Search results for "aqueous solution"
showing 10 items of 1610 documents
Stopped-Flow and DFT Studies of Proton Transfer and Isomerization of 5-Amino-3-imino-1,2,6,7-tetracyano-3H-pyrrolizine and Its Related Base 2-(5-Amin…
2001
International audience; A complete kinetic study of pH-dependent isomerization of 5-amino-3-imino-1,2,6,7-tetracyano-3H-pyrrolizine (HL) and 2-(5-amino-3,4-dicyano-2H-pyrrol-2-ylidene)-1,1,2-tricyanoethanide (L‘-) in the pH range from −0.5 to +13 in aqueous solution, which spans over 7 orders of magnitude for the pseudo-first-order rates (log k from −4.8 to +2.5), has revealed for the first time the existence of the corresponding conjugate species L- and HL‘. The study has allowed the determination of the acid dissociation constants of HL (pKa) and HL‘ (pKa‘), as well as all of the individual forward and reverse isomerization rates of the acidic (HL/HL‘) and basic (L-/L‘-) forms. Although L…
Anion coordination chemistry in aqueous solution of polyammonium receptors
2006
The behavior of polyamines as receptors of selected families of anions in water is explored. First metallocyanide interaction with saturated polyammonium hosts is analyzed both in solution and in the solid state. The utility of potentiometry, multinuclear NMR, microcalorimetry and cyclic voltammetry to describe solution features of this chemistry is described for selected systems. Sulfate, phosphate, polyphosphate and nucleotide interactions with large polyammonium receptors are then reviewed. Hydrogen bond formation is discussed from a thermodynamic point of view. The influence of the presence of aromatic fragments within the structure on the binding strength is discussed. Factors affectin…
Robust Lanthanoid Picolinate-Based Coordination Polymers for Luminescence and Sensing Applications
2021
Picolinate-based segmented dianionic ligands L12– (5-((4-carboxyphenyl)ethynyl)picolinate) and L22– (5,5′-(ethyne-1,2-diyl)dipicolinate) have been used in the synthesis of the highly robust and luminescent europium(III) coordination polymers [(CH3)2NH2][Eu(H2O)2(L1)2] (1) and [(CH3)2NH2][Eu(L2)2]·H2O·CH3COOH (2). Both 1 and 2 exhibit high selectivity for detection of nitroaromatic compounds since they act as quenchers of the Eu3+ emission. Stern–Volmer plots, using nitrobenzene as a quencher, yielded values of KSV = 150 M–1 and 160 M–1 for 1 and 2, respectively. Luminescence studies in the presence of different metal ions indicate a high selectivity for Fe3+ detection, with KSV values of 47…
Metal ion affinity-based biomolecular recognition and conjugation inside synthetic polymer nanopores modified with iron-terpyridine complexes.
2011
Here we demonstrate a novel biosensing platform for the detection of lactoferrin (LFN) via metal-organic frameworks, in which the metal ions have accessible free coordination sites for binding, inside the single conical nanopores fabricated in polymeric membrane. First, monolayer of amine-terminated terpyridine (metal-chelating ligand) is covalently immobilized on the inner walls of the nanopore via carbodiimide coupling chemistry. Second, iron-terpyridine (iron-terPy) complexes are obtained by treating the terpyridine modified-nanopores with ferrous sulfate solution. The immobilized iron-terPy complexes can be used as recognition elements to fabricate biosensing nanodevice. The working pri…
Photodegradation of polyglycidol in aqueous solutions exposed to UV irradiation
2011
The photodegradation of polyglycidol in aqueous solution with UV wavelength of 254 nm was investigated. The experiments were carried out in air at a constant temperature and the photodegradation of polyglycidol (PGl) was compared to that of poly(ethylene oxide) (PEO), the most widely studied polyether. Size exclusion chromatography with multiangle light scattering detection (SEC-MALLS) was used to measure the changes in the molar masses and molar mass dispersities of polymers during degradation. The molar mass of PGl decreased dramatically during the first period of UV irradiation and then gradually approached a limiting value of 17,000 g/mol, regardless of the initial polymer concentration…
Modified Halloysite Nanotubes: Nanoarchitectures for Enhancing the Capture of Oils from Vapor and Liquid Phases
2013
We prepared hybrid halloysite nanotubes (HNT/sodium alkanoates) in which the inner cavity of the nanoclay was selectively modified. Physicochemical studies evidenced the interactions between HNT and sodium alkanoates, ruled out clay exfoliation, quantified the amount of the loaded substance, and showed an increase of the total net negative charge, allowing us to obtain rather stable aqueous nanoclay dispersions. These dispersions were exploited as inorganic micelles to capture hydrocarbon and aromatic oils in the vapor and liquid states and were revealed to be nonfoaming but very efficient in encapsulating oils. Here, we have fabricated biocompatibile and low-cost inorganic micelles that ca…
Effect of carboxymethyl cellulose concentration on rheological behavior of milk and aqueous systems. A creep and recovery study
2009
Carboxymethyl cellulose (CMC) is an anionic polysaccharide used mainly as stabilizer and thickener agent. The purpose of this study was to investigate the effect of CMC concentration on viscoelasticity of dairy and aqueous model systems through the analysis of creep and recovery tests. The viscoelastic properties of different concentrations of CMC (0.75, 1.00, 1.25, and 1.50% w/w) in two milk systems (skimmed milk and whole milk) were compared with those of the same concentration of biopolymer in aqueous solution. Creep curves were fitted to a six parameter mechanical model (Burger + Kelvin-Voigt), whereas an empirical equation was used for recovery. The creep and recovery properties of sam…
A distorted honeycomb motif in divalent transition metal compounds based on 4-phosphonbenzoic acid and exchange coupled Co(II) and Cu(II): synthesis,…
2013
The first example of a two-dimensional inorganic hybrid material with cobalt as an open-shell transition metal ion and 4-phosphonbenzoic acid as a linker is presented together with its copper analogue. For both metal ions the inorganic part consists of edge-sharing metal–oxygen octahedra leading to a metal honeycomb motif. The magnetic properties of the cobalt compound are reported together with those of the corresponding copper compound based on the remarkably six-coordinated copper(II) ions.
MODIFICATION OF HUMIC SUBSTANCES FOR DEVELOPMENT OF MATERIALS FOR ENVIRONMENTAL TECHNOLOGIES
2019
Humic substances are high molecular weight refractory polycationites formed during decay of living organic matter and through biosynthesis of low molecular weight organic substances (metabolites or decay products of living organisms). Presence of many functional groups in the structure of humic substances determines their ability to interact with metal ions forming stable complexes and influencing metal ion speciation in the environment and mobility, behaviour and speciation forms in the environment. Presently humic substances are a product of industrial scale and quantities in amounts of hundreds of tons are produced. The aim of this study is to analyse derivatization possibilities of humi…
Volumes and heat capacities of the aqueous sodium dodecanoate/sodium perfluorooctanoate mixtures in the presence of β-cyclodextrin
2003
Apparent molar volumes (VΦ) and heat capacities (CΦ) of the sodium dodecanoate (NaL)/sodium perfluorooctanoate (NaPFO) mixtures in the water/β-cyclodextrin (β-CD) solvent as functions of the surfactant total molality (mt) were determined at 25°C. For a given surfactant mixture, VΦ decreases with mt to ca. 0.05 mol kg−1 thereafter it increases tending to a constant value. CΦ displays a behaviour opposite to VΦ. The mt values where the apparent molar properties exhibit extrema are nearly coincident with the critical micellar concentrations determined by conductivity. An equation correlating VΦ to mt was derived by assuming that the equilibria for the 1∶1 surfactant/cyclodextrin complex format…