Surface modification of multi-walled carbon nanotubes (MWCNT) was achieved by covalent grafting of 1,3,5,7tetra(2-ferrocenylethyl)-1,3,5,7-tetramethylcyclotetrasiloxane (Fc(4)D(4)) and in situ forming polyFc(4)D(4) in the presence of catalytic mixture AlCl3 and metallic Al. For composite preparation, MWCNT modified with ferrocenyl-containing oligo- and polysiloxanes were incorporated into the silicone compound and high-quality soft flexible silicone composites was obtained. In a stress-strain tests of the obtained composites, elongation at break value was an approx. two times higher that in the initial silicone matrix. The conducted modification of MWCNT surface significantly improve dispersion of modified MWCNT in silicone polymer matrix even at higher filler concentration using simple solution blending method of composite preparation. The composites demonstrated conductivity at the level of semiconductors.

In order to enhance the corrosion resistance and bioactivity of the additively manufactured nitinol alloy, ZnO-TiO2 (ZTO) nanocoatings have been synthesised by atomic layer deposition. The supercycle approach was employed to deposit 40 nm coatings with varying ZnO/TiO2 ratios: 5/1, 1/1, 1/5 and 1/20. The results demonstrated that this approach permitted the coating composition to be varied over a wide range. The study of anticorrosion properties in physiological Ringer's solution revealed that the coatings, depending on their composition, are capable of reducing the corrosion rate of nitinol by a value ranging from 4 to 58 times. In vitro studies have demonstrated high viability, good adhesion and spreading of human osteoblast-like MG-63 and mesenchymal stem FetMSC cells on the surface of all samples except those with high zinc content (ZnO and ZTO-5/1). All coatings induced differentiation of both cell lines in the osteogenic direction and demonstrated antibacterial activity against multi-drug resistant A. baumannii (>96 %) and P. aeruginosa (>90 %) strains. The results indicate the considerable potential of the developed methodology for the ALD of ZTO that combine the biocompatibility of titanium oxide, the antibacterial properties of zinc oxide and their overall stability and effectiveness for the protection of nitinol against biocorrosion.

In this study, a comprehensive structural analysis of the linear redox-active ferrocenyl-containing polysiloxanes (FPSs) was performed by the liquid-state 1 H, 13 C, and 29 Si nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and cyclic voltammetry. FPSs with tunable Fc unit content ranging from 20 to 100 mol% were obtained by anionic ring-opening polymerization (AROP). The 29 Si NMR spectroscopy indicates the successful anionic homopolymerization of the mono- and tetraferrocenyl-substituted cyclotetrasiloxanes (Fc4D4 4 D 4 and Fc1D4) 1 D 4 ) by appearance of new signals of Si atoms corresponding to a polymer backbone. An analysis of pentad assignments in 29 Si NMR determined the anionic copolymerization of Fc4D4 4 D 4 with D4 4 by indicating signals of neighboring Si atoms from different types of polymer units (DF F and D), which differ from the signals of homopolymers. The Mayo-Lewis copolymerization constants of Fc4D4 4 D 4 and D4 4 were determined by the Fineman-Ross method. The molecular masses and unimodal molecular weight distribution of FPSs were estimated by using GPC. FPSs possess redox-activity. Thus, the proposed comprehensive approach analyzes structural features of the functional silicones with enhanced redox properties, which can be applied in (opto) electronics, coatings, and biomedicine.

Ligand exchange reaction (LER) between carbon nanoparticles and ferrocene (Cp2Fe) was conducted several times, but there was no convincing evidence of half-sandwich CpFe+ coordination to multiwalled carbon nanotubes (MWCNT). In this study, MWCNT is modified by LER with ferrocene using AlCl3/Al as a catalytic system. The modified MWCNT (Fc-MWCNT) are investigated for better understanding of the processes taking place on the surface of MWCNT using different spectroscopic and electrochemical methods. The formation of the Fe-C covalent bond between CpFe+ and MWCNT is confirmed by changes in the Raman spectrum of Fc-MWCNT compared to pristine MWCNT. The densest structure of Fc-MWCNT is investigated by transmission electronic microscopy. According to density-functional theory calculations of the model interaction between Fe and coronene, the Fe-C bond length is 2.1687-2.1855 Å. X-ray photoelectron spectroscopy also confirms the coordination of the Fe atom to MWCNT by analysis of oxidation states of Fe 2p and deconvolution of C 1s. Utilization of cyclic voltammetry corroborated MWCNT modification via LER. These data are important for both theoretical and practical applications due to increased interest in LER-modified compounds in different areas including thermoelectric devices, sensors, and its potential application in the field of molecular machine construction.

Recently, there has been an active search for new modifiers to create hybrid polymeric materials for various applications, in particular, membrane technology. One of the topical modifiers is metal-organic frameworks (MOFs), which can significantly alter the characteristics of obtained mixed matrix membranes (MMMs). In this work, new holmium-based MOFs (Ho-MOFs) were synthesized for polyether block amide (PEBA) modification to develop novel MMMs with improved properties. The study of Ho-MOFs, polymers and membranes was carried out by methods of X-ray phase analysis, scanning electron and atomic force microscopies, Fourier transform infrared spectroscopy, low-temperature nitrogen adsorption, dynamic and kinematic viscosity, static and dynamic light scattering, gel permeation chromatography, thermogravimetric analysis and contact angle measurements. Synthesized Ho-MOFs had different X-ray structures, particle forms and sizes depending on the ligand used. To study the effect of Ho-MOF modifier on membrane transport properties, PEBA/Ho-MOFs membrane retention capacity was evaluated in vacuum fourth-stage filtration for dye removal (Congo Red, Fuchsin, Glycine thymol blue, Methylene blue, Eriochrome Black T). Modified membranes demonstrated improved flux and rejection coefficients for dyes containing amino groups: Congo Red, Fuchsin (PEBA/Ho-1,3,5-H3btc membrane possessed optimal properties: 81% and 68% rejection coefficients for Congo Red and Fuchsin filtration, respectively, and 0.7 L/(m2s) flux).

Cs2O–Al2O3 ceramic samples containing 20 and 33 mol

Flexible ferrocenyl-containing silicone rubbers (FSRs) with various ferrocenyl-substituted unit contents of 25, 50, and 75 mol% were obtained by applying a simple method included catalytic hydrosilylation (between polymethylhydrosiloxane and vinylferrocene) and self-cross-linking reactions (dehydrocou-pling between Si-H groups). Self-cross-linking is one of the most suitable and simple methods to coat and obtain FSRs on various contact conductive surfaces, such as onto indium tin oxide (ITO) glass or ITO-poly(ethylene terephthalate). The synthesized FSRs exhibit the electrochromic (EC) properties, resulting from the reduction-oxidation of ferrocenyl groups (Fc/Fc thorn transformations at E0 c.a. 0.36 V) and leading to color change: oxidation causes new band formation at 634 nm in ultraviolet-visible spectra. FSRs with ferrocenyl-substituted unit content of 50 mol% (FSR50) is the most optimal in terms of EC (coloration efficiency of 10.98 cm2/C, coloring and bleaching times of c.a. 49 and 66 s, which are close to undoped oligoaniline-functionalized polysiloxanes and carbazolyl-modified polysiloxanes) and mechanical properties (the tensile strength, Young's modulus, and elongation at break are 2.80 MPa, 25.33 MPa, and c.a. 50%, respectively). The previously reported EC polysiloxanes have lack of mechanical characteristics. Both electrochromism and flexibility predominantly make FSR50 promising materials for the creation of flexible and stretchable EC devices.(c) 2023 Elsevier Ltd. All rights reserved.

Cs2O–Al2O3 ceramic samples containing 20 and 33 mol % cesium oxide were prepared by сeramic technique and by the glycine–nitrate combustion process. The prepared samples were identified and characterized by X-ray powder diffraction and X-ray fluorescence analyses, scanning electron microscopy, and differential thermal analysis. X-ray powder diffraction and scanning electron microscopy showed that the phase composition and surface of the samples change significantly and nonmonotonically depending on the synthetic method used and the heat treatment parameters of the batch. Optimal synthetic conditions and heat treatment parameters for preparing Cs2O–Al2O3 samples were elucidated.

The presented work is devoted to the study of the possibility of using planar materials consisting of ultramicroelectrode arrays for voltammetric analysis of compounds with close redox potential, but with different diffusion coefficients, which has great prospects in the analysis of various oligomers, including oligopeptides. A feature of the electrochemical behavior of materials containing arrays of ultramicroelectrodes is the realization of hemispherical diffusion, which can lead to the steady state or unsteady state regime of the electrode depending on the intersection or non-intersection of the hemispheres. There is also a transient mode of operation of electrodes at partial intersection: voltammetry diagrams obtained in this mode may contain analytical information on the concentrations of substances with one redox potential, which favorably distinguishes the approach from the classical cyclic voltammetry using macroelectrodes. The prospects of the proposed approach are confirmed by the example of analysis using ultramicroelectrode arrays of ferrocenemethanol and triglycene ferrocenemethanol ester. The results obtained prove the possibility of applying the approach to the analysis of electroactive oligopeptide derivatives.

Increasing the duration and quality of human life requires solving a number of medical and materials science problems, in particular, the creation of materials designed for long-term work in contact with the biological environment. When creating such materials for medical devices, it is necessary to take into account that they must meet strict requirements, namely, be biologically compatible with tissues, have corrosion resistance to various biological fluids and have increased wear resistance. The study of the effect of Ti microstructure on microhardness and its corrosion resistance in physiological environments is necessary to create implants designed for long-term work in contact with the biological environment of the body. In accordance with this, the purpose of this work was to establish the nature of the relationship between the structural properties of ultrafine-grained Ti with different sizes of crystallites (grains) obtained using equal-channel angular pressing (ECAP) of different intensity, namely with a different number of processing cycles, on the microhardness and stability of Ti in a corrosive environment.

The spherical diffusion that occurs when using ultramicroelectrodes (i.e., electrodes with a characteristic size of 1–10 µm) contributes to a higher mass transfer rate. This leads to equalization of the depletion rates of the near-electrode layer due to the electrochemical reaction and to the supply of the product from the solution depth. This is the reason why, for ultramicroelectrodes, a limiting size of the spherical layer exists in which the concentration gradient is localized (diffusion layer). Thus, a stationary mass transfer mode is achieved, which is expressed in the sigmoidal CV curve’s shape. In ultramicroelectrode arrays, when the diffusion hemispheres are separated, a steady-state diffusion is realized. However, with a decrease in the interelectrode distance, which leads to the diffusion spheres intersection, a mixed regime arises, which is not fully time-independent. The resulting voltammogram’s shape change can serve as an analytical signal in the study of substances with differing diffusion coefficients, since the diffusion layer growth rate and, consequently, the area of intersection of neighboring spheres, depends on it. This work shows the applicability of voltammetry using ensembles of ultramicroelectrodes operating in the transient mode for the analysis of mixtures of electrochemically active compounds with close electrode reaction parameters, such as exchange currents and electrode potential. Ferrocenemethanol esters are used as an example. The applicability of cyclic voltammetry on the UME array for analysis of mixtures was illustrated by means of finite element modelling. The reliability of the modelling results was experimentally proved for ferrocenemethanol esters with glycine and triglycine.

AbstractScroll-like crystals of molybdenite, 2–5 mm in size, were found in phengite rock from the outer contact of the granular quartz vein of the Kyshtym quartz deposit. Platy and partly scrolled molybdenite occur in the same phengite rock from the outer contact of the quartz–feldspar pegmatite of the Slyudyanogorsk mica deposit. Both occurrences are located in the Ufaley metamorphic block in the South Urals. Scroll-like molybdenite crystals can associate with platy and partly twisted crystals in the same samples. The chemical composition of molybdenite was studied by inductively coupled plasma mass spectrometry (ICP-MS) and electron probe microanalysis (EPMA). Polytypes of molybdenite were identified with electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD). Both scroll-like and platy molybdenite crystals are only represented by the 3R polytype, are enriched in Re up to 1 wt.% and contain no other significant impurities. Scroll-like molybdenite is twisted mainly around the crystallographic axis X. Twinning with a rotation of 60 degrees around the Z crystallographic axis is fixed in the plane (ab). The most probable origin of scroll molybdenites is the consequent growth of molybdenite around nucleation centres, which are commonly represented by mica crystals. The formation of the 3R polytype is caused by the difference in dimension of the layers enriched and depleted in rhenium.

Numerous articles have been presented on efficient liquid-liquid extraction procedures from aqueous samples using deep eutectic solvents based on quaternary ammonium salts or natural terpenoids as hydrogen bond acceptors and fatty acids as hydrogen bond donors. However, precursors of these solvents are soluble in the aqueous phase and the composition of the solvents can be changed in the presence of water. In this research the stability and composition of deep eutectic solvents based on quaternary ammonium salts (tetrabutylammonium bromide and tetraoctylammonium bromide), terpenoids (menthol and thymol) and fatty acids (hexanoic, heptanoic, octanoic, nonanoic and decanoic acids) in aqueous phase were systematically investigated. It was shown that all studied two-component solvents are transformed into three-component solvents in the presence of water. Effects of hydrogen bond acceptors and donors type on formation of three-component solvents were investigated and discussed. It was established that, the ratio of aqueous and organic phases plays a key-role for stability of the solvents based on tetrabutylammonium bromide. The solvents based on terpenoids and tetraoctylammonium bromide remain stable in the wide range of phases ratios. In addition to the study of stability, changes in the physicochemical and extraction properties of ternary eutectic solvents in comparison with two-component solvents have been shown. (C) 2021 Elsevier B.V. All rights reserved.

Selective heterocyclization leading to 1,2,3,4-tetrahydrobenzo[h]quinazolines from ortho-ketimines of 1,8-bis(dimethylamino)naphthalene (DmanIms) under acid catalysis has been revealed. In contrast to the rather unreactive N,N-dimethylaniline ortho-ketimine, DmanIms readily undergo this transformation without an additional catalyst. This distinction in the reactivity underscores the importance of the second peri-NMe2 group in DmanIms, which facilitates a [1,5]-hydride shift and the subsequent cyclization. The cascade of peri-interactions emerging between 1-NMe2 and 8-NMe2 groups has been identified as a reason for the catalytic effect: (1) the hydrogen bond in the DmanIm dication constrains 1-NMe2 in the desired position providing proximity of reaction centers, (2) the repulsion of the lone pairs of 8-NMe2 group and unrelaxed 1-NMe2 group arising right after deprotonation process reduces the Gibbs free energy of activation (ΔG‡) for the straight hydride shift, and (3) the electrostatic interaction between 8-NMe2 and the charged NCH2+ group in the intermediate increases the ΔG‡ for the reverse hydride shift.

This communication reports the detailed description of a technology for the manufacturing of stretchable and biointegrated neuronal implants based on carbon nanotubes (CNTs) and poly(dimethylsiloxane) (PDMS). An essential part of the proposed technology is the fabrication of PDMS-CNT composite materials which are characterized by their high level of biocompatibility, long-term biostability, outstanding tensile strength, high values of charge storage capacity, and non-Faradaic type of electrode processes. To fabricate the stretchable spinal cord implants from obtained PDMS-CNT composite materials, sophisticated casting metal molds were used. The mechanical, electrical and biological properties of PDMS-CNT composite materials and neuronal implants were characterized using multiple methods such as SEM, EDXRF analysis, tensile mechanical testing, cytotoxicity testing and cyclic voltammetry (CV). Furthermore, the functionality of stretchable spinal cord implants based on PDMS-CNT composite materials was studied using in-vivo tests on laboratory animals that indicated high efficiency of the proposed technology for monitoring and stimulation of neuronal activity in mammals.

A synthetic method involving hydrosilylation reactions was developed to produce nanocomposites of elastic ferrocenyl-containing silicone rubber (EFSR) and multi-walled carbon nanotubes (MWCNT). The EFSR-MWCNT nanocomposites have a satisfactory elongation at break ~80%, tensile strength (2.4 MPa), as well as electrical conductivity comparable to that of semiconductors (7 center dot 10- 5 S center dot cm- 1), all of which are necessary for application as neuronal implants. A novel prototype of a spinal cord neuronal interface based on EFSR-MWCNT was created as a prosthetic for impaired neuronal functions and to access spinal sensorimotor networks. Ferrocenyl groups in nanocomposites increase the charge injection that declines the risks of negative effects of electrical stimulation including nerve tissue damage.

Cobalt( II) -pyridinedicarboxamide-co-polydimethylsiloxane (Co-Py-PDMSs) and cobalt(II)-bipyridinedicarboxamide-co-polydimethyl-siloxane (Co-Bipy-PDMSs) polymer-metal complexes were prepared by complexation between Py-PDMSs or Bipy-PDMSs ligands and cobalt(II); the metal content in these complexes varied from 0.09 to 2.41 wt %. The Co-II binding patterns (the Co-N-Py and Co-O coordination in Co-Py-PDMSs and Co-N-Bipy in Co-Bipy-PDMSs) were established by UV-vis and IR methods and by comparison with model C-II complexes exhibiting relevant O,N,O- and N,N-coordination environments, respectively. The mechanical properties of the polymer-metal complexes were controlled by the coordination of Py-PDMSs or Bipy-PDMSs to Co-II at various metal-to-ligand molar ratios (1:(1-6)) and by the variation of the polydimethylsi- loxane unit length (M-n: 850-900, 5000, or 25000 g.mol(-1)). Utilization of the chelated Py-PDMSs and Bipy-PDMSs polymer ligands, which are capable of tri- or bidentate binding of Co-II, led to (2-4)-fold increases in tensile strength (up to 1.75 MPa) and much higher elongation at break ((2-3)-fold increase up to 2100%) compared with the previously reported Co-II-based polymer-ligand systems featuring monodentate ligation entities. Changing the main-chain ligand from Py-PDMSs to Bipy-PDMSs led to an increase in tensile strength of (2-4)-fold in comparison with Py-PDMS and a lower hysteresis (4%). The room temperature self-healing efficiency was up to 96% for Co-Py-PDMSs and 40% for Co-Bipy-PDMSs, as measured for a polydimethylsiloxane unit with M-n= 25 000 g.mol(-1).

Two series of hybrid inorganic-organic derivatives, obtained via the modification of protonated Ruddlesden–Popper phases H2Ln2Ti3O10 (Ln = La, Nd) with intercalated n-alkylamines and grafted n-alkoxy groups, have been systematically investigated in relation to photocatalytic hydrogen production from a model of 1 mol % aqueous solution of methanol for the first time. Photocatalytic measurements were performed both for bare samples and for their composites with Pt nanoparticles as a cocatalyst using an advanced scheme, including dark stages, monitoring of the volume concentration of the sample in the reaction suspension during the experiment, shifts of its pH and possible exfoliation of layered compounds into nanolayers. It was found that the incorporation of organic components into the interlayer space of the titanates increases their photocatalytic activity up to 117 times compared with that of the initial compounds. Additional platinization of the hybrid samples’ surface allowed for achieving apparent quantum efficiency of hydrogen evolution of more than 40%. It was established that the photocatalytic activity of the hybrid samples correlates with the hydration degree of their interlayer space, which is considered a separate reaction zone in photocatalysis, and that hydrogen indeed generates from the aqueous methanol solution rather than from organic components of the derivatives.

Self‐cross‐linkable ferrocenyl‐containing polymethylhydrosiloxanes were synthesized. Karstedt's catalyst and cis‐[PtCl2(BnCN)2] were examined as cross‐linking catalysts at room temperature for the reaction between Si–H groups of the ferrocenyl‐containing polymethylhydrosiloxanes. Cis‐[PtCl2(BnCN)2] is an effective catalyst that allows cross‐linked ferrocenyl‐containing silicones (silicone rubbers) to be obtained with no visible mechanical defects (bubbles or cracks) compared with Karstedt's catalyst. The ferrocene content of the ferrocenyl‐containing silicone rubbers was found to be approximately 50 wt.% by energy‐dispersive X‐ray analysis. Compared with cross‐linked non‐modified polymethylhydrosiloxanes, the ferrocenyl‐containing silicone rubbers exhibited improved tensile properties (the tensile strength increased from 0.47 to 0.75 MPa) and a 1.5–2.5 times lower cross‐linking degree. The surface resistivity of the ferrocenyl‐containing silicone rubbers (50 wt.% ferrocenyl units) was approximately 7 × 109 Ω/□, which was 10,000 times lower than that of pure polymethylhydrosiloxane. The obtained flexible electroactive ferrocenyl‐containing silicone rubbers can potentially be applied as coatings for electronic and electrostatic‐sensitive devices, interfaces, and sensors.

The nickel(II)-pyridinedicarboxamide-co-polydimethylsiloxane complexes as elastic silicone rubbers were prepared. The structure of the Ni(II) coordination cross-links was fully characterized by X-ray crystallography, high-resolution mass spectrometry, IR and UV-vis spectroscopy of the low-molecular weight model complex. The nickel content in the polymer-metal complexes varied from 2.78 to 0.12 wt%. Mechanical properties of the polymer-metal complexes was controlled by the Ni(II) load variations, metal to ligand molar ratios of 1:(1-8), and by the polydimethylsiloxane unit length, M-n: 850-900, 5000 or 25000 g.mol(-1); an increase of the polysiloxane chain length and a decrease of Ni(II) load led to higher elasticity and lower hysteresis (3%). The elongation at break of the polymer-metal complexes was up to 1800% and the self-healing efficiency was up to 92.5% at room temperature (for the rubber with a polydimethylsiloxane unit M-n = 25000 g.mol(-1)). The glass transition temperatures of the nickel(II)-pyridinedicarboxamide-co-polydimethylsiloxanes were from -123 degrees C to -112 degrees C, and the electroconductivity was 10(-13) -10(-11 )S.cm(-1).