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N2 Sorption (n2 + sorption)

Distribution by Scientific Domains

Chemistry	60%
Polymers and Materials Science	40%

Selected Abstracts

Direct Synthesis of Zr-Containing Hybrid Periodic Mesoporous Organosilicas with Tunable Zirconium Content

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2007
Shang-Ru Zhai
Abstract Highly ordered Zr-containing periodic mesoporous organosilicas (ZrPMO) with different Zr/Si ratios were successfully synthesized, for the first time, by employing a ZrOCl2/NaCl combination as the promoting agent and by simply adjusting the molar ratio of the zirconium species to the organosilica precursor; no addition of mineral acids was necessary. The effect of preparation parameters on the structural and textural properties were carefully investigated by using different ratios of NaCl/Si and Zr/Si. It was found that both salts are essential for this system and highly ordered ZrPMOs can be prepared within fairly wide Si/Zr ratios (5,100) while keeping the NaCl/Si ratio constant. To prove the effectiveness of this synthetic pathway with a higher Zr incorporation, ZrPMO materials were also synthesized under strongly acidic conditions for the purpose of comparison. The synthesized ZrPMO materials were thoroughly characterized by ICP-AES, SAXS, N2 sorption, TEM, SEM, 13C CP/29Si MAS NMR spectroscopy, XPS, and TGA. Elemental analyses show that the amount of Zr incorporated into ZrPMO, which was synthesized under mild conditions, is greater than that obtained in a strongly acidic environment, and the Zr content, with a Si/Zr ratio up to 12, is close to that in the initial gel composition. A plausible assembly mechanism based on the synergistic effect of both "nonhydrolyzable" (NaCl) and "hydrolyzable" (ZrOCl2) inorganic salts was discussed in detail, where the "salting out" effect and self-generated acidity from both inorganic salts, respectively, are believed to be key factors for the formation of ordered SBA-15-type ZrPMO materials under the synthetic conditions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Monodisperse Mesoporous Silica Spheres Inside a Bioactive Macroporous Glass,Ceramic Scaffold,

ADVANCED ENGINEERING MATERIALS, Issue 7 2010
Renato Mortera
In the field of bone tissue engineering, monosized MCM-41 spheres have been incorporated inside a bioactive glass,ceramic macroporous scaffold belonging to the SiO2CaOK2O (SCK) system so obtaining a multiscale hierarchical composite. The MCM-41-SCK system was prepared by dipping the glass,ceramic scaffold into the MCM-41 synthesis solution and was characterized by means of XRD, micro-XRD, N2 sorption and scanning electron microscopy. The MCM-41 spheres inside the scaffold are highly uniform in diameter, as those synthesized in powder form. The adsorption capacity of the composite toward ibuprofen is three times higher than that of the MCM-41-free scaffold, because of the presence of the ordered mesoporous silica. Also the release behavior in SBF at 37,°C is strongly affected by the presence of MCM-41 inside the scaffold macropores. [source]

Selective Zinc(II)-Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2009
Krishanu Sarkar
Abstract A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+ -bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87,×,104M,1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy. [source]

Periodic Mesoporous Organosilicas: A Type of Hybrid Support for Water-Mediated Reactions

CHEMISTRY - AN ASIAN JOURNAL, Issue 7 2007
Ying Wan Prof.
Abstract Hybrid mesoporous periodic organosilicas (Ph-PMOs) with phenylene moieties embedded inside the silica matrix were used as a heterogeneous catalyst for the Ullmann coupling reaction in water. XRD, N2 sorption, TEM, and solid-state NMR spectroscopy reveal that mesoporous Ph-PMO supports and Pd/Ph-PMO catalysts have highly ordered 2D hexagonal mesostructures and covalently bonded organic,inorganic (all Si atoms bonded with carbon) hybrid frameworks. In the Ullmann coupling reaction of iodobenzene in water, the yield of biphenyl was 94,%, 34,%, 74,% and for palladium-supported Ph-PMO, pure silica (MCM-41), and phenyl-group-modified Ph-MCM-41 catalysts, respectively. The selectivity toward biphenyl reached 91,% for the coupling of boromobenzene on the Pd/Ph-PMO catalyst. This value is much higher than that for Pd/Ph-MCM-41 (19,%) and Pd/MCM-41 (0,%), although the conversion of bromobenzene for these two catalysts is similar to that for Pd/Ph-PMO. The large difference in selectivity can be attributed to surface hydrophobicity, which was evaluated by the adsorption isotherms of water and toluene. Ph-PMO has the most hydrophobic surface, and in turn selectively adsorbs the reactant haloaryls from aqueous solution. Water transfer inside the mesochannels is thus restricted, and the coupling reaction of bromobenzene is improved. [source]

Catalytic Performances of Binder-free ZSM-5 Catalysts for Dehydration of Crude Methanol to Dimethyl Ether

CHINESE JOURNAL OF CHEMISTRY, Issue 2 2010
Jing Wang
Abstract A series of binder-free ZSM-5 catalysts and a binder-containing catalyst were prepared and characterized with X-ray diffraction (XRD), X-ray fluorescence (XRF), 27Al magic-angle spinning (MAS) nuclear magnetic resonance (NMR), N2 sorption and ammonia temperature-programmed deposition (TPD) methods. The catalytic activity and selectivity in the dehydration of crude methanol to dimethyl ether (DME) were evaluated in a fixed-bed reactor for the catalysts. The outstanding structural characters such as high zeolite contents, sufficiently open channels and richness in mesopores have been proved on these binder-free catalysts. The influence of the solid-acidity, which is closely related to the framework silica alumina ratio (SAR) of the catalysts, on the catalytic properties has been discussed. A binder-free catalyst with a better potential in application has been selected for its high activity and selectivity, long life-time and non-sensitivity to water contents in the feed. The reason for its excellent performance of the catalyst was discussed. [source]