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Kochkar H.,Center National Of Recherches En Science Des Materiaux Cnrsm | Aouine M.,CNRS Research on Catalysis and Environment in Lyon | Ghorbel A.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Berhault G.,CNRS Research on Catalysis and Environment in Lyon
Journal of Physical Chemistry C | Year: 2011

Shape-controlled silver and palladium nanoparticles were for the first time synthesized by seed-mediated techniques in the presence of β-cyclodextrin (β-CD). Palladium and silver seeds were prepared by reduction of palladium or silver ions with sodium borohydride in the presence of sodium citrate dihydrate as a stabilizer. Seeds were then injected into a "growth" solution containing the same Pd (or Ag) precursor, ascorbic acid (as a weak reducing agent), and β-CD. Using β-cyclodextrin impacts the final morphology of silver nanoparticles through a strong capping effect slowing down the growth regime and shifting it to thermodynamiccontrolled conditions. Adjusting the β-CD/Ag molar ratio can lead to the selective formation of multiply twinned icosahedral particles presenting mainly {111} facets. On palladium, β-cyclodextrin selectively led to the controlled aggregation of primary nanoparticles into nanodendrites or multipods. After deposition on TiO 2, these nanostructured Pd catalysts show excellent activity for the hydrogenation of cinnamaldehyde. © 2011 American Chemical Society.

Turki A.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Turki A.,Institute National Of Recherche Et Danalyse Physico Chimique | Kochkar H.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Kochkar H.,Center National Of Recherches En Science Des Materiaux Cnrsm | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2013

The influence of the sodium content on thermal stability and photocatalytic activity of calcined titanate nanotubes (TNT) was herein evaluated by preparing different samples through hydrothermal treatment of TiO2 powder (P25) in a concentrated NaOH solution (11.25M) at 130°C during 20h followed by acid washing steps. Titanate nanotubes samples with sodium (Na-TNT) and sodium-free (H-TNT) were then obtained using different concentrations of HCl aqueous solutions namely 0.1M and 1M respectively. As synthesized nanomaterials with different Na percentages were then calcined at temperatures varying between 400°C and 700°C. Samples were characterized by means of nitrogen adsorption-desorption isotherms at 77K, thermal analysis (DTA, TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance spectroscopy (DRS). The photocatalytic activities of Na-TNT and H-TNT derived nanomaterials were then evaluated through the photocatalytic degradation of formic acid (FA).Results show that the presence of sodium retards the dehydration process during the transformation of titanate into TiO2 shifting the formation of anatase phase to higher temperatures. However, sodium is not necessary to preserve the nanotubular morphology. The presence of sodium after calcination strongly impacts negatively the photocatalytic properties. If sodium is completely removed from the initial titanate orthorhombic phase, calcination leads to TiO2 anatase materials with enhanced photocatalytic properties compared to P25 in the degradation of formic acid, particularly if nanotubular morphology is preserved. The highest activity was therefore achieved for the H-TNT sample calcined at 400°C. The photodegradation activity of formic acid depends on the specific surface areas and TiO2 crystallinity. In pure anatase nanoparticles the activity strongly decreases with coherent crystallographic domains ≥10nm. © 2013 Elsevier B.V.

Khedher I.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Ghorbel A.,Laboratoire Of Chimie Des Materiaux Et Catalyse
Journal of Porous Materials | Year: 2010

The heterogeneous Kagan-type catalyst was prepared by an in situ method using MCM-41 as support. The influence of the incorporation process on the structure of MCM-41 was studied using XRD, FT-IR, UV-vis, 29Si-MAS- NMR and N2 adsorption-desorption. The obtained materials showed a definite catalytic activity on the oxidation of sulfide to sulfoxide in the medium containing dichloromethane (solvent) and H2O2 or TBHP (oxidant). © 2009 Springer Science+Business Media, LLC.

Tonelli D.,University of Bologna | Ghorbel S.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Colombari M.,University of Bologna | Guadagnini L.,University of Bologna | Ghorbel A.,Laboratoire Of Chimie Des Materiaux Et Catalyse
Journal of Electroanalytical Chemistry | Year: 2013

An ion-selective electrode (ISE) for monohydrogen phosphate, based on a dispersion of Mg/Al hydrotalcite-like compound particles into a polymeric membrane of polyvinyl butyral, in the coated-wire configuration, is described. The inorganic ionophore was ad hoc synthesized and characterized. The electrode showed a Nernstian response towards monohydrogen phosphate independently from the pH of the solution in the range 4.5-7.8 with a linearity range from 5.0 × 10-5 to 2.0 × 10-2 M and a limit of detection of 3.0 × 10-5 M. The response time varied from 10 to 25 s. Potentiometric selectivity coefficients for the proposed sensor were evaluated over several mono- and divalent anions, chosen among the most common ones. The results pointed out a reasonably good selectivity for monohydrogen phosphate. A successful application of the developed ISE for phosphate determination in hydroxyapatite samples using direct potentiometry is presented. © 2012 Elsevier B.V. All rights reserved.

Mehri A.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Kochkar H.,Center National Of Recherches En Science Des Materiaux Cnrsm | Daniele S.,CNRS Research on Catalysis and Environment in Lyon | Mendez V.,CNRS Research on Catalysis and Environment in Lyon | And 2 more authors.
Journal of Colloid and Interface Science | Year: 2012

One-pot deposition of Pd onto TiO 2 has been achieved through directly contacting palladium(II) salt with nanosized functionalized TiO 2 support initially obtained by sol-gel process using titanium isopropoxide and citric acid. Citrate groups act as functional moieties able to directly reduce the Pd salt avoiding any further reducing treatment. Various palladium salts (Na 2PdCl 4 and Pd(NH 3) 4Cl 2·H 2O) and titanium to citrate (Ti/CA) ratios (20, 50, and 100) were used in order to study the effect of the nature of the precursor and of the citrate content on the final Pd particle size and catalytic properties of the as-obtained Pd/TiO 2 systems. Characterization was performed using N 2 adsorption-desorption isotherms, ICP-AES, FTIR, XRD, XPS, and TEM. The as-obtained hybrid Pd/TiO 2 catalysts were tested in the selective hydrogenation (HYD) of an α,β-unsaturated aldehyde, i.e. cinnamaldehyde. Citrate-free Pd/TiO 2-based catalysts present lower selectivity into saturated alcohol. However, citrate-functionalized Pd/TiO 2 catalyst seems to control the selectivity, the particle size and dispersion of Pd NPs leading to high intrinsic activity. © 2011 Elsevier Inc.

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