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The method of synthesis of unmodified and organo‐modified silica hydrogels and their composites with orotic acid as a model drug was developed. The hydrogels had a pH of 6.5–7.8. The particulate nature and highly porous structures of the hydrogel materials were revealed using scanning electron and optical microscopy methods. The content of aqueous phase in the hydrogels was 99% or more. In order to evaluate the possibility of their application as a basis for development of novel soft drug formulations and cosmetic compositions, rheological properties of the hydrogels and in vitro release kinetics of the drug were studied. The effects of synthesis conditions (increasing concentration of catalyst of silica sol formation, drug loading) and the silica matrix modification with various organic groups on the indicated properties were investigated. It was found that all synthesized hydrogels exhibited pseudoplasticity, thixotropy and controlled release of the drug, which are important for their potential application. However, in general, the indicated effects led to worsening the properties of the hydrogel materials in comparison with the unmodified silica hydrogels. [ABSTRACT FROM AUTHOR]

BACKGROUND The presented work focuses on the comparison of sorption and photocatalytic properties of TiO2 doped with molybdenum using different methods of Mo loading. The structural and photocatalytic characteristics of doped TiO2 are determined by the method of synthesis and loading of the dopant element. As an alternative to simple wet chemical loading, three types of low‐temperature plasma in contact with liquid are considered: atmospheric pressure glow discharge, underwater diaphragm discharge, and underwater plasma. RESULTS: The results show that the introduction of Mo, regardless of the doping method, leads to a decrease in the band gap. The surface characteristics of powders depend on the doping method. The sorption capacity increases two to three times, and the efficiency of photodestruction increases from 52% to 96% when exposed to visible light for 60 min. CONCLUSIONS: A comparison of the sorption and photocatalytic activity of Mo‐doped TiO2 showed the inexpediency of using a glow discharge for doping. The synthesis of a highly efficient sorbent or photocatalyst can be determined by the type of underwater plasma. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Plasmas in contact with liquids represent a green chemistry method for the synthesis of metal oxides. In this work, underwater plasma was used for the synthesis of molybdenum and tungsten oxides. The obtained samples were analyzed by various techniques. Results showed that underwater plasma with Mo electrodes allows obtaining non-stoichiometric molybdenum oxide (MoOx). In the case of tungsten electrodes, monoclinic WO3 was formed. The synthesized oxides have a wide band gap (3.21 eV for MoOx and 3.27 eV for WO3). The photocatalytic and sorption activities of the synthesized oxides towards the decomposition of cationic and anionic dyes (Methylene Blue, Rhodamine B, and Reactive Red 6C) were studied. MoOx shows excellent photocatalytic performance under UV and visible light irradiation. The photocatalytic activity of WO3 under visible light is less than that under UV irradiation. [ABSTRACT FROM AUTHOR]

Nanoparticles of MnO2 with different shapes (needle-like α-MnO2 and spherical δ-MnO2) were proposed as promising fillers for electrorheological fluids (ERFs). A thorough study of the dielectric properties of α-MnO2 and δ-MnO2 suspensions in silicone oil enabled estimation of the values of their dielectric permittivity and dielectric relaxation times. The study of MnO2-filled materials with various filler contents, and under various electric field strengths, in shear and uniaxial tensile and compressive stress regimes, revealed that needle-like α-MnO2 nanoparticles, in comparison with spherical δ-MnO2 particles, lead to better mechanical properties of the fluids. The most intriguing property of MnO2-based electrorheological fluids is their high electrorheological response at low filler content: ERF containing only 4.5 vol.% of α-MnO2 in silicone oil demonstrated a 18 kPa tensile strength in a 5 kV electric field. [ABSTRACT FROM AUTHOR]

Mesoporous alumina and γ-Al2O3–NaAlO2 composites with different morphology were produced by soft chemistry methods using polyethylenimine (PEI), pluronic P123 (P123), and polymer–colloid complex (PCC) derived from them as templates in solution. Sodium aluminate was applied as an additive for production of the mesoporous γ-Al2O3–NaAlO2 composite. The obtained samples were characterized by scanning and transmission electron microscopy, atomic force microscopy, Fourier transform IR spectrometry, X-ray diffraction analysis, and low-temperature N2 adsorption–desorption analysis. The effect of sodium aluminate introduction on the morphological features of the obtained samples was investigated. Mesostructured aluminum oxide obtained using individual templates such as P123 and PEI possesses cylindrical pores, whereas applying PCC resulted in the formation slit-shaped pores. The produced mesoporous aluminum oxide and γ-Al2O3–NaAlO2 composite had a narrow pore size distribution and large surface area. This approach was demonstrated to allow for the control of pore sizes and shapes. Highlights: Mesoporous alumina and γ-Al2O3–NaAlO2 composites with different morphology were produced by soft chemistry approach in solution. Polyethylenimine (PEI), pluronic P123 (P123), and polymer–colloid complex (PCC) derived from them were used as templates. Obtained porous materials were characterized by SEM, AFM, FTIR, XRD, and gas sorption techniques. Formation mechanisms for mesoporous structures were elucidated and compared for synthesis of pure alumina and of γ-Al2O3–NaAlO2 composites. [ABSTRACT FROM AUTHOR]

For the first time, electroactive nanocomposite elastomers based on polydimethylsiloxane and filled with rod-like α-MnO2 nanoparticles have been obtained. The curing of the filled elastomer in an electric field, resulting in the ordering of the α-MnO2 particles, had a significant effect on the degree of polymer crosslinking, as well as on the electrorheological characteristics of the nanocomposites obtained through this process, namely the values of the storage and loss moduli. The dielectric spectra of filled elastomers in the frequency range 25–106 Hz were analysed in terms of interfacial relaxation processes. It has been shown, for the first time, that the application of an electric field leads to a decrease in the value of the Payne effect in composite elastomers. Analysis of the rheological effect in the obtained materials has demonstrated the possibility of designing highly efficient electrorheological elastomers that change their elastic properties by 4.3 times in electric fields of up to 2 kV/mm. [ABSTRACT FROM AUTHOR]

Electrorheological elastomers based on polydimethylsiloxane filled with hydrated titanium dioxide with a particle size of 100-200 nm were obtained by polymerization of the elastomeric matrix, either in the presence, or in the absence, of an external electric field. The viscoelastic and dielectric properties of the obtained elastomers were compared. Analysis of the storage modulus and loss modulus of the filled elastomers made it possible to reveal the influence of the electric field on the Payne effect in electrorheological elastomers. The elastomer vulcanized in the electric field showed high values of electrorheological sensitivity, 250% for storage modulus and 1100% for loss modulus. It was shown, for the first time, that vulcanization of filled elastomers in the electric field leads to a significant decrease in the degree of crosslinking in the elastomer. This effect should be taken into account in the design of electroactive elastomeric materials.

Plasmas in contact with liquids represent a green chemistry method for the synthesis of metal oxides. In this work, underwater plasma was used for the synthesis of molybdenum and tungsten oxides. The obtained samples were analyzed by various techniques. Results showed that underwater plasma with Mo electrodes allows obtaining non-stoichiometric molybdenum oxide (MoOx). In the case of tungsten electrodes, monoclinic WO3 was formed. The synthesized oxides have a wide band gap (3.21 eV for MoOx and 3.27 eV for WO3). The photocatalytic and sorption activities of the synthesized oxides towards the decomposition of cationic and anionic dyes (Methylene Blue, Rhodamine B, and Reactive Red 6C) were studied. MoOx shows excellent photocatalytic performance under UV and visible light irradiation. The photocatalytic activity of WO3 under visible light is less than that under UV irradiation.