Crystal Growth & Design最新文献

The rational design of tubular nanostructures with controllable spatial distribution of bimetallic nanoparticles(NPs) is of vital importance for advancing high-performance catalytic systems, yet remains a significant synthetic challenge. To address this, we developed two synthetic routes to obtain one-dimensional (1D) tubular CoNi-based magnetic nanostructures through a combination of hydrothermal reaction, classical Stöber method, mussel-inspired coating, and carbonization strategy. Route 1 involves MoO₃@CoNi-LDH microrods coated with SiO₂ and subsequently with a polydopamine-Ni²⁺ (PDA-Ni²⁺) layer, followed by pyrolysis under nitrogen to yield CoNi@SiO₂@NC-Ni composites; Route 2 employs MoO₃@CoNi-LDH coated first with PDA-Ni²⁺ and then with SiO₂, followed by thermal treatment to give CoNi@NC@SiO₂ composites. Notably, our findings confirm that only Route 1 leads to the formation of both a high-coverage outer layer of Ni NPs and inner CoNi bimetallic NPs. Detailed characterization of the CoNi-based magnetic composites obtained via Route 1 revealed superior catalytic performance compared to Route 2, attributed to their unique structure and high density of Ni and CoNi NPs. These results demonstrate that this coating strategy is highly beneficial for the synthesis of CoNi-based bimetallic composites with 1D hollow structures, paving a novel pathway for preparing high-density bimetallic magnetic composites.

ROY is an iconic polymorphic system, known for its red, orange, and yellow crystal forms that arise from subtle differences in molecular conformation and packing. Here, we examine how this well-established solid-state landscape responds to one of the smallest possible structural modifications: selective H/D substitution. Three selectively deuterated analogues, ROY-D1, ROY-D4, and ROY-D8, containing one, four, and eight deuterium atoms, respectively, were synthesized and subjected to systematic polymorph screening using solution crystallization, solvothermal methods, liquid-assisted grinding, and melt crystallization. The resulting forms reveal extensive isostructural relationships with known ROY polymorphs while preserving the characteristic correlation between molecular torsion angle and crystal color. Overall, the deuterated analogues largely preserve the ROY crystal-structure landscape, retaining known packing types and the torsion-angle−color relationship, while showing subtle differences in polymorph formation, thermal transitions, and storage-related thermal response.

Coamorphous formulations have emerged as a promising strategy to improve the solubility and bioavailability of poorly soluble drugs, but their application is often limited by inherent thermodynamic instability. Herein, we propose an unconventional plasticizer strategy to stabilize coamorphous systems. The ternary coamorphous systems of baicalein (Bai), piperine (Pip), and resveratrol (Res) at 1:1:1, 1:2:1, 1:3:1, and 1:4:1 molar ratios were successfully prepared and exhibited enhanced supersaturated dissolution profiles, with approximately 3.4-, 5.3-, and 4.6-fold increases in the apparent solubilities of Bai, Pip, and Res, respectively. Pip as a plasticizer increased molecular mobility and lowered T_g from 107.5 to 52.3, 45.7, and 37.5 °C with increasing Pip content. Unexpectedly, coamorphous systems with higher Pip ratios exhibited enhanced physical stability. Fourier-transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance spectroscopy, molecular dynamics simulations, and quantum chemical calculations revealed a composition-dependent redistribution of intermolecular interactions. With increasing Pip content, Pip preferentially associated with Res and subsequently interacted with Bai, progressively disrupting the pre-existing Res−Bai hydrogen bond (HB). Meanwhile, the normalized HB numbers decreased, while the normalized binding energies remained nearly unchanged. Furthermore, the systems with a higher Pip ratio prolonged the intermittent HB lifetime with fast HB breaking and reformation (i.e., dynamic hydrogen bonding). Pip-mediated interaction reorganization and dynamic HB jointly contributed to the improved stability. This work provides a promising strategy for stabilizing coamorphous systems via plasticizers capable of establishing reorganized heteromolecular interactions and dynamic hydrogen bonding.

Hydrate formation on ice is an interfacial crystallization process governed by thermodynamic driving force and the evolving state of the ice surface and hydrate shell. Here, in situ micro-X-ray computed tomography was used to visualize xenon hydrate formation on single ice particles after ethanol-vapor exposure from −50 to −5 °C under different operational ethanol addition levels. These levels were defined by injection duration and do not represent measured interfacial ethanol doses. Without ethanol, hydrate formation proceeded slowly through surface-layer growth; at −50 °C, only a very thin local hydrate layer was observed after 77.8 h. Under high operational ethanol addition at −10 °C, the ice surface evolved before xenon charging, followed by loose flocculent hydrate formation, shell growth around a shrinking ice core, and late-stage hydrate dissociation. At −20 °C, increasing operational ethanol addition was associated with an ordered progression toward greater shell roughness and spatial heterogeneity. At −50 °C, a clear shell was visible by 620 min after xenon charging without XCT-resolved pre-charging surface deformation. Thus, the XCT observations establish distinct, condition-dependent pathways of hydrate-shell development and persistence following ethanol-vapor conditioning, while their molecular origins require further compositional and spectroscopic verification.

Two structurally similar cocrystals, colchicine/L-malic acid (COL/L-MA) and colchicine/D-tartaric acid (COL/D-TA), were prepared to investigate their co-crystallization behavior via in situ ATR-FTIR spectroscopy. Ternary-phase diagrams combined with a 1:1 solution complexation model revealed a strong complexation effect between the active pharmaceutical ingredient and both co-crystal formers. The conventional calibration strategy was applicable to the COL/L-MA system; however, an alternative calibration method was established for the COL/D-TA system to avoid undesired premature nucleation during spectral calibration. Kinetic analysis indicates that cocrystal formation governs the overall rate of the COL/L-MA process, while dissolution of D-TA constitutes the rate-determining step for COL/D-TA, which originates largely from the solubility difference between the two co-crystal formers. Intriguingly, abnormal apparent concentration rises were detected for both systems, yet they arise from fundamentally different origins: mutual solubilization accounts for the concentration surge in COL/L-MA, whereas the anomaly in the COL/D-TA system stems from complexation-induced spectral enhancement instead of real concentration variation. The proposed model successfully distinguishes these spectral artifacts, allowing credible identification of intensive nucleation events and supporting process-condition optimization. This work offers mechanistic understanding and practical guidance for co-crystallization systems containing structurally similar co-crystal formers.

Hydrates are common solid forms that can significantly affect a compound’s stability, physicochemical properties, and commercial viability. Despite their importance in pharmaceutical development, hydrate structures, their relationship to material properties, and their propensity for formation remain poorly understood. In 2003, Gillon et al. introduced a simple yet powerful framework for the structural classification of hydrates based on the hydrogen-bonding environment of crystalline water molecules. This framework categorizes water molecules according to the number of hydrogen-bond donor (D) and acceptor (A) interactions in which they participate, giving rise to eight distinct environments. In the original study, the DDA environment, where water donates two hydrogen bonds and accepts one, was reported as the most common. The statistical distribution of these environments in the Cambridge Structural Database (CSD) has since provided a useful benchmark for the qualitative assessment of hydrate structures. Here, we revisit Gillon’s water environment classification using a substantially expanded data set comprising 13,881 hydrate entries from the CSD and provide updated statistics on hydrate structures. Our analysis confirms that the DDA environment remains the most prevalent, followed by DDAA and DD, while the remaining environments occur less frequently. Extending beyond the original work, we quantify the energetics associated with each environment and demonstrate that the four-hydrogen-bond DDAA environment is energetically the most favorable, followed by environments involving three, two, and one hydrogen bonds, respectively. We further show that water-mediated intermolecular interactions contribute up to 40% of the total lattice interaction energy in the hydrate structures, highlighting the surprisingly large influence of this small solvent molecule on crystal stability. Despite its superior energetic stability, the DDAA environment is not the most frequently observed experimentally. This apparent discrepancy arises because the hydrogen-bonding capability and topology of the main component in the hydrate constrains the maximum hydrogen-bonding environment that water can achieve. Overall, this work provides a comprehensive analysis of hydrate structures and energetics across the CSD. The resulting insights offer a valuable framework for the qualitative assessment of newly discovered hydrate forms and for evaluating whether their structures conform to established crystallographic trends.

Distinguishing the salt versus cocrystal character in acid-base multi-component crystals is pharmaceutically important and can be challenging for both theory and experiment. On the theory side, commonly-used generalized gradient approximation (GGA) functionals in periodic density functional theory (DFT) artificially stabilize salt forms, sometimes even erroneously transferring the acidic proton from the acid to the base. The inclusion of exact exchange in hybrid density functionals reduces the problem. However, proton-transfer energies can be very sensitive to the specific fraction of exact exchange included and the optimal fraction is not always readily apparent. Here, a pragmatic approach which combines periodic GGA or hybrid DFT with local corrections computed on the acid-base pair at a higher level of theory is shown to predict the correct salt, cocrystal, or intermediate behavior for ten different acid-base multi-component crystals. This approach greatly reduces the sensitivity of the proton transfer energies to the underlying periodic DFT functional, and the correction increases the overall computational costs only marginally. On the other hand, it has limitations when applied to crystals where the acid-base pair is not uniquely defined.

β-Ga₂O₃ is a promising ultrawide-bandgap semiconductor for high-power electronics; however, the realization of thick, low-defect drift layers at high growth rates remains challenging. In this work, metalorganic chemical vapor deposition (MOCVD) growth of (011) β-Ga₂O₃ drift layers on (011) β-Ga₂O₃ substrates is optimized using a far-injection showerhead reactor with trimethylgallium (TMGa) and O₂ precursors. The effects of chemical pre-treatment, in situ oxygen annealing, wafer carrier rotation, and pulse-flow (PF) β-Ga₂O₃ interlayers are systematically investigated to correlate growth conditions with defect density. Chemical treatment B [18% HCl (10 min) + deionized (DI) water (10 min) + 49% HF (30 min)], combined with 1 h of in situ annealing at 900 °C, minimizes defect density under the selected growth conditions. Incorporation of a single PF1 interlayer (∼30 nm thick) further suppresses defect formation, reducing the defect density by more than one order of magnitude. Atomic force microscopy (AFM) reveals sub-nanometer root mean square (RMS) roughness and step-flow morphology for ∼11 μm thick films. High-resolution X-ray diffraction (XRD) rocking curves confirm the preserved crystalline quality. Field-plated Schottky barrier diodes (SBDs) fabricated on optimized films exhibit excellent forward conduction, low reverse leakage, and improved breakdown performance, highlighting the importance of defect control for high-performance vertical power devices.

In a previous paper (J. Am. Chem. Soc. 2024, 146, 18836-18840), crystal microwires composed of (Z)-5-(anthracen-9-ylmethylene)-3-butylthiazolidine-2,4-dione (C4-ATD) were shown to undergo sustained oscillatory motion under constant 405 nm or solar illumination. In order to determine whether this oscillatory behavior can be generalized, the length n of the alkyl chain attached to the nitrogen of the thiazolidine-2,4-dione headgroup was varied from n = 0 to n = 8. Changing the alkyl chain length had little effect on the molecular properties, as measured by the molecules’ absorption spectra and Z→E reactivities in solution. Density functional calculations confirmed the electronic inertness of the alkyl sidechain. But when this family of molecules was crystallized, the length of the alkyl chain strongly impacted both the formation of reactive head-to-head versus nonreactive head-to-tail polymorphs and the crystal growth modes. n ≤ 5 derivatives all supported a head-to-head polymorph that enabled the Z$\leftrightarrow$E photoisomerization while growing in different morphologies, ranging from dendritic shapes to long, thin wires. Only the latter shape was suited for observing photomechanical oscillations, and we identified two new members of the ATD family (n = 0 and n = 2) that support robust oscillatory dynamics similar to those seen for the n = 4 derivative. The results illustrate how small changes in the molecular structure can change the crystal packing and growth kinetics that ultimately determine whether a molecular crystal exhibits photo-induced motor-like behavior.

The electrocatalytic nitrate reduction reaction (eNO₃RR) offers an effective pathway for carbon-neutral ammonia synthesis; however, its efficiency is severely hampered by the intricate thermodynamics of proton-coupled electron transfer (PCET) and by competition from the hydrogen evolution reaction (HER). To address these challenges, we engineered two ternary composite catalysts (PMo₁₂@Cu-BTC/Ti₃C₂T_x and PW₁₂@Cu-BTC/Ti₃C₂T_x) incorporating distinct polyoxometalate anions (H₃PMo₁₂O₄₀, noted as PMo₁₂; H₃PW₁₂O₄₀, noted as PW₁₂) by integrating polyoxometalate-based metal−organic frameworks (POMOFs) with a Ti₃C₂T_x MXene scaffold. This architectural design synergistically couples redox-active POMOFs, facilitating optimized PCET, with a three-dimensionally interconnected porous MXene network, effectively mitigating the inherent inferior conductivity of POMOFs. Comparative studies reveal that the phosphomolybdate (PMo₁₂)-based catalyst exhibits superior electrocatalytic activity, achieving an NH₃ yield of 12.86 mg h⁻¹ mg_cat.⁻¹ at −0.8 V vs RHE, alongside a large electrochemical active surface area (ECSA) and exceptional stability. This work validates the significant potential of the POMOF−MXene hybrid platform in reducing the competing HER and promoting eNO₃RR, offering a viable strategy for decentralized wastewater treatment and green ammonia synthesis.