Search results for "aqueous solution"
showing 10 items of 1610 documents
Soft Nanoonions: A Dynamic Overview onto Catanionic Vesicles Temperature-Driven Transition.
2020
Catanionic vesicles are emerging interesting structures for bioapplications. They self-generate by a pairing of oppositely charged ionic surfactants that assemble into hollow structures. Specifically, the anionic-cationic surfactant pair assumes a double-tailed zwitterionic behavior. In this work, the multilamellar-to-unilamellar thermal transition of several mixed aqueous systems, with a slight excess of the anionic one, were investigated. Interestingly, it was found that the anionic counterion underwent a dissociation as a consequence of a temperature increase, leading to the mentioned thermal transition. The present work proposed the spectroscopic techniques, specifically multinuclear NM…
Radiation-Engineered Functional Nanoparticles in Aqueous Systems.
2015
Controlled synthesis of nanoscalar and nanostructured materials enables the development of novel functional materials with fine-tuned optical, mechanical, electronic, magnetic, conductive and catalytic properties that are of use in numerous applications. These materials have also found their potential use in medicine as vehicles for drug delivery, in diagnostics or in combinations thereof. In principle, nanoparticles can be divided into two broad categories, organic and inorganic nanoparticles. For both types of nanoparticles there are numerous possible synthetic routes. Considering the large difference in nature of these materials and the elementary reactions involved in the synthetic rout…
Physico-chemical state influences in vitro release profile of curcumin from pectin beads
2014
International audience; Curcumin is a polyphenolic compound with diverse effects interesting to develop health benefit products but its formulation in functional foods or in food supplement is hampered by its poor water solubility and susceptibility to alkaline conditions, light, oxidation and heat. Encapsulation of curcumin could be a mean to overcome these difficulties. In this paper, curcumin was encapsulated by ionotropic gelation method in low methoxyl pectin beads associated with different surfactants: Solutol®, Transcutol® and sodium caseinate. After encapsulation, physico-chemical properties of encapsulated curcumin such as its solubility, physical state, tautomeric forms and encaps…
Donnan equilibrium of ionic drugs in pH-dependent fixed charge membranes: theoretical modeling.
2002
Abstract We have studied theoretically the partition equilibrium of a cationic drug between an electrolyte solution and a membrane with pH-dependent fixed charges using an extended Donnan formalism. The aqueous solution within the fixed charge membrane is assumed to be in equilibrium with an external aqueous solution containing six ionic species: the cationic drug (DH + ), the salt cations (Na + and Ca 2+ ), the salt anion (Cl − ), and the hydrogen and hydroxide ions. In addition to these mobile species, the membrane solution may also contain four fixed species attached to the membrane chains: strongly acid sulfonic groups (SO 3 − ), weakly acid carboxylic groups in dissociated (COO − ) a…
Self-consistent continuum solvation (SCCS): the case of charged systems.
2013
The recently developed self-consistent continuum solvation model (SCCS) [O. Andreussi, I. Dabo, and N. Marzari, J. Chem. Phys. 136, 064102 (2012)] is applied here to charged species in aqueous solutions. Describing ions in solution represents a great challenge because of the large electrostatic interactions between the solute and the solvent. The SCCS model is tested over 106 monocharged species, both cations and anions, and we demonstrate its flexibility, notwithstanding its much reduced set of parameters, to describe charged species in solution. Remarkably low mean absolute errors are obtained with values of 2.27 and 5.54 kcal/mol for cations and anions, respectively. These results are co…
Do zwitterionic species exist in the non-enzymatic peptide bond formation?
2012
The use of proper computational methods and models has allowed answering the controversial question of whether zwitterionic species exist in the mechanism of peptide bond synthesis in aqueous solution. In fact, the different conformations of zwitterionic species open the door to different mechanistic paths.
Long-ranged and soft interactions between charged colloidal particles induced by multivalent coions
2015
Forces between charged particles in aqueous solutions containing multivalent coions and monovalent counterions are studied by the colloidal probe technique. Here, the multivalent ions have the same charge as the particles, which must be contrasted to the frequently studied case where multivalent ions have the opposite sign as the substrate. In the present case, the forces remain repulsive and are dominated by the interactions of the double layers. The valence of the multivalent coion is found to have a profound influence on the shape of the force curve. While for monovalent coions the force profile is exponential down to separations of a few nanometers, the interaction is much softer and lo…
Reversible Colorimetric Probes for Mercury Sensing
2005
The selectivity and sensitivity of two colorimetric sensors based on the ruthenium complexes N719 [bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) bis(tetrabutylammonium) bis(thiocyanate)] and N749 [(2,2':6',2' '-terpyridine-4,4',4' '-tricarboxylate)ruthenium(II) tris(tetrabutylammonium) tris(isothiocyanate)] are described. It was found that mercury ions coordinate reversibly to the sulfur atom of the dyes' NCS groups. This interaction induces a color change in the dyes at submicromolar concentrations of mercury. Furthermore, the color change of these dyes is selective for mercury(II) when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II). The detection limit…
Thermodynamics of transfer of polar additives from the aqueous to the dodecylsurfactant micellar phases
1990
The enthalpies of transfer from water to aqueous surfactant solutions, ΔH(W→W+S), of polar additives have been determined as a function of the surfactant concentration at fixed additive concentration. The surfactants used are sodium dodecylsulfate (NaDS), dodecyltrimethylammonium bromide and dodecyldimethylamine oxide (DDAO). The additives used are iso-butanol t-butanol, butoxyethanol, phenol, benzene, tributylphosphine oxide (TBPO), octyldimethylphosphine oxide (ODPO), octydimethylamine oxide (ODAO), DDAO and NaDS. A maximum was observed in the plots of ΔH(W→W+S) vs. fsms curves for ODPO and ODAO in NaDS while a small minimum was observed for TBPO. The experimental data are rationalized on…
Binding of Short Alkyl Chain Surfactants to the (Ethylene oxide)13−(Propylene oxide)30−(Ethylene oxide)13and (Ethylene oxide)75−(Propylene oxide)30−(…
2002
The enthalpy of transfer (ΔHt) of neutral copolymers, at a fixed and low concentration ca. 10-3 mol kg-1, from water to the aqueous surfactant solutions as a function of the surfactant concentration (fSmS) was determined at 25 °C. The surfactants studied are sodium octanoate, sodium decanoate, N-octylpyridinium chloride (OPC), and N,N-dimethyloctylamine-N-oxide (ODAO). The copolymers are (ethylene oxide)13−(propylene oxide)30−(ethylene oxide)13 (L64) and (ethylene oxide)75−(propylene oxide)30−(ethylene oxide)75 (F68). The two copolymers show different hydrophilic−hydrophobic ratios, the larger being for F68. As a general feature, the shape of the ΔHt vs fSmS curve depends on the nature of t…