Clarence Charnay

Interactions of phenol with cationic micelles of hexadecyltrimethylammonium bromide studied by titration calorimetry, conductimetry, and 1H NMR in the range of low additive and surfactant concentrations

Interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC and phenol contents of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of titration calorimetry, solution conductimetry, and (1)H NMR spectroscopy. Estimates of the main thermodynamic parameters related to HTAB micellization were made for PhOH/HTAB/H(2)O systems based on the specific conductivity measurements and calorimetric determination of the cumulative enthalpy of dilution as functions of the surfactant concentration at a fixed additive content. The combined analysis of the results obtained in H(2)O solutions pointed to the preferential location of PhOH in the outer micelle parts by an enthalpy-driven mechanism. Additional PhOH molecules were located increasingly deeper within the micelle core. The (1)H NMR study of PhOH solubilization by 1.5 mmol kg(-1) HTAB solutions in D(2)O indicated that the two categories of the solubilization site became saturated with the solubilizate already at the lowest additive content. Dissimilar amounts of the solubilized material in H(2)O and D(2)O solutions were ascribed to the difference in the initial micelle structures formed in the two solvents, as inferred from calorimetry and (1)H NMR studies of the HTAB micellization in D(2)O and H(2)O.

Aqueous behaviour of cationic surfactants containing a cleavable group.

The aggregation behaviour of two novel cationic RAFT agents (transfer surfactants); N,N-dimethyl-N-(4-(((phenylcarbonothioyl)thio)methyl)benzyl)ethanammonium bromide (PCDBAB) and N-(4-((((dodecylthio)-carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium bromide (DCTBAB) in diluted solutions have been investigated by surface tension, conductimetry and microcalorimetry measurements. The thermodynamic parameters i.e. the critical micelle concentration (cmc), the degree of micelle ionization (alpha), the head group surface area (a 0), Delta H mic, Delta G mic and T Delta S mic are reported at 303 K. The thermodynamic parameters have been compared to those of the conventional surfactant cetyltrimethylammonium bromide (CTAB) in order to specify structural relationships. The obtained results have been discussed considering the hydrophobic behaviour of the S-C=S- linkage and the specific interactions that arise from the introduction of the benzene ring into the hydrophobic part.

Poly(ethylene glycol)‐Based Ionic Liquids: Properties and Uses as Alternative Solvents in Organic Synthesis and Catalysis

PEG-based ionic liquids are a new appealing group of solvents making the link between two distinct but very similar fluids: ionic liquids and poly(ethylene glycol)s. They find applications across a range of innumerable disciplines in science, technology, and engineering. In the last years, the possibility to use these as alternative solvents for organic synthesis and catalysis has been increasingly explored. This Review highlights strategies for their synthesis, their physical properties (critical point, glass transition temperature, density, rheological properties), and their application in reactions catalyzed by metals (such as Pd, Cu, W, or Rh) or as organic solvent (for example for multicomponent reactions, organocatalysis, CO2 transformation) with special emphasis on their toxicity, environmental impact, and biodegradability. These aspects, very often neglected, need to be considered in addition to the green criteria usually considered to establish ecofriendly processes.

Competitive Solubilization of Phenol by Cationic Surfactant Micelles in the Range of Low Additive and Surfactant Concentrations

Competitive interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) against 1-butanol (BuOH) in aqueous solutions at surfactant concentrations close to the critical micelle concentration (CMC), BuOH concentration of 0.5 mmol kg(-1), and phenol contents of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of (1)H NMR spectroscopy, titration calorimetry, and solution conductimetry. The solubilization loci for phenol were deduced from the composition-dependence of the (1)H chemical shifts assigned to various protons in the surfactant and additive units. Since in pure HTAB solutions phenol is already in competition with Br(-), addition of 1 mmol kg(-1) NaBr to the system weakens the phenol competitiveness. The presence of butanol in the HTAB micelles causes phenol to penetrate deeper toward the hydrophobic micelle core. For higher phenol contents, the butanol molecules are constrained to remain in the bulk solution and are progressively replaced within the HTAB micelles by the aromatic units. The competitive character of phenol solubilization against butanol is well supported by changes in the thermodynamic parameters of HTAB micellization in the presence of both of the additives.

One Step Synthesis of Gold-Loaded Radial Mesoporous Silica Nanospheres and Supported Lipid Bilayer Functionalization: Towards Bio-Multifunctional Sensors

A simple synthetic route is developed to achieve gold functionalized radial mesoporous silica nanoparticles (Au-MsNP) synthesized by a one step procedure fully compatible with basic conditions required for the preparation of monodispersed nanospheres. In a second step, Au-MsNP particles have been coated with phospholipid bilayers in order to design an advanced biofunctional platform with the gold metallic nanoparticles previously grown into the pore channels and responsible for a plasmonic activity relevant for biosensing. The size of Au-MsNP is checked by dynamic light scattering while zeta potential measurements reflect their surface charge. The particle morphology is characterized by transmission and scanning electron microscopy and the Si/Au ratios are obtained from energy dispersive X-ray analysis. The textural properties of Au-MsNP, specific surface area and pore size, are determined from N(2) adsorption. The supported bilayers are achieved from vesicles of different phospholipids incubated with Au-MsNP particles. The coating efficiency is investigated by zeta potential and cryo- transmission electron microscopy. The plasmonic activities of bare Au-MsNP particles and coated lipid bilayer Au-MsNP platform are evidenced for two model systems: direct adsorption of bovine serum albumin and molecular recognition events between avidin molecules and biotin receptors integrated in the supported lipid bilayer.

Ring‐Closing Metathesis in Aqueous Micellar Medium

Underwater exploration: The ring-closing metathesis of N,N-diallyltosylamine (DATs) and diallyldiethyl malonate has been studied in aqueous micellar medium, at room temperature, in the presence of four different gemini cationic surfactants and various ruthenium catalysts. For the first time, the adsorption mechanisms and the reaction steps involved in this heterogeneous catalytic process were elucidated.

Synthesis, decoration, and cellular effects of magnetic mesoporous silica nanoparticles

Mesoporous Silica Nanoparticles (MSN) are now considered as multifunctional platforms for pharmaceutical development. The goal of this study was to optimize a synthesis procedure to obtain reproducible monodisperse magnetic core@shell Fe3O4@MSN with different coatings and study their uptake by cells. 100 nm core@shell nanoparticles with a unique 18 nm magnetic core were synthesized and covered with PEG groups or coated with a lipid bilayer in a controlled manner and their cellular fate was investigated. Both PEG and lipidic coated nanoparticles exhibit a low toxicity when incubated with Hep-G2 cells compared to pristine ones. Furthermore, the different real-time impedance cellular profiles that were observed and the particles uptake by the cells investigated by TEM suggest different internalization mechanisms or uptake kinetics depending on MSN coverage. This study is a first essential step to ensuring the preparation of well-defined nanomaterials for medical applications; it is considered as a crucial step to be able to perform detailed research about cellular trafficking and signaling pathways.

Microwave-ultrasound simultaneous irradiation: a hybrid technology applied to ring closing metathesis

A new hybrid microwave (MW) and ultrasound (US)-assisted reactor concept was investigated. The 2.45 GHz microwaves were delivered by a semiconductor generator via a coaxial cable to a monomode Transverse Electric (TE) microwave resonant cavity within which the reactor was placed; the US (25 kHz) were delivered at the bottom of the TE cavity via a novel designed sonotrode consisting of a detachable metallic plate-probe (indirect sonication). The semiconductor microwave generator helped to optimize the absorbed energy via its automatic frequency tuning function. The dual MW/US device allowed the use of both technologies separately or in a simultaneous combined manner. The ring-closing metathesis of diethyl diallyl malonate in glycerol micellar conditions was studied as an example using this novel hybrid technology. The results were compared with those obtained when microwaves or ultrasound were applied individually. Various benzylidene-, indenylidene- and Hoveyda–Grubbs-type catalysts were screened. The novel reactor for combined MW/US irradiation showed beneficial effects on the outcome of the reaction.

Recent developments in nanostructured inorganic materials for sorption of cesium and strontium: Synthesis and shaping, sorption capacity, mechanisms, and selectivity-A review

Liquid wastes containing non-ferrous heavy metal ions and some radionuclides, 137Cs and 90Sr in particular, represent one of the most dangerous sources of environmental contamination. The remediation of wastewater containing such pollutants continue to be among the biggest challenges of Sustainable Development and Environmental Safety. Sorption-based technologies have proven their efficiency also in reducing the radionuclide content in aqueous streams to low-level residual activity, with the concomitant decrease in the amount of ultimate solid waste generated. Although sorption of cesium and strontium by resins, clays, and zeolites has been investigated intensively and even used in real applications, there is still considerable scope for improvement in terms of retention capacity and selectivity. Recent progress in design and preparation of nanostructured inorganic materials has attracted growing interest based on the potential for improving the retention performance when coupling such functionalities as ion exchange capacity, structural flexibility that may result in steric retention effects, as well as the propensity to interact specifically with the target metal cations. Titanate, vanadate, and tungsten based materials, manganese oxides, hexacyanoferrates, metal sulfides, ammonium molybdophosphates, or hydroxyapatite, characterized by various structures and morphologies, are reviewed with the emphasis being put on synthesis and shaping of such materials, their structure in relationship with the capacity and selectivity of trapping cesium and strontium from either single or multi-component aqueous solutions, as well as the possible retention mechanism. The potential candidates for remediation uses are selected with regard to their sorption capacity and distribution coefficient towards target cations, and also the pH window for an optimum cation capture.

Conductivity and dielectric relaxation in crosslinked PVA by oxalic and citric acids

In this work we investigated polyvinyl alcohol films which we crosslinked at various crosslinking degrees by oxalic and citric acids for the fuel cell applications. We studied the effects of the crosslinking on structure, thermal properties, electric conductivity and dielectric relaxations. The glass transition temperature is increased indicating the lowering of the local mobility of the polymer chains. X-ray diffraction showed the presence of non-dissociated acid phases in dried samples. The Dc conductivity increases by increasing both the relative humidity and the temperature obeying to an Arrhenius law with activation energy compatible with proton conductivity type. The Ac conductivity studied between 10−1 Hz and 1 MHz showed a power law response in the high frequency range. This behavior characterizes the charge transport in disordered materials. At low frequencies the Ac conductivity is governed by the electrode/sample interface polarization. The use of the dielectric permittivity indicates the presence of a relaxation process attributed to electrode/sample interface polarization and another relaxation process attributed to alpha relaxation of the polyvinyl alcohol chains.