Alignment control of a cyanine dye using a mesoporous silica film with uniaxially aligned mesochannels

The feasibility of alignment control of low-molecular-weight guest species by controlling the orientation of mesochannels in a mesoporous silica host has been shown for the first time; spectroscopically anisotropic absorption behaviour of a cyanine dye was observed upon its incorporation into the mesochannels of a mesoporous silica film with uniaxially aligned porous structure, proving that the preferred alignment of the dye molecules was achieved on a macroscopic scale.     

Synthesis and fluorescence study of the grafted salicylidene Schiff base onto SBA-15 mesoporous silica for detecting Zn<Superscript>2+</Superscript> traces in aqueous medium

A selective fluorescent chemosensor was prepared by anchoring pyridine-2-carbaldehyde Schiff base ligand onto mesochannels of organically modified SBA-15 mesoporous silica. The resulting organic-inorganic hybrid mesoporous chemosensor was characterized by X-ray diffraction, Fourier transform IR spectroscopy, transmission electron microscopy, UV-visible diffuse reflectance spectra, and photoluminescence spectra. All the results support the idea that successive attachment of the ligand moiety onto one-pot-modified mesoporous scaffold has not altered its basic hexagonally arranged structure. Upon introducing trace amounts of zinc ions into aqueous solution, remarkable enhancement in the fluorescence was observed.     

Deoxycholate as an efficient coating agent for hydrophilic silicon nanocrystals

A layer of macrocyclic calix[4]arene derivatives has been grafted on the internal surface of the mesochannels of the ordered mesoporous SBA-15 to develop highly efficient trap for heavy transition metal (HTM) ions. To ensure the successful anchoring of calix[4]arene derivatives on the surface of SBA-15, two different types of calix[4]arene derivatives, one with one trimethoxysilane functional group and another with two trimethoxysilane functional groups have been explored. XRD, N(2) adsorption and TEM results provide strong evidence that the mesoporous structure of the supporting materials retain their long range ordering throughout the grafting process. Solid-state NMR, TG and FT-IR spectroscopy indicate that both types of calix[4]arene derivatives can be well-anchored on the surface of the wall of SBA-15. Calix[4]arene derivative with only one trimethoxysilane functional group showed high grafting efficiency compared to that with two trimethoxysilane functional groups due to the intramolecular and intermolecular polycondensation between two trimethoxysilane functional groups. The HTM ions extraction capacity in aqueous solution of macrocycle functionalized SBA-15 nanohybrides for a series of HTM ions has been studied. The obtained materials demonstrated very high HTM ions extraction capacity up to 96% for Pb(2+) in aqueous solution.     

Anisotropy property of CdS and PbS quantum dots encapsulated in silica film with uniformly oriented mesochannel

In this paper, hybrid film of mesoporous silica film with oriented mesochannels and semiconductor quantum dot has been prepared. Encapsulation of CdS and PbS within the oriented mesochannels leads to a regular arrangement at the macro scale. The hybrid film thus obtained showed remarkable anisotropic photoelectronic properties due to the confinement effect of the oriented mesochannels. Furthermore, due to the independence of the orientations of the mesochannels on the substrate, bilayer films containing both CdS and PbS could be prepared. This design has allowed an extension of the range of light absorption by the thin film as well as an amplification of the response to external photoelectronic effects. Such a hybrid film may prove useful in the design of anisotropic electrodes and electronic nanodevices.     

Fabrication of nanoporous nanocomposites entrapping Fe3O4 magnetic nanoparticles and oxidases for colorimetric biosensing

A nanostructured multicatalyst system consisting of Fe(3)O(4) magnetic nanoparticles (MNPs) as peroxidase mimetics and an oxidative enzyme entrapped in large-pore-sized mesoporous silica has been developed for convenient colorimetric detection of biologically important target molecules. The construction of the nanocomposites begins with the incorporation of MNPs on the walls of mesocellular silica pores by impregnating Fe(NO(3))(3)·9H(2)O, followed by the immobilization of oxidative enzymes. Glutaraldehyde crosslinking was employed to prevent enzymes leaching from the pores and led to over 20 wt% loading of the enzyme. The oxidase in the nanocomposite generates H(2)O(2) through its catalytic action for target molecules and subsequently activates MNPs to convert selected substrates into colored products. Using this strategy, two different biosensing systems were constructed employing glucose oxidase and cholesterol oxidase and their analytical capabilities were successfully verified by colorimetrically detecting the corresponding target molecules with excellent selectivity, sensitivity, reusability, and stability. Future potential applications of this technology range from biosensors to multicatalyst reactors.     

Pt nanoworms: creation of a bumpy surface on one-dimensional (1D) Pt nanowires with the assistance of surfactants embedded in mesochannels

A new type of platinum nanowire with a bumpy surface "Pt nanoworm" is electrochemically synthesized in mesochannels of mesoporous silica films with the assistance of a nonionic surfactant (C(16)EO(8)).     

Facile unidirectional alignment of mesochannels in a mesoporous silica film on a freshly cleaved mica surface

The alignment of mesochannels in a mesoporous silica film on a freshly cleaved mica surface, prepared by an evaporation-induced self-assembly process, is unexpectedly found to be unidirectional with the narrowest directional distribution.     

A novel enzyme-mimic nanosensor based on quantum dot-Au nanoparticle@silica mesoporous microsphere for the detection of glucose

QD-Au NP@silica mesoporous microspheres have been fabricated as a novel enzyme-mimic nanosensor. CdTe quantum dots (QDs) were loaded into the core, and Au nanoparticles (NPs) were encapsulated in the outer mesoporous shell. QDs and Au NPs were separated in the different space of the nanosensor, which prevent the potential energy or electron transfer process between QDs and Au NPs. As biomimetic catalyst, Au NPs in the mesoporous silica shell can catalytically oxidize glucose as glucose oxidase (GOx)-mimicking. The resultant hydrogen peroxide can quench the photoluminescence (PL) signal of QDs in the microsphere core. Therefore the nanosensor based on the decrease of the PL intensity of QDs was established for the glucose detection. The linear range for glucose was in the range of 5–200 μM with a detection limit (3σ) of 1.32 μM.     

单分散核-壳结构介孔二氧化硅微球的合成

在酸性条件下, 采用非离子表面活性剂嵌段共聚物为模板剂, 季铵盐阳离子表面活性剂为共导向剂, 在预先合成的尺寸均一的单分散实心氧化硅微球表面包裹了有序介孔氧化硅层, 进一步通过高温水热处理, 获得了具有良好分散性和均匀尺寸的介孔壳层(孔径7 nm)氧化硅微球(~500 nm). 氧化硅微球外部包裹的介孔壳层具有较大的比表面积(188 m2/g)和孔容(0.23 cm3/g).     

Enzyme Entrapped in Polymer‐Modified Nanopores: The Effects of Macromolecular Crowding and Surface Hydrophobicity

Macromolecular crowding is an ubiquitous phenomenon in living cells that significantly affects the function of enzymes in vivo. However, this effect has not been paid much attention in the research of the immobilization of enzymes onto mesoporous silica. Herein, we report the combined effects of macromolecular crowding and surface hydrophobicity on the performance of an immobilized enzyme by accommodating lipase molecules into a series of mesoporous silicas with different amounts of inert poly(methacrylate) (PMA) covalently anchored inside the nanopores. The incorporation of the PMA polymer into the nanopores of mesoporous silica enables the fabrication of a crowded and hydrophobic microenvironment for the immobilized enzyme and the variation in polymer content facilitates an adjustment of the degree of crowding and surface properties of this environment. Based on this system, the catalytic features of immobilized lipase were investigated as a function of polymer content in nanopores and the results indicated that the catalytic efficiency, thermostability, and reusability of immobilized lipase could all be improved by taking advantage of the macromolecular crowding effect and surface hydrophobicity. These findings provide insight into the possible functions of the macromolecular crowding effect, which should be considered and integrated into the fabrication of suitable mesoporous silicas to improve enzyme immobilization.     

Robust Amino-Functionalized Mesoporous Silica Hollow Spheres Templated by CO2 Bubbles

Hollow-structured mesoporous silica has wide applications in catalysis and drug delivery due to its high surface area, large hollow space, and short diffusion mesochannels. However, the synthesis of hollow structures usually requires sacrificial templates, leading to increased production costs and environmental problems. Here, for the first time, amino-functionalized mesoporous silica hollow spheres were synthesized by using CO₂ gaseous bubbles as templates. The assembly of anionic surfactants, co-structure directing agents, and inorganic silica precursors around CO₂ bubbles formed the mesoporous silica shells. The hollow silica spheres, 200–400 nm in size with 20–30 nm spherical shell thickness, had abundant amine groups on the surface of the mesopores, indicating excellent applications for CO₂ capture, Knoevenagel condensation reaction, and the controlled release of Drugs.     

Vertically Oriented Silica Mesochannels as the Template for Electrodeposition of Polyaniline Nanostructures and Their Electrocatalytic and Electroanalytical Applications

A mesoporous silica film (MSF) with vertically oriented mesochannels on a conductive substrate serves as a hard‐template for electrodeposition of polyaniline (PANI). The PANI nanostructures thus prepared are orderly confined in silica mesochannels, eventually producing a robust hybrid film. The film displays a good electrocatalytic activity toward oxidation of ascorbic acid, and can be used for potentiometric pH sensing with a Nernstian response.     

A fluorescence nanosensor for Cu2+ on silica particles

A fluorescence nanosensor for Cu2+ ions has been obtained by surface functionalization of silica particles with trialkoxysilane derivatized ligand and fluorescent dye.     

Synthesis of confined Ag nanowires within mesoporous silica via double solvent technique and their catalytic properties

Ag nanowires within the channels of mesoporous silica have been successfully synthesized via a double solvent technique, in which n-hexane is used as a hydrophobic solvent to disperse mesoporous silica and an AgNO(3) aqueous solution is used as a hydrophilic solvent to fill mesochannels. The morphology of the obtained Ag (nanowires, nanoparticles or nanorods) can be controlled by adjusting the concentration of AgNO(3) solution and the template pore size. HRTEM images demonstrate extensive Ag nanowires with several to tens of hundreds nanometers in length are deposited along the long axis of mesochannels when the atomic AgNO(3)/Si ratio is 0.090. When the atomic AgNO(3)/Si ratio is 0.068 or 0.11, there is a combination of Ag nanoparticles and nanowires; nanoparticles are mainly formed when the atomic AgNO(3)/Si ratio is higher than 0.14. Further, the catalytic results of the oxidation of styrene show that styrene oxide and benzaldehyde are the main products of the reaction, and the morphology and diversity of Ag in Ag/mesoporous silica composites have an effect on the conversion of styrene and selectivity of styrene oxide.     

Quiescent hydrothermal synthesis of reduced graphene oxide–periodic mesoporous silica sandwich nanocomposites with perpendicular mesochannel alignments

Quiescent hydrothermal conditions were applied to synthesis of the sandwich nanocomposites of reduced graphite oxide (rGO) and periodic mesoporous silica (PMS) with vertically aligned mesochannels. It was found that the formation of the PMS–rGO–PMS sandwich structure is very sensitive to the surface and synthesis conditions. Although a higher temperature hydrothermal condition promotes reduction of GO and formation of bulky mesoporous nanoparticles, quiescent hydrothermal condition can serve as an alternative approach to obtain the unusual nanocomposites and slightly promote the structural stability of PMS on the surface of rGO.     

Aqueous‐Phase Synthesis of Mesoporous Zr‐Based MOFs Templated by Amphoteric Surfactants

Zr‐based mesoporous metal–organic frameworks (mesoMOFs) with uniform mesochannels and crystallized microporous framework were constructed in a water‐based system using amphoteric surfactants as templates. Aqueous‐phase synthesis guaranteed the formation of rod‐shaped surfactant micelles. Meanwhile, the carboxylate groups of amphoteric surfactants provided the anchoring to bridge Zr‐oxo clusters and surfactant assemblies. As a result, the directed crystallization of MOFs proceeded around cylindrical micelles and the hierarchical micro‐ and mesostructure was produced. The dimensions of mesopores were easily tailored by changing the alkyl chain length of the applied surfactants. The included surfactant was effectively extracted thanks to the exceptional stability of the obtained Zr‐based mesoMOFs. The almost complete occupation of the mesopore by cytochrome c exemplifies the accessibility of the mesochannels, suggesting the potential applications of the obtained mesoMOFs with bulky molecules.     

Immobilization of palladium in mesoporous silica matrix: preparation, characterization, and its catalytic efficacy in carbon-carbon coupling reactions

Palladium(0) has been immobilized into the silica-based mesoporous material to develop catalyst Pd(0)-MCM-41, which is found to be highly active in carbon-carbon coupling reactions. [Pd(NH3)4]2+ ions have been incorporated into the mesoporous material during synthesis of MCM-41 and subsequently upon treatments with hydrazine hydrate Pd2+ ions present in mesoporous silica matrix were reduced to Pd(0) almost instantaneously. The catalyst has been characterized by small-angle X-ray diffraction, N2 sorption, and transmission electron microscopy (TEM). TEM and surface area measurements clearly demonstrate that the immobilization of Pd(0) into the mesoporous silica has a significant effect on pore structure of the catalyst. Nevertheless, after immobilization of palladium the meso-porosity of the material is retained, as evidenced in the nitrogen sorption measurement. The TEM micrograph shows that both MCM-41 and Pd(0)-MCM-41 have similar types of external surface morphology; however, Pd(0)-MCM-41 was less ordered. Pd(0)-MCM-41 showed high catalytic activity toward carbon-carbon bond formation reactions like Heck and Sonogashira coupling, as evidenced in high turn-over numbers. In contrast to many other Pd-based catalysts reported so far, Pd(0)-MCM-41 acts as a truly heterogeneous catalyst in C-C coupling reactions. Notably, the new heterogeneous catalyst is found to be efficient in the activation of arylchloride to give impressive conversion in cross coupling (15-45% for Heck and 30% for Sonogashira) reactions under mild conditions.     

Characterization of ESR active species on lithium chloride-modified mesoporous silica

The surface of mesoporous silica with regular nanometer-sized pores and high surface area has been modified by metal ions or functional groups to introduce specific interactions. We found that ESR active species were formed on lithium chloride (LiCl)-modified mesoporous silica after heat treatment. The structure and the surface properties of LiCl-modified mesoporous silica were characterized by XRD, ESR, nitrogen adsorption, UV-vis-NIR, and TPD. The results suggest that the ESR active species were generated on the surface in response to heat treatment above 673 K. Moreover, it was found for the first time that LiCl-modified mesoporous silica after the heat treatment has reversible adsorption properties for hydrogen under room temperature and atmospheric pressure.     

Selective separation of Th(IV) from its solutions using amine modified silica gel produced from leached zircon

A solution of sodium silicate produced as a waste from the alkali fusion of Egyptian Rosetta zircon mineral was used for preparation of a silica gel in the pH range 6–7. A silica gel modified with tetraethylenepentamine (TEP) and diethylenetriamine (DET) functionalities were prepared. The success of immobilization process was confirmed by means of FT-IR, energy dispersive X-ray spectrometric analysis (EDX) and elemental analysis. The surface properties of the modified silica obtained were investigated by means of nitrogen surface area. The uptake behaviour of the modified silica towards Th(IV) ions at different experimental conditions of pH, time, concentration and temperature using batch method was studied. Kinetics and thermodynamics studies showed an endothermic pseudo-second order adsorption process. Regeneration of the loaded silica was performed using 1 M HNO₃. The investigated silicas have successfully been applied for separating of Th(IV) from U(VI) in nitric acid solution obtained from alkaline leaching of Egyptian monazite sand.     

Synthesis of 2-aryl-2,3-dihydroquinazolin-4(1<Emphasis Type="Italic">H</Emphasis>)-ones using boric acid-functionalized MCM-41 as a novel heterogeneous catalyst under solvent-free condition

Ordered mesoporous silica material MCM-41 with covalently anchored boric acid groups located inside the mesochannels has been utilized as an acid catalyst for the ‘green’ synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H)-one derivatives under solvent-free condition. This novel synthetic method offers advantages, such as excellent yields, simple reaction procedure, short reaction times and mild reaction conditions.