Entity

Time filter

Source Type

Montpellier, France

Zaggia A.,University of Padua | Ameduri B.,Charles Gerhardt Institute
Current Opinion in Colloid and Interface Science | Year: 2012

Fluorinated surfactants are exceptional compounds that have found many applications in everyday life. This review focuses on severe issues on the toxicity, persistency and bioaccumulation of these halogenated products, especially perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), the half-lives of which are several years in human serum. After an introduction on their productions, uses and hazards, this minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants that may be potentially non-bioaccumulable. These routes have been devoted on: (i) the preparation of CF 3-X-(CH 2) n-SO 3Na (with X=O, C 6H 4O or N(CF 3) and n=8-12), (ii) the use of fluorinated polyethers (achieved either by oligomerization of hexafluoropropylene oxide (HFPO) or by ring opening cationic oligomerization of fluorinated oxetanes; (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodoperfluoralkanes to produce C nF 2n+1-(VDF) 2-CH 2CO 2R (n=2 or 4, R=H or NH 4), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide to prepare (CF 3) 2CF(TFP) x-R H, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of either (CF 3) 2CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above pathways led to various highly fluorinated (but yet not perfluorinated) telomers or cooligomers, the chemical changes of which enabled to obtain original surfactants as novel alternatives to PFOA, ammonium perfluorooctanoate (APFO), or PFOS regarded as the PCBs of the XXIst century. © 2012 Elsevier Ltd. Source


Debecker D.P.,Catholic University of Louvain | Mutin P.H.,Charles Gerhardt Institute
Chemical Society Reviews | Year: 2012

Oxides and mixed oxides have a tremendous importance in the field of heterogeneous catalysis, serving either as catalysts or as supports for active species. The performance of a catalyst depends directly on its composition, texture, structure and surface properties, which have to be precisely controlled and adapted to each application. In this context, the sol-gel process is a unique tool for the preparation and understanding of catalytic materials, owing to its exceptional versatility. In the last 10 years, the non-hydrolytic sol-gel (NHSG) or non-aqueous sol-gel process based on nonhydrolytic condensations in nonaqueous media has established itself as a simple and powerful method for the design of a wide range of oxide, mixed oxide and hybrid materials with controlled composition, morphology, texture and structure. NHSG proved particularly interesting for the preparation of catalytic materials, notably mesoporous xerogels, single site catalysts and highly crystalline nanoparticles. This critical review addresses the application of NHSG to the preparation of heterogeneous catalysts, emphasizing the specificities of this process, and giving a comprehensive overview of the literature (251 references). © The Royal Society of Chemistry 2012. Source


Mehdi A.,Charles Gerhardt Institute
Journal of Materials Chemistry | Year: 2010

This paper is devoted to layered hybrid organic-inorganic materials obtained by self-assembly of organosilica precursors during the hydrolytic sol-gel process. The self-assembly is induced by lipophilic van der Waals interactions between alkylene chains. The introduction of functional groups such as -SS- gives rise to -SH or -SO 3H functionalized materials after chemical modifications. This methodology has been extended to the formation of lamellar hybrid materials containing amino groups thanks to CO 2 as bridging groups as well as the formation of lamellar hybrid materials containing carboxylic groups. In this last case, the material was elaborated thanks to in situ hydrogen bond formation between carboxylic acid groups. An easy preparation of bis-zwitterionic lamellar material from only 3-aminopropyltriethoxysilane, succinic anhydride, and ethylene diamine will be also presented. All these functional materials exhibit a very high chelating capability towards transition metal and lanthanide ions and can be used for environmental remediation. © 2010 The Royal Society of Chemistry. Source


Croissant J.,University of California at Los Angeles | Croissant J.,Charles Gerhardt Institute | Zink J.I.,University of California at Los Angeles
Journal of the American Chemical Society | Year: 2012

The synthesis and operation of a light-operated nanovalve that controls the pore openings of mesoporous silica nanoparticles containing gold nanoparticle cores is described. The nanoparticles, consisting of 20 nm gold cores inside ∼150 nm mesoporous silica spheres, were synthesized using a unique one-pot method. The nanovalves consist of cucurbit[6]uril rings encircling stalks that are attached to the ∼2 nm pore openings. Plasmonic heating of the gold core raises the local temperature and decreases the ring-stalk binding constant, thereby unblocking the pore and releasing the cargo molecules that were preloaded inside. Bulk heating of the suspended particles to 60 °C is required to release the cargo, but no bulk temperature change was observed in the plasmonic heating release experiment. High-intensity irradiation caused thermal damage to the silica particles, but low-intensity illumination caused a local temperature increase sufficient to operate the valves without damaging the nanoparticle containers. These light-stimulated, thermally activated, mechanized nanoparticles represent a new system with potential utility for on-command drug release. © 2012 American Chemical Society. Source


Diaz U.,Polytechnic University of Valencia | Brunel D.,Polytechnic University of Valencia | Brunel D.,Charles Gerhardt Institute | Corma A.,Polytechnic University of Valencia
Chemical Society Reviews | Year: 2013

Organic-inorganic hybrid materials with different levels of structuration and porous hierarchy and one or several types of active sites in the framework can catalyze multistep chemical processes in a one-pot reactor system following a cascade of reaction events. It will show how the different active sites can act in a synergistic or in a consecutive way following a similar functionality model to biological multisite catalysts. Research on this subject for heterogeneous catalysts is still in the beginning stage and very interesting results can be expected if we are able to successfully combine the properties of organic and inorganic catalysts. © The Royal Society of Chemistry 2013. Source

Discover hidden collaborations