O. A. Shilova

Synthesis and structure features of composite silicate and hybrid TEOS-derived thin films doped by inorganic and organic additives

The results of long-term researches of thin films prepared from tetraethoxysilane-derived sols containing inorganic and organic additives are systematized and analyzed. These additives give to films certain physicochemical properties for their application in electronic techniques, optics, power engineering, in biological technologies etc. The influence both inorganic (salts, acids) and organic (polyols, polyionenes, epoxy resin) additives on rheological properties and aggregate stability of sols as well as films surface morphology is minutely considered. The explanations of phenomena during film formation, including spin-coating process, are given. Essential influence of temperature and humidity on films surface morphology is shown. Influence of heat treatment modes on structure and composition of films is analyzed. Recommendations about optimization of thin films sol–gel processing are offered.

Effect of the modification of barium titanate on the permittivity of its composites with cyanoethyl ester of polyvinyl alcohol

The effect of chemical modification of submicron barium titanate particles by the deposition of MxOy (x = Ti, Co, Ni) oxide layers from aqueous solutions of the corresponding precursors is studied upon the surface properties of modified BaTiO3 particles and dielectric permittivity of organo-inorganic composites obtained by their dispersion in the matrix of cyanoethyl ester of polyvinyl alcohol and useful in electroluminescent light sources. It is shown that a significant increase (by about 25%) of the dielectric permittivity is observed only when adding Nb2O5, in comparison with a similar composite which contains unmodified BaTiO3. A correlation is found between the dielectric permittivity of the organo-inorganic composites and the presence of Brensted neutral and basic centers with pKa = 6−13, localized on the surface of a filler, being capable of interacting with the polymer matrix. It is shown that an increase of the dielectric permittivity upon deposition of niobium oxide on the surface of BaTiO3 is caused by formation of such centers and modification of the surface layer structure of BaTiO3 particles, with transformation of rutile-like Ti-O bonds to anataselike ones.

Sol-gel synthesis and investigation of proton-conducting hybrid organic-inorganic silicophosphate materials

Proton-conducting silicophosphate sol-gel systems modified by water-and alcohol-soluble low-molecular and high-molecular organic compounds (such as polyionenes, polyaminoguanidine, and organosilicon monomer) are synthesized by the sol-gel method. The physicochemical processes occurring in the course of the synthesis are investigated. It is revealed that the introduction of polyionenes into the sol-gel systems prevents the formation of silicon pyrophosphate crystals in the resulting silicophosphate nanocomposites (upon their heat treatment) and favors an increase in the protonic conductivity to 10−2 S/cm over a wide range of temperatures (0–120°C).

Recombinant targeted toxin based on HER2-specific DARPin possesses a strong selective cytotoxic effect in vitro and a potent antitumor activity in vivo.

DARPins fused with other proteins are promising non-immunoglobulin scaffolds for specific binding to target cells. In this study HER2-specific DARPin (DARPin_9-29) was used as a tumor-targeting moiety for the delivery of a cytotoxic agent - the fragment of Pseudomonas aeruginosa exotoxin A. It was determined that DARPin-PE40 possesses a considerable cytotoxic activity and induces apoptosis in HER2-positive cells. Cytotoxic effect of DARPin-PE40 strongly correlates with the HER2 expression level. The effect of intravenous administration of DARPin-PE40 was tested in the xenograft model of breast cancer. It was shown that treatment of animals with DARPin-PE40 caused strong and prolonged suppression of xenograft tumor growth.

Sol-Gel Preparation of Ceramic Coatings for Electrical, Laser, Space Engineering and Power

The brief review, based on long-term experience of authors on preparation of temperature-resistant electric insulating and optical light-reflecting ceramic coatings on metal surface is offered. The main components of TEOS-, H3PO4- and alkali silicates-derived sols and suspensions for deposition of ceramic coatings are listed. Some features of preparation of the coatings from the sols containing fillers are analysed. Two approaches to improve bending and electrical strength of flexible insulation are developed. The techniques of synthesis of “modified” fillers for preparing gas-proof and anticorrosive coatings are offered. The wide functional possibility and extensive list of application areas of the coatings and some materials prepared from sols with fillers, including on far prospect are given.

Bioactive coatings based on nanodiamond-modified epoxy siloxane sols for stone materials

Using a sol-gel process, we have prepared bioactive organic-inorganic hybrid coatings based on epoxy siloxane sols modified with detonation nanodiamond. The microstructure of the coatings was studied by scanning electron microscopy. The coatings were tested—under both laboratory and urban conditions—for bioactivity against the mold fungi most frequently encountered in the air in large cities. The results suggest that such coatings are potentially attractive for protecting historic monuments from biodeterioration.

Sol-gel synthesis and investigation of hybrid organic-inorganic borosilicate nanocomposites

Borosilicate sols based on tetraethoxysilane and boric acid (or trimethyl borate) are synthesized. It is demonstrated that the introduction of organic oligomers into borosilicate sols changes the gelation kinetics, affects the composition and structure of the prepared nanocomposites, and makes it possible to produce so-called ormoborosils. Ultrasonic treatment has a strong effect on the gelation kinetics in borosilicate sols, the characteristics of the sol-gel system, and the structure and composition of the borosilicate composites. The phase composition of the synthesized xerogels is investigated by thermal analysis, and the chemical composition is studied by IR spectroscopy. The inference is made that the sol-gel synthesis of borosilicate nanocomposites leads to the formation of multilevel fractally aggregated nanocomposites.

Relationship between the composition of functional groups on the surface of hybrid silicophosphate membranes and their proton conductivity

The surface composition of a set of hybrid silicophosphate membranes has been studied by a method based on the adsorption of acid-base indicators; the relationship between the derived data and the proton conductivity of the test materials has been analyzed. It has been found that the proton conductivity of the membranes increases with an increase in the amount of nearly neutral hydroxyl groups with pKa ∼ 7.3, which slowly dissociate to form protons, and decreases with an increase in the number of acid hydroxyl groups with pKa ∼ 2.5, which exhibit fast dissociation to release protons that are rapidly washed out of the system.

Features of the synthesis and the study of nanocrystalline cobalt-nickel spinel

A nanocrystalline compound nickel cobaltite (NiCo2O4) with the average size of crystals of ∼20 nm at 700°C has been synthesized using the method of combined crystallization of solutions of nitrates with the subsequent thermal and ultrasonic treatment. The optimal sintering mode of the NiCo2O4 powder (1300°C, 2 h, air) has been selected, and ceramics (60–65 nm) with open porosity of 25–30% have been prepared. The temperature and frequency dependences of the electrical conductivity of nickel cobaltite have been studied. It has been assumed that the high values of the electrical conduction and pseudo-capacity of NiCo2O4 are due to the variable valence of Ni and Co in oxides. It is recommended to use cobaltite nickel as an electrode material of a supercapacitor and a catalyst of the oxygen isolation in fuel elements.

Organic-Inorganic Insulating Coatings Based on Sol-Gel Technology

The approach for improving bending strength of temperature-resistant flexible ceramic electric insulating coatings prepared by sol-gel processing is considered. Starting suspensions, based on both tetraethoxysilane (TEOS)-derived modified sols and highly dispersed fillers such as Cr2O3, are used to deposit the coatings on metals and alloys. Some polymers and organic substances are tested as additives for improving flexibility of the ceramic coatings. The results of study of both bending strength and electrical strength of flexible hybrid organic-inorganic insulation formed on a nichrome wire are discussed. The data obtained on the chemical and phase structure of the coatings, which have been heat treated at temperatures from 95 to 1100°C, using DSC as well as X-ray scattering techniques are presented.