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The temperature and interfacial behaviors of water bound to various sorbents (silicas, carbons, polymers, etc.) are of interest from both theoretical and practical points of view because a certain amount of water could be always adsorbed from air and can affect the material properties, especially at low temperatures due to possible frost damage. These behaviors could be studied using low-temperature ¹H NMR spectroscopy of static samples. The particulate morphology and texture of sorbents were characterized using microscopic and nitrogen adsorption methods. The study well demonstrates the influence of various factors including the morphology, texture, and surface structure of sorbents on the temperature and interfacial behaviors of bound water in the amounts smaller than the pore volume of sorbents. Upon volume infilling of pores by water, the textural and morphological effects (leading to the freezing/melting point depression) could be stronger than the effect of the surface structure (leading to the reorganization of bound water), because only one-two adsorption layers are well sensitive to the surface structure (polar or nonpolar surface functionalities). Therefore, changes in the relative amounts of unfrozen water Cuw(T)/C280K vs. temperature (at 200 K < T < 273 K) are similar for very different sorbents such as nanosilica, nano/mesoporous silica gel, and activated carbon (at close water amounts in the hydration range of h = 0.04–0.06 g/g) in contrast to that for microcrystalline cellulose. There are strong effects caused by the bound water amounts that are better observed for sorbents with a great contribution of nanopores, e.g., activated carbon AC–86 possessing very high specific surface area due to significant nanoporosity. A nonmonotonic effect of the amounts of water bound to AC–86 could be explained by nonuniform distribution of O-containing functionalities (mainly located at the edges of carbon sheets at the entrances into slitshaped hydrophobic nanopores). The clustered adsorption of water around these functionalities inhibits penetration of water into nanopores (formed by hydrophobic basal planes) especially at small amounts of water. An increase in the water content causes more intensive diffusion of the water molecules into narrower but less hydrophilic pores of AC–86 that results in enhanced freezing/melting point depression. The obtained results are of interest from a practical point of view since very different and practically important sorbents were analyzed in parallel at low temperatures upon various wetting. [ABSTRACT FROM AUTHOR]

Production of valuable industrial materials from lignins as byproducts of different origin is of importance to solve the utilization problem for large amounts of these byproducts. One of the corresponding pathways is the production of water-soluble lignins, for which, interactions with water and aqueous solutions play an important role in practical application efficiency of these materials. One could assume that interactions of lignins with bound water and solutions depend strongly on the dispersion media and the presence of various (e.g., polar and ion-generating) solutes in water. The interfacial and temperature behaviors of water (solutions) bound to lignin particles in wetted powders could be effectively studied using low-temperature ¹H NMR spectroscopy applied to static samples that allows one to separate mobile and immobile phases vs. temperature below freezing point (Tf,b) of bulk liquid. At T < Tf,b several effects could be observed in wetted lignin powders such as confined space effects (CSE) in pores or voids between or inside crosslinked macromolecules, cryoscopic effects (CE) in bound solutions, partial freezing of liquids with cryoconcentration and differentiation of solutions, clusterization of bound liquids, etc. To elucidate some of these effects, wetted water-soluble lignin powders at a constant degree of hydration (h = 0.3 g/g) were studied in such dispersion media as air and chloroform-d alone or in a mixture with deuterated trifluoroacetic acid using the lowtemperature ¹H NMR spectroscopy method. Additionally, hydrated lignin molecules of different sizes were studied using quantum chemistry methods. Obtained results show that both CSE and CE affect the temperature behavior of bound water and related solutions. However, there is no their strong synergetic impact because the stronger bound the water (solution) the lower the activity of water as a solvent; i.e., CSE could partially inhibit CE. The obtained results are of interest in order to better understand different aspects of applications of water-soluble lignins under various conditions [ABSTRACT FROM AUTHOR]

Low-temperature ¹H NMR spectroscopy was used to study the pig spinal and brain tissues of the original samples at different temperatures, in chloroform, including that with the addition of hydrochloric acid, and in a mixture of chloroform and trifluoroacetic acid (TFAА) in a ratio of 6:1. It has been found that water in the tissues of the pig's brain and spinal cord is bound and is part of polyassociates, the radius of which is in the range R = 1–100 nm. During the freezing-thawing process, only the signal of bound water is observed in the ¹H NMR spectra, while the protons of biopolymers and phospholipid membranes are not detected in the spectra, which indicates their low molecular mobility. Chloroform dissolves in the substance of cell membranes, increasing the mobility of aliphatic groups, and the membrane material passes from an ordered to a partially disordered state. This effect is much stronger for spinal cord tissue, which is due to the lower content of interstitial water. The characteristics of interstitial water layers were calculated: the concentration of strongly and weakly bound water, the maximum decrease in the Gibbs free energy in the layer of strongly bound water and interfacial energies. It has been found that for spinal cord tissue, the introduction of chloroform into the system is accompanied by a decrease in the binding of water in the nervous tissue (the amount of highly bound water decreases from 180 to 250 mg/g), and the value of interfacial energy decreases from 24 to 19.6 J/g. However, these changes have little effect on the radius distributions of interstitial water clusters. The main maximum of the distribution does not change and is observed at R = 20 nm. In the presence of TFAА, the amount of strongly bound water increases to 1400 mg/g, and the value of interfacial energy increases to 77.6 J/g. For brain tissue, their value turned out to be significantly less. Thus, chloroform had virtually no effect on the binding energy of water in the tissue, and the effect of TFAА also turned out to be half that for spinal cord tissue. [ABSTRACT FROM AUTHOR]

With the development of nanotechnology, new scientific directions have been initiated and a significant amount of researches has been carried out, dedicated to the creation and search for promising applications in medicine, in particular, oncology, of nanocomposites based on bioinert, biocompatible and bioactive nanoparticle materials and modern chemotherapeutic drugs with different mechanisms of action. These works contain data indicating the advantages to introduce nanocomposite drugs into clinical practice, compared to the traditional use of chemotherapeutic drugs. The research results confirm the priority of works in the field of creation of new nanocomposite chemotherapeutic drugs for use in antitumor therapy and overcoming of drug resistance of malignant cells and neoplasms. The purpose of the review is to generalize and analyze the authors’ experimental works performed at Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, concerning the specifics of the effect of chemotherapeutic drugs with different mechanisms of action and related nanocomposites, on cellular systems and tumors. Such data are relevant to determine promising directions and ways of creation of new effective nanocomposite drugs for use, in particular, in antitumor chemotherapy. At Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, using the chemical engineering method, magnetically sensitive core-shell nanocomposites were synthesized with a multi-level hierarchical nanoarchitecture capable of performing a complex of diagnostic and therapeutic functions with various mechanisms of action, characteristic of medico-biological nanorobots. Their use makes it possible to implement the principle of targeted delivery of antitumor drugs, to carry out real-time local therapy by various methods and MRI diagnosis of the disease, to realize the synergy of treatment with antitumor drugs of different mechanisms of action, to reduce the toxic side effects of oncological drugs on the body. The combination of the above features of nanocomposites, as well as their role in overcoming the drug resistance of cells of malignant neoplasms to cisplatin, testify to the perspective of creation and research of nanocomposite drugs in solving the problem of increase in the efficiency of chemotherapy. [ABSTRACT FROM AUTHOR]

The use of hydrophobic silicas as medical adsorbents in comparison with hydroxyl silicas allows to increase the adsorption of some toxins on their surface due to the reduction of water adsorption. The purpose of this study was to find a co-adsorbate that, adsorbed on a hydrophobic surface, would allow the preparation of aqueous suspensions of an enterosorbent based on methylsilica, and, once inside the body, would be easily destroyed by the enzymes of the gastrointestinal tract, freeing its surface for the adsorption of toxins on it. The structure of the hydrate shell and the adsorption capacity of composite materials based on methyl silica and gelatin obtained by different methods were investigated by a set of physical and chemical methods. Low-temperature ¹ H NMR-spectroscopy has been used to study of water clusters bound to composite surface. It has been found that the water in the composite on the basis of hydrophobic methyl silica and gelatin gel is present in the form of clusters with a radius of 0.5–15 nm and is in a strongly associated state when measured in air. When a liquid hydrophobic medium is added, the water partially passes into a weakly associated state. The bound water reacts to the presence of chloroform by changing the radial distribution of the adsorbed water clusters. It has been shown that for the composite system methyl silica AM-1/gelatin (5/1), the introduction of chloroform into the interfacial space leads to a significant decrease in the interfacial energy, which indicates a partial displacement of water by the hydrophobic solvent at the interface. At the same time, for composites made on the basis of dry powders, this effect is not observed and its interfacial energy has an intermediate value between the interfacial energies of methyl silica and gelatin containing the same amount of water. Adsorption of Congo red as the medium molecular weight toxins marker from aqueous solutions on the studied composites was studied in comparison with methylsilica. It has been found that gelatin in the composition of composites contributes to increasing dye adsorption. The amount of adsorbed Congo red depends on the method of preparation of the composite and the ratio of silica to gelatin. It is concluded that AM-1/gelatin composite systems can serve as effective adsorbents for removing medium molecular weight molecules from aqueous solutions. [ABSTRACT FROM AUTHOR]

The temperature and interfacial behaviors of individual and mixed liquids are of importance from a practical point of view because changes in the phase state of compounds with decreasing temperature could lead to negative effects (e.g., frost damage of porous materials). However, the use of certain mixtures may prevent these negative effects due to the colligative properties of the solutions (cryscopic effects, CE) that lead to several effects including relative lowering of vapor pressure, boiling point elevation, and freezing point depression (FPD). Confined space effects (CSE) also leading to the freezing point depression can affect the colligative properties of liquid mixtures with respect to FPD. One could assume that for some systems with certain FPD due to CE for bulk solutions, there is no additivity (synergetic effect) of CSE and CE, but for others, the opposite results could be. To elucidate these interfacial phenomena, a set of liquid mixtures bound to different adsorbents could be studied using low-temperature NMR spectroscopy. The solutions included acids, bases, and salts as solutes, some liquids (e.g., dimethylsulfoxide, acetonitrile, n-decane) as co-sorbates and others (e.g., CDCl3, CCl4) as dispersion media. The adsorbents included various porous and highly disperse silicas, fumed alumina, carbons (activated carbons, graphene oxides), and porous polymers. So wide ranges of the systems studied could allow one a deeper insight into competitive or additive CSE and CE influencing the interfacial and temperature behaviors of bound liquids. The results of this analysis are of interest from both practical and theoretical points of view. [ABSTRACT FROM AUTHOR]

Low turn-on field (Eto) and high current emission stability of cold field emission (FE) cathodes are crucial for their practical application in electronic devices. However, the FE cathodes' emission sites are still weaker and insufficient for use in actual applications. These issues can be resolved by focusing on the design and assembly of the individual building blocks into a specific three-dimensional (3D) structure. In the current study, a single-crystal integrated N-doped 3D branched SiC nanowire FE cathode was fabricated by controlling the epitaxial growth of high-density SiC dendrites around the SiC backbone nanowires. These nanowires were obtained via repeated pyrolysis of a polymeric precursor and the facile in situ gas-phase cation exchange technique. In addition to offering a large number of electron emission sites, the sturdy 3D branched SiC nanowires may prevent structure degradation brought on by electrostatic forces and Joule heat during long-duration FE operation. The Eto and field enhancement factor (β) of the branched SiC field emitters are respectively measured to be 0.61 V μm−1 and 9530, which are superior in comparison to the majority of reported SiC nanostructure-based FE cathodes. In addition, the cathode possesses extremely high electron emission stability with only 3.5% fluctuation in current emission over a 10 h long operation, suggesting that the findings of the present investigation could furnish a solid foundation for the application of SiC nanostructures as high-performance FE cathodes. [ABSTRACT FROM AUTHOR]

The interactions of water and aqueous solutions of HCl with the Enoxil preparation and its composite system Enoxil-Si[O.sub.2] (1:1) have been studied by low-temperature ¹H NMR spectroscopy. The antacid properties in the preparation, manifested in the transformation of a concentrated solution of HCl in a weakly concentrated one, have been established. In the composite system, adsorbed HCl in a hydrophobic environment of CD[Cl.sub.3] may generate a system of clusters with different acid concentrations, while the equilibrium is shifted toward less concentrated forms. Key words: antacid properties, bioactive Enoxil preparation, composite Enoxil-Si[O.sub.2], low-temperature NMR spectroscopy, thermodynamic properties of bound water. Resume : Par la spectroscopie RMN a basse temperature, les interactions de l'eau et des solutions aqueuses de HCl avec la preparation Enoxil et son systeme composite Enoxil-Si[O.sub.2] (1:1) ont ete etudies. Les proprietes anti-acides de la preparation, qui se manifestentpar la transformation de la solution concentree de HCl dans une faiblement concentree, ont ete etablis. Dans le systeme composite, l'acide HCl adsorbe dans un milieu hydrophobe de CD[Cl.sub.3] peut generer un systeme de clusters avec une concentration d'acide different, tandis que l'equilibre est deplace vers des formes moins concentres. Mots-cles : proprietes antiacides, preparation bioactive Enoxil, composite Enoxil-Si[O.sub.2], spectroscopie RMN a basse temperature, proprietes thermodynamiques de l'eau liee., Introduction The Enoxil preparation, developed by the Institute of Chemistry of the Academy of Sciences of Moldova, (1) is a set of biologically active substances obtained by extraction from grape [...]