Search results for "ionic"

Easy Route to Functionalize Iron Oxide Nanoparticles via Long-Term Stable Thiol Groups

2009

International audience; The functionalization of superparamagnetic iron oxide nanoparticles (SPIOs) by meso-2,3-dimercaptosuccinic acid (DMSA) was investigated. Under ambient conditions, the thiol groups from DMSA are not stable and do not allow a direct functionalization without storage in stringent conditions or a chemical regeneration of free thiols. In this study, we have developed a protocol based on poly(ethylene glycol) (PEG) grafting of SPIO prior to DMSA anchoring. We have observed that PEG helps to increase the stability of thiol groups under ambient conditions. The thiol functionalized SPIOs were stable under physiological pH and ionic strength as determined by Ellman's essay and…

Alkaline titrations of poly(dG-dC).poly(dG-dC): microemulsion versus solution behaviour

2007

PolyGC was titrated with a strong base in the presence of increasing concentrations of NaCl (from 0.00 to 0.60M) either in water solution or with the polynucleotide solubilized in the aqueous core of reverse micelles, i.e., the cationic quaternary water-in-oil microemulsion CTAB/n-hexane/n-pentanol/water. The results for matched samples in the two media were compared. CD and UV spectroscopies and, for the solution experiments, pH measurements were used to follow the course of deprotonation. In both media the primary effect of the addition of base was denaturation of the polynucleotide, reversible by back-titration with a strong acid. In solution, the apparent pK(a) of the transition decreas…

Estimation of Solute-Stationary Phase and Solute-Mobile Phase Interactions in the Presence of Ionic Liquids

2019

The presence of free silanols on alkyl-bonded reversed-phase stationary phases is responsible for broad and asymmetrical peaks when basic drugs are chromatographed with conventional octadecylsilane (C18) columns due to ionic interactions. In the last few years, ionic liquids (ILs) have attracted attention to reduce this undesirable silanol activity. ILs should be considered as dual modifiers (with a cationic and anionic character), which means that both cations and anions are able to adsorb on the stationary phase, creating a positively or negatively charged layer, depending on the relative adsorption. The accessibility of basic compounds to the silanols is prevented by both the IL cation a…

Interfacial Self-Assembly of Water-Soluble Cationic Porphyrins for the Reduction of Oxygen to Water

2012

Meet at the border: Assembly of the water-soluble cobalt tetrakis(N-methylpyridinium-4-yl)porphyrin [CoTMPyP]4+ at soft interfaces is enhanced and stabilized by its interfacial interaction with the lipophilic anion (C6F5)4B−. The supramolecular structure thus formed (see picture) provides excellent catalytic activity in the four-electron reduction of oxygen.

Versatile supramolecular self-assembly. Part I. Network formation and magnetic behaviour of the alkaline salts of the bis(malonate)cuprate(ii) anion

2006

Five malonate-containing copper(II) compounds of formula {[A(H2O)n]2 [Cu(mal)2(H2O)m]} [A = Li (1), Na (2), K (3), Rb (4) and Cs (5); H2mal = malonic acid] have been synthetized and characterized by X-ray diffraction. The structure of these compounds consists of bis(malonate)cuprate(II) anions and alkaline cations that are held together by means of carboxylate bridges and water molecules leading to 3D networks. A study of the self-assembling of the bis(malonate)cuprate(II) and the alkaline cations is carried out, the size of the alkaline metal ion playing an important role in the control of the resulting malonate-bridged copper(II) structure. A regular alternation of layers of anionic malon…

Redox-Responsive Host–Guest Chemistry of a Flexible Cage with Naphthalene Walls

2020

"Naphthocage", a naphthalene-based organic cage, reveals very strong binding (up to 1010 M-1) to aromatic (di)cationic guests, i.e., the tetrathiafulvalene mono- and dication and methyl viologen. Intercalation of the guests between two naphthalene walls is mediated by C-H···O, C-H···π, and cation···π interactions. The guests can be switched into and out of the cage by redox processes with high binding selectivity. Oxidation of the flexible cage itself in the absence of a guest leads to a stable radical cation with the oxidized naphthalene intercalated between and stabilized by the other two. Encapsulated guest cations are released from the cavity upon cage oxidation, paving the way to futur…

Associative behaviour of κ-carrageenan in aqueous solutions and its modification by different monovalent salts as reflected by viscometric parameters

2019

Abstract The viscometric behaviour of κ-carrageenan in aqueous solutions and in the presence of monovalent salts was investigated at 25 °C. Coil, helix or double helix conformations were induced by cooling hot κ-carrageenan solutions under appropriate ionic conditions. A new viscometric approach was used for modeling the behaviour of κ-carrageenan solutions. The intrinsic viscosity, [η], is markedly changed by the presence of different monovalent salts (NaCl, NaI and CsI). In pure water, the intrinsic viscosity amounts to 48 dL·g−1. In 0.1 M NaCl solutions (single helix state) [η] is 6.2 dL·g−1, whereas in 0.1 M NaI (double helix conformation) it is approximately twice as large. In 0.1 M Cs…

Does transvaginal color Doppler sonography differentiate between developing and involuting ectopic pregnancies?

1995

The objective of this study was to assess the addition of transvaginal color Doppler imaging to transvaginal ultrasonography and beta-human chorionic gonadotropin values to differentiate between developin and involuting ectopic pregnancies. Forty surgically confirmed ectopic pregnancies were classified into developing or involuting according to histopathologic findings. Results were compared retrospectively with the plasma beta-human chorionic gonadotropin values as well as the resistive index and pulsatility index obtained in corpora lutea and peritrophoblastic flow in serial examinations. Student's t-test was used for comparison of means. Logistic regression analysis was applied to predic…

Self strengthening, Load Bearing Ionic Liquid Gels for Environmental Remediation

Di- and Tricationic Organic Salts: an Overview of Their Properties and Applications

2014

During recent years growing interest has been devoted to the synthesis and applications of polycationic organic salts. Among them, di- and tricationic organic salts can be considered the natural evolution of monocationic ones. These last have given rise to the large class of ionic liquids. In the cases of di- and tricationic organic salts, the potential to change their structural features simply by varying the properties either of the charged heads or of the spacers separating them provides the opportunity to obtain materials suitable for different applications. This review article highlights recent progress in the study of the properties of di- and tricationic organic salts, as well as in …