We found for the first time a new origin of selection of perovskite crystallization pathways from DMF solutions containing MAI and PbI 2 to present here a comprehensive study of a full set of essential intermediate phases determining the perovskite's morphology. For all three discovered structurally different intermediate phases forming at a given precursor ratio, we refined their crystal structures by synchrotron X-ray radiation and investigated dynamics and phase assemblage in the course of decomposition. As a result, we revealed a clear correlation between the composition of the intermediate phases, peculiarities of their crystal structure, and the morphology of the final perovskite films. Using the DFT method we calculated formation enthalpies of these intermediate phases and explained the preferential precipitation of DMSO-adduct rather than DMF-adduct in an antisolvent approach. This finding opens up a possibility of design-on-demand of perovskite materials using simple soft chemistry approaches.

We describe a first open-access database of experimentally investigated hybrid organic-inorganic materials with two-dimensional (2D) perovskite-like crystal structure. The database includes 515 compounds, containing 180 different organic cations, 10 metals (Pb, Sn, Bi, Cd, Cu, Fe, Ge, Mn, Pd, Sb) and 3 halogens (I, Br, Cl) known so far and will be regularly updated. The database contains a geometrical and crystal chemical analysis of the structures, which are useful to reveal quantitative structure-property relationships for this class of compounds. We show that the penetration depth of spacer organic cation into the inorganic layer and M-X-M bond angles increase in the number of inorganic layers (n). The machine learning model is developed and trained on the database, for the prediction of a band gap with accuracy within 0.1 eV. Another machine learning model is trained for the prediction of atomic partial charges with accuracy within 0.01 e. We show that the predicted values of band gaps decrease with an increase of the n and with an increase of M-X-M angles for single-layered perovskites. In general, the proposed database and machine learning models are shown to be useful tools for the rational design of new 2D hybrid perovskite materials.

Small cations such as guanidinium and cesium can act as templating cations to form low dimensional phases (2D, 1D, 0D) in the case of excess of organic halides. However, such phases with the widely used formamidinium (FA + ) cation have not been reported so far. In this study, we discovered two novel low dimensional phases with composition of FA2PbBr4 and investigated the prerequisites of their formation upon crystallization of FABr-excessive solutions of FAPbBr3. We found that both phases have the structure of (110) layered perovskite but is represented by two different polymorphs with "eclipsed" and "staggered" arrangement of adjacent layers. It was shown that FA2PbBr4 phases usually exist in a labile equilibrium with FAPbBr3 3D perovskite and can form composites with it. The optical properties of both polymorphs were comprehensively studied by means of absorption spectroscopy, diffuse reflection spectroscopy and photoluminescence spectroscopy. DFT calculations were applied to investigate the band structure of the FA2PbBr4 and to corroborate the conclusions on their optoelectronic properties. As a result, we found that FA2PbBr4 phases irradiated by UV can exhibit effective green photoluminescence due to a transfer of excitation energy to defective states or 3D perovskite inclusions.

Good cyclability is essential for the potential application of cathode materials. We investigated electrochemical properties of Mg in layered intercalation compound from first-principles using TiS3 as a model system. The calculations showed exothermic phase transformation upon intercalation of Mg from the electrolyte: the geometry optimization of the structure containing 0.5 Mg showed the shift of layers accompanied by change of Mg coordination from square pyramidal to trigonal prismatic. Further increase of the Mg content leads to break of the S–S bonds in the disulfide ion and conversion of the TiS3 layers into ribbons. The obtained phase is metastable and can easily and irreversibly decompose to MgS and TiS2. This means that in order to achieve full theoretical capacity of TiS3 this decomposition has to be suppressed. A very low migration barrier of 0.292–0.698 eV (depending on the Mg content) was found in the [010] direction, which is much lower than the value of analogues, such as layered and spinel TiS2. This finding reveals the potential of TiS3 to become Mg cathode with superior performance compared to similar analogues.

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the leading cause of senile dementia in the United States. Accumulation of amyloid-b (Ab) and the effects of this peptide on microglial cells contribute greatly to the etiology of AD. Experiments were carried out to determine whether the panselective s-receptor agonist afobazole can modulate microglial response to the cytotoxic Ab fragment, Ab [25][26][27][28][29][30][31][32][33][34][35] . Treatment with afobazole decreased microglial activation in response to Ab, as indicated by reduced membrane ruffling and cell migration. The effects of afobazole on Ab 25-35 -evoked migration were concentration dependent and consistent with s-receptor activation. When afobazole was coapplied with either BD-1047 [N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(dimethylamino)ethylamine dihydrobromide] or rimcazole, which are s-1-and s-2-selective antagonists, respectively, the inhibition of Ab 25-35 -induced migration by afobazole was reduced. Prolonged exposure of microglia to Ab 25-35 resulted in glial cell death that was associated with increased expression of the proapoptotic protein Bax and the death protease caspase-3. Coapplication of afobazole with Ab 25-35 decreased the number of cells expressing both Bax and caspase-3 and resulted in a concomitant enhancement in cell survival. Although afobazole inhibited activation of microglia cells by Ab [25][26][27][28][29][30][31][32][33][34][35] , it preserved normal functional responses in these cells after exposure to the amyloid peptide. Intracellular calcium increases induced by ATP were depressed in microglia after 24-hour exposure to Ab [25][26][27][28][29][30][31][32][33][34][35] . However, coincubation in afobazole returned these responses to near control levels. Therefore, stimulation of s-1 and s-2 receptors by afobazole prevents Ab [25][26][27][28][29][30][31][32][33][34][35] activation of microglia and inhibits Ab 25-35 -associated cytotoxicity, suggesting that afobazole may be useful for AD therapeutics.