Search results for "Surface Chemistry"

Influence of drug polarity upon the solid-state structure and release properties of self-emulsifying drug delivery systems in relation with water aff…

2009

To overcome low oral bioavailability of poorly water-soluble drugs, self-emulsifying drug delivery systems (SEDDS) have been noted as a promising strategy. However, incorporation of drugs into SEDDS composed of Gelucire44/14 could induce interactions not yet well understood. The aim of this study was to investigate the influence of drug polarity upon the solid-state structure of SEDDS formulation, particularly in terms of wettability, thermal behaviour and microscopic aspects and their effect upon the release properties of the SEDDS. Model drugs were naproxen and sodium naproxen (10% w/w), two drugs with similar chemical structure but different water solubilities. Both drugs had an effect o…

Fluoride Complexation of Element 104, Rutherfordium

2004

Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the 18O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effects on the fluoride complexation of Rf.

First Ionization Potentials of Fm, Md, No, and Lr

2018

We report the first ionization potentials (IP1) of the heavy actinides, fermium (Fm, atomic number Z = 100), mendelevium (Md, Z = 101), nobelium (No, Z = 102), and lawrencium (Lr, Z = 103), determined using a method based on a surface ionization process coupled to an online mass separation technique in an atom-at-a-time regime. The measured IP1 values agree well with those predicted by state-of-the-art relativistic calculations performed alongside the present measurements. Similar to the well-established behavior for the lanthanides, the IP1 values of the heavy actinides up to No increase with filling up the 5f orbital, while that of Lr is the lowest among the actinides. These results clear…

Interaction of ionic compounds with multilamellar liposomes. An electrokinetic model

1998

Abstract We have proposed a theoretical model of interaction of ionic compounds (ionic adsorbate or ionic drugs), with multilamellar-liposomes, by means of their electrokinetic property variation with the ionic compound concentration. In this work, we show the complete development of the model proposed. Its theoretical results have been analysed to study the influence on the zeta-potential value of the following: number of membranes, size, shear-plane situation, critical concentration of formation (ccf), and the ionic compound concentration which annuls the zeta-potential value of the multilamellar-liposomes formed.

Structural and vibrational study of the tautomerism of histamine free-base in solution.

2003

Infrared and Raman spectroscopy in H(2)O and D(2)O and quantum Density Functional calculations were used to determine the structure of histamine free-base in aqueous solution. A quantum mechanical study of the tautomeric equilibrium of histamine free-base in solution was performed at the 6-311G level. Electronic correlation energies were included by using the hybrid functional B3LYP. The solvent was simulated as a continuum characterized by a dielectric constant, and the quantum system (solute) was placed in an ellipsoidal cavity. Solute-solvent electrostatic interaction was calculated by means a multipolar moment expansion introduced in the Hamiltonian. Four relevant histamine conformation…

Ettringite surface chemistry: Interplay of electrostatic and ion specificity

2011

International audience; This paper presents a detailed experimental study combined with Monte Carlo (MC) simulations within the primitive model of the physical chemistry at the ettringite-water interface over a wide range of pH and bulk conditions for which ettringite exists thanks to its solubility in aqueous solutions. Ettringite, which is an important phase in hydrated cement-based systems, bears a permanent and positive structural charge. In contrast with previous studies, electrokinetic measurements together with the careful chemical analysis of the equilibrium solutions of the dispersions have brought strong support to designate sulfate as being the ion determining the potential. Simu…

Electrophoretic flow behaviour and mobility of colloidal fluids and crystals.

2007

We report on measurements of the electrophoretic mobility mu of charged colloidal spheres in the deionized state, where the suspensions show fluid or crystalline order. In the fluid state, parabolic flow profiles are observed due to electro-osmotic solvent flow. In the crystalline state, complex flow profiles occur due to additional crystal cohesion. The mobility mu then may inferred from the flow velocity averaged over the complete cell cross section as performed in our home built super-heterodyne Doppler velocimeter. For two particle species of 68 and 122 nm diameter we measured mu as a function of particle concentration. Starting from a plateau value at low concentration, mu decreases ap…

2020

The reaction of the copper(I) β-diketiminate copper complex {(Cu(BDIMes))2(μ-C6H6)} (BDIMes = N,N'-bis(2,4,6-trimethylphenyl)pentane-2,4-diiminate) with the low-valent group 13 metal β-diketiminates M(BDIDip) (M = Al or Ga; BDIDip = N,N'-bis(2,6-diisopropylphenyl)pentane-2,4-diiminate) in toluene afforded the complexes {(BDIMes)CuAl(BDIDip)} and {(BDIMes)CuGa(BDIDip)}. These feature unsupported copper-aluminum or copper-gallium bonds with short metal-metal distances, Cu-Al = 2.3010(6) A and Cu-Ga = 2.2916(5) A. Density functional theory (DFT) calculations showed that approximately half of the calculated association enthalpies can be attributed to London dispersion forces.

Ionic liquids gels: Soft materials for environmental remediation

2017

Abstract Hypothesis Nanostructured sorbents and, in particular, supramolecular gels are emerging as efficient materials for the removal of toxic contaminants from water, like industrial dyes. It is also known that ionic liquids can dissolve significant amounts of dyes. Consequently, supramolecular ionic liquids gels could be highly efficient sorbents for dyes removal. This would also contribute to overcome the drawbacks associated with dye removal by liquid–liquid extraction with neat ionic liquids which would require large volumes of extractant and a more difficult separation of the phases. Experiments Herein we employed novel supramolecular ionic liquid gels based on diimidazolium salts b…

Fast Access to Amphiphilic Multiblock Architectures by the Anionic Copolymerization of Aziridines and Ethylene Oxide.

2018

An ideal system for stimuli-responsive and amphiphilic (block) polymers would be the copolymerization of aziridines with epoxides. However, to date, no copolymerization of these two highly strained three-membered heterocycles had been achieved. Herein, we report the combination of the living oxy- and azaanionic ring-opening polymerization of ethylene oxide (EO) and sulfonamide-activated aziridines. In a single step, well-defined amphiphilic block copolymers are obtained by a one-pot copolymerization. Real-time 1H NMR spectroscopy revealed the highest difference in reactivity ratios ever reported for an anionic copolymerization (with r1 = 265 and r2 = 0.004 for 2-methyl- N-tosylaziridine/EO …