Rare-earth-doped yttrium aluminum garnets (RE³⁺:YAG) are widely used in a variety of applications, including materials processing, remote sensing, free-space and underwater communications, laser particle acceleration, gravitational wave interferometers, inertial confinement fusion. Moreover, RE³⁺-doped YAG materials show strong prospects for quantum information storage and processing, as well as for biological imaging, due to their high-Q 4f - 4f optical transitions.

Here we report the fabrication and characterization of the Er:YAG and Er:YSAG ceramics for implementing analysis as an active medium for 1500 nm lasing. High erbium content yttrium aluminum garnet (Er:YAG) and yttrium scandium aluminum garnet (Er:YSAG) ceramics have been fabricated from Er:YAG and Er:YSAG powders, respectively. All ceramic samples belong to the garnet-type cubic structure (space group Ia3d) without any traceable impure phases. The surface of Er:YSAG has fine-grained and homogeneous texture. The YSAG ceramics are harder to scratch with the grinding powder particles. Including Sc³⁺ in the Er:YAG crystal structure leads to decreasing melting temperature and improving mechanical characteristics and elastic-plastic properties of the materials. Based on SEM EDS cross-section analysis of Er:YSAG ceramic samples it can be deduced that all chemical elements (Er, Y, Al, Sc, O) are homogeneous distributed between grains and boundaries.

The optical transmittance of ceramics is affected strongly by the including Sc³⁺ which leads to decreasing melting temperature of the ceramic powders and consequently decreasing amount of the pores and producing more homogeneous media. Changing Al³⁺ with lager Sc³⁺ ion leads to increasing ceramic transmittance up to 60% at about 1500 nm.

Quaternary compounds Tl₂CdSi₃Se₈ and Tl₂CdGe₃Se₈ were found at the Tl₂CdSi(Ge)Se₄–Si(Ge)Se₂ sections of the quasi-ternary systems Tl₂Se–CdSe–Si(Ge)Se₂ by XRD and microstructure analysis methods.

Similar quaternary chalcogenides A^I₂B^IID^IV₃X₈ were reported earlier with alkaline elements (A^I = Cs, Rb, K, Na; В^II = Mg, Mn, Zn, Cd, Hg; D^IV = Ge, Sn; Х = S, Se, Te. Several types of crystal structures were observed in this family of compounds, orthorhombic (S.G. Р2₁2₁2₁), monoclinic (S.G. P2₁/c or P2₁/n), cubic Pa-3. Additionally, similar compositions Cu(Ag)₂CdSn₃S₈ were found in the Cu(Ag)₂S–CdS–SnS₂ systems. The Cu₂CdSn₃S₈ compound is a synthetic analoque of the natural mineral rhodostannite Cu₂FeSn₃S₈ and crystallizes in the tetragonal S.G. I4₁/a. The Ag₂CdSn₃S₈ crystal structure refines well in both tetragonal rhodostannite type (S.G. I4₁/a) and cubic chalcospinel type (S.G. Fd–3m).

The Tl₂CdD^IV₃X₈ compounds (M^IV = Si, Ge; X = Se) are closer to the quaternary phases with alkaline metals with orthorhombic structure. Their structure was determined in the isotropic approximation using the Cs₂CdGe₃Se₈ structure as a model, S.G. Р2₁2₁2₁ with the lattice parameters a=0.7485(1), b=1.2117(3), c=1.7134(3) nm, R_I=0.0953 (Tl₂CdSi₃Se₈) and a=0.7602(3), b=1.2071(2), c=1.7474(2) nm, R_I=0.1204 (Tl₂CdGe₃Se₈).

Each layer 2/_∞[CdD^IV₃Se₈]²⁻ consists of chains 1/_∞[CdD^IVSe₆]^6– that are linked by alternating [CdSe₄] and [D^IVSe₄] tetrahedra by corner sharing along the direction a. Moreover, the adjacent chains are connected into a layer by [D^IV₂Se₆]⁴⁻ dimers by corner sharing along the direction c.

To improve drug product quality, the size and shape of active pharmaceutical ingredient (API) crystals need to meet tight specifications, in part determined by downstream manufacturing requirements. Improved critical quality attributes may also lead to better solubilisation and bioavailability during drug product delivery. Milling-aided and sonication crystallisation are practical means to reduce the mean particle size and aspect ratio to meet these requirements and to improve downstream manufacturability. Other methods to control crystal shape employ temperature cycling during solution state crystallisation, e.g. Direct Nucleation Control (DNC) may be used to alter the particle morphology and size distribution through successive heating-cooling cycles for dissolution and recrystallisation.

In this work, the objective is to produce uniformly sized, equant shaped crystals with enhanced quality using DNC combined with in-situ wet-milling and sonication. The experiments were conducted using mefenamic acid in 2-butanol, starting with a standard linear cooling profile to help identify suitable settings for the DNC which is essentially a model-free closed-loop feedback control strategy. The wet-milling and sonicating approaches were compared in terms of cycle time and final crystal size and shape, by varying the inputs of wet-milling speed, sonication cycle and amplitude. It was shown that the in-situ sonicated DNC based crystallisations reaches the targeted quality bounds within a reduced number of cycles and delivers enhanced crystal morphology compared to the wet-mill aided DNC approach.

Hydrogen bonds are of paramount importance for biological processes, they are energetically weaker than covalent bonds, and their cumulative effect strengthens the three-dimensional shape of macromolecules and maintains their structure. The weakness of these bonds is responsible for the flexibility and conformational dynamics that are necessary for the flexibility of biomolecules, which gives them their recognition capacity and therefore their very high specificity.

New compounds have been obtained by proton transfer reactions between organic compounds of type nitrogenous substance and dicarboxylic acid. These reactions present interesting aspects for the realization of molecular systems whose properties can be monitored by X-ray diffraction.

In recent literature there are many examples of organic molecules functionalized with hydrogen bond donor-acceptor groups. Carboxylic acids are a few examples which illustrate excellent model systems for the preparation of new compounds with proton transfer, hence our interest in studying new organic compounds based on creatinine and organic acids which form complexes with many organic molecules

In this study, we shed light on the structural study of a new proton transfer compound. In this crystal structure, creatinine is protonated by two hydrogens of fumaric acid, forming a new organic compound, Bis Creatinium fumarate fumaric acid, that is rich in strong hydrogen bonds.

Heterocyclic ligands and their metallic complexes are biologically active materials [1–5], especially pyrazole-based ones, which are used in the pharmaceutical and agrochemical fields [6]. Accordingly, pyrazole-based copper and cobalt complexes showed excellent antibacterial and antifungal activities [7-9]. Particularly, the copper complexes were reported to have biological properties and some of them were active both in vivo and in vitro [9, 10]. On the other hand, many stable [M(Hpyrazole)₄X₂] complexes resulting from several transition metal cations with pyrazole and substituted-pyrazoles were reported [11-16]. In order to contribute to this complexes’ family, a Co(II) complex, namely dichloro-tetrakis(1H-pyrazole)-cobalt(II) [17], was synthesized and structurally characterized by means of single-crystal X-ray diffraction. The hydrogen-bonds and the non-covalent interactions within the complex were explicitly analyzed by means of the Hirshfeld surface analysis which showed the presence of N—H···Cl and C—H···Cl hydrogen-bonding networks in addition to weak non-classical H…H, N─H...C, C─H…N, N—H…π, π…lp/lp…π and lp…lp interactions. Additionally, interactions energy and energy frameworks analyses were performed in order to compute the total energies of the possible intermolecular interactions. The empty space in the crystal lattice was also analyzed using void mapping which lead to the presence of small cavities. The structure was furthermore examined by means of topological analysis, which revealed the presence of 0-periodic binodal 1,6-connected 1,6M7-1 and 14-connected uninodal bcu-x topologies.

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CH₃NH₃PbI₃ perovskite solar cells are expected to be alternative photovoltaic devices of silicon solar cells, because of their high conversion efficiency, easy fabrication process and low cost. On the other hand, they have a serious problem of low durability. In order to improve the stability and conversion efficiencies of the devices, one of the effective methods is to introduce additives into the perovskite photoactive layer. The purpose of this study is to improve the stability and conversion efficiency of the perovskite solar cells by incorporating copper (Cu) at the lead site, and potassium (K) or guanidinium (GA) at the CH₃NH₃ site. Additive effects on the photovoltaic properties and crystalline structures are investigated by the experimental results, and theoretical calculation such as electronic structures and thermodynamic stabilities. As a result, the simultaneous addition of Cu and K to the CH₃NH₃PbI₃ perovskite crystal improved the stability and open-circuit voltage, which was due to the suppression of decomposition of the perovskite crystals.

Perovskite solar cells are being studied because of their high efficiencies, low cost and easy fabrication process. However, perovskite crystals are unstable and decompose into PbI₂ in ambient air, and durability is one of the important issues for the perovskite solar cells. It has been reported that the photovoltaic properties and stability could be improved by adding polymers on the perovskite layer. In the present work, CH₃NH₃PbI₃ perovskite photovoltaic devices treated with a polysilane layer were fabricated and characterized. A decaphenylcyclopentasilane (DPPS) in chlorobenzene solution was spin-coated between the perovskite layer and the hole transport layer (spiro-OMeTAD), and the resulting device was annealed at 190 °C. The DPPS-treated devices had higher conversion efficiencies than the standard one, and they were stable in ambient air. Microstructural observations suggested that DPPS would work effectively as a bulk-hetero structure along with perovskite layers.

Effects of maxed-valence states on electronic structures of europium (Eu)-incorporated CH(NH₂)₂PbI₃ (FAPbI₃) and CH₃NH₃PbI₃ (MAPbI₃) perovskite crystals were investigated by first-principles calculation. Partial replacements of europium ions into the perovskite crystal influenced the electronic structures and the effective mass related to carrier mobility. In the case of the FAPb(Eu⁺³)I₃ crystal, there was wide distribution of the 5p orbital of iodine near the valence band, and the 3d orbital of the Eu³⁺ ion near the conductive band. The incorporation of Eu³⁺ ion into the crystal slightly caused to increase the effective mass ratio (m_e*/m₀, m_h*/m₀) as compared with those of the FAPbI₃ crystal, provided the wide distribution of 3d, 4f-5p hybrid orbitals near the valence band, and influenced the band dispersion with a decrease of m_e^*/m₀ and m_h^*/m₀, which is expected for improving the carrier mobility. The chemical shifts of ¹²⁷I-NMR of the MAPb(Eu²⁺)I₃ crystal indicated isotropic behavior. The chemical shifts of ¹⁵⁷Eu-NMR and g-tensor depended on the quadrupole interaction based on the electron field gradient and asymmetry parameter in the coordination structure. The electronic correlation based on hybrization of the 3d, 4f-5p orbital in the Eu²⁺-iodine band promoted the carrier itinerary, which was expected to improve the carrier mobility related to the short circuit current density and the conversion efficiency as the photovoltaic performance.