A series of electrochemically generated polymeric nickel (II) Schiff base complexes was investigated by in situ electron spin resonance (ESR)/ultraviolet–visible–near infrared (UV–vis–NIR) ...spectroelectrochemistry and the combination of cyclic voltammetry and quartz crystal microbalance (QCM) techniques. The comparative analysis of the in situ ESR and UV–vis–NIR (including low-energy NIR range) spectra of poly-Ni(Schiff) films recorded during their oxidation at ambient temperature was performed, which allowed us to monitor the formation of different charge carriers in the polymer at different doping levels and elucidate their structure as well as the extent of their delocalization. The polymer doping level achieved by its oxidation within selected range of potentials was determined by combining the results of cyclic voltammetry and QCM measurements. The influence of the substituents in the diamine backbone and phenolate moieties of the ligand on the spectroscopic properties of the oxidized polymers and number of electrons per monomer unit exchanged in the redox processes was studied in detail. Integration of data from all techniques allowed us to propose the existence of both inter- and intrachain delocalization of radical cations generated in the doped polymers and show that the highest doping levels (up to two positive charges per a monomer unit) are attained in the poly-Ni(Schiff) films with highly localized biphenoxyl radical cations.
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Aqueous solutions of nonionic surfactants are of interest for bioprocesses, particularly as solubilizing agents for hydrophobic substances. To design such processes, the data on ...partition coefficients of solutes between micelles and their aqueous surrounding (Pmw) are of high value. An extended understanding of the partition behavior can be achieved from the structural information such as the micelle size and micelles composition.
In this work, mixtures of nonionic surfactants Triton X-100 and Brij 35 were under study. The data on critical micelle concentrations showed partly non-ideal behavior of the solutions. The compositions of mixed micelles at different molar Brij 35/Triton X-100 ratios in the surfactant mixture were estimated from the data on self-diffusion coefficients (NMR diffusometry) and were calculated within the regular solution approach and predicted by Motomura’s model. The change of the mixed micelle composition in dependence on the total surfactant concentration was observed. It has been found, that the average value of the mixed micelles radii is ∼4nm. Whereas, the polydispersity indexes and the aggregation numbers increased with Triton X-100 fraction. Moreover, the Pmw values of different non-dissociated solutes (phenyl derivatives with various functional groups) were determined by means of micellar liquid chromatography (MLC) and were predicted using the thermodynamic model COSMOmic, an extension of COSMO-RS. In general, it has been proved that COSMOmic is able to predict Pmw in the mixed micellar system formed by nonionic surfactants.
The obtained data show the possibility of modulating the partition behavior of solutes using the mixtures of nonionic surfactants. Apart from the hydrophobicity, the «surfactants – solute» specific interactions play an important role in the partition behavior of the investigated systems.
Graphene nanostructures (GNSs) are among the most promising materials for producing supercapacitors. However, GNSs are still not used in creating supercapacitors due to the impossibility of obtaining ...large volumes of high-quality material at an acceptable cost. In our previous works, we have shown the possibility of synthesizing large volumes of few-layer graphene (FLG, the number of layers is not more than five) from cyclic biopolymers under conditions of self-propagating high-temperature synthesis (SHS). Using the SHS process makes it possible to synthesize large volumes of FLG without Stone–Wales defects. This work is devoted to the study of the possibility of using FLG synthesized under the conditions of the SHS process in the creation of supercapacitors. It was found that the synthesized FLG makes it possible to obtain better results than using classical materials, namely activated carbon (AC). It was found that the sample based on FLG had a higher specific capacitance of 65 F × g−1 compared to the sample from AC, the specific capacitance of which was 35 F × g−1; for a speed of 5 mV × s−1, these values were170 and 64 F × g−1, respectively. The drop in capacitance over 1000 cycles was 4%, indicating a sufficiently high FLG stability, allowing us to consider FLG as a prospective material for use in supercapacitors.
The healthcare system plays an undisputed role in the issues of human potential reproduction and is an integral part of ensuring national security. A key and important factor for ensuring sustainable ...development of the country and its future is investment in the health of citizens. The purpose of the study is to explore the healthcare system as one of the most important spheres, which is one of the primary components of public life. The methodological basis of the study consists of an analysis of statistical indicators of morbidity in Russia from 2020 to 2023, as well as an analysis of the total number of medical workers over the past two years. This allowed to identify the main problems in the healthcare system that can be addressed through the national project “Healthcare”. The implementation of the national project “Healthcare” in Russia will significantly improve the healthcare system in the future, increase access and quality of medical care for citizens, and reduce the level of morbidity and mortality from various diseases. This is an important step towards creating a healthy nation and developing the country as a whole.
A series of polymeric cobalt (II) complexes with tetradentate N2O2 Schiff base ligands (poly-Co(Schiff)) are prepared via oxidative electrochemical polymerization and characterized by scanning ...electron microscopy, cyclic voltammetry, quartz crystal microgravimetry, and in situ UV/Vis spectroscopy in inert atmosphere. Integration of data from all techniques revealed that (a) all studied poly-Co(Schiff) films demonstrate multi-electron redox switching between 0 V and +1.4 V (vs. Ag/AgCl); (b) the Co(II) to Co(III) conversion takes place in the early stage of polymer oxidation, which is followed by both one- and two-electron ligand-based redox processes in the later stages; (c) the number of electrons exchanged by each monomer unit during oxidation/reduction of the polymer depends on the substituents in the imine bridge and aldehyde moieties of the ligand, as well as on the donor number of the electrolyte solvent. The poly-Co(CH3O-SaltmEn) film demonstrates the ability to be reversibly oxidized by three electrons per a monomer unit in an acetonitrile-based electrolyte, which makes it a viable candidate for energy storage applications.
Left: critical micelle concentration of NaDS in aqueous solutions containing C
4mimPF
6, C
6mimBF
4 or C
10mimBr versus the ionic liquid solvent-free mole fraction;
T
=
298.15
K. Right: mixed micelle ...of NaDS–C
10mimBr.
Experimental data on micellization in aqueous solutions of 1-alkyl-3-methylimidazolium salts C
n
mimX and their mixtures with sodium dodecyl sulfate (NaDS) are reviewed. New results (the critical micelle concentration and enthalpy of micellization) are presented for mixtures of C
4mimPF
6, C
6mimBF
4, C
6mimBr and C
10mimBr with NaDS. Our data cover a wide range (from 0 to 0.9) of solvent-free based mole fractions of ionic liquid (IL). Even very small addition of ILs substantially decreases the cmc of NaDS due to the combined effect of electrostatic and hydrophobic interactions, and formation of mixed micelles. It is shown that the quasichemical aggregation model by Nagarajan and Ruckenstein may be successfully applied to aqueous solutions of long-chain ILs and their mixtures with NaDS. The local structure of micelles is obtained from all-atom MD simulations for C
n
mimBr and C
n
mimX
+
NaDS in aqueous medium.
Aqueous biphasic systems containing ionic liquids (ILs) attract rather high attention; in particular their application in liquid–liquid extraction is very attractive due to the specificity of the ...systems and great possibilities in the modification of IL chemical structures. In the present work, a series of amino acid ionic liquids (AAILs) based on the 1-alkyl-3-methylimidazolium cation and l-glutamic acid anion C n mimGlu (n = 4, 6, 8) were synthesized. Densities, refractive indices, and specific electrical conductivities of aqueous solutions of these AAILs in the concentration range 0–70 wt % (for C4mimGlu solutions up to 87 wt %) were measured at temperature 298.15 K and ambient pressure 0.1 MPa. The liquid–liquid equilibria for ternary solutions C n mimGlu + salt (K2CO3) + water at 298.15 K were under study. In aqueous solutions of C8mimGlu micellization is observed, whereas C4mimGlu and C6mimGlu in aqueous solutions form small ordinary aggregates. The critical micellar concentration for C8mimGlu aqueous solutions at 298.15 K was estimated from the experimental data on the concentration dependence of the specific electrical conductivities of the solutions.
•Experimental analysis of vanillin partitioning in aqueous micellar biphasic systems.•Mixed micellar systems are perspective for cloud point extraction of ionized solutes.•Predictions with COSMO-RS ...are a helpful tool for the effective design of the cloud point extraction.•We use a mixed surfactant system for vanillin extraction by the continuous countercurrent cloud point extraction.
Aqueous biphasic systems based on nonionic surfactants have perspective applications in extraction processes, in particular, cloud point extraction of hazardous compounds or high valued products, especially biomolecules. Additives (e.g., ionic surfactants, salts) and variations in pH can significantly affect the surfactant-based separation processes, representing an additional degree of freedom for their optimization. However, there are few systematic studies of phase and partition behavior for these multicomponent surfactant systems.
In this study we examined the clouding, phase compositions and partitioning equilibria for aqueous mixed surfactant systems of a nonionic surfactant (Triton X-114), ionic surfactants (cetyltrimethylammonium bromide or sodium dodecyl sulfate) and NaCl, in order to improve the extraction efficiency. Vanillin was used as a model substance at three different pH values, specifically in (partly) dissociated or non-dissociated states. The partition coefficients obtained in the batch experiments were compared to the predictions by the thermodynamic model COSMO-RS. Based on this knowledge a continuous multistep extraction process was carried out.
To the best of our knowledge this is the first demonstration of using a mixed surfactant system for continuous countercurrent cloud point extraction.
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