acid as a nonsurfactant template or pore-forming agent in HCl-catalyzed sol-gel reactions of tetraethylorthosilicate,followed by removing the ascorbic acid compound by extraction with ethanol.Characterization results from nitrogen sorption isotherm,powder X-ray diffraction and transmission electron microscopy indicate that the materials have large specific surface areas (e.g.1000 m2/g) and pore volumes (e.g.0.8 cm3/g).The rnesoporosity is arisen from interconnecting disordered wormlike channels and pores with relatively broad size distributions.As the ascorbic acid concentration is increased,the pore diameters and pore volumes of the materials increase.     

Functionalisation of mesoporous silica nanoparticles with 3-isocynatopropyltrichlorosilane

The functionalisation of Mesoporous Silica Nanoparticles (MSN) with the isocyanate group was carried out. The excellent reactivity of 3-isocynanatopropyltrichlorosilane allowed its grafting on the surface of MSN in mild conditions. Further reaction with different nucleophiles bearing primary amino groups led to the formation of a urea linkage and thus the covalent grafting of the nucleophiles to the MSN surface.     

Thin films of mesoporous silica: preparation and characterization

Preparation of mesoporous materials in a thin film geometry was first reported in 1996. Recently, improvement of the preparation methods yielded stable films with well-defined symmetries, controlled pore orientation, continuity and film thickness. The ability to tailor film properties is important for their utilization in applications ranging from catalysis to microelectronics, where morphological control in the meso-domain is vital.     

Structure and infrared emissivity of polyimide/mesoporous silica composite films

Polyimide/mesoporous silica composite films were prepared by direct mixing of polyamic acid solution and silylated mesoporous silica particles, or by condensation polymerization of dianhydride and diamine with silylated mesoporous silica particles in N,N-dimethylacetamide, followed with thermal imidization. Structure and glass transition temperatures of the composite films were measured with FTIR, SEM, EDX, XPS and DMTA. The results show that the silylated mesoporous silica particles in the composites tend to form the aggregation with a strip shape due to phase separation. The composite films exhibit higher glass transition temperature as comparing with that of pure polyimide. It is found that the composite films present lower infrared emissivity value than the pure polyimide and the magnitude of infrared emissivity value is related to the content of silylated mesoporous silica in the composite films. Inhibiting actions of silylated mesoporous silica on infrared emission of the composite films may be owing to presence of nanometer-scale pores in silylated mesoporous silica.     

Controllable preparation and fluorescence properties of Y and Eu co-doped mesoporous silica

The controllable preparation and forming mechanism of rare-earth Y³⁺ and Eu³⁺ chemically co-doped fluorescent mesoporous silica were studied in detail. Their structures, morphologies, chemical compositions and emission properties were characterized and evaluated by small angle X-ray scattering, nitrogen adsorption/desorption measurements, high resolution transmission electron microscopy, inductive coupled plasma-atomic emission, X-ray photoelectron spectra and fluorescent spectroscopy. The results show that chemical composition of the resultant mesoporous materials were significantly affected by solution acidity condition, and can be effectively adjusted by varying the feed ratio of raw materials at a suitable solution acidity condition. These materials with a well-ordered two-dimensional hexagonal mesoporous structure and high specific surface area exhibit significantly broadened emission band from 526 to 682 nm and the fluorescent emission mechanism and influence of materials structure on optical properties were investigated.     

Organization of helical mesoporous silica nanotubes

Mesoporous silica nanotubes with coiled pore channels in the walls were prepared using the self-assemblies of a gelator as template previously. The TEM images were simulated using Autodesk 3D studio MAX 9.0 here. These hierarchical nanotubes were organized into μm-size balls by increasing the concentration of gelator and controlling stirring speed. Bimodal pore structure was identified by a N₂ adsorption method.     

Synthesis of mesoporous silicas inside large pores of inorganic matrix

Template syntheses of mesoporous silicas have been carried out inside large pores of inorganic matrix. Portions of tetraethoxysilane and cetyltrimethylammonium bromide micellar solution were incorporated step-by-step inside pore volume of silica gel with large pore size. Synthesized materials were characterized using thermal analysis, adsorption-desorption of nitrogen and X-ray diffraction scattering.     

Mixed surfactants-directed the mesoporous silica materials with various morphologies and structures

A new mixed surfactants system using alkyl carboxylic acids and quaternized poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl] urea] (PEPU) as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures, including flakes, regular spheres, nanoparticles, and tube-spheres. The cationic polymer connected the anionic surfactant micelle to the anionic polysilicate species to induce the synthesis of the mesoporous silica materials. The structure and property of the surfactant and the cationic polymer determined the formation of mesoporous silica, and also had a signification influence on the morphology and structure of the final materials. To further explore the possible formation mechanism of these mesoporous materials, zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. In addition, the structure, morphology, and porosity of these materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ adsorption-desorption measurements.     

Syntheses of ordered mesoporous silica by new hybrid template

Ordered mesoporous silica with macroscopic shape has been prepared with a hybrid template of gel and poly(ethylene oxide)₁₀₆–poly(propylene oxide)₇₀–poly(ethylene oxide)₁₀₆ (pluronic F127) surfactant, where both water-soluble agar gel and pluronic F127 significantly affect the mesoporous structure and morphology of silica. The thermal analysis revealed the noticeable interaction between agar and F127, which contributes to the formation of homogenous hybrid template. In the hybrid template, agar gel contributed to the maintenance of morphology structure, while F127 was responsible for the formation of ordered porous structure in silica solids.