State-of-the-Art Materials Science in Russia

Hybrid nanocomposite materials Bu₄NBF₄–MgO were obtained using a nanocrystalline MgO with a specific surface area of 324 m²/g and the grains size of 5.1 nm. As a result of the strong adhesion, the salt transforms into an interface-stabilized amorphous state within the thin layer near the interface. The analysis of the DSC data allowed one to estimate the concentration and the thickness of this amorphous layer as 4.8 nm. The amorphous interface phase has an enhanced ionic conductivity. As a result, conductivity of the nanocomposite increases with the concentration of the amorphous phase and reaches 1.1 × 10⁻³ S/cm at 150 °C at a concentration of the MgO additive x = 0.90 corresponding to the maximum content of the amorphous phase. The conductivity of the nanocomposite is by three orders of magnitude higher than the conductivity of pure Bu₄NBF₄. The nanocomposites are electrochemically stable up to 2.5 V. At high concentrations of MgO when the total volume of the salt is small the composites become nano- and mesoporous. Full article

A series of complexes [Cu₂X₂(Pic₃PO)₂] (X = Cl, Br, I) based on tris(pyridin-2-ylmethyl)phosphine oxide (Pic₃PO) has been synthesized. At 298 K, these compounds exhibit thermally activated delayed fluorescence (TADF) of ¹(M+X)LCT type with λ_max varying from 485 to 545 nm, and quantum efficiency up to 54%. In the TADF process, the halide effect appears as the emission intensification and bathochromic shift of λ_max in the following order X = I < Br < Cl. Upon X-ray irradiation, the title compounds emit radioluminescence, the emission bands of which have the same shape as those at TADF, thereby meaning a similar radiative excited state. By contrast to TADF, the halide effect in the radioluminescence is reversed: its intensity grows in the order X = Cl < Br < I, since heavier atoms absorb X-rays more efficiently. These findings essentially contribute to our knowledge about the halide effect in the photo- and radioluminescent Cu(I) halide emitters. Full article

Equipment scaling leads to reduced production efficiency in a wide range of industrial applications worldwide. Various antiscaling agents are currently commonly used to mitigate this problem. However, irrespective of their long and successful application in water treatment technologies, little is known about the mechanisms of scale inhibition, particularly the localization of scale inhibitors on scale deposits. The lack of such knowledge is a limiting factor in the development of applications for antiscalants. Meanwhile, fluorescent fragments integrated into scale inhibitor molecules have provided a successful solution to the problem. The focus of this study is, therefore, on the synthesis and investigation of a novel fluorescent antiscalant: (2-(6-morpholino-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)yl)ethylazanediyl)bis(methylenephosphonic acid) (ADMP-F) which is an analog of the commercial antiscalant: aminotris(methylenephosphonic acid) (ATMP). ADMP-F has been found to effectively control the precipitation of CaCO₃ and CaSO₄ in solution and is a promising tracer for organophosphonate scale inhibitors. ADMP-F was compared with two other fluorescent antiscalants—polyacrylate (PAA-F1) and bisphosphonate (HEDP-F)—and was found to be highly effective: PAA-F1 > ADMP-F >> HEDP-F (CaCO₃) and PAA-F1 > ADMP-F > HEDP-F (CaSO₄·2H₂O). The visualization of the antiscalants on the deposits provides unique information on their location and reveals differences in the “antiscalant-deposit” interactions for scale inhibitors of different natures. For these reasons, a number of important refinements to the mechanisms of scale inhibition are proposed. Full article

In searching for a tool for optimizing the band gap of a hybrid compound capable of serving as a light-harvesting material in lead-free photovoltaics, we synthesized a new polyiodoantimonate (HpipeH₂)₂[Sb₂I₁₀](I₂) and analyzed its crystal and electronic structure by application of X-ray crystal structure analysis, Raman and diffuse reflectance spectroscopies, and quantum chemical calculations. It was demonstrated that I₂ molecules link Sb₂I₁₀ edge-sharing octahedra into zig-zag chains, whereas the organic cations link inorganic anionic chains into a 3D structure featuring a complex pattern of covalent bonds and non-covalent interactions. Overall, these features provide the background for forming the electronic structure with a narrow band gap of 1.41 eV, therefore being a versatile tool for optimizing the band gap of a potential light-harvesting hybrid compound. Full article

A new 1D-coordination polymer [Co(Piv)₂(NH₂(CH₂)₆NH₂)]_n (1, Piv is Me₃CCO₂⁻ anion) was obtained, the mononuclear fragments {Co(O₂CR)₂} within which are linked by μ-bridged molecules of hexamethylenediamine (NH₂(CH₂)₆NH₂). For this compound, two different monoclinic C2/c (α-1) and P2/n (β-1) phases were found at room temperature by single-crystal X-ray diffraction analysis, with a similar structure of chains and their packages in unit cells. The low-temperature phase (γ-1) of crystal 1 at 150 K corresponds to the triclinic space group P-1. As the temperature decreases, the structural phase transition (SPT) in the α-1 and β-1 crystals is accompanied by an increase in the crystal packing density caused by the rearrangements of both H-bonds and the nearest ligand environment of the cobalt atom (“octahedral CoN₂O₄ around the metal center at room temperature” → “pseudo-tetrahedral CoN₂O₂ at 150 K”). The SPT was confirmed by DSC in the temperature range 210–150 K; when heated above 220 K, anomalies in the behavior of the heat flow are observed, which may be associated with the reversibility of SPT; endo effects are observed up to 300 K. The SPT starts below 200 K. At 100 K, a mixture of phases was found in sample 1: 27% α-1 phase, 61% γ-1 phase. In addition, at 100 K, 12% of the new δ-1 phase was detected, which was identified from the diffraction pattern at 260 K upon subsequent heating: the a,b,c-parameters and unit cell volume are close to the structure parameters of γ-1, and the values of the α,β,γ-angles are significantly different. Further heating leads to a phase transition from δ-1 to α-1, which both coexist at room temperature. According to the DC magnetometry data, during cooling and heating, the χ_MT(T) curves for 1 form a hysteresis loop with ~110 K, in which the difference in the χ_MT values reaches 9%. Ab initio calculations of the electronic structure of cobalt(II) in α-1 and γ-1 have been performed. Based on the EPR data at 10 K and the ab initio calculations, the behavior of the χ_MT(T) curve for 1 was simulated in the temperature range of 2–150 K. It was found that 1 exhibits slow magnetic relaxation in a field of 1000 Oe. Full article

In this study, organo-inorganic nanohybrids LHGd-MTSPP with enzyme-like activity were prepared by in situ intercalation of anionic 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin and its complexes with Zn(II) and Pd(II) (MTSPP, M = 2H, Zn(II) and Pd(II)) into gadolinium layered hydroxide (LHGd). The combination of powder XRD, CHNS analysis, FT-IR, EDX, and TG confirmed the layered structure of the reaction products. The basal interplanar distances in LHGd-MTSPP samples were 22.3–22.6 Å, corresponding to the size of an intercalated tetrapyrrole molecule. According to SEM data, LHGd-MTSPP hybrids consisted of individual lamellar nanoparticles 20–50 nm in thickness. The enzyme-like activity of individual constituents, LHGd-Cl and sulfoporphyrins TSPP, ZnTSPP and PdTSPP, and hybrid LHGd-MTSPP materials, was studied by chemiluminescence analysis using the ABAP/luminol system in phosphate buffer solution. All the individual porphyrins exhibited dose-dependent antioxidant properties with respect to alkylperoxyl radicals at pH 7.4. The intercalation of free base TSPP porphyrin into the LHGd preserved the radical scavenging properties of the product. Conversely, in LHGd-MTSPP samples containing Zn(II) and Pd(II) complexes, the antioxidant properties of the porphyrins changed to dose-dependent prooxidant activity. Thus, an efficient approach to the design and synthesis of advanced LHGd-MTSPP materials with switchable enzyme-like activity was developed. Full article

The co-crystallization of the lead(II) complex [Pb(S₂CNEt₂)₂] with tetraiodoethylene (C₂I₄) gave the co-crystal, [Pb(S₂CNEt₂)₂]∙½C₂I₄, whose X-ray structure exhibits only a small change of the crystal parameters than those in the parent [Pb(S₂CNEt₂)₂]. The supramolecular organization of the co-crystal is largely determined by an interplay between Pb⋯S tetrel bonding (TeB) and I⋯S halogen bonding (HaB) with comparable contributions from these non-covalent contacts; the TeBs observed in the parent complex, [Pb(S₂CNEt₂)₂], remain unchanged in the co-crystal. An analysis of the theoretical calculation data, performed for the crystal and cluster models of [Pb(S₂CNEt₂)₂]∙½C₂I₄, revealed the non-covalent nature of the Pb⋯S TeB (−5.41 and −7.78 kcal/mol) and I⋯S HaB (−7.26 and −11.37 kcal/mol) interactions and indicate that in the co-crystal these non-covalent forces are similar in energy. Full article

Currently, the synthesis of active photocatalysts for the evolution of hydrogen, including photocatalysts based on graphite-like carbon nitride, is an acute issue. In this review, a comprehensive analysis of the state-of-the-art studies of graphic carbon nitride as a photocatalyst for hydrogen production under visible light is presented. In this review, various approaches to the synthesis of photocatalysts based on g-C₃N₄ reported in the literature were considered, including various methods for modifying and improving the structural and photocatalytic properties of this material. A thorough analysis of the literature has shown that the most commonly used methods for improving g-C₃N₄ properties are alterations of textural characteristics by introducing templates, pore formers or pre-treatment method, doping with heteroatoms, modification with metals, and the creation of composite photocatalysts. Next, the authors considered their own detailed study on the synthesis of graphitic carbon nitride with different pre-treatments and respective photocatalysts that demonstrate high efficiency and stability in photocatalytic production of hydrogen. Particular attention was paid to describing the effect of the state of the platinum cocatalyst on the activity of the resulting photocatalyst. The decisive factors leading to the creation of active materials were discussed. Full article