11 research outputs found

    One-pot deposition of gold on hybrid TiO2 nanoparticles and catalytic application in the selective oxidation of benzyl alcohol

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    [EN] One-pot deposition of Au onto TiO2 has been achieved through directly contacting gold (III) salt with nanosized functionalized TiO2 support initially obtained by sol-gel process using titanium isopropoxide and citric acid. Citrate groups act as functional moieties able to directly reduce the Au salt avoiding any further reducing treatment. Various gold salts (NaAuCl4 center dot 2H(2)O or HAuCl4 center dot 3H(2)O) and titanium to citrate (Ti/Cit) molar 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 Au particle size and catalytic properties of the as-obtained Au/TiO2 materials. Au/(TiO2)(x)(Cit)(1) catalysts characterization was performed using N-2 adsorption-desorption, ICP-AES, X-ray diffraction and TEM. The effect of the Ti/Cit molar ratio and of the gold precursor was evaluated. The selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) was studied as a model reaction. Kinetic analysis showed that the catalytic reaction rate was pseudo first-order and the values of activation energy have been reported. Results showed that the functionalization of TiO2 by citrate allows tuning the size of the Au nanoparticles deposited onto TiO2 as well as their morphology. Citrate also strongly enhances the benzyl alcohol oxidation through the control of the size and morphology of gold nanoparticles. (C) 2014 Elsevier B.V. All rights reserved.This work has been supported by the Instituto de Tecnologia Quimica (UPV-CSIC), Universidad Politecnica de Valencia-Consejo Superior de Investigaciones Cientificas, project number A/020411/08 et du Ministere Tunisien de l'Enseignement Superieur et de la Recherche Scientifique.Mehri, A.; Kochkar, H.; Berhault, G.; Combita MerchĂĄn, DF.; Blasco Lanzuela, T. (2015). One-pot deposition of gold on hybrid TiO2 nanoparticles and catalytic application in the selective oxidation of benzyl alcohol. Materials Chemistry and Physics. 149:59-68. doi:10.1016/j.matchemphys.2014.09.033S596814

    Combined effect of magnesium and amino glutamic acid on the structure of hydroxyapatite prepared by hydrothermal method

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    International audienceMagnesium modified calcium hydroxyapatite of different Mg/Ca compositions have been synthesized using the hydrothermal method in the presence of glutamic acid. The resulting materials have been characterized by X-ray powder diffraction, chemical analysis, IR Spectroscopy and Transmission Electron Microscopy (TEM). X-ray diffraction analysis shows that the resulting materials consist of a single phase having an apatitic structure. IR spectroscopy highlights the presence of carboxylic groups for the organic moieties grafted onto the apatitic surface. The surface properties of apatite samples are determined

    Epidemiology and antibiotic resistance of Salmonella enterica Serovar Kentucky isolates from Tunisia: The new emergent multi-drug resistant serotype

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    International audienceSince 2002, the emergence of multidrug resistant Salmonella enterica serovar Kentucky (S. Kentucky) and the associated salmonellosis with treatment failure were declared in different parts of the world and were in most of the case contracted during travels to Northeast and Eastern Africa. In the present work, we reported an epidemiological study of S. Kentucky isolated from different environmental and clinical origins in Tunisia, using Pulsed-field gel electrophoresis (PFGE); Enterobacterial Repetitive Intergenic Consensus (ERIC-2) fingerprinting; Plasmid profiling; and antibiotic resistance profiles. ERIC-2 fingerprinting allowed the differentiation of 14 different patterns versus only 4 pulsotypes. Besides, a high proportion of strains were found to be nontypeable by XbaI-PFGE and/or by plasmid profiling (plasmid-free strains). The antibiotic resistance was mainly detected against streptomycin (80.7%), sulfonamides (42.1%) and tetracycline (15.7%). Furthermore, two avian strains were shown to be resistant to trimethoprim-sulfamethoxazole and three clinical strains have demonstrated multidrug-resistant phenotypes (against 5 to 10 antibiotics) and all of them exhibited resistance against nalidixic acid, ciprofloxacin, ofloxacin and tetracycline. ERIC-2 PCR was found to be the most discriminative. However, combination of the three typing methods offer a better mean for differentiating S. Kentucky isolates, monitoring the multiresistant types and determination of their origin. (C) 2011 Elsevier Ltd. All rights reserved

    Low-Temperature O3 Decomposition over Pd-TiO2 Hybrid Catalysts

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    International audienceIn aircraft and spacecraft, outside air is not directly fed to the passenger because it contains ozone at elevated altitudes. The decomposition of low concentration ozone in the air was carried out at 25 °C by catalytic oxidation on Pd-based catalysts supported on a high surface area hybrid TiO2. The use of these hybrid catalysts has shown a beneficial effect, both on the catalytic activity and on the catalyst stability. Kinetic studies showed that the most promising catalytic phase (Pd/TiO2_100) was the one obtained from the TiO2 support containing the lowest content of citrate ligands and leading to small Pd particles (around 4 nm). The effect of catalyst synthesis on the decomposition of O3 gas (15 ppm) in a dry and humid (HR = 10%) stream in a closed environment such as aircraft or spacecraft was also investigated in this study and further elucidated by detailed characterizations. It was shown that the system could be used as an effective treatment for air coming from outside