Crystal Growth & Design最新文献

We investigate the growth by metal–organic vapor phase epitaxy of InGaN/GaN multiple quantum wells on organized N-polar GaN μ-platelets on a graphene/SiO₂/Si wafer. The structural properties of μ-platelets have been studied by transmission electron microscopy and reveal a Ga-polar inclusion located at the center. The μ-platelets exhibit convex top facets revealing special features of the growth mechanism on the N-polar surface. First, biatomic steps play a crucial role by increasing the growth rate, as the confinement of adatoms on small terraces enhances material incorporation. In the absence of biatomic steps, the growth rate is strongly limited. Second, we observe an In-content variation along terraces attributed to preferential adsorption above the downward biatomic step. According to the cathodoluminescence study, the central Ga-polar inclusion changes the morphology of quantum wells by creating pyramidal structures that favor high In-content incorporation and show long wavelength emission in the amber/red region.

To meet the requirements of extreme environments, desensitivity, and the development of high-temperature-resistant energetic materials are urgently needed. Herein, two high-temperature-resistant fluorescent energetic materials, 9,10-dichloro-2,4,8-trinitrobenzo[4′,5′][1,2,3]triazolo[2′,1′:2,3][1,2,3]triazolo[4,5-b]pyridin-6-ium-5-ide (5a) and 3,9,10-trichloro-2,4,8-trinitrobenzo[4′,5′][1,2,3]triazolo[2′,1′:2,3][1,2,3]triazolo[4,5-b]pyridin-6-ium-5-ide (5b), were synthesized. The thermal decomposition temperatures were determined to be 339 °C for 5a and 272 °C for 5b. Both meet the requirements for heat-resistant explosive materials. By the BAM method test, 5b (IS = 20 J, FS > 360 N) displayed similar friction sensitivity (FS) but better impact sensitivity (IS) than 5a (IS = 18 J, FS > 360 N). The optimized geometries and electrostatic potential (ESP) surface analysis proved the dipole–dipole interactions of Cl with the O atoms in adjacent –NO₂ groups in 5b, and from the perspective of compound structures, the main reason for the better impact sensitivity of 5b may be due to Cl^···O dipole–dipole interactions. Besides, 5a exhibited an emission peak at 551 nm, 5b displayed a red-shift emission peak at 562 nm, manifesting their potential in the use of energetic compound detection. This work could offer guidelines for designing and synthesizing new insensitive heat-resistant fluorescent energetic materials and evidence the effectiveness of dipole–dipole interactions in reducing sensitivity of energetic explosives.

Doramectin is a broad-spectrum antiparasitic drug used in veterinary medicine. However, there have been no reports on doramectin solvates and their formation mechanisms so far. In this study, three doramectin solvates, doramectin-ethyl acetate (S1), propyl acetate (S2), and butyl acetate (S3), were successfully prepared using the solution crystallization method. Single-crystal X-ray diffraction analyses confirmed that all three solvates are isomorphous crystals. Additionally, the crystal structure results revealed that solvent molecules form hydrogen bonds with doramectin in a 1:1 molar ratio and exist in a channel-like structure. Furthermore, the desolvation temperature of these solvates was positively correlated with the strength of the intermolecular interactions. Overall, this study provides a significant theoretical foundation and methodological guidance for research on doramectin solvates and their subsequent formulation development as well as providing valuable references and research approach for the development of more solid forms of doramectin.

The structural and optical properties of 3 monolayer (ML) thick InAs quantum dots (QDs) grown by migration-enhanced epitaxy (MEE), conventional molecular beam epitaxy (CON), and hybrid methods combining the two were investigated. The hybrid approaches included QD growth initiated with MEE and terminated with CON (MEE-CON) and the reverse sequence (CON-MEE). The results indicate that the deposition method used for the final 1 ML of InAs critically influences the structural and optical properties of the QDs. QDs with MEE termination on CON-initiated layers exhibited structural and optical features comparable to those grown entirely by MEE, and similar for the reverse case. These findings demonstrate that the final growth stage plays a decisive role in defining QD properties, regardless of the initial growth method.

Developing effective combination drug therapies with enhanced control over drug properties is critical for improving patient outcomes. This study explores a novel approach to producing composite crystals of valsartan and amlodipine besylate via nanoparticle assembly through reverse antisolvent crystallization. The method involves controlled injection of drug solutions into an antisolvent, manipulating parameters like injection sequence and timing to influence the resulting crystal properties. Results demonstrate that the injection order significantly impacts the crystal structure and drug release kinetics of the composite particles. Specifically, amlodipine injection timing plays a crucial role in crystal growth and interaction with valsartan. Furthermore, postcrystallization after injection promotes the formation of stable amlodipine monohydrate crystals within the composite particles. Observed differences in release behavior suggest that drug phases locate in different regions within the composite particles, depending on the injection order. This work provides insights into engineering composite drug particles with tailored properties, offering a promising new route for developing more effective pharmaceutical formulations.

Chiral halide emitters demonstrate great potential in circularly polarized organic light-emitting diodes for future 3D displays. However, achieving circularly polarized luminescence with cost-effective and environmentally friendly halide materials remains a significant challenge. In this study, we introduced classic chiral organic ligands into a [Cu₄I₄] inorganic core to develop efficient circularly polarized luminescence (CPL)-active halide materials. Through the synergistic design of (S/R)-3-methylmorpholine with the [Cu₄I₄] core, we successfully synthesized a pair of copper(I) enantiomers Cu₄I₄(S/R-3-methylmorpholine)₄ (S/R-Cu₄I₄). These enantiomers not only exhibit distinct mirror-image CPL signals but also possess excellent thermal stability and high luminescence efficiency. OLED devices fabricated based on the S/R-Cu₄I₄ enantiomers achieved high-performance circularly polarized electroluminescence (CPEL), with a brightness of 6506 cd m^–2, an external quantum efficiency (EQE) of 4.2%, a CPEL dissymmetry factor (g_EL) of +8 × 10^–3, and an extremely low efficiency roll-off of only ∼6% at 1000 cd m^–2 brightness. This study demonstrates the feasibility of employing simple chiral ligands and low-cost metals to develop highly efficient CPL-active halide materials. The findings provide a practical strategy for constructing high-performance chiral copper-based halide emitters while also establishing the first pioneering implementation of Cu₄I₄ cluster materials in CPEL applications.

Deep eutectic solvents (DES) have emerged as environmentally friendly alternatives to conventional crystallization media in pharmaceutical applications. In this work, a phenol-based DES, in which phenol acts as the volatile hydrogen bond donor, was employed to regulate the polymorphism of aripiprazole (APZ). The results demonstrated that DES composition strongly affected the polymorphic outcome of APZ: a 1:6 molar ratio predominantly produced form III, 1:7–1:8 ratios yielded form V, and 1:9–1:10 ratios led to form VII. However, this tunability was lost when the phenol removal rate increased under vacuum, where only a single polymorph was obtained, indicating that the nucleation pathway was restricted by rapid solvent loss. Conformational analysis revealed that an excess of hydrogen bond donors promoted stronger multidirectional coordination and steric filling effects, driving APZ to adopt a noncoplanar conformation. Moreover, the rapid removal of phenol drives the composition swiftly beyond the metastable regions, resulting in the exclusive formation of a single polymorph. The DES composition influenced the formation of rhombic and star-like crystal morphologies, whereas the phenol removal rate had minimal impact, indicating its primary role in nucleation rather than crystal growth. Overall, this study highlights DES as promising crystallization media for the effective control of drug polymorphism and morphology, providing new insights into their application in pharmaceutical crystallization design.

Titanium dioxide (TiO₂) polymorphs, whether used individually or in heterostructures, are pivotal for technological applications such as white pigments, lithium-ion battery anodes, and photocatalysts due to their optical and charge-carrier transport properties. Understanding phase transformation mechanisms among TiO₂ polymorphs is critical for synthesizing desired metastable structures and tuning their properties predictively.

Elucidating the thermal transformation pathways of molecular precursors, such as the dimeric zirconium oxo cluster investigated herein, is crucial for the rational design of functional zirconia nanomaterials with tailored properties. This study primarily employed synchrotron X-ray pair distribution function (PDF) analysis of ex situ annealed samples, complemented by SCXRD, TGA, FTIR, and EPR spectroscopy, to track the detailed stepwise structural evolution from the molecular precursor to the final oxide. Key results demonstrate a sequential transformation: initial desolvation (100 °C) largely preserves the local dimer structure; further heating (220 °C) after removal of eight acetate equivalents forms a unique condensed dimeric intermediate; and finally, complete acetate decomposition by 480 °C leads to crystallization into black, nanocrystalline tetragonal ZrO₂. We interpret these transformations as a topochemical-like process where core Zr₆ structural motifs are remarkably preserved, and specific oxygen-retaining acetate decomposition mechanisms create an intrinsically oxygen-excess framework that stabilizes the oxygen-centered radicals (g ≈ 2.001) detected by EPR in the final black zirconia. Ultimately, this work reveals a controlled pathway from a well-defined molecular cluster to defect-engineered black zirconia nanocrystals, highlighting how precursor architecture and specific decomposition routes govern the material’s structural evolution and ultimately defect chemistry.

A structurally defined zirconium oxo cluster is shown to transform into a defect-rich black zirconia nanocrystal via a stepwise, topochemical pathway. X-ray pair distribution function (PDF) analysis reveals that the precursor’s core Zr₆ building blocks are preserved during thermal annealing, guiding the formation of an oxygen-excess framework that hosts oxygen-centered radicals.

Casopitant mesylate Form 1 and Form 3 form an inseparable crystalline polymorphic mixture, showing very similar powder X-ray diffraction (PXRD) charts. Using three-dimensional electron diffraction/microcrystal electron diffraction (3D ED/MicroED), we succeeded in elucidating crystal structures of casopitant mesylate Forms 1 and 3, which have been enveloped in mystery. We emphasize that the structures were determined from only one lot of crystalline fine powder containing a mixture of the crystalline polymorphs. Importantly, we find the crystal structures and conformations of the two polymorphs to be just differentiated by a slight shift in packing, explaining the highly similar PXRD charts. 3D ED/MicroED analysis enables direct structure determination from polymorph mixtures, which was previously nearly impossible, and there is no doubt that it will become an indispensable analysis in the pharmaceutical industry focusing on crystal polymorphism.