Synthesis of hollow spherical silica with MCM-41 mesoporous structure

Anchoring of Pd(ii) complex in functionalized MCM-41 as an efficient and recoverable novel nano catalyst in C–C, C–O and C–N coupling reactions using Ph3SnCl

Pd(ii) complex on functionalized mesoporous MCM-41 as an efficient and recoverable novel nano catalyst in C–C, C–O and C–N coupling reactions using Ph₃SnCl.

Silica composite nanoparticles containing fluorescent solid core and mesoporous shell with different thickness as drug carrier

Nonporous silica transitional approach was employed to create core-shell architectural nanocomposites, which performed particularly well in morphology and controllable synthesis. The silica nanocomposites containing fluorescent solid SiO2 core and mesoporous silica shell (F-nSiO2/mSiO2) presented distinct structures of narrow size distribution, stable and shell thickness independent fluorescence, and high specific surface area. Furthermore, the thickness of mesoporous shell could be precisely tailored by the amount of TEOS and solid SiO2 seeds. Drug delivery study of F-nSiO2/mSiO2 with different mesoporous thicknesses were carried out, and Peppas equation was adopted to demonstrate the controlled releasing mechanism of doxorubicin (DOX). The diffusion rate of DOX from F-nSiO2/mSiO2 nanocomposites depended on the thickness of mesoporous shell and electrostatic interaction between drug and silanol group, which facilitated an enhanced drug releasing activity at pH 5.5 than 7.4. What's more, particles loaded DOX showed similar cytotoxicity compared with pure DOX, while no obvious cytotoxicity of carrier was observed in MTT tests for blank particles. These characteristics mentioned above implied that core/shell structured F-nSiO2/mSiO2 had a great potential for controlled drug delivery system.

Facile synthesis of monodisperse microspheres and gigantic hollow shells of mesoporous silica in mixed water-ethanol solvents

Mesoporous silica materials with a variety of morphologies, such as monodisperse microspheres, gigantic hollow structures comprising a thin shell with a hole, and gigantic hollow structures consisting of an outer thin shell and an inner layer composed of many small spheres, have been readily synthesized in mixed water-ethanol solvents at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained mesoporous silica generally shows a disordered mesostructure with typical average pore sizes ranging from 3.1 to 3.8 nm. The effects of the water-to-ethanol volume ratio (r), the volume content of tetraethyl orthosilicate TEOS (x), and the CTAB concentration in the solution on the final morphology of the mesoporous silica products have been investigated. The growth process of gigantic hollow shells of mesoporous silica through templating emulsion droplets of TEOS in mixed water-ethanol solution has been monitored directly with optical microscopy. Generally, the morphology of mesoporous silica can be regulated from microspheres through gigantic hollow structures composed of small spheres to gigantic hollow structures with a thin shell by increasing the water-to-ethanol volume ratio, increasing the TEOS volume content, or decreasing the CTAB concentration. A plausible mechanism for the morphological regulation of mesoporous silica by adjusting various experimental parameters has been put forward by considering the existing state of the unhydrolyzed and partially hydrolyzed TEOS in the synthesis system.

Fabrication of hollow multifunctional spheres containing MCM-41 nanoparticles and magnetite nanoparticles using layer-by-layer method

Macroscopic mesoporous silica spheres have been fabricated by alternatively depositing preformed MCM-41 nanoparticles and polyelectrolytes onto polystyrene lattices. High surface area hollow mesoporous spheres were obtained by removal of the core by solvent or calcination. Further, the versatility of the layer-by-layer (LBL) method was extended to fabricate magnetite-mesoporous silica composites by depositing magnetite and MCM-41 nanoparticles onto polystyrene beads. Such high surface area composites are important since the mesopores can be used for encapsulation of varied materials like enzymes and drugs while the presence of magnetite ensures application in biocatalysis and separation under magnetic field.

Surfactant-templated mesostructured materials from inorganic silica

Mesoporous silica materials made by the use of self-assembled surfactants as templates have attracted a lot of interest in recent years. The number of publications on the topic has increased by a factor of 100 between 1993 and 2003. The vast majority of the papers deal with syntheses from organosilicates, such as tetramethylorthosilicate (TMOS) and tetraethylorthosilicate (TEOS), as the silica source. These alkoxides are convenient as a starting material but they are expensive and the products made from them can only find use in applications where price is not a major issue. This review summarizes the published work on the preparation of mesoporous silica from inorganic sources, such as water glass and silica sol, still using self-assembled surfactants as the template. The use of such raw materials instead of the organosilicates will radically change the production price of the products and may open up completely new fields of application. Much less work has been put into the synthesis of mesoporous silica from these starting materials and relatively little is known about the reaction mechanism. The current understanding is summarized and discussed and comparisons are made with the conventional route that originates from the organosilicates.