Experimentally realized mechanochemistry distinct from force-accelerated scission of loaded bonds

Stretching polymer chains accelerates dissociation of a variety of internal covalent bonds, to an extent that correlates well with the force experienced by the scissile bond. Recent theory has also predicted scenarios in which applied force accelerates dissociation of unloaded bonds and kinetically strengthens strained bonds. We report here unambiguous experimental validation of this hypothesis: Detailed kinetic measurements demonstrate that stretching phosphotriesters accelerates dissociation of the unloaded phosphorus-oxygen bond orthogonal to the pulling axis, whereas stretching organosiloxanes inhibits dissociation of the aligned loaded silicon-oxygen bonds. Qualitatively, the outcome is determined by phosphoester elongation and siloxane contraction along the pulling axis in the respective rate-determining transition states. Quantitatively, the results agree with a simple mechanochemical kinetics model

Azetidinium lead iodide for perovskite solar cells

Hybrid organic–inorganic perovskites have been established as good candidate materials for emerging photovoltaics, with device efficiencies of over 22% being reported. There are currently only two organic cations, methylammonium and formamidinium, which produce 3D perovskites with band gaps suitable for photovoltaic devices. Numerous computational studies have identified azetidinium as a potential third cation for synthesizing organic–inorganic perovskites, but to date no experimental reports of azetidinium containing perovskites have been published. Here we prepare azetidinium lead iodide for the first time. Azetidinium lead iodide is a stable, bright orange material which does not appear to form a 3D or a 2D perovskite. It was successfully used as the absorber layer in solar cells. We also show that it is possible to make mixed cation devices by adding the azetidinium cation to methylammonium lead iodide. Computational studies show that the substitution of up to 5% azetidinium into the methylammonium lead iodide is energetically favourable and that phase separation does not occur at these concentrations. Mixed azetidinium–methylammonium cells show improved performance and reduced hysteresis compared to methylammonium lead iodide cells

Modernisation of Social Conscience: Topical Problems of Literary Local Lore

Literary study of local lore is a specific area of knowledge about the history of literature, which is distinct in a special selection of material, and an aspect of its consideration. Local lore contributes to the learning of historical, cultural, geographical peculiarities of a particular territory. This paper deals with the issues of local lore. The research of the artistic heritage of poets and writers of the Cis-Ural Region, West-Kazakh District is one of the topical problems of contemporary literature.In this paper, the works of the Russian poets are discussed considering the writers of the 20th –early 21st centuries, such as A.S. Pushkin, V.I. Dahl, M.A. Sholokhov and the great Tatar poet Gabdulla Tuqay. It has been establishedthat the best of Gabdulla’sworks, included in the gold reserves of the Tartar literature, was written in the town of Uralsk. It has also been establishedthat the poets and writers of the Cis-Ural Region contributed new genres to the literature, namely prose and drama. The study of cultural and spiritual ties with kindred Turkic-speaking peoples today is one of the priorities of the Kazakh literary criticism. At the same time, the authors have found the following ways of solution of such tasks: the introduction of the “LiteraryLocal Lore” elective course to the study process of secondary and high schools, writing of monographs, and compilation of anthologies. The paper will be useful for teaching the subject of "Literary Regional Studies" becausethe course based on the cognitive material, which considers and propagates the development and prosperity of the national fictional literature, as well as its investigation from a scientific point of view and transmission of the values to the younger generation

Tuning hardness in calcite by incorporation of amino acids

Structural biominerals are inorganic/organic composites that exhibit remarkable mechanical properties. However, the structure–property relationships of even the simplest building unit—mineral single crystals containing embedded macromolecules—remain poorly understood. Here, by means of a model biomineral made from calcite single crystals containing glycine (0–7 mol%) or aspartic acid (0–4 mol%), we elucidate the origin of the superior hardness of biogenic calcite. We analysed lattice distortions in these model crystals by using X-ray diffraction and molecular dynamics simulations, and by means of solid-state nuclear magnetic resonance show that the amino acids are incorporated as individual molecules. We also demonstrate that nanoindentation hardness increased with amino acid content, reaching values equivalent to their biogenic counterparts. A dislocation pinning model reveals that the enhanced hardness is determined by the force required to cut covalent bonds in the molecules

Probing local photocurrent in inorganic CsPbBr3 perovskite films by scanning probe microscopy

Hybrid organic-inorganic halide perovskites are among the most promising materials for solar cells. Rapid growth of their power conversion efficiency (PCE) from 3.8% in 2009 [1] to more than 22% in 2017 [2] made them attractive for commercial applications. However, rapid degradation of organic-inorganic perovskites under operating conditions – photon flux, electric field, heating – remains unsolved in spite of tremendous research effort [3,4]. Their fully inorganic counterparts possess similar optoelectronic properties [5] and better stability [6]. Still, their PCE is below 10%, which requires further investigation and optimization

XPS SPECTRA AS A TOOL FOR STUDYING PHOTOCHEMICAL AND THERMAL DEGRADATION IN APbX3 HYBRID HALIDE PEROVSKITES

Our results show that the resistance of hybrid lead halide perovskites to stress factors (light or heat) is gradually increased while substituting the A-site cation going from CH3NH3+ to CH(NH2)2+ and then to Cs+.This study was supported by Russian Foundation for Basic Research (grants 20-24-660003 and 21-52-52002)

Selective Electron Beam Melting of Intermetallic Alloy Based on Gamma Titanium Aluminide TiAl: Composition, Microstructure, Porosity

В условиях НИЦ «Курчатовский институт» - ВИАМ методом газовой атомизации получена металлопорошковая композиция отечественного интерметаллидного β-затвердевающего γ-TiAl-сплава марки ВИТ7Л (Ti– 44,5Al–2V–1Nb–2Cr–0,1Gd, ат.%). Выделена целевая фракция 40–100 мкм с высокими показателями качества по текучести и сферичности. Селективным электронно-лучевым сплавлением с варьируемой линейной плотностью энергии (EL) синтезированы элементарные образцы 11×11×40 мм3. Установлен оптимальный интервал 250≤EL≤285 Дж/м, обеспечивающий отсутствие несплавлений и остаточную пористость менее 0,5 об.%, при потерях Al на испарение не более 1 ат.% и приемлемой неоднородности микроструктуры вдоль вертикального сечения (направление построения Z).A metal powder composition (MPC) of a Russian intermetallic β-solidifying γ-TiAl alloy grade VIT7L (Ti–44.5Al–2V–1Nb–2Cr–0.1Gd, at.%) has been produced at NRC “Kurchatov Institute” - VIAM by inert gas atomization. The sifted target fraction 40–100 μm demonstrated high quality indicators in terms of flowability and sphericity. Simple-shaped parts of 11×11×40 mm3 have been printed by selective electron beam melting with varied line energy input (EL). An optimal interval 250≤EL≤285 J/m has been established, which provides absence of fusion faults, residual porosity of less than 0.5 vol.%, Al evaporation losses of not more than 1 at.%, and acceptable microstructure inhomogeneity along vertical section (building direction Z).Исследование выполнено за счет грантов Российского научного фонда № 18-79-10249-П, https://rscf.ru/project/18-79-10249/ (в части получения МПК), и № 24-19-00717, https://rscf.ru/project/24-19-00717/ (в части исследования влияния СЭЛС на структуру и пористость образцов)

Polymer Mechanochemistry: A New Frontier for Physical Organic Chemistry

© 2018 Elsevier Ltd Polymer mechanochemistry aims at understanding and exploiting the unique chemistry that is possible when stretching macromolecular chains beyond their strain-free contour lengths. This happens when chains are subject to a mechanical load, in bulk, in solution, at interfaces or as single molecules in air. Simple polymers such as polystyrene or polymethacrylate fragment via homolysis of a backbone C–C bond, and much contemporary effort in polymer mechanochemistry has focused on creating polymers which undergo more complex and interesting reactions, with such productive mechanochemical responses including mechanochromism and load strengthening. Comparatively less progress has been achieved in creating an internally coherent, theoretically sound interpretational framework to organize, systematize, and generalize the existing manifestations of polymer mechanochemistry and to guide the design of new mechanochemical systems. The experimental, computational, and conceptual tools of physical organic chemistry appear particularly well suited to achieve this goal, benefiting both fields

The Photochemical Stability of PbI2 and PbBr2: Optical and XPS and DFT Studies

We investigated the photochemical stability of PbX2 (X = I and Br) halides by optical and X-ray photoelectron spectroscopy (XPS). The optical absorbance displayed a strong reduction for PbI2 with light soaking and permanent behavior for PbBr2. The XPS survey spectra showed a sharp drop in the I:Pb ratio for PbI2 from 1.63 to 1.14 with exposure time from 0 to 1000 h while for PbBr2, it remains practically unchanged (1.59–1.55). The measurements of the XPS Pb 4f and Pb 5d spectra have shown the partial photolysis of PbI2 with the release of metallic lead whereas PbBr2 demonstrated remarkable photochemical stability. According to the density functional theory (DFT), calculations of the metal and iodide vacancy formation energies for PbBr2 are higher than for PbI2 which confirms the better stability to light soaking. The high photochemical stability of PbBr2 means that it can be used as excess under MAPbBr3 perovskite synthesis to improve not only the power conversion efficiency but also stability to light soaking. © 2023 by the authors.Russian Foundation for Basic Research, РФФИ: 21-52-52002; Ministry of Education and Science of the Russian Federation, Minobrnauka: AAAA-A18-118020190098-5, FEUZ-2023-0013; Fédération pour la Recherche sur le Cerveau, FRC: 0089-2019-0010/AAAA-A19-119071190044-3This work was supported by the Ministry of Science and Higher Education of the Russian Federation under the theme “Electron” No. AAAA-A18-118020190098-5 and Project FEUZ-2023-0013. The XPS measurements were supported by the Russian Foundation for Basic Research (Project No. 21-52-52002). Sample preparation was supported at FRC PCP MC RAS by the Ministry of Science and Higher Education of the Russian Federation (Project No. 0089-2019-0010/AAAA-A19-119071190044-3)