Periodic mesoporous organosilica grafted palladium organometallic complex: efficient heterogeneous catalyst for water‐medium organic reactions

Water‐medium organic reactions were studied over periodic mesoporous silica (PMO) containing Pd(II) organometallic complex. This heterogeneous catalyst was achieved by Pd(II) compound coordinated with the PPh₂‐ligand onto the pore surface of phenylene‐bridged PMO support. This catalyst displayed ordered mesoporous channels, which ensured the high dispersion of Pd(II) active sites and the convenient diffusion of reactant molecules into the pore channels. Meanwhile, the phenyl group in the pore wall of PMO could enhance the surface hydrophobicity which promoted the adsorption of organic reactant molecules on the catalyst in aqueous environment. As a result, this elaborated catalyst exhibited comparable activity and selectivity with the corresponding PdCl₂(PPh₃)₂ homogeneous catalyst in the water‐medium organic reactions, and could be used repeatedly, showing a good potential in industrial applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of Mesoporous Silica Molecular Sieves via a NovelTemplating Scheme

ThediscoveryofM41SfamilyofmesoporousmolecularsievesbyMobilresearchersI'2hasstimulatedconsiderableinterestintheuseofthesematerialsascatalysts,catalystsupports,aswellasadsorbents3'#.Intheoriginalreport"=,MCM-41waspreparedfromaself-assemblyprocesswhichinvolveselectrostaticinteractionsbetweenpositivelychargedquaternaryammoniummicelles(S )andinorganicanions(l-)usedasframeworkprecursors.Huoetal5extendedtheelectrostaticassemblyapproachesbyproposingfourcomplementarysynthesisschemes(S l-,S-I ,S X-…     

Triacontyl modified silica gel as a sorbent for the preconcentration of polycyclic aromatic hydrocarbons in aqueous samples prior to gas chromatographic-mass spectrometry determination

<正>Triacontyl modified silica gel as a sorbent coupled with gas chromatography-mass spectrometry(GC-MS) was developed to determine EPA prior 16 polycyclic aromatic hydrocarbons(PAHs) in water samples.Various parameters of solid-phase extraction such as organic modifier solvent,eluent,sample flow rate and volume were optimized.The developed method was found to yield a linear calibration curve in the concentration range of 0.05-8μg/L with respect to naphthalene,acenaphthylene,acenaphthene and 0.01-8μg/L for dibenz[a,h]anthracene and 0.05-14μg/L for fluorene,phenanthrene,anthracene and 0.01-14μg/L for the rest of analytes.Furthermore,the good accuracy and repeatability of the method made sure the requirements for achieving reliable analysis of PAHs in the environmental water samples,and the recoveries of optimal method were in the range of 80-120%except to higher volatility PAHs.C_(30)-bonded silica was proved to be an efficient sorbent for extraction of high molecular weight PAHs.     

The interaction between silica flat substrate and functional group–modified nanoparticles

Inspired by nature, the research of functionalized nanoparticles and nanodevices has been in-depth developed in recent years. In this paper, we theoretically studied the interaction between functional polyelectrolyte brush layer–modified nanoparticles and a silica flat substrate. Based on the Poisson–Nernst–Planck equations, the mathematical model is established. The changes of the volume charge density and electric field energy density when the nanoparticle interacts with the silica flat substrate under multi-ions regulation were investigated. The results show that when there is a strong interaction between the silica flat substrate and nanoparticles, such as the distances between the nanoparticle and silica flat substrate, which are 2 or 5 nm, the isoelectric point shift under the influence of silica flat substrate and the total charge density in the brush layer is jointly controlled by the cations in the solution and the volume charge density of the brush layer. With the increase of the distances between the nanoparticle and silica flat substrate, the regulation of the volume charge density of the brush layer dominates. These results will provide guidance for the movement mechanism of functionalized nanoparticles in silica nanochannels.     

Mesoporous Hybrid Materials by Simultaneous Pseudomorphic Transformation and Functionalization of Silica Microspheres

Non‐agglomerated amino‐functionalized mesoporous silica microspheres are synthesized by a one‐pot synthesis from a parent silica material. Narrow pore size distributions in the range from 3 to 5 nm are obtained with alkyltrimethylammonium structure‐directing agents (SDAs). By following the pseudomorphic transformation pathway, the particle size distribution and spherical morphology of the parent silica are retained during the synthesis. The products contain accessible and uniformly distributed amino groups. The average pore size and the ratio of small uniform mesopores (<5 nm) to larger mesopores and macropores can be controlled by choosing the appropriate SDA and by adjusting the concentration of the amino‐functionalized alkoxysilane precursor, leading to a variety of meso‐macroporous hybrid materials.     

Cytotoxicity and Cellular Uptake of Amorphous Silica Nanoparticles in Human Cancer Cells

The cytotoxic effects of silica nanoparticles (SNPs) on different human cancer cells, as well as the uptake kinetics and pathways of SNPs have been studied here. SNPs with the diameter of ≈20 nm induced a dose‐dependent cytotoxicity in both gastric cancer cells (MGC80–3) and cervical adenocarcinoma epithelial cells (HeLa), but MGC80–3 cells were more susceptible to the cytotoxic effect induced by SNPs. Changes in the nuclear morphology and flow cytometric analysis with annexin V/PI double staining show that SNPs induced a higher degree of apoptosis in MGC80–3 cells. Accordingly, more remarkable reactive oxygen species (ROS) burst is detected in SNP‐treated MGC80–3 cells. Using fluorescein isothiocyanate (FITC)‐labeled SNPs and flow cytometry, it is found that the uptake of SNPs is more efficient in MGC80–3 than in HeLa cells. SNPs are internalized into both cancer cells through energy‐dependent pathway. Inhibitor studies with dynasore and methyl‐β‐cyclodextrin show that these cancer cells took up 20 nm SNPs mainly through the caveolin‐mediated endocytosis, while in HeLa cells SNPs internalization was also via dynamin‐dependent clathrin‐mediated pathway. These findings indicate that SNPs cause differential cytotoxic effects in different human cancer cells, which might be related to the uptake process and efficiency toward these cancer cells.     

Spherical Polyolefin Particles from Olefin Polymerization in the Confined Geometry of Porous Hollow Silica Particles

Porous hollow silica particles (HSPs) are presented as new templates to control the product morphology in metallocene‐catalyzed olefin polymerization. By selectively immobilizing catalysts inside the micrometer‐sized porous hollow silica particles, the high hydraulic forces resulting from polymer growth within the confined geometries of the HSPs cause its supporting shell to break up from the inside. As the shape of the support is replicated during olefin polymerization, perfectly spherical product particles with very narrow size distribution can be achieved by using HSPs exhibiting a monomodal size distribution. Furthermore, the size of the obtained product particles can be controlled not only by the polymerization time but also by the size of the support material.

     

Novel inorganic morphologies formed in polyimide/silica hybrid films

2-(4-Aminophenyl)-5-aminobenzimidazole was used to prepare polyimide/silica hybrid films via sol-gel process. At 40 wt.% silica content, hybrid films were still translucent. No noticeable silica particle has been observed. Unexpectedly, after treating at 800 °C, novel morphologies of silica were observed on the surface of inorganic films, which changed from homogeneous to sea-island and to co-continuous structure with increasing silica content in the matrix. Hydrogen bonding between NH in imidazole and silanol group results that silica tends to linear structures, which is considered as the main reason for this morphological change.     

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.