Single Crystal Research Articles

EXPERIMENTAL AND THEORETICAL INTERPRETATIONS OF STRUCTURAL, OPTICAL, MECHANICAL AND THERMAL PROPERTIES OF 2 AMINOPYRIDINIUM PHTHALATE SINGLE CRYSTALS

Nonlinear optical good quality single crystals of 2-aminopyridinium phthalate single crystals are synthesized by solution growth technique. Structural parameters are elucidated by Single Crystal X-ray diffraction method which reveals that the material crystallizes in non-centrosymmetric crystalline framework. Vibrational assignments are interpreted by Fourier Transform Infrared spectral analysis. The thermal, mechanical and laser stability are explored by TG/DTA, microhardness and Laser Damage threshold analysis. The material has good emission nature in the violet emission region. The linear optical properties are elucidated with the help of UV-visible spectral analysis. The intermolecular charge transfer interactions are analyzed by HOMO-LUMO and MESP maps by using Gaussian ’09 software program. The second harmonic generation efficiency of the synthesized material are predicted by Kurtz Perry powder technique.

Improvement of scintillation light yield of Tb:CaHfO3 by Mg-substitution

1.0 % Tb:Ca1-xMgxHfO3 (x = 0.05, 0.075, and 0.1) single crystals were synthesized by the floating zone technique, and their photoluminescence and scintillation properties were evaluated. The x = 0.1 sample showed the highest quantum yield of 18.7 % under excitation at 250 nm among all the samples. All the samples showed scintillation with multiple emission lines originating from the 4f–4f transitions of Tb3+. From the pulse height spectra, the highest light yield was 17,400 photons/MeV in the x = 0.075 sample among the samples, and all the samples outperformed the light yield of the unsubstituted one.

Exploring the Nonlinear Optical Properties of 6-Ethoxy-2-Aminobenzothiazolium-4-Methoxyphenyl Acetate: Experimental and Computational Insights into a Monoclinic Single Crystal

The study aims to investigate the third-order nonlinear optical properties of a single crystal of 6-ethoxy-2-aminobenzothiazolium-4-methoxyphenylacetate (EABT), which is synthesized via solvent evaporation. The X-ray structural analysis revealed that the crystal possesses a monoclinic structure, characterized by a centrosymmetric P21/c space group. Various analytical methods were employed to study the existence of various functional groups, crystallinity, thermal stability, and the solubility of the crystal. Optical absorption, transmittance, and emission behavior of the crystal were examined by UV-Vis-NIR and photoluminescence spectroscopy. The third harmonic generation (THG) studies were conducted on well-polished single crystals using the Z-scan method. In addition to experimental investigations, computational calculations were conducted to assess the properties of the molecular structure. The geometry optimization of the molecule was performed using Density Functional Theory (DFT) methods, specifically employing the B3LYP 6-311G level of theory.

On the selective formation of cubic tetrastack crystals from tetravalent patchy particles.

Achieving the formation of target open crystalline lattices from colloidal particles is of paramount importance for their potential application in photonics. Examples of such desired structures are the diamond, tetrastack, and pyrochlore lattices. Here, we demonstrate that the self-assembly of tetravalent patchy particles results in the selective formation of cubic tetrastack crystals, both in the bulk and in the systems subjected to external fields exerted by the solid substrate. It is demonstrated that the presence of an external field allows for the formation of well-defined single crystals with a low density of defects. Moreover, depending on the strength of the applied external field, the mechanism of epitaxial growth changes. For weakly attractive external fields, the crystallization occurs in a similar manner as in the bulk, since the fluid does not wet the substrate. Nonetheless, the formed crystal is considerably better ordered than the crystals formed in bulk, since the surface induces the ordering in the first layer. On the other hand, it is demonstrated that the formation of well-ordered cubic tetrastack crystals is considerably enhanced by the increase in external field strength, and the formation of the thick crystalline film occurs via a series of layering transitions.

Controlling the Orientation-Dependent Second Harmonic Generation in Hybrid Germanium Perovskite Crystals.

Manipulating the crystal orientation plays a crucial role in the conversion efficiency during second harmonic generation (SHG). Here, we provide a new strategy in controlling the surface-dependent anisotropic SHG with the precise design of (101) and (20) MAGeI3 facets. Based on the SHG measurement, the (101) MAGeI3 single crystal exhibits larger SHG (1.3 × (20) MAGeI3). Kelvin probe force microscopy imaging shows a smaller work function for the (101) MAGeI3 compared with the (20), which indirectly demonstrates the stronger intrinsic polarization on the (101) surface. X-ray photoelectron spectroscopy confirms the band bending within the (101) facet. Temperature-dependent steady-state and time-resolved photoluminescence spectroscopy show shorter lifetime and wider emission band in the (101) MAGeI3 single crystal, revealing the higher defect states. Additionally, powder X-ray diffraction patterns show the (101) MAGeI3 possesses larger in-plane polar units [GeI3]- density, which could directly enhance the spontaneous polarization in the (101) facet. Density functional theory (DFT) calculation further demonstrates the higher intrinsic polarization in the (101) facet compared with the (20) facet, and the larger built-in electric field in the (101) facet facilitates surface vacancy defect accumulation. Our work provides a new angle in tuning and optimizing hybrid perovskite-based nonlinear optical materials.

High-Pressure Synthesis and Recovery of Single Crystals of the Metastable Manganese Carbide, MnCx.

Transition metal carbides find widespread use throughout industry due to their high strength and resilience under extreme conditions. However, they remain largely limited to compounds formed from the early d-block elements, since the mid-to-late transition metals do not form thermodynamically stable carbides. We report here the high-pressure bulk synthesis of large single crystals of a novel metastable manganese carbide compound,MnCxP63/mmc, which adopts the anti-NiAs-type structure with significant substoichiometry at the carbon sites. We demonstrate how synthesis pressure modulates the carbon loading, with~40% occupancy being achieved at 9.9 GPa.

Piperidine and Pyridine Series Lead-Free Dion-Jacobson Phase Tin Perovskite Single Crystals and Their Applications for Field-Effect Transistors.

Two-dimensional (2D) organic-inorganic metal halide perovskites have gained immense attention as alternatives to three-dimensional (3D) perovskites in recent years. The hydrophobic spacers in the layered structure of 2D perovskites make them more moisture-resistant than 3D perovskites. Moreover, they exhibit unique anisotropic electrical transport properties due to a structural confinement effect. In this study, four lead-free Dion-Jacobson (DJ) Sn-based phase perovskite single crystals, 3AMPSnI4, 4AMPSnI4, 3AMPYSnI4, and 4AMPYSnI4 [AMP = (aminomethyl)-piperidinium, AMPY = (aminomethyl)pyridinium] are reported. Results reveal structural differences between them impacting the resulting optical properties. Namely, higher octahedron distortion results in a higher absorption edge. Density functional theory (DFT) is also performed to determine the trends in energy band diagrams, exciton binding energies, and formation energies due to structural differences among the four single crystals. Finally, a field-effect transistor (FET) based on 4AMPSnI4 is demonstrated with a respectable hole mobility of 0.57 cm2 V-1 s-1 requiring a low threshold voltage of only -2.5 V at a drain voltage of -40 V. To the best of our knowledge, this is the third DJ-phase perovskite FET reported to date.

A single crystal study of Kagome metals U2Mn3Ge and U2Fe3Ge.

Single crystals of U2Mn3Ge and and U2Fe3Ge with a Kagome lattice structure were synthesized using a high-temperature self-flux crystal growth method. The physical properties of these crystals were characterized through measurements of resistivity, magnetism, and specific heat. U2Fe3Ge exhibits ferromagnetic ground state and Anomalous Hall Effect, and U2Mn3Ge demonstrates a complex magnetic structure. Both compounds exhibit large Sommerfeld coefficient, indicating coexistence of heavy Fermion behaviour with magnetism. Our results suggest that this U2TM3Ge (TM = Mn, Fe, Co) family is a promising platform to investigate the interplay of magnetism, Kondo physics and the Kagome lattice.

Структура, ріст та оптичні характеристики монокристалів сульфанілату гуанідинію (GSA)

Guanidine Sulphanilate (GSA) single crystal was grown by slow evaporation growth method. Single crystal X-ray diffraction studies show that the crystal grows in a centro symmetric monoclinic system and its space group is P21/c. Optical studies were carried out using UV visible spectroscopy and the grown crystal shows the the lower cutoff wavelength of 220 nm. Photoluminescence studies show that GSA crystals have good luminescence properties. Laser damage threshold was found to be 0.24GW/cm2. Nonlinear optical studies show green light emission.

Generation and Evolution Mechanism of Cracks in HMX Single Crystals around Phase Transition Temperature

Generation and Evolution Mechanism of Cracks in HMX Single Crystals around Phase Transition Temperature

Br-Vacancies Induced Variable Ranging Hopping Conduction in High-Order Topological Insulator Bi4Br4.

The defects have a remarkable influence on the electronic structures and the electric transport behaviors of the matter, providing the additional means to engineering their physical properties. In this work, a comprehensive study on the effect of Br-vacancies on the electronic structures and transport behaviors in the high-order topological insulator Bi4Br4 is performed by the combined techniques of the scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and physical properties measurement system along with the first-principle calculations. The STM results show the defects on the cleaved surface of a single crystal and reveal that the defects are correlated to the Br-vacancies with the support of the simulated STM images. The role of the Br-vacancies in the modulation of the band structures has been identified by ARPES spectra and the calculated energy-momentum dispersion. The relationship between the Br-vacancies and the semiconducting-like transport behaviors at low temperature has been established, implying a Mott variable ranging hopping conduction in Bi4Br4. The work not only resolves the unclear transport behaviors in this matter, but also paves a way to modulate the electric conduction path by the defects engineering.

Photoexcited Carrier Dynamics in Iodine-Doped CH3NH3PbBr3 Single Crystals.

Iodine-doped bromide perovskite single crystals (IBPSCs) have important applications in optoelectronic fields, such as in solar cells. Currently, much research has aimed to study the phase separation phenomenon and device performance improvements in IBPSCs. However, important intrinsic photoexcited carrier dynamics are often overlooked in IBPSCs. Here, we explored the photoexcited carrier dynamics in typical iodine-doped MAPbBr3 single crystals using the excitation intensity-dependent steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) technique. We found that the trap state density changes with an increase in the amount of doped iodine. Further, we noticed that there is an influence of carrier diffusion on the photoexcited carrier dynamics, and then, we evaluated the carrier diffusion coefficients and recombination constants via numerical simulations of the PL kinetics. Consequently, we found that the electron shallow trap-related carrier behaviors substantially impacted the PL kinetics. Our results greatly facilitate a deeper understanding of the fundamental characteristics of mixed halide perovskite material.

Study of rutile TiO2(110) single crystal by transient absorption spectroscopy in the presence of Ce4+ cations in aqueous environment. Implication on water splitting

Ce4+ cations are commonly used as electron acceptors during the water oxidation to O2 reaction over Ir- and Ru-based catalysts. They can also be reduced to Ce3+ cations by excited electrons from the conduction band of an oxide semiconductor with a suitable energy level. In this work, we have studied their interaction with a rutile TiO2(110) single crystal upon band gap excitation by femtosecond transient absorption spectroscopy (TAS) in solution in the 350–900 nm range and up to 3.5 ns. Unlike excitation in the presence of water alone the addition of Ce4+ resulted in a clear ground-state bleaching (GSB) signal at the band gap energy of TiO2 (ca. 400 nm) with a time constant t = 4–5 ps. This indicated that the Ce4+ cations presence has quenched the e-h recombination rate when compared to water alone. In addition to GSB, two positive signals are observed and are attributed to trapped holes (in the visible region, 450–550 nm) and trapped electrons in the IR region (>700 nm). Contrary to expectation, the lifetime of the positive signal between 450 and 550 nm decreased with increasing concentrations of Ce4+. We attribute the decrease in the lifetime of this signal to electrostatic repulsion between Ce4+ at the surface of TiO2(110) and positively charged trapped holes. It was also found that at the very short time scale (<2–3 ps) the fast decaying TAS signal of excited electrons in the conduction band is suppressed because of the presence of Ce4+ cations. Results point out that the presence of Ce4+ cations increases the residence time (mobility) of excited electrons and holes at the conduction band and valence band energy levels (instead of being trapped). This might provide further explanations for the enhanced reaction rate of water oxidation to O2 in the presence of Ce4+ cations.

Synthesis, Stability, Meisenheimer Complex Formation, and Charge‐Transfer Properties of Ultra‐Electron‐Deficient Tetracyano‐Naphthalene Diimides

Tetra‐cyano substituted naphthalene diimides (TCNDIs) with calculated LUMO of ‐5.2 eV, form one of the strongest electron‐acceptors known to date. However, the synthesis and isolation of this class of molecules remain challenging due to its reactivity emanating from its ultra‐electron‐deficiency. Herein we have established an improved synthetic methodology of TCNDIs with cost‐effective reagents and circumventing metallic catalysts. The synthesis is amenable to TCNDIs with the shortest axial alkyl groups, i.e., methyl group and also longer alkyl chains. We also gained insight on how axial alkyl chain lengths influence electron‐deficiency, Meisenheimer complex formation, reactivity, and charge‐transfer of TCNDIs from computation, spectroscopy, and electrochemical studies. The TCNDIs with Me/Et axial groups were found to be more susceptible to moist solvents vis‐à‐vis the TCNDIs with longer alkyl groups. The single crystal structures of the TCNDIs show infinitely π‐stacked structure, and a new C=O···C≡N or C≡N···π motif is discerned. Finally, toluene‐mediated charge‐transfer properties of TCNDIs in the single crystals as well as in solution have been examined.

Application of laboratory micro X-ray fluorescence devices for X-ray topography

It is demonstrated that high-resolution energy-dispersive X-ray fluorescence mapping devices based on a micro-focused beam are not restricted to high-speed analyses of element distributions or to the detection of different grains, twins and subgrains in crystalline materials but can also be used for the detection of dislocations in high-quality single crystals. Si single crystals with low dislocation densities were selected as model materials to visualize the position of dislocations by the spatially resolved measurement of Bragg-peak intensity fluctuations. These originate from the most distorted planes caused by the stress fields of dislocations. The results obtained by this approach are compared with laboratory-based Lang X-ray topographs. The presented methodology yields comparable results and it is of particular interest in the field of crystal growth, where fast chemical and microstructural characterization feedback loops are indispensable for short and efficient development times. The beam divergence was reduced via an aperture management system to facilitate the visualization of dislocations for virtually as-grown, non-polished and non-planar samples with a very pronounced surface profile.

Mixed occupancy: the crystal structure of scheelite-type LiLu[MoO4]2

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry \overline{4}) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078–18089.] all atoms were refined with anisotropic displacement parameters.

Upconversion luminescence and temperature sensing properties of Tm³+, Yb³+, and Ho³+ doped 12CaO·7Al₂O₃ single crystals

Upconversion luminescence and temperature sensing properties of Tm³+, Yb³+, and Ho³+ doped 12CaO·7Al₂O₃ single crystals

Thermal Field Simulation and Optimization of PbF2 Single Crystal Growth by the Bridgman Method

PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF2 single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF2 crystals by the Bridgman method.

Novel Pyrido[4,3-d]pyrimidine Derivatives as Potential Sterol 14α-Demethylase Inhibitors: Design, Synthesis, Inhibitory Activity, and Molecular Modeling.

Thirty-four new pyrido[4,3-d]pyrimidine analogs were designed, synthesized, and characterized. The crystal structures for compounds 2c and 4f were measured by means of X-ray diffraction of single crystals. The bioassay results showed that most target compounds exhibited good fungicidal activities against Pyricularia oryzae, Rhizoctonia cerealis, Sclerotinia sclerotiorum, Botrytis cinerea, and Penicillium italicum at 16 μg/mL. Compounds 2l, 2m, 4f, and 4g possessed better fungicidal activities than the commercial fungicide epoxiconazole against B. cinerea. Their half maximal effective concentration (EC50) values were 0.191, 0.487, 0.369, 0.586, and 0.670 μg/mL, respectively. Furthermore, the inhibitory activities of the bioactive compounds were determined against sterol 14α-demethylase (CYP51). The results displayed that they had prominent activities. Compounds 2l, 2m, 4f, and 4g also showed better inhibitory activities than epoxiconazole against CYP51. Their half maximal inhibitory concentration (IC50) values were 0.219, 0.602, 0.422, 0.726, and 0.802 μg/mL, respectively. The results of molecular dynamics (MD) simulations exhibited that compounds 2l and 4f possessed a stronger affinity to CYP51 than epoxiconazole.

Single Crystal Growth and Transport Properties of Narrow Band Gap Semiconductor RhP2

Abstract Here, we report the growth of high-quality single crystals of RhP2, and systematically study its structure and physical properties by transport, magnetism, and heat capacity measurements. Single-crystal X-ray diffraction revealed RhP2 adopts a monoclinic structure with the cell parameters a=5.7347(10) Å, b=5.7804(11) Å, and c=5.8222(11) Å, space group P21/c (No. 14). The electrical resistivity ρ(T) measurements indicate that RhP2 exhibits a narrow band gap behavior with the activation energies of 223.1 m eV and 27.4 m eV for two distinct regions, respectively. The temperature-dependent Hall effect measurements show electron domain transport behavior with a low charge carrier concentration. We found that RhP2 has a high mobility μe~210 cm2v-1s-1 with carrier concentrations ne~3.3×1018 cm-3 at 300 K with a narrow band gap feature. The high mobility μe reached a maximum of approximately 340 cm2v-1s-1 with carrier concentrations ne~2×1018 cm-3 at 100 K. No magnetic phase transitions were observed from the susceptibility χ(T) and specific heat Cp(T) measurements of RhP2. Our results not only offer effective potential as a material platform for studying exotic physical properties and electron band structures but also motivate further exploration of their potential photovoltaic and optoelectronic applications.