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).     

乙烯基Ia3d介孔硅分子筛的环氧化及其固定化青霉素酰化酶(英文)

采用直接共聚法合成表面含有乙烯基的具有立方相Ia3d结构的介孔硅分子筛(V-ClMS),然后对乙烯基团进行环氧化制备得到表面环氧基功能化的介孔硅分子筛(E-CIMS),采用X射线衍射、N2吸附-脱附、透射电镜、热重分析和13C固体核磁共振对制备的介孔硅分子筛进行了表征.结果表明,表面含有乙烯基的V-ClMS介孔硅分子筛能被一步成功合成,并易于发生环氧化而获得表面环氧基功能化的E-CIMS介孔硅分子筛.将E-CIMS介孔硅分子筛作为载体用于固定化青霉素G酰化酶(PGA),研究了表面环氧基团对固定化PGA初活性和操作稳定性的影响.结果表明,随着表面环氧基团数量的增加,介孔硅分子筛孔径减小,表面疏水性增加,导致载酶量和初活性减小.但介孔硅分子筛表面适量的环氧基团能增强E-CIMS介孔硅分子筛与PGA之间的相互作用,从而提高固定化PGA的操作稳定性.     

内扩散行为对F-T合成反应过程影响的研究

选用Co/ZrO2催化剂,通过改变催化剂颗粒径,在积分固定床反应器上研究了内扩散行为对F-T合成反应过程的影响。以表观活化能、烯/烷比的变化等为依据,考察了内扩散行为对F-T合成反应历程、催化剂活性及产物选择性的影响。催化剂颗粒径不同,内扩散限制程度会发生相应变化。实验结果表明,不同程度的内扩散限制条件下,F-T合成反应历程会有较大差异。当反应开始后,颗粒内孔从"干"到"湿",不同粒径的催化剂颗粒上气态烯/烷比变化均呈"U"型趋势。在固定床反应器上,增加空速通常会有CH4选择性升高、气态烯/烷比略有增加的现象,这是由于内扩散限制未完全消除的缘故。     

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 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.     

Factors affecting the reactivity of thiol-functionalized mesoporous silica adsorbents toward mercury(II)

Numerous mercaptopropyl-functionalized silica spheres have been prepared by either post-synthesis grafting of MCM-41 and MCM-48 or self-assembly co-condensation of mercaptopropyltrimethoxysilane (MPTMS) or mercaptopropyltriethoxysilane (MPTES) and tetraethoxysilane (TEOS) precursors in hydroalcoholic medium in the presence of a cationic surfactant as templating agent and ammonia as catalyst. These materials of approximately the same particle size and morphology featured different functionalization levels, various degrees of structural order, and variable distribution of thiol groups in the mesopores. Their reactivity in solution has been studied using Hg(II) as model analyte. Total accessibility (on a 1:1 S:Hg stoichiometry basis) was demonstrated and quantified for well-ordered materials whereas less open and less organized structures with high degrees of functionalization were subject to less-than-complete loadings. Capacities measured at pH 2 were lower than at pH 4 because of distinct mercury-binding mechanisms. Kinetics associated to the uptake process were studied by in situ electrochemical monitoring of Hg(II) consumption from aqueous suspensions containing the various adsorbents. They indicate only little difference between materials of the MCM-41 and MCM-48 series at similar functionalization levels, fast mass transport in well-ordered mesostructures in comparison to the poorly or non-ordered ones (except at pH 2 where charge formation induced some restriction in materials characterized by long-range structural order), and even faster processes in the wormlike frameworks (characterized by shorter range structural order). Hg(II) binding to thiol-functionalized materials obtained by post-synthesis grafting was found to occur more rapidly in the early beginning of the uptake process as a result of a higher concentration of binding sites at the pore entrance in comparison to the more homogeneous distribution of these groups in the mesochannels of materials obtained by co-condensation.     

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.     

Determination of transport coefficients in microporous solids

Macroscopic transient methods are reviewed with respect to their applicability to the investigation of molecular transport in microporous sorption systems. Various levels of sophistication of data evaluation for nonequilibrium sorption results obtained by means of batch methods are identified and characterised. Special attention is paid to the characterisation ofFickian (intracrystalline) diffusion as well as to the identification and quantification of additional rate mechanisms that, in general, may simultaneously occur in molecular sieve systems. A state-of-art determination of transport coefficients is exemplified for the systems benzene/microporous gallosilicate of MFI-type, n-hexane/silicalite-I and p-ethyltoluene/ZSM-5. Their sorption rate behaviour can be understood either byFickian diffusion or byFickian diffusion and intracrystalline molecular immobilisation/mobilisation and surface barrier penetration, respectively. To analyse complex sorption rate patterns in microporous systems, the method oftotal curve fitting with full parameter region consideration becomes mandatory.     

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 and characterization of nanoparticulate MnS within the pores of mesoporous silica

Mesoporous silica was loaded with nanoparticulate MnS via a simple post-synthesis treatment. The mesoporous material that still contained surfactant was passivated to prevent MnS formation at the surface. The surfactant was extracted and a novel manganese ethylxanthate was used to impregnate the pore network. This precursor thermally decomposes to yield MnS particles that are smaller or equal to the pore size. The particles exhibit all three common polymorphs. The passivation treatment is most effective at lower loadings because at the highest loadings (SiO₂:MnS molar ratio of 6:1) large particles (>50 nm) form at the exterior of the mesoporous particles. The integrity of the mesoporous network is maintained through the preparation and high order is maintained. The MnS particles exhibit unexpected ferromagnetism at low temperatures. Strong luminescence of these samples is observed and this suggests that they may have a range of important application areas.     

Hierarchical dendritic gold microstructure-based aptasensor for ultrasensitive electrochemical detection of thrombin using functionalized mesoporous silica nanospheres as signal tags

A sensitive electrochemical approach for the detection of thrombin was designed by using densely packed hierarchical dendritic gold microstructures (HDGMs) with secondary and tertiary branches as matrices, and thionine-functionalized mesoporous silica nanospheres as signal tags. To prepare the signal tags, the positively charged thionine (as an indicator) was initially adsorbed onto the mesoporous silica nanoparticles (MSNs). Then [AuCl₄]⁻ ions were in situ reduced on the thionine-modified MSNs by ascorbic acid to construct nanogold-decorated MSNs (GMSNs). The formed GMSNs were employed as label of the aminated aptamers. The assay was carried out in PBS, pH 7.4 with a sandwich-type assay mode by using the assembled thionine in the GMSNs as indicators. Compared with the pure silica nanoparticles, mesoporous silica could provide a larger surface for the immobilization of biomolecules and improve the sensitivity of the aptasensor. Under optimal conditions, the electrochemical aptasensors exhibited a wide linear range from 0.001 to 600 ng mL⁻¹ (i.e. 0.03 pM to 0.018 μM thrombin) with a low detection limit (LOD) of 0.5 pg mL⁻¹ (≈15 fM) thrombin at 3σ. No obvious non-specific adsorption was observed during a series of analyses to detect target analyte. The precision, selectivity and stability of the aptasensors were acceptable. Importantly, the methodology was evaluated with thrombin spiked samples in blank fetal calf serum, and the recoveries were 94.2–112%, indicating an exciting potential for thrombin detection.     

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.     

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.     

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.     

Sub-1-micron mesoporous silica particles functionalized with cyclodextrin derivative for rapid enantioseparations on ultra-high pressure liquid chromatography

Mesoporous silica particles of relatively uniform sub-1-micron size (0.6-0.9 μm) were successfully prepared by a modified synthesis strategy and applied in chiral separation in an ultra-high pressure liquid chromatography system. These particles were prepared via a ternary surfactant system (Pluronic P123, F127 and hexadecyltrimethyl-ammonium bromide) and subsequently derivatized with perphenylcarbamoylated-β-cyclodextrin moieties. The mesoporous silica particles, despite their submicron size, enabled low back-pressure operation on an ultra-high pressure liquid chromatography system at a maximum flow rate of 2 ml/min. In addition, the particles possessed high surface area (480 m(2)/g) and thus afforded high cyclodextrin derivative loading (32 μmol/g), demonstrating rapid enantioseparation and good resolution of 6 basic and neutral racemates.     

Catalytic application of sulfonic acid functionalized mesoporous benzene–silica with crystal-like pore wall structure in esterification

The first catalytic applications of sulfonic acid-functionalized hydrophobic mesoporous benzene–silica with lamellar pore wall structure are reported. The mesoporous benzene–silica attached with propylsulfonic groups to the crystal-like periodic pore walls exhibited the catalytic activity in the esterification of acetic acid with ethanol. The catalytic results show the higher conversion compared to the commercial Nafion-H.     

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.     

A controlled release of ibuprofen by systematically tailoring the morphology of mesoporous silica materials

A series of mesoporous silica materials with similar pore sizes, different morphologies and variable pore geometries were prepared systematically. In order to control drug release, ibuprofen was employed as a model drug and the influence of morphology and pore geometry of mesoporous silica on drug release profiles was extensively studied. The mesoporous silica and drug-loaded samples were characterized by X-ray diffraction, Fourier transform IR spectroscopy, N₂ adsorption and desorption, scanning electron microscopy, and transmission electron microscopy. It was found that the drug-loading amount was directly correlated to the Brunauer-Emmett-Teller surface area, pore geometry, and pore volume; while the drug release profiles could be controlled by tailoring the morphologies of mesoporous silica carriers.     

Porous properties of silylated mesoporous silica and its hydrogen adsorption

Porous properties of mesoporous silica silylated with various organic silanes were examined and their hydrogen adsorption properties were measured at 77 K. By silylation of the mesoporous silica, the specific surface area, pore radius and pore volume steeply decreased depending on both the size of the silane and the amount actually incorporated into the mesoporous framework. The pores reduced in size depending on the amount of modifying silane and vanished completely in the samples silylated with 3-aminopropyltriethoxysilane and phenyltrichlorosilane. Hydrogen adsorption isotherms of the silylated samples were measured at 77 K. With the exception of the sample with phenyltrichlorosilane, hydrogen adsorption volumes were proportional to the surface area with a slope of around 1.1 molecules/nm². On the other hand, for the sample treated with phenyltrichlorosilane, a large hydrogen adsorption volume of around 38.1 molecules/nm² was obtained. On heating the silylated compounds at 500 °C, micropores formed and the hydrogen adsorption volume increased by 1.5 times or more due to the development of micropores.