Search results for "Sol–gel"
showing 10 items of 12 documents
Preparation of photocatalytic brookite thin films
2007
Pure brookite films were deposited from a brookite dispersion obtained by peptizing a mixture brookite–rutile prepared by thermolysis of TiCl4 in a HCl solution. The films were characterised by X-ray diffraction and Raman spectroscopy. The photoactivity of the samples was tested by using the photo-oxidation of 2-propanol in gas–solid regime as a probe reaction. The brookite films efficiently degraded 2-propanol under UV illumination.
Sol–gel material as a support of organometallic catalyst for ethylene polymerization
2008
Abstract The sol–gel procedure was applied to obtain powdery materials with different structures and morphology. It was possible to produce almost non-porous silica powder, with an extremely low surface area (ca. 4 m 2 /g) and very high uniformity of spherical particles as well as materials with various uniformity of particles and different porosity, most likely associated with increasing pore volume. Dependent on the properties of the carrier, the resulting supported vanadium catalysts (VOCl 3 /AlEt 2 Cl) showed significant differences concerning activity and stability. It was confirmed that improved hydrophobicity of the carrier’s surface may be useful and improve the activity of the syst…
Effect of silica-type sol–gel carrier’s structure and morphology on a supported Ziegler–Natta catalyst for ethylene polymerization
2006
Abstract Silica xerogels with different structures and morphology, synthesized using a sol–gel procedure, were used as a carrier of vanadium catalysts (VOCl 3 /AlEt 2 Cl) for ethylene polymerization. Two techniques of catalyst synthesis were applied: slurry impregnation and gas-phase adsorption and the relevant polymerization methods were then employed. The effect of the carrier structure and morphology on the vanadium loading in the catalysts, the catalyst’s activity and kinetic stability were investigated.
Dynamics of myoglobin in confinement: An elastic and quasi-elastic neutron scattering study
2008
In order to clarify the role of hard confinement on protein dynamics, elastic and quasi-elastic neutron scattering experiments have been performed on ferric horse myoglobin in two different systems: the protein embedded in a porous silica matrix, and the corresponding hydrated protein powder. Elastic data have been analysed using two different models (dynamical heterogeneity and anharmonic double-well potential) that take into account deviations of elastic intensity from Gaussian behaviour. The profile of quasi-elastic spectra has been approximated by a combination of Lorentzian and Gaussian components. Comparison between the data relative to the two different samples indicates that geometr…
Hydration dependent dynamics in sol-gel encapsulated myoglobin.
2008
In this work we study the effect of hydration on the dynamics of a protein in confined geometry, i.e. encapsulated in a porous silica matrix. Using elastic neutron scattering we investigate the temperature dependence of the mean square displacements of non-exchangeable hydrogen atoms of sol-gel encapsulated met-myoglobin. The study is extended to samples at 0.2, 0.3 and 0.5 g water/g protein fractions and comparison is made with met-myoglobin powders at the same average hydration and with a dry powder sample. Elastic data are analysed using a model of dynamical heterogeneity to take into account deviations of elastic intensity from gaussian behaviour in a large momentum transfer range and r…
Spectroscopic markers of the T-R quaternary transition in human hemoglobin
2004
n questo lavoro, usiamo un protocollo sol-gel per intrappolare e confrontare gli stati quaternari R e T di entrambi i deossigenati (deossiHb) ederivati di ossido di carbonio (HbCO) dell'emoglobina umana. La banda di assorbimento ottico del vicino infrarosso III e lo stretching di CO a infrarossibanda sono utilizzati per rilevare l'effetto della struttura quaternaria sulle proprietà spettrali di deoxyHb e HbCO; confronto con mioglobinaconsente una valutazione dei contributi terziari e quaternari ai turni di banda misurati. La RXLa transizione T è indicata per causare un bluspostamento della banda III di ~ 35 cm?1per deoxyHb e uno spostamento rosso della banda di allungamento CO di soli ~ 0…
Enhanced Solar Light Photocatalytic Activity of Ag Doped TiO2–Ag3PO4 Composites
2020
Composites comprised of Ag3PO4 and bare TiO2 (TiO2@Ag3PO4) or silver doped TiO2 (Ag@TiO2&ndash
Nanoparticles of AlTiZr mixed oxides as support of hydrodesulfurizaton catalysts: Synthesis and characterisation
2012
Abstract TiAlZr mixed oxides, synthesized using sol–gel method, were characterized and used as supports of hydrodesulfurization catalysts (12 wt% Mo) prepared by impregnation either with molybdenum heteropolyacid H3PMo12O40 or its cobalt salt Co1.5PMo12O40. Structure, morphology and textural properties of oxides and catalysts were characterized using X-ray powder diffraction (XRD), Raman spectroscopy, Nitrogen adsorption porosimetry, TEM-EDS, temperature-programmed desorption (TPD) and temperature-programmed reduction (TPR) techniques. Activity of the catalytic systems was tested in thiophene hydrodesulfurization (HDS). No formation of a new oxide phase was revealed in the synthesized mixed…
Dynamic properties of solvent confined in silica gels studied by broadband dielectric spectroscopy
2007
Abstract We report the results of a broadband (10−2–107 Hz) dielectric spectroscopy study on a solvent system (glycerol–water solution) confined in a porous silica matrix. The dielectric relaxation of the system is studied as a function of both temperature (120–280 K) and solvent composition (0–36 glycerol molar percentage), at constant matrix composition. Our data show that glycerol–water systems confined inside silica gel are characterized by a very complex dynamics quite different from that observed in solution, thus indicating that confinement may deeply modify solvent dynamics. Indeed in addition to the relaxation processes similar to those occurring in bulk samples, new dielectric rel…
Titania–Silica Materials for Enhanced Photocatalysis
2015
Mesoporous titania–organosilica nanoparticles comprised of anatase nanocrystals crosslinked with organosilica moieties have been prepared by direct co-condensation of a titania precursor, tetrabuthylortotitanate (TBOT), with two organosilica precursors, 1,4-bis(triethoxysilyl) benzene (BTEB) and 1,2-bis(triethoxysilyl) ethane (BTEE), in mild conditions and in the absence of surfactant. These hybrid materials show both high surface areas (200–360 m2 g−1) and pore volumes (0.3 cm3 g−1) even after calcination, and excellent photoactivity in the degradation of rhodamine 6G and in the partial oxidation of propene under UV irradiation, especially after the calcination of the samples. During calci…