Crystal Growth & Design最新文献

Crystal structure prediction (CSP) plays a significant role in exploring the crystal polymorphism of pharmaceutical solids. Determination of the atomic-level structures of crystalline materials is a fundamental step in understanding their bulk physical and chemical properties and behavior in drug products. CSP can be performed using numerous computational approaches, but all ultimately require comparison with experimental measurements to confirm the CSP findings. In this work, terahertz (THz) vibrational spectroscopy is combined with powder X-ray diffraction (PXRD) to demonstrate a new metrics framework for the validation of CSP investigations. Terahertz spectroscopy probes the low-frequency (≤150 cm⁻¹) lattice vibrations of molecular crystals and provides a polymorph specific spectral profile that complements diffraction methods. This methodology is applied to the anti-epileptic drug lamotrigine, the subject of multiple crystal engineering studies to improve its formulated performance. A CSP search was performed on lamotrigine starting with a fast molecular mechanics survey for initial crystal structure candidates (∼800,000 structures), followed by high-accuracy solid-state density functional theory to refine the most promising candidates. The accuracy of the CSP output was evaluated by numerical comparison of simulated and experimental PXRD and THz datasets, with both benchmarks unambiguously indicating the lowest energy CSP candidate to be a structural match to the published lamotrigine polymorph (Form I, C 2/c space group). The success of the overall approach highlights THz spectroscopy as an effective orthogonal experimental benchmark for CSP and the combined experimental validation process represents a compelling procedure for advancing predictive solid-state modeling of pharmaceutical materials.

Supramolecular assembly of small molecules occasionally leads to viscoelastic materials like supramolecular gels that are important for various applications in material science including drug delivery. However, the a priori design of such soft materials remains an elusive goal. Understanding of the supramolecular synthon and its importance in the context of crystal engineering proved to be handy in occasional prediction of gelation. Herein, we report the supramolecular synthon-driven design, synthesis, and single-crystal structures of a series of diacylhydrazines as potential supramolecular gelators. Conjugation of various arylcarboxylic acids including a few non-steroidal-anti-inflammatory drugs (NSAIDs), namely, naproxen (NAP), ibuprofen (IBU), and flurbiprofen (FLB), with hydrazine afforded seven diacylhydrazine molecules, all of which were found to be gelators of various solvents. The gels were routinely characterized by dynamic rheology and electron microscopy. While hydrogen-bonded self-assembly involving the N−N fused amide moieties in these molecules as revealed by single-crystal structures appeared to have played a pivotal role in gelation, one such gelator NAP_Hydz showed the capability of loading drugs like sulfasalazine or SUL (NSAID) and doxorubicin or DOX (anti-cancer) onto the corresponding supramolecular gel matrix. In vitro studies revealed that the drug-loaded xerogels, i.e., NAP_Hydz@SUL (xerogel) and NAP_Hydz@DOX (xerogel), were effective in reducing inflammation in inflamed normal cells RAW 264.7 and killing melanoma cells (B16−F10), respectively. The rheoreversibility, injectability, and shape sustainability of the supramolecular gels of NAP_Hydz suggested a plausible drug delivery application via the topical route.

Current birefringent crystals (e.g., MgF₂, α-BBO, and YVO₄) are limited by either small birefringence or insufficient deep-UV transparency. Achieving both properties simultaneously remains a key challenge. To address this issue, recent research based on the “confined π-conjugated” strategy has turned its attention to fluoroaluminoborates. In this structural design, non-π-conjugated [Al−O/F] units connect and isolate planar π-conjugated groups, effectively broadening the bandgap while maintaining optical anisotropy. Building on this concept and incorporating different cations, this study reports two new fluoroaluminoborate compounds: CaAlB₃O₆F₂ (CABOF) and its isostructural analogue, PbAlB₃O₆F₂ (PABOF). In PABOF, the introduction of Pb²⁺ induces local structural distortion, thereby enhancing the optical anisotropy. Both CABOF and PABOF exhibit birefringence values exceeding 0.1 at 546 nm, with PABOF demonstrating the largest birefringence among the known fluoroaluminoborates. In addition, both compounds exhibit excellent thermal stability. This work identifies two potential UV-birefringent materials, further enriching the fluoroaluminoborate family.

Liquid−liquid phase separation (LLPS) can severely hinder controlled nucleation and crystal growth during cocrystallization, restricting access to phase-pure polymorphs and stoichiomorphs. During the cocrystallization of the Pterostilbene-(E)-1,2-bis(pyridin-4-yl)ethene (PTB-BPE) system, LLPS emerged as a major experimental barrier to crystal development. In situ microscopic observations revealed that strong PTB-solvent interactions under specific solvent environments promoted LLPS, thereby suppressing nucleation and crystal growth. This limitation was overcome through mechanochemical crystallization approaches combined with the ability of BPE to form stabilizing O−H···N hydrogen bond interactions with PTB. Systematic solvent modulation afforded four crystalline phases of PTB-BPE: Form I (plate, PTB/BPE = 1:0.5), Form II (needle, PTB/BPE = 1:0.5), and Form III (block, PTB/BPE = 2:1) as polymorphic forms, while Form IV (rod, PTB/BPE = 1:1.5) represents a distinct stoichiomorph. Mechanical pretreatment followed by slow evaporation enabled the formation of multiple solid forms; other mechanochemical routes predominantly yielded Form III, and slurry conversion selectively produced bulk Form IV. Single-crystal X-ray diffraction confirmed differences in packing, symmetry, and asymmetric unit composition among the forms. Lattice energy calculations and void analysis indicate comparable thermodynamic stability among the polymorphs, with Form III exhibiting strong intermolecular interactions and efficient packing within the PTB-BPE solid-form landscape.

The construction of efficient and durable photocatalysts for antibiotic elimination remains a formidable challenge. Herein, two novel polyoxometalate-based metal−organic complexes, [Zn₄(Hppb)₆(ppb)₂(H₂O)₂][PW₁₂O₄₀]₂·H₂O (1) and [Ni(Hppb)₂(H₂O)₂]₂[PW₁₂O₄₀]·COOH·4H₂O (2), were successfully synthesized via a hydrothermal method by incorporating Keggin-type [PW₁₂O₄₀]^3- polyanions and transition metal ions (Zn²⁺/Ni²⁺) with a rigid π-conjugated Hppb ligand (where Hppb = 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)benzoate). Both compounds feature stable three-dimensional supramolecular architectures constructed through coordination bonds, C−H···O hydrogen bonds, and π−π interactions, which bridge the metal−organic units and polyoxoanions. The π-conjugated Hppb ligand facilitates light harvesting and charge transfer, while the synergistic cooperation between the metal−organic matrix and POM units endows the hybrids with excellent photocatalytic activity for tetracycline degradation under both visible and UV light. Under optimized visible light, 1 and 2 achieved high degradation efficiencies of 92.7% and 90.6% within 110 and 140 min, respectively; under UV light, the degradation proceeded more rapidly, with 1 and 2 attaining 93.8% and 89.7% degradation within just 80 and 100 min, respectively. Structure−activity and photoelectrochemical analyses reveal that 1 outperforms 2 due to its more favorable structural features and charge separation efficiency. EPR results, together with radical trapping experiments, identified ^•O₂⁻ as the dominant reactive species. Both catalysts exhibited good recyclability. This work provides a viable strategy for designing robust POM-based photocatalysts for antibiotic-contaminated water remediation.

Gallium nitride (GaN) is a wide-bandgap semiconductor with excellent electrical and optical properties, making it a leading candidate for next-generation power electronic devices and optoelectronic devices. The widespread adoption of GaN in high-power applications is hindered by the lack of inexpensive, large-area, high-quality single crystals for substrates. In this work, we demonstrate the growth of GaN single crystals from a lithium (Li)-flux at temperatures and nitrogen pressures up to 935 °C and 10 MPa, respectively, expanding the previously reported growth window by approximately 130 °C and a 35-fold increase in pressure. Through systematic systematically increasing synthesis temperature at elevated pressures, we identify parameters that influence crystal morphology and quality. Spontaneously nucleated, single crystals grown from the melt achieved sizes up to 3 mm in 100 h, with best growth conditions achieved at 935 °C, ∼ 8 MPa N₂ pressure and a 2.4 Ga/Li₃N ratio. Characterization of the grown crystals demonstrates promising structural properties consistent with high-purity, low-defect, chemically and phase-pure wurtzite GaN with an ω-rocking curve full width at half maximum of 87 arcsec.

Ultrawide-bandgap (UWBG) semiconductors are central to next-generation power electronics and deep-UV optoelectronics, yet the absence of reliable p-type materials remains a critical bottleneck. Here, we demonstrate stable intrinsic p-type conductivity in the spinel UWBG oxide ZnGa₂O₄, epitaxially grown on c-plane sapphire via mist chemical vapor deposition. The films exhibit high crystalline quality, evidenced by relatively narrow rocking curves and atomically smooth surfaces. Hall measurements confirm stable p-type conduction with a hole mobility of 4.43 cm² V⁻¹ s⁻¹ and a carrier concentration on the order of 10¹⁵ cm⁻³ in the optimized film at room temperature. By off-stoichiometrically tuning the Zn/Ga precursor ratio, we reveal that intrinsic p-type behavior originates from the antisite defect, establishing cation disorder as an important mechanism governing carrier polarity. Comprehensive structural, optical, electrical, and first-principles analyses indicate the interplay between defect chemistry and charge transport in spinel oxides. These results position ZnGa₂O₄ as a viable p-type UWBG semiconductor and introduce defect-controlled spinel oxides as promising materials for future high-power and extreme-environment electronics.

A binary n-alkane blend (nC22+nC24) with a rotator phase stable over a wide temperature range is characterized with X-ray scattering, differential scanning calorimetry (DSC), and the ASTM needle penetration test method, which is the commonly practiced industrial specification method used to quantify the softness of wax. For wax-like solids, penetration is commonly associated with the amount of non-crystallizing liquid entrained between the alkane crystallites. Our model system has no non-crystallizable material but rather fully crystallizes first into the rotator phases, which are 3D crystals but softer than the lower-temperature non-rotator crystal phase. The penetration was measured as a function of temperature and was found to increase strongly at higher temperatures through the rotator phases, prior to the beginning of melting, where there is no entrained liquid. This shows clearly that, in addition to the entrained oil content when present, the stability of the rotator phases is an important mechanism for increased penetration and thus reduced hardness of wax.

Tin-based sulfides have attracted considerable interest because of their distinctive electronic structures and promising optoelectronic, photovoltaic, electrochemical, and photocatalytic properties. However, the phase-controlled synthesis of tin sulfides remains challenging because competing Sn−S phases can readily form during growth. In addition, the thermodynamic and kinetic factors governing phase evolution among tin sulfides are still not fully understood, which limits rational phase engineering and device-oriented optimization. Here, we report a facile chemical vapor deposition strategy using fluorine-doped tin oxide as an in situ tin source for the controllable growth of large-area SnS₂ nanosheet arrays and Sn₂S₃ nanostructures. By tuning the growth temperature, sulfur precursor dosage, and reaction duration, SnS₂ nanosheets can be transformed into Sn₂S₃ under sulfur-deficient, high-temperature conditions. The optimized window for pure Sn₂S₃ formation is 525 °C, 50 mg sulfur precursor, and 10 min growth duration, under sulfur-deficient Ar/H₂ atmosphere. Comprehensive structural and chemical characterizations, together with Gibbs free-energy analysis and density functional theory calculations, suggest that sulfur vacancies play a key role in weakening Sn−S bonding and promoting lattice reconstruction. These results provide an experimentally accessible route for the phase-controlled synthesis of tin sulfides and offer mechanistic insight into vacancy-mediated phase transformation in two-dimensional metal chalcogenides.