Physics

Based on a literature analysis, we have compiled a database of fusion temperatures and enthalpies for two-component molecular cocrystals and their pure components (3032 occurrences). To estimate the formation thermodynamics of two-component crystals, we have developed a database on the basis of the values reported in the literature from 1900 to 2024, inclusive. The database comprises the enthalpy and Gibbs energy values of individual molecular crystals obtained by various methods. An equation that allows for the estimation of the Gibbs free energy of formation of a two-component molecular crystal from the Gibbs free energy of sublimation of its coformers has been proposed. An approach has been developed to evaluate all cocrystallization/formation thermodynamic functions for two-component crystals. This approach is based on the sublimation Gibbs energy, enthalpy, and melting points of the individual coformers as well as the melting point of the resulting cocrystal/salt. Using this approach, we evaluated and analyzed the formation thermodynamic functions for 934 two-component crystals from a total database of 3032 occurrences. It is shown that for all stoichiometric compositions, the formation processes for 22.8% of the systems studied are entropy-driven. Using the example of Carbamazepine (CBZ) based two-component crystals (for which all cocrystallization thermodynamic functions were calculated), we analyzed the molecular packing in crystals located in different sectors of the diagram characterizing the main driving forces of cocrystallization. It was found that for cocrystals/salts located in sectors with entropy-driven processes, the molecular packing forms agglomerates in the shape of tetramers, which are packed into columns. Within these columns, the tetramers interact with each other through either van der Waals forces or hydrogen bonding. All columns interact with each other via van der Waals forces. In contrast for cocrystals/salts with enthalpy-driven processes, the molecular packing forms agglomerates (tetramers, hexamers), which are packed into layers and interconnected by hydrogen bonds. Within the layers, a two-dimensional network of hydrogen bonds is formed. These layers interact with each other via van der Waals forces.

The mild hydrothermal method using sodium carbonate in the presence of HF(aq) resulted in a series of high-quality single crystals of Na3xLn(2-x)F6 (Ln = Er–Lu). Sodium carbonate was found to strongly promote the formation and crystallization of the Na3xLn(2-x)F6 phase under hydrothermal conditions. Structure determination was carried out by single-crystal X-ray diffraction. All four phases are isostructural and crystallize in the hexagonal space group P-6. Pure polycrystalline powders of Na3xLn(2-x)F6 (Ln = Er–Lu) were obtained via flux synthesis using NaNO3/NaF as the flux.

The development of electronic devices toward miniaturization and integration has put forward higher requirements for the crystal quality of aluminum nitride (AlN). However, the AlN films prepared experimentally often contain defects, which greatly reduces their crystal quality and limits their application in the field of microelectronics and semiconductors. To clarify the mechanism for improving the crystal quality, the AlN film homoepitaxial growth processes on polar substrates with various vacancy concentrations were studied by molecular dynamics. The film deposition on perfect substrate was used as the control group. The results show that the epilayer is composed of alternating layers of hexagonal diamond and cubic diamond in a lamellar structure. The dislocation 1/3 ⟨1–210⟩ within epitaxial layers has a strong longitudinal growth ability, while there is a stronger horizontal growth trend for 1/3 ⟨1–100⟩. The film grown on the Al-polar substrate has a higher density and lower roughness compared to the N-polar substrate. The epitaxial layers prepared on the Al3 substrate and N1 substrate have more abundant hexagonal diamond structure and lower dislocation density, indicating that the internal structure of the film can be controlled by the synergy of polarity and vacancy defect. The lower residual stress of the film prepared on the Al-polar substrate makes it more suitable for precision machining. This study has revealed the influence of substrate polarity and vacancy defect on AlN films quality, providing theoretical guidance for the preparation of high-quality AlN films.

The effect of deuteration on crystallization is under discussion. Glycine is a model system extensively investigated because of discrepancies in the literature, particularly on the appearance of γ-glycine in heavy water. In this study, we combined single crystal nucleation spectroscopy (SCNS) and bulk crystallization to systematically investigate the effect of deuteration on glycine crystallization. SCNS results showed that deuterated glycine (d-glycine) in heavy water crystallizes via a nonclassical nucleation pathway, as observed in water. In these experiments, however, γ-d-glycine was never observed. β-d-glycine appears first, but quickly disappears while α-d-glycine grows. Statistical analysis revealed that β-d-glycine in D2O was more stable than β-glycine in H2O. Bulk crystallization experiments revealed that the γ-polymorph can be observed when the nucleation rate is high in both H2O and D2O. The major difference between them is the stability of the β-polymorph in D2O. Differential scanning calorimetry (DSC) and thermogravimetric (TG) experiments demonstrated that β-d-glycine is more stable than β-glycine, which can be explained by higher hydrogen-bonding strength because of deuteration. These findings suggest that deuteration increases the stability of β-glycine, possibly facilitating γ-glycine formation. This study provides new insights into the role of solvent isotope effects on crystallization toward rational polymorph control.

Understanding and controlling polymorphism in active pharmaceutical ingredients are essential for optimizing drug efficacy, stability, and manufacturing. In this study, we investigate the liquid–liquid phase transition (LLPT) and polymorph selection of paracetamol in ethanol–water binary solvents using a multitechnique approach, including transmission electron microscopy, dynamic light scattering (DLS), 1H NMR, UV–vis absorption spectroscopy, and atomistic molecular dynamics simulations. Our findings reveal that solvent composition critically modulates paracetamol’s self-assembly, yielding diverse colloidal morphologies such as pearl-necklace-like and fiber-like aggregates. These structures arise from a balance between hydrogen bonding and aromatic ring stacking, governed by ethanol-to-water ratios. At low ethanol content, strong paracetamol–water interactions are favorable, whereas higher ethanol concentrations favor paracetamol–ethanol binding and promote hydrogen bonding and aromatic ring stacking. This shift in solvent-mediated preferential interactions drives the formation of nucleation-competent aggregates, influencing crystal outcomes. Again, while crystallization under ethanol-rich conditions favors the monoclinic form I, introducing bulkier alcohols like benzyl alcohol enhances π-stacking and stabilizes the orthorhombic form II. A ternary phase diagram delineates the solvent-driven evolution from colloidal intermediates to crystalline phases. By linking solvent-mediated molecular interactions to colloidal behavior and polymorphic outcomes, this study offers a scalable and broadly applicable strategy for ambient-condition polymorph control─enabling rational crystal engineering across diverse pharmaceutical compounds.

The rich functionality of porous supramolecular assemblies is critically dependent on their topological diversity. However, constructing ionic frameworks with predictable topologies remains challenging due to the nondirectional nature of ionic interactions. This work presents a coassembly strategy using bola-cationic rotaxanes as cationic linkers and nanosized giant polyoxometalate clusters as anionic building blocks. Both size and charge of these polyanions are demonstrated to crucially govern the network topology. By modulating the structure parameters of these giant ions, the resulting ionic assemblies have been tuned from nonporous to one featuring well-defined dual channels. This approach achieves precise control over rotaxane spatial arrangement and pore architecture, advancing the design strategies for functional ionic porous materials.

Dendrite orientation plays a critical role in governing the expansion growth of nickel-based single-crystal superalloys within the platform region. The three-dimensional relationship between the dendrite orientation and platform configurations needs to be deciphered. This work aims to address this problem by systematically investigating how the orientations of the primary arm and secondary branches affect the dendrite growth behavior in the platform region. The results indicate that both primary arm inclination and secondary branch deviation enhance dendrite asymmetry at the platform bottom, increase the proportion of higher-order branches, promote the convergence interface among the high-order branches, and amplify misorientation and grain boundary formation. The initial orientation of secondary branches exerts a more pronounced effect on their growth behavior in the platform region. The larger deviation angles of the primary/secondary branches and the greater curvature of the solid–liquid interface contribute to an enhanced tendency for dendrite deflection during the directional solidification. This mechanism provides a rationale for the observed dendritic morphological asymmetry, nonuniform distribution, and grain boundary formation in the platform region. This work provides a comprehensive 3D understanding of dendrite growth and grain boundary formation during platform solidification in single-crystal turbine blades, thereby providing theoretical guidance for manufacturing high-quality single crystals.

Metastable α-Ga2O3 possesses a wider bandgap and higher symmetry compared to the stable β-phase, making it a premier candidate for next-generation power electronics and deep ultraviolet optoelectronics. However, achieving pure-phase epitaxy and understanding the nanoscale defect evolution remain significant challenges. Here, we report the high-crystallinity growth of pure α-Ga2O3 thin films on (112̅0) Al2O3 substrates via pulsed laser deposition. By systematically tailoring the growth temperature (600–800 °C) and O2 partial pressure (0.01–10 Pa), we identified 750 °C and 5 Pa as the optimal parameters for growing α-Ga2O3 thin films. Aberration-corrected scanning transmission electron microscopy reveals that an atomically flat and coherent interface is formed between α-Ga2O3 and Al2O3, characterized by direct Ga–O bonding without elemental diffusion. A high-density network of stacking faults (SFs) was formed in the α-Ga2O3 thin film. It revealed that the basal-plane SFs have sharp interfaces, and the faults are caused by the relative sliding between Ga and O atomic layers along the (0001) plane. Our findings provide critical atomic-scale insights into the structural engineering of corundum-structured oxides for advanced semiconductor applications.

Metal ions influence the self-assembly behavior of crystallization solvents within low-dimensional coordination polymers, thereby determining pore geometry and (ir)reversibility. In this study, we investigate two isomorphous one-dimensional (1D) chain compounds, {[Mn(2,2′-bpy)(CA)]·2EtOH} (1) and {[Zn(2,2′-bpy)(CA)]·5H2O} (2) (2,2′-bpy = 2,2′-bipyridine; CA2– = chloranilate), crystallized from the same EtOH/H2O mixed solvent. Notably, these compounds selectively incorporate EtOH in 1 and H2O in 2 as continuous hydrogen-bonded “molecular pillars.” Single-crystal X-ray diffraction analysis revealed π-stacked −M–(μ2-CA)–M– chain columns that form molecular-pillar-stabilized 1D channels. Thermal and vacuum desolvation induced an irreversible transformation to a distinct phase, and resoaking in the original solvent failed to restore the initial diffraction pattern. Attenuated total reflectance infrared analysis using an area-normalized band ratio confirmed the selective attenuation of guest bands after desolvation with limited recovery upon resoaking. Combined thermogravimetric analysis and differential scanning calorimetry further quantified guest-retention energetics, yielding ΔH per guest of approximately 20 kJ mol–1 for EtOH in 1 and 5 kJ mol–1 for H2O in 2. Gas and vapor sorption measurements exhibited negligible uptake after activation, consistent with pore collapse in the guest-free state. These findings establish crystallization solvents as integral structural components that dictate metastable porosity and irreversible structural fixation in 1D coordination polymers.

The development of uniform GaN micropyramids and platelets via selective area growth is a critical step toward advancing III-nitride device technologies, particularly for microlight-emitting diode applications. This work investigates the origins of morphological nonuniformity in micropyramids and microplatelets grown by metal–organic chemical vapor deposition (MOCVD). We observe that a direct one-step growth approach leads to significant growth rate inhomogeneity across arrays. To shed light on this issue, we examine the mechanisms driving nonuniformity and explore process modifications aimed at mitigating these effects. Building on these insights, we propose a controlled multistep growth strategy that combines sequential growth and thermal treatment phases. This approach is demonstrated to enhance the surface morphology and structural regularity. The work contributes to the broader objective of enabling scalable and high-precision GaN microstructure fabrication for next-generation optoelectronic applications.

The energy crisis, along with environmental deterioration and climate change caused by fossil fuel combustion, has propelled scientific and technological developments for versatile renewable energy applications. As a green technology, photocatalysis enables the conversion of abundant solar energy into useful chemical energy, in which advanced photocatalysts play a crucial role. Among various photocatalysts, layered double hydroxides (LDHs), a class of two-dimensional (2D) materials, and their derivatives, such as mixed metal oxide (MMO) and spinel, have attracted considerable attention in solar energy conversion. This review summarizes the recent achievements of LDHs and their derivatives used in photocatalysis. First, the LDHs, MMO, and spinel photocatalysts are briefly introduced. Next, the advanced strategies of structure modulation for photocatalytic properties are systematically elaborated. Then, the photocatalytic performance of LDHs and their derivatives is described concerning their applications in photocatalysis, including water splitting, CO₂ reduction, and N₂ fixation. Finally, the challenges and opportunities for the future development of this fast-growing area are presented and thoroughly discussed.

Poly(ethylene oxide) (PEO) solid electrolytes offer great promise to realize all-solid-state lithium metal batteries with both high energy density and safety. However, it remains challenging to fabricate ultrathin PEO-based solid electrolytes that can operate at practical current densities with a long lifespan. Here, we develop a 19 μm-thick PEO-based solid electrolyte with a porous polyethylene support, which provides mechanical strength and blocks lithium dendrites. By repeatedly plating and stripping lithium at a high current density and low areal capacity, we ingeniously transform otherwise detrimental "dead lithium" into functional fillers within the PEO solid electrolytes. Results show that LiOH, Li₂CO₃, Li₂O, and LiF form on the surface of the "dead lithium", blocking electronic transport and thus rendering them as effective fillers. These in situ formed fillers simultaneously enhance lithium-ion transport and act as a barrier to suppress dendrite growth, thus facilitating uniform lithium deposition. As a result, this approach enables Li||Li symmetric cells to achieve a critical current density of as high as 1 mA cm^-2 and operate stably for 400 h at 0.5 mA cm^-2 and 0.5 mAh cm^-2 without short-circuits. Importantly, a precycled Li||LiFePO₄ full cell can retain 90.9% capacity after 600 cycles at 1C charging and 3C discharging.

This work presents a temperature-dependent micro-Raman spectroscopy study (300-573 K) of homoepitaxial n-type GaN layers with different Si doping levels ranging from 10¹⁵ to a few 10¹⁸ cm^-3, where the analysis of different vibrational modes enables simultaneous extraction of structural and electronic properties. The evolution of the E₂(high) mode and the associated phonon correlation length with doping and temperature reveal progressive lattice disorder, allowing static disorder related to dopant incorporation to be distinguished from dynamic disorder arising from phonon interactions. In parallel, the A₁(LO) mode highlights the Fano interaction between the discrete phonon and the electron continuum, where the asymmetry parameter provides access to the Fermi level <i>E</i>_F position. At 300 K, the energy separation between the conduction band and <i>E</i>_F decreases from ∼0.19 eV for the lightly doped sample to ∼0.03 eV for the heavily doped sample. At 573 K, this distance increases to ∼0.43 eV and ∼0.08 eV, respectively, reflecting the temperature-dependent shift of the chemical potential. These results confirm both efficient dopant activation and the transition toward quasi-degenerate behavior at high carrier concentrations. Finally, analysis of A₁(LO) phonon-plasmon coupling within the LPP model allows the determination of carrier mobility as a function of doping and temperature: at 300 K, the mobility decreases from 916 cm²/V·s in lightly doped samples to 355 cm²/V·s in heavily doped layers, with further reductions at elevated temperatures due to thermally activated scattering and carrier redistribution. These results demonstrate that Raman spectroscopy is a powerful nondestructive tool to simultaneously assess electronic transport properties and crystalline disorder in vertical GaN-based power electronics.

Bacterial infections severely impede the healing process of infected wounds, and the key challenge to achieving efficient healing of infected wounds lies in precisely regulating the generation and clearance of reactive oxygen species (ROS) across spatiotemporal scales. However, traditional nanozymes struggle to dynamically adapt to fluctuating ROS demands at different stages within the microenvironment. To address this, we designed and synthesized the GO-FePPOP_TFP nanocomposite, which promotes wound healing by dynamically regulating ROS levels through synergistic multienzyme cascade reactions, photodynamic therapy, and photothermal therapy. This composite exhibits outstanding photothermal properties and exceptional photodynamic therapeutic effects, significantly impairing bacterial antioxidant defense capabilities. Furthermore, GO-FePPOP_TFP enables dynamic ROS regulation via near-infrared (NIR) switching. Under NIR irradiation, it exhibits enhanced oxidase-like activity, generating abundant ROS and demonstrating outstanding antibacterial performance. Upon cessation of NIR irradiation, GO-FePPOP_TFP exerts superoxide dismutase-like and catalase-like activities, effectively scavenging residual ROS and alleviating inflammatory responses. Consequently, the cascade self-cyclic enzyme activity system based on GO-FePPOP_TFP coordinates ROS dynamic equilibrium and modulates the inflammatory microenvironment at the wound site, significantly promoting wound healing. This work overcomes the limitation of single-therapy approaches prone to inducing drug resistance, offering important insights for developing highly effective antimicrobial materials to treat infected wounds.

Precise control of capillary-driven liquid transport in porous media underpins numerous interfacial processes in microfluidics, water harvesting, and biomimetic systems. Conventional random porous materials exhibit structural heterogeneity that yields stochastic and irreproducible flow behavior. It was hypothesized that three-dimensional ordered lattices with well-defined geometry, particularly body-centered-cubic (BCC) lattices, could realize deterministic and tunable capillary rise by regulating structural parameters such as the strut diameter, aspect ratio, and unit-cell configuration. To validate this hypothesis, BCC lattices with systematically varied structural parameters were produced by using an additive-manufacturing approach, and capillary rise behavior was examined across geometries. Visualization techniques, including optical- and X-ray-based methods, were used to elucidate the progression of liquid fronts and meniscus evolution. A force-balance model was developed to predict the maximum rise height by incorporating adhesive and gravitational effects within the lattice. Geometric periodicity and asymmetry were found to strongly govern the interfacial transport behavior. Larger strut diameters and denser lattice arrays enhance the capillary height by increasing Laplace pressure and extended liquid-solid contact perimeter. Multicell configurations promoted cooperative meniscus coalescence and triangular wetting fronts, yielding predictable and anisotropic fluid propagation. Moreover, gradient-configured lattices with asymmetric strut distributions yield passive yet directional liquid transport, driven by spatial variations in hydraulic resistance. These findings extend classical capillary theory to ordered three-dimensional porous networks, unveiling geometry as a powerful design parameter for programmable, energy-efficient fluidic, and interfacial systems.

Persistent photocurrent is widely observed in van der Waals (vdW) heterostructures and is often attributed to trap-assisted photogating, yet its microscopic origin remains unclear. Here, we clarify the mechanism in a gate-tunable MoS₂/black phosphorus (BP) <i>p</i>-<i>n</i> heterojunction by combining DC and lock-in measurements with time-resolved decay. We simultaneously measure the general photocurrent (DC difference between illuminated and dark currents) and the net photocurrent extracted by the lock-in detection of a modulated laser. The net photocurrent is small and short-lived, whereas the DC photocurrent shows decay lifetimes (τ) exceeding hundreds of seconds at negative back-gate voltage (<i>V</i>_<i>g</i>) but collapses rapidly for positive <i>V</i>_<i>g</i> or under reverse bias. This τ-<i>V</i>_<i>g</i> and bias dependence is incompatible with a purely trap-dominated picture. We show that the long-lived response is dominated by majority-carrier recombination-induced self-heating in the forward-biased <i>p</i>-<i>n</i> junction, which drives thermoelectric and bolometric currents. By tuning the heterostructure between a <i>p</i>-<i>n</i> and an <i>n</i>-<i>n</i> configuration, the back gate effectively switches this thermal channel on and off. Using the experimentally extracted τ(<i>V</i>_<i>g</i>) in a leaky integrate-and-fire model, we further demonstrate an in-sensor spiking neural network with 91.95% accuracy on MNIST, highlighting the potential of thermally engineered persistent-photocurrent devices for neuromorphic vision.

The long-term reliability of epoxy-based anisotropic conductive films (ACFs) is limited by moisture-induced degradation arising from the hydrophilic nature of epoxy matrices. In this work, an intrinsically hydrophobic anisotropic conductive film (H-ACF) is developed by engineering the hydrophobic composite surface through the incorporation of core-shell structured hydrophobic alumina (H-Al₂O₃) nanoparticles into the epoxy surface. The fluorinated polysiloxane shell forms covalent Al-O-Si linkages with the alumina core, creating a durable low-surface-energy composite that simultaneously imparts micro/nanoscale hierarchical roughness and strong interfacial bonding. The optimized H-ACF exhibits exceptional hydrophobicity (water contact angle = 157.06°), high bonding strength (26.12 MPa), and enhanced electrical conductivity. It maintains the hydrophobic performance after 400 abrasion cycles and 20 tape-peeling tests and demonstrates superior stability under hygrothermal aging (85 °C/85% RH), showing only a 59% resistance increase compared with 228% for the pristine ACF. A self-assembled μ-LED array confirms reliable <i>Z</i>-axis conductivity with negligible <i>XY</i>-plane leakage. This intrinsic hydrophobic modification strategy herein overcomes the durability limitations of conventional coatings and commercial ACFs, offering a scalable, roll-to-roll compatible solution toward high-reliability electronic interconnections in demanding hygrothermal environments.