Search results for "Aqueous solution"
showing 10 items of 1610 documents
Steroid-based gelators of A(LS)2 type: Tuning gel properties by metal coordination
2020
By utilizing up-to-date knowledge about gelators, we designed and synthesized a novel low-molecular-weight gelator bearing a pyridine-2,6-dicarboxylic acid moiety and two cholesteryl glycinate units. In order to demonstrate the ingenuity of our design, we prepared a series of structurally related compounds and studied their gelation properties. Based on the results, we determined structural features of the gelator molecules which were important for successful gel formation. We showed that the properties of the gel systems (transparency, morphology, etc.) can be tuned by coordination with different metal ions, as well as by changing the solvent. Gelators, and their gels and xerogels were stu…
XAFS study of short range order in the heavily disordered MoxW1−wO3 oxides
1995
We have done comparative XAFS analysis on the MoK and WL 3 edges of polycrystalline Mo x W 1-x O 3 solid solutions. It was found that their structures are closely related to corner-shared WO 3 -type for x<0.9 while α-MoO 3 -type structure is present for x≥0.9. The obtained structural parameters for the first shell around metal ions allow to distinguish several structural phase transitions due to the change of composition. A set of subshells within the first shell was found, and they are in good agreement with Raman data
Modulation of the magnetic anisotropy of octahedral cobalt(ii) single-ion magnets by fine-tuning the axial coordination microenvironment
2019
Two mononuclear cobalt(II) complexes, with the formulas [Co(2,6-dfba)2(bpp)2(H2O)2]n (1) and [Co(2,6-dfba)2(bpe)2(H2O)2]n (2) (2,6-Hdfba = 2,6-difluorobenzoic acid, bpp = 1,3-bis(4-pyridyl)propane, bpe = 1,2-bis(4-pyridyl)ethylene), have been synthesized by combining Co(II) ions with benzoate derivatives and two homogeneous N-donor ligands, respectively. Constrained by the analogous CoN2O4 coordination spheres, the discretely hexa-coordinated Co(II) cores in both complexes display stretched octahedral geometries. The equatorial environments in both complexes are identical, whereas the axial sites are finely modulated by the different chemical natures of the terminal N-donor ligands. The com…
Preparation of cholesteric particles from cellulose derivatives in a microfluidic setup
2011
A microfluidic setup was used to process lyotropic cholesteric liquid crystalline mixtures of cellulose derivatives into spherical particles in the micrometre scale. By the method of co-flowing injection, monodisperse droplets of the liquid crystal, dispersed in an aqueous carrier fluid, were prepared. Polymerization of the acrylic solvent with UV-light fixed the orientation obtained by the flowing motion. The resulting particles were characterized by polarizing optical microscopy.
Dispersions of Nanoclays of Different Shapes into Aqueous and Solid Biopolymeric Matrices. Extended Physicochemical Study
2010
Dispersions of nanofillers into aqueous and solid biopolymeric matrices were studied from the physicochemical viewpoint. This work was carried out based on the idea that the combination of biopolymers, derived from renewable resources, and nanofiller, environmentally friendly, may form a new generation of nanomaterials with excellent and unique properties at low cost. To this purpose, two pectins with different degrees of methyl esterification and nanoclays like halloysite and laponite RD were selected. The thermodynamic and structural studies on the aqueous mixtures of pectin and nanoclay were able to discriminate the interactions, which control the adsorption of pectin onto the filler and…
Splitting of Surface-Immobilized Multicompartment Micelles into Clusters upon Charge Inversion
2016
International audience; We investigate a morphological transition of surface-immobilized triblock terpolymer micelles: the splitting into well-defined clusters of satellite micelles upon pH changes. The multicompartment micelles are formed in aqueous solution of ABC triblock terpolymers consisting of a hydrophobic polybutadiene block, a weak polyanionic poly(methacrylic acid) block, and a weak polycationic poly(2-(dimethylamino)ethyl methacrylate) block. They are subsequently immobilized on silicon wafer surfaces by dip-coating. The splitting process is triggered by a pH change to strongly basic pH, which goes along with a charge reversal of the micelles. We find that the aggregation number…
Template Electrochemical Growth and Properties of Mo Oxide Nanostructures
2014
This work is aimed at studying the growing process of nanostructures electrodeposited from molybdate aqueous solutions at different pH values into pores of polycarbonate membrane templates. The challenging issue was the opportunity to investigate a rather complex deposition process in a confined ambient, where electrochemical conditions are quite different from those usually established for deposition on a flat substrate. Nanostructures were grown from a bath containing Mo7O246– (NH4)6Mo7O24·4H2O) at different concentrations (50–100 g/L), at a constant cathodic current density of 2 mA/cm2 (electrodeposition area ∼8 cm2). Nanostructured deposit was characterized by XRD, EDS, Raman, XPS, and …
Femtosecond laser fragmentation from water-dispersed microcolloids: toward fast controllable growth of ultrapure Si-based nanomaterials for biologica…
2020
International audience; An ultrashort laser-assisted method for fast production of concentrated aqueous solutions of ultrapure Si-based colloidal nanoparticles is reported. The method profits from the 3D geometry of femtosecond laser ablation of water-dispersed microscale colloids, prepared preliminarily by the mechanical milling of a Si wafer, in order to avoid strong concentration gradients in the ablated material and provide similar conditions of nanocluster growth within a relatively large laser caustics volume. We demonstrate the possibility for the fast synthesis of non-aggregated, low-size-dispersed, crystalline Si-based nanoparticles, whose size and surface oxidation can be controll…
The role of molecular oxygen in the formation of radiation-engineered multifunctional nanogels
2019
Abstract Nanogels are very promising biomedical nanodevices. The classic “radiation chemistry-based” approach to synthetize nanogels consists in the irradiation with pulsed electron beams of dilute, N2O-saturated, aqueous solutions of water-soluble polymers of the “crosslinking type”. Nanogels with controlled size and properties are produced in a single irradiation step with no recourse to initiators, organic solvents and surfactants. This paper combines experimental syntheses, performed with two e-beam irradiation setups and dose-ranges, starting from poly(N-vinyl pyrrolidone) solutions of various concentrations, both in N2O-saturated and air-saturated initial conditions, with the numerica…
Evidence of nickel ions dimerization in NiWO4 and NiWO4-ZnWO4 solid solutions probed by EXAFS spectroscopy and reverse Monte Carlo simulations
2021
Abstract The existence of exchange-coupled Ni 2 + ions – the so-called magnetic dimers – in wolframite-type NiWO 4 and Zn c Ni 1 − c WO 4 solid solutions with high nickel content was discovered by X-ray absorption spectroscopy combined with reverse Monte Carlo (RMC) simulations. Temperature- (10–300 K) and composition-dependent X-ray absorption spectra were measured at the Ni K-edge, Zn K-edge, and W L 3 -edge of microcrystalline NiWO 4 , Zn c Ni 1 − c WO 4 and ZnWO 4 . Structural models were obtained from simultaneous analysis of the extended X-ray absorption fine structure (EXAFS) spectra at three metal absorption edges using RMC simulations. The obtained radial distribution functions for…