Conductive Mesocellular Silica–Carbon Nanocomposite Foams for Immobilization,Direct Electrochemistry,and Biosensing of Proteins

A mesocellular silica–carbon nanocomposite foam (MSCF) is designed for the immobilization and biosensing of proteins. The as‐prepared MSCF has a highly ordered mesostructure, good biocompatibility, favorable conductivity and hydrophilicity, large surface area, and a narrow pore‐size distribution, as verified by transmission electron microscopy (TEM), IR spectroscopy, electrochemical impedance spectroscopy (EIS), nitrogen adsorption–desorption isotherms, pore size distribution plots, and water contact angle measurements. Using glucose oxidase (GOD) as a model, the MSCF is tested for immobilization of redox proteins and the design of electrochemical biosensors. GOD molecules immobilized in the mesopores of the MSCF show direct electrochemistry with a fast electron transfer rate (14.0 ± 1.7 s^–1) and good electrochemical performance. Based on a decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen, the proposed biosensor exhibits a linear response to glucose concentrations ranging from 50 μM to 5.0 mM with a detection limit of 34 μM at an applied potential of –0.4 V. The biosensor shows good stability and selectivity and is able to exclude interference from ascorbic acid (AA) and uric acid (UA) species that always coexist with glucose in real samples. The nanocomposite foam provides a good matrix for protein immobilization and biosensor preparation.     

Synthesis of a Hydrothermally Stable,Periodic Mesoporous Material Containing Magnetite Nanoparticles,and the Preparation of Oriented Films

Magnetite nanoparticles modified covalently with triethoxysilane having a quaternary dicetyl ammonium ion are used together with tetraethylorthosilicate as building blocks to prepare a mesoporous material. Cetyltrimethylammonium bromide is used as a structure‐directing agent under conditions typically used for mesoporous MCM‐41 silicas. The resulting mesoporous material (MAG‐MCM‐41), containing up to 15 wt % of magnetite is characterized by transmission electron microscopy (TEM), isothermal gas adsorption, and X‐ray diffraction. In contrast to siliceous MCM‐41, mesoporous MAG‐MCM‐41 exhibits a remarkable hydrothermal stability. The magnetic properties of MAG‐MCM‐41 are characterized by DC and AC magnetic susceptibility, and by isothermal hysteresis cycles, confirming the long‐range magnetic ordering above 400 K. As evidenced by atomic force microscopy and TEM, the ability to respond to magnetic fields is used to orient films of MAG‐MCM‐41 with the channels perpendicular to a support.     

Colloidal Suspensions of Nanometer‐Sized Mesoporous Silica

Nanometer‐sized surfactant‐templated materials are prepared in the form of stable suspensions of colloidal mesoporous silica (CMS) consisting of discrete, nonaggregated particles with dimensions smaller than 200 nm. A high‐yield synthesis procedure is reported based on a cationic surfactant and low water content that additionally enables the adjustment of the size range of the individual particles between 50 and 100 nm. Particularly, the use of the base triethanolamine (TEA) and the specific reaction conditions result in long‐lived suspensions. Dynamic light scattering reveals narrow particle size distributions in these suspensions. Smooth spherical particles with pores growing from the center to the periphery are observed by using transmission electron microscopy, suggesting a seed‐growth mechanism. The template molecules could be extracted from the nanoscale mesoporous particles via sonication in acidic media. The resulting nanoparticles give rise to type IV adsorption isotherms revealing typical mesopores and additional textural porosity. High surface areas of over 1000 m² g^–1 and large pore volumes of up to 1 mL g^–1 are obtained for these extracted samples.     

Facile Synthesis of Manganese‐Loaded Mesoporous Silica Materials by Direct Reaction Between KMnO4 and an In‐Situ Surfactant Template

A series of manganese oxide‐loaded SBA‐15 (MnSBA‐xh, x = 1, 2, 3, 4, 5, 6; h: hour(s)) mesoporous materials are synthesized via a facile, in‐situ reduction method with a surfactant template. The composite materials are characterized using Fourier‐transform infrared spectroscopy, X‐ray diffraction, N₂ sorption isotherms, X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy, energy‐dispersive spectroscopy, and CO oxidation catalysis. The results show that a high content of manganese (an atomic ratio of Mn/Si from 0.12 up to approximately 1) could be loaded into the channels of SBA‐15 when treated with an aqueous solution of potassium permanganate, while retaining the ordered mesostructure and large surface area of SBA‐15. Increasing the manganese oxide content results in a gradual decrease in the specific surface area, pore size, and pore volume. XPS spectra are employed to confirm the redox reaction between KMnO₄ and the surfactant. CO‐conversion tests on the calcined MnSBA‐2h sample (MnSBA‐2h‐cal) shows that it has a repeatable, and relatively high, catalytic activity.     

Cd1–xMnxS Diluted Magnetic Semiconductors as Nanostructured Guest Species in Mesoporous Thin‐Film Silica Host Media

Recently, we demonstrated the possibility of synthesizing ordered nanowires of diluted magnetic II/VI semiconductors inside the channels of mesoporous silica host structures. Here, we expand this procedure from mesoporous powders to mesoporous thin films. Diluted magnetic semiconductors Cd_1–xMn_xS were synthesized within the pores of mesoporous thin‐film silica host structures by a wet‐impregnation technique using an aqueous solution of the respective metal acetates, followed by drying steps and a conversion to sulfide by thermal H₂S treatment. The presence of Cd_1–xMn_xS nanoparticles inside the pores was proved by powder X‐ray diffraction, infrared and Raman spectroscopy, and transmission electron microscopy. Photoluminescence excitation measurements clearly demonstrate the quantum size effect of the incorporated nanostructured guest species. The quality of the nanoparticles incorporated into the mesoporous films is comparable to that of those inside the mesoporous powders.     

Spherical MSU‐1 Mesoporous Silica Particles Tuned for HPLC

Among the mesoporous silica micellar templated structures (MTSs), MSU‐X silica, obtained through an N⁰I⁰ assembly between non‐ionic polyethyleneoxide‐based surfactants (N⁰) and silica neutral inorganic precursors (I⁰), exhibits a regular ordered structure with a 3D wormhole porous framework and an easily controlled pore size. These materials have been tested for applications requiring both a narrow mesopore size distribution and isotropic properties. A specific double‐step synthesis that we developed recently for MSU‐X materials has allowed us to prepare mesoporous silica particles with the required shape, size, and properties. Both the particles’ synthesis and comparative HPLC separation tests with a commercial ungrafted silica HPLC powder of identical shape and size are reported.     

Polyamidoamine Dendrimers Prepared Inside the Channels of Pore‐Expanded Periodic Mesoporous Silica

Polyamidoamine dendrimers up to the fourth generation have been grown with unprecedentedly high loading within the channels of pore‐expanded (10.6 nm) MCM‐41 silica. In‐depth characterization using nitrogen adsorption, solid‐state NMR, FTIR, thermogravimetry, and elemental analysis showed that the dendrimers grow inside the channels with an average yield better than 99 %. The pore size and structure of the support have been found to be determining factors as to how much dendrimer growth can be achieved.     

Preparation of Hollow Silica Nanospheres by Surface‐Initiated Atom Transfer Radical Polymerization on Polymer Latex Templates

Poly(vinylbenzyl chloride), (PVBC) latex particles of about 100 nm in size are prepared by emulsion polymerization. Silyl functional groups are introduced onto the PVBC‐nanoparticle templates via surface‐initiated atom transfer radical polymerization of 3‐(trimethoxysilyl)propyl methacrylate. The silyl groups are then converted into a silica shell, approximately 20 nm thick, via a reaction with tetraethoxysilane in ethanolic ammonia. Hollow silica nanospheres are finally generated by thermal decomposition of the PVBC template cores. Field‐emission scanning electron microscopy and field‐emission transmission electron microscopy are used to characterize the intermediate products and the hollow nanospheres. Fourier‐transform infrared spectroscopy results indicate that the polymer cores are completely decomposed.     

Water‐Stable,Magnetic Silica–Cobalt/Cobalt Oxide–Silica Multishell Submicrometer Spheres

A method to produce monodisperse magnetic composite spheres with diameters from less than 100 nm to more than 1 μm in water solution is reported. The spheres consist of a dielectric silica core and a cobalt/cobalt oxide shell which can be protected from further oxidation with an outer shell of silica or, alternatively, they can be covered with the polymer polyvinylpyrrolidone as a stabilizer. The formation of a uniform magnetic shell proceeds with the adsorption of metallic cobalt seeds, produced by the reduction of cobalt chloride with sodium borohydride, on a self‐assembled layer of polyelectrolytes on the silica core. In the second step, an outer silica shell can be formed by the hydrolysis and condensation of (3‐aminopropyl)trimethoxysilane and tetraethoxysilane. The double‐shell composite spheres show excellent sphericity, monodispersity, and a magnetic hysteresis loop at room temperature.     

Multiple Functionalization of Mesoporous Silica in One‐Pot: Direct Synthesis of Aluminum‐Containing Plugged SBA‐15 from Aqueous Nitrate Solutions

Aluminum‐containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X‐ray diffraction, transmission electron microscopy, and N₂ sorption measurements show that the Al‐containing plugged silicas possess well‐ordered hexagonal mesostructures with high surface areas (700–860 m² g^–1), large pore volume (0.77–1.05 cm³ g^–1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma–atomic emission spectrometry results show that 0.7–3.0 wt % aluminum can be introduced into the final samples. ²⁷Al MAS NMR results display that about 43–60% aluminum species are incorporated into the skeleton of the Al‐containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al‐containing plugged silica has a similar morphology to that of traditional SBA‐15. Furthermore, the Al‐containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities.     

Transparent Mesoporous Nanocomposite Films for Self‐Cleaning Applications

A versatile approach is studied for the elaboration of TiO₂ based photocatalytic coatings for self‐cleaning applications on transparent substrates. The basic principle of the synthesis relies on the use of preformed TiO₂ colloidal particles that are further dispersed within a transparent silica binder with a mesoporous structure. Film porosity in the nanometer range is controlled by achieving the sol–gel silica condensation around self‐organized micellar assemblies of a templating copolymer surfactant. The latter also acts as a stabilizer for the TiO₂ particles, thus preserving their high dispersion within the film so that excellent optical properties are maintained even for high TiO₂ loading (up to 50 %). Studies of photodegradation kinetics show that such mesoporous films are at least 15 times more active than films synthesized with a usual microporous silica binder. Moreover, the measured quantum‐yield efficiency (1.1 %) is found to be among the highest reported up to now. Improved photoactivity of the films is discussed as resulting from the closer proximity between the organic molecules and the surface of the TiO₂ crystallites as well as the improved diffusion rate of water and oxygen through the interconnected pore network.     

Encapsulation and Ostwald Ripening of Au and Au–Cl Complex Nanostructures in Silica Shells

We report a general template strategy for rational fabrication of a new class of nanostructured materials consisting of multicore shell particles. Our approach is demonstrated by encapsulating Au or Pt nanoparticles in silica shells. Other superstructures of these hollow shells, like dimers, trimers, and tetramers can also be formed by nanoparticle‐mediated self‐assembly. We have also used the as‐prepared multicore Au–silica hollow particles to perform the first studies of Ostwald ripening in confined microspace, in which chloride was found to be an efficient mediating ligand. After treatment with aqua regia, Au–Cl complex is formed inside the shell, and is found to be very active under in situ transmission electron microscopy observations while confined in a microcell. This aspect of the work is expected to motivate further in situ studies of confined crystal growth.     

Mesocellular Silica Foam as an Epoxy Polymer Reinforcing Agent

A new type of mechanically improved rubbery epoxy composite is demonstrated based on the use of a mesocellular silica foam, denoted MSU‐F, as the reinforcement agent. The silica exhibits a surface area of 540 m² g^–1, a cell size of 26.5 nm (14.9 nm window size) and a pore volume of 2.2 cm³ g^–1. Most notably, the silica foam particles readily disperse in the epoxy matrix without the need for an organic surface modifier or dispersing agent. Relative to the pristine polymer, the tensile modulus, strength, strain‐at‐break, and toughness for the mesocomposites are systematically enhanced at relatively low silica loading over the range 1–9 wt %. Moreover, all of these benefits are realized without a sacrifice in thermal stability or optical transparency of the polymer. The results demonstrate that silica in mesocellular foam form can provide polymer reinforcement far beyond the level realized for non‐porous silica or silica with small mesopores at the same weight loading.     

Silica–Carbon Nanocomposites—A New Concept for the Design of Solar Absorbers

To create materials that are composites or hybrids structured on the nanometer scale or the meso‐domain, respectively, is one of the major tasks in modern materials science. In this paper, we demonstrate general strategies on how to obtain these nanocomposites founded on the knowledge about ordered mesoporous materials. One strategy involves the formation of the composite by performing a chemical reaction in the pores of a pre‐formed ordered mesoporous silica while the other strategy uses compounds that first mold their porous environment in the silica and in a succeeding step react to the final composite. As a model system, here, we present the formation of porous silica–carbon hybrid materials. Besides this more general question, we also tackle the task of finding a suitable application for the obtained nanocomposites. We chose an application as selective solar‐absorber materials.     

Shape‐ and Orientation‐Controlled Gold Nanoparticles Formed within Mesoporous Silica Nanofibers

Mesoporous silica nanofibers with longitudinal pore channels are synthesized in high yields using cetyltrimethylammonium bromide as the structure‐directing agent in hydrobromic acid solutions. These nanofibers are used as templates to prepare gold nanoparticles along the fiber axis. For the gold‐precursor‐loaded nanofibers that are not completely dried, nearly spherical gold nanoparticles are produced by hydrogen reduction. As the reduction temperature is lowered, the size of the gold nanoparticles decreases and the number density greatly increases, resulting in surface plasmon coupling between neighboring gold nanoparticles. For the gold‐precursor‐loaded nanofibers that undergo an additional drying process, ellipsoidal gold nanoparticles are obtained, with their major axes oriented along the direction of the pore channels. The major axes of ellipsoidal gold nanoparticles can be controlled to be oriented either parallel or perpendicular to the fiber axis by use of nanofibers with either longitudinal or circular pore channels, respectively. These gold‐nanoparticle‐embedded nanofibers can be expected to find interesting applications in the area of photonics and optoelectronics.     

Mesoporous Silica with Multiple Catalytic Functionalities

Mesoporous silica containing multiple organometallic active sites is synthesized using a traditional post‐synthesis complexation technique and a surfactant‐directed assembly approach. Systematic spectroscopic studies and structure analysis indicate that catalytic mesoporous silica with controlled composition and pore structure can be readily synthesized. Catalytic performance examined by an aqueous medium two‐step cascade reaction indicates that these materials possess excellent catalytic activity, reusability, and an interesting synergic effect. This work provides novel synthesis platforms towards multifunctional catalysts for more efficient chemical transformations.     

Synthesis of New RuO2@SiO2 Composite Nanomaterials and their Application as Catalytic Filters for Selective Gas Detection

RuO₂@SiO₂ nanomaterials are prepared using hybrid mesostructured silica (EtO)₂P(O)(CH₂)₃SiO_1.5/x SiO₂ (x = 9, 16) by anchoring the metal precursor [Ru(COD)(COT)] (COD is 1,3‐cyclooctadiene, COT is 1,3,5‐cyclooctatriene) inside the pores of the organized silica matrix through the phosphonate moieties. Following this task, the nanoparticles are fabricated by i) decomposing the metal precursor with hydrogen at room temperature in tetrahydrofuran to achieve ruthenium nanoparticles and ii) thermally treating the ruthenium particles in silica at 450 °C in air to fabricate RuO₂. The materials containing Ru and RuO₂ nanoparticles are characterized by elemental analysis, transmission electron microscopy (TEM), X‐ray diffraction (XRD), nitrogen sorption measurements, and ³¹P and ¹³C NMR. The obtained RuO₂@SiO₂ nanomaterials are evaluated as catalytic filters when deposited onto gas sensors for the preferential detection of propane in the multicomponent gas mixture propane/carbon monoxide/nitrogen dioxide.     

扩展电阻技术在硅,硅基材料测试中的应用

本文利用扩展电阻技术对半导体硅、硅基材料进行测试分析 ,从而用以开发新材料和评估材料的质量。     

Meso‐SiO2–C12EO10OH–CF3SO3H—A Novel Proton‐Conducting Solid Electrolyte

This paper describes the synthesis and characterization of a novel mesostructured solid electrolyte composite material, denoted meso‐SiO₂–C₁₂EO₁₀OH–CF₃SO₃H. A lyotropic non‐ionic surfactant–triflic acid–silicate liquid crystal is used as a supramolecular template for a “one‐pot” synthesis of the material. Within this structure, the oligoethyleneoxide head groups of the non‐ionic surfactant that is imbibed within the channels of hexagonal mesoporous silica act in a crown‐ether‐like fashion towards the protons. The structure and dynamics of the silicate–oligo(ethylene oxide)surfactant–triflic acid co‐assembly has been studied via several analytical techniques. These methods include polarized optical microscopy (POM), powder X‐ray diffraction (PXRD), transmission electron microscopy (TEM), multinuclear nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), and Fourier transform (FT) Raman spectroscopy. Together these results imply that the protons coordinate to the oxygen atoms of the ethylene oxide units on the non‐ionic surfactant and the compound has the structural integrity of the silicified liquid crystal. AC impedance spectroscopy was used to determine the proton conductivity of the meso‐SiO₂–C₁₂EO₁₀OH–CF₃SO₃H composite material at different relative humidity values giving some insight into its potential utility as a proton conducting solid electrolyte in a proton‐exchange membrane fuel cell.     

Fabrication and Size‐Selective Bioseparation of Magnetic Silica Nanospheres with Highly Ordered Periodic Mesostructure

In this paper, we report a novel synthesis and selective bioseparation of the composite of Fe₃O₄ magnetic nanocrystals and highly ordered MCM‐41 type periodic mesoporous silica nanospheres. Monodisperse superparamagnetic Fe₃O₄ nanocrystals were synthesized by thermal decomposition of iron stearate in diol in an autoclave at low temperature. The synthesized nanocrystals were encapsulated in mesoporous silica nanospheres through the packing and self‐assembly of composite nanocrystal–surfactant micelles and surfactant/silica complex. Different from previous studies, the produced magnetic silica nanospheres (MSNs) possess not only uniform nanosize (90 ～ 140 nm) but also a highly ordered mesostructure. More importantly, the pore size and the saturation magnetization values can be controlled by using different alkyltrimethylammonium bromide surfactants and changing the amount of Fe₃O₄ magnetic nanocrystals encapsulated, respectively. Binary adsorption and desorption of proteins cytochrome c (cyt c) and bovine serum albumin (BSA) demonstrate that MSNs are an effective and highly selective adsorbent for proteins with different molecular sizes. Small particle size, high surface area, narrow pore size distribution, and straight pores of MSNs are responsible for the high selective adsorption capacity and fast adsorption rates. High magnetization values and superparamagnetic property of MSNs provide a convenient means to remove nanoparticles from solution and make the re‐dispersion in solution quick following the withdrawal of an external magnetic field.