Defect Induced Structural Transition and Lipase Immobilization in Mesoporous Aluminum Metal-Organic Frameworks.

The transition from disorder to order and structural transformation are distinctive metal-organic framework (MOF) features. How to adapt or control both behaviors in MOF has rarely been studied. In this case, we demonstrate that our successful synthesis of [Al(OH)(PDA)]n (AlPDA-53-DEF, AlPDA-53-H, and AlPDA-68) with H2PDA=4,4'-[1,4-phenylenebis(ethyne-2,1-diyl)]-di benzoic acid has shown the intricate world of Aluminum Metal-Organic Frameworks (Al-MOFs). It offers profound insights into defect structures to order and transformations. AlPDA-53-DEF, in particular, revealed a fascinating interplay of various pore sizes within both micro and mesoporous regions, unveiling a unique lattice rearrangement phenomenon upon solvent desorption. Defects and disorders emerged as crucial impacts of transforming AlPDA-53-DEF, with its initially imperfect crystallinity, into the highly crystalline, hierarchically porous AlPDA-53-H.

Amorphous-Like Ultralow Thermal Transport in Crystalline Argyrodite Cu7PS6.

Due to their amorphous-like ultralow lattice thermal conductivity both below and above the superionic phase transition, crystalline Cu- and Ag-based superionic argyrodites have garnered widespread attention as promising thermoelectric materials. However, despite their intriguing properties, quantifying their lattice thermal conductivities and a comprehensive understanding of the microscopic dynamics that drive these extraordinary properties are still lacking. Here, an integrated experimental and theoretical approach is adopted to reveal the presence of Cu-dominated low-energy optical phonons in the Cu-based argyrodite Cu7PS6. These phonons yield strong acoustic-optical phonon scattering through avoided crossing, enabling ultralow lattice thermal conductivity. The Unified Theory of thermal transport is employed to analyze heat conduction and successfully reproduce the experimental amorphous-like ultralow lattice thermal conductivities, ranging from 0.43 to 0.58 W m-1 K-1, in the temperature range of 100-400 K. The study reveals that the amorphous-like ultralow thermal conductivity of Cu7PS6 stems from a significantly dominant wave-like conduction mechanism. Moreover, the simulations elucidate the wave-like thermal transport mainly results from the contribution of Cu-associated low-energy overlapping optical phonons. This study highlights the crucial role of low-energy and overlapping optical modes in facilitating amorphous-like ultralow thermal transport, providing a thorough understanding of the underlying complex dynamics of argyrodites.

Soft Phonon Mode Triggering Fast Ag Diffusion in Superionic Argyrodite Ag8 GeSe6.

The structural coexistence of dual rigid and mobile sublattices in superionic Argyrodites yields ultralow lattice thermal conductivity along with decent electrical and ionic conductivities and therefore attracts intense interest for batteries, fuel cells, and thermoelectric applications. However, a comprehensive understanding of their underlying lattice and diffusive dynamics in terms of the interplay between phonons and mobile ions is missing. Herein, inelastic neutron scattering is employed to unravel that phonon softening on heating to Tc ≈ 350 K triggers fast Ag diffusion in the canonical superionic Argyrodite Ag8 GeSe6 . Ab initio molecular dynamics simulations reproduce the experimental neutron scattering signals and identify the partially ultrafast Ag diffusion with a large diffusion coefficient of 10-4 cm-2 s-1 . The study illustrates the microscopic interconnection between soft phonons and mobile ions and provides a paradigm for an intertwined interaction of the lattice and diffusive dynamics in superionic materials.

Acute and Chronic Effects of Fin Amputation on Behavior Performance of Adult Zebrafish in 3D Locomotion Test Assessed with Fractal Dimension and Entropy Analyses and Their Relationship to Fin Regeneration.

The fin is known to play an important role in swimming for many adult fish, including zebrafish. Zebrafish fins consist of paired pectoral and pelvic with unpaired dorsal, anal, and caudal tail fins with specific functions in fish locomotion. However, there was no study comparing the behavior effects caused by the absence of each fin. We amputated each fin of zebrafish and evaluated their behavior performance in the 3D locomotion test using fractal dimension and entropy analyses. Afterward, the behavior recovery after the tail fin amputation was also evaluated, together with the fin regeneration process to study their relationship. Finally, we conducted a further study to confirm whether the observed behavior alterations were from pain elicited by fin amputation procedure or not by using lidocaine, a pain-relieving drug. Amputation in the caudal fin resulted in the most pronounced behavior alterations, especially in their movement complexity. Furthermore, we also found that their behavior was fully recovered before the caudal fin was fully regenerated, indicating that these behavioral changes were not majorly due to a mechanical change in tail length; instead, they may come from pain elicited from the fin amputation, since treatment with lidocaine could ameliorate the behavioral effects after the amputation procedure. However, lidocaine did not accelerate the behavior recovery process; instead, it caused the fishes to display some slight side effects. This study highlights the potential moderate severity of fin amputation in zebrafish and the importance of analgesia usage. However, side effects may occur and need to be considered since fin amputation is routinely conducted for various research, especially genomic screening.

Evaluation of Locomotion Complexity in Zebrafish after Exposure to Twenty Antibiotics by Fractal Dimension and Entropy Analysis.

Antibiotics are extensively used in aquaculture to prevent bacterial infection and the spread of diseases. Some antibiotics have a relatively longer half-life in water and may induce some adverse effects on the targeted fish species. This study analyzed the potential adverse effects of antibiotics in zebrafish at the behavioral level by a phenomic approach. We conducted three-dimensional (3D) locomotion tracking for adult zebrafish after acute exposure to twenty different antibiotics at a concentration of 100 ppb for 10 days. Their locomotor complexity was analyzed and compared by fractal dimension and permutation entropy analysis. The dimensionality reduction method was performed by combining the data gathered from behavioral endpoints alteration. Principal component and hierarchical analysis conclude that three antibiotics: amoxicillin, trimethoprim, and tylosin, displayed unique characteristics. The effects of these three antibiotics at lower concentrations (1 and 10 ppb) were observed in a follow-up study. Based on the results, these antibiotics can trigger several behavioral alterations in adult zebrafish, even in low doses. Significant changes in locomotor behavioral activity, such as total distance activity, average speed, rapid movement time, angular velocity, time in top/bottom duration, and meandering movement are highly related to neurological motor impairments, anxiety levels, and stress responses were observed. This study provides evidence based on an in vivo experiment to support the idea that the usage of some antibiotics should be carefully addressed since they can induce a significant effect of behavioral alterations in fish.

Compositional Fluctuations Locked by Athermal Transformation Yielding High Thermoelectric Performance in GeTe.

Phase transition in thermoelectric (TE) material is a double-edged sword-it is undesired for device operation in applications, but the fluctuations near an electronic instability are favorable. Here, Sb doping is used to elicit a spontaneous composition fluctuation showing uphill diffusion in GeTe that is otherwise suspended by diffusionless athermal cubic-to-rhombohedral phase transition at around 700 K. The interplay between these two phase transitions yields exquisite composition fluctuations and a coexistence of cubic and rhombohedral phases in favor of exceptional figures-of-merit zT. Specifically, alloying GeTe by Sb2 Te3 significantly suppresses the thermal conductivity while retaining eligible carrier concentration over a wide composition range, resulting in high zT values of >2.6. These results not only attest to the efficacy of using phase transition in manipulating the microstructures of GeTe-based materials but also open up a new thermodynamic route to develop higher performance TE materials in general.

Publisher Correction: Rapid desolvation-triggered domino lattice rearrangement in a metal-organic framework.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Rapid desolvation-triggered domino lattice rearrangement in a metal-organic framework.

Topological transitions between considerably different phases typically require harsh conditions to collectively break chemical bonds and overcome the stress caused to the original structure by altering its correlated bond environment. In this work we present a case system that can achieve rapid rearrangement of the whole lattice of a metal-organic framework through a domino alteration of the bond connectivity under mild conditions. The system transforms from a disordered metal-organic framework with low porosity to a highly porous and crystalline isomer within 40 s following activation (solvent exchange and desolvation), resulting in a substantial increase in surface area from 725 to 2,749 m2 g-1. Spectroscopic measurements show that this counter-intuitive lattice rearrangement involves a metastable intermediate that results from solvent removal on coordinatively unsaturated metal sites. This disordered-crystalline switch between two topological distinct metal-organic frameworks is shown to be reversible over four cycles through activation and reimmersion in polar solvents.

Thermoelectric Figure-of-Merit of Fully Dense Single-Crystalline SnSe.

Single-crystalline SnSe has attracted much attention because of its record high figure-of-merit ZT ≈ 2.6; however, this high ZT has been associated with the low mass density of samples which leaves the intrinsic ZT of fully dense pristine SnSe in question. To this end, we prepared high-quality fully dense SnSe single crystals and performed detailed structural, electrical, and thermal transport measurements over a wide temperature range along the major crystallographic directions. Our single crystals were fully dense and of high purity as confirmed via high statistics 119Sn Mössbauer spectroscopy that revealed <0.35 at. % Sn(IV) in pristine SnSe. The temperature-dependent heat capacity (C p) provided evidence for the displacive second-order phase transition from Pnma to Cmcm phase at T c ≈ 800 K and a small but finite Sommerfeld coefficient γ0 which implied the presence of a finite Fermi surface. Interestingly, despite its strongly temperature-dependent band gap inferred from density functional theory calculations, SnSe behaves like a low-carrier-concentration multiband metal below 600 K, above which it exhibits a semiconducting behavior. Notably, our high-quality single-crystalline SnSe exhibits a thermoelectric figure-of-merit ZT ∼1.0, ∼0.8, and ∼0.25 at 850 K along the b, c, and a directions, respectively.

High-Temperature Structural and Thermoelectric Study of Argyrodite Ag8GeSe6.

Argyrodites with a general chemical formula of A8BX6 (A = Cu, Ag; B = Si, Ge, Sn; and X = S, Se, and Te) are known for the intimate interplay among mobile ions, electrons, and phonons, which yields rich material physics and materials chemistry phenomena. In particular, the coexistence of fast ionic conduction and promising thermoelectric performance in Ag8GeTe6, Ag8SnSe6, Ag8SiTe6, Ag8SiSe6, and Cu8GeSe6 at high temperatures ushered us to their chemical neighbor Ag8GeSe6, whose high-temperature crystal structure and thermoelectric properties are not yet reported. In this work, we have employed a growth-from-the-melt technique followed by hot pressing to prepare polycrystalline Ag8GeSe6 samples, on which the crystal structure, micro-morphology, compositional analysis, UV-vis absorption, specific heat, speed of sound, and thermoelectric properties were characterized as a function of the Se-deficiency ratio and temperature. We found that (i) the crystal structure of Ag8GeSe6 evolved from orthorhombic at room temperature to face center cubic above 410 K, with a region of phase separations in between; (ii) like other argyrodite 816 phases, Ag8GeSe6 exhibited ultralow thermal conductivities over a wide temperature range as the phonon mean free path was down to the order of interatomic spacing; and (iii) varying Se deficiency effectively optimized the carrier concentration and power factor, a figure of merit zT value ∼0.55 was achieved at 923 K in Ag8GeSe5.88. These results not only fill a knowledge gap of Ag8GeSe6 but also contribute to a comprehensive understanding of 816 phase argyrodites at large.

Metal-Organic-Framework-Derived Hollow N-Doped Porous Carbon with Ultrahigh Concentrations of Single Zn Atoms for Efficient Carbon Dioxide Conversion.

The development of efficient and low energy-consumption catalysts for CO2 conversion is desired, yet remains a great challenge. Herein, a class of novel hollow porous carbons (HPC), featuring well dispersed dopants of nitrogen and single Zn atoms, have been fabricated, based on the templated growth of a hollow metal-organic framework precursor, followed by pyrolysis. The optimized HPC-800 achieves efficient catalytic CO2 cycloaddition with epoxides, under light irradiation, at ambient temperature, by taking advantage of an ultrahigh loading of (11.3 wt %) single-atom Zn and uniform N active sites, high-efficiency photothermal conversion as well as the hierarchical pores in the carbon shell. As far as we know, this is the first report on the integration of the photothermal effect of carbon-based materials with single metal atoms for catalytic CO2 fixation.

Characterization of coumarin-6 polycrystalline films growth from vacuum deposition at various substrate temperatures.

Coumarin-6 polycrystalline films were fabricated from vacuum deposition at various substrate temperatures Tsub from 106 to 178 °C with a fixed source temperature of 185 °C. Because of its slenderer and more asymmetric structure, the adhered coumarin-6 molecule on top of the growing interface encounters a larger steric energetic barrier of 0.92 eV as estimated from the Arrhenius plot of growth rate versus 1/Tsub. From top-view SEM pictures, the as-deposited coumarin-6 thin films exhibit a twisted pattern and a kinematic roughness for Tsub < 150 °C; while clear facets emerge for Tsub ≥ 150 °C due to the increase of surface diffusion energy of the adhered molecules. From XRD analysis, besides the confirmation of the triclinic structure two anomalous peaks observed at 2θ ~ 9.007° and 7.260° are explained due to the co-existence of N- and S-coumarin-6-isomers within the crystalline grains. Furthermore, for coumarin-6 polycrystalline films deposited at Tsub = 150 °C with high crystallinity of the constituent grains, the bandgap determined from optical transmission is around 2.392 eV; and from photoluminescence spectra, the fitted four emission components are assigned to the Frenkel and charge transfer excitons recombination with participation of molecular vibrational states.

An Efficient Evaluation of F-doped Polyanion Cathode Materials with Long Cycle Life for Na-Ion Batteries Applications.

A series of Na3-x V2(PO4-x F x )3 (x = 0, 0.1, 0.15 and 0.3) polyanion cathode materials are synthesized via a sol-gel method. The optimal doping concentration of F in Na3V2(PO4)3 is 0.15 mol %. By neutron powder diffraction data, the chemical composition of as-synthesized material is Na2.85V2(PO3.95F0.05)3. The half-cell of Na2.85V2(PO3.95F0.05)3 cathode exhibits a stable discharge capacity of 103 mAh g-1 and 93% of capacity retention over 250 cycles without decay at 0.1 A g-1, which is higher than that of bare Na3V2(PO4)3 (98 mAh g-1). The high rate capability of Na2.85V2(PO3.95F0.05)3 is also dramatically enhanced via increase the conductivity of host material by F-doping. Moreover, the symmetrical Na-ion full-cell is fabricated using Na2.85V2(PO3.95F0.05)3 as cathode and anode materials. It is achieved that the good reversibility and superior cycling stability about 98% of capacity retention with ~100% of coulombic efficiency at 1.0 A g-1 throughout 1000 cycles. These results demonstrate that the optimal amount of Na2.85V2(PO3.95F0.05)3 is a distinctive potential candidate for excellent long-term cyclic stability with high rate low-cost energy storage applications.

Electrical bistability in a metal-organic framework modulated by reversible crystalline-to-amorphous transformations.

Electrically bistable materials have important applications in memory, displays, switches, sensors, and quantum computation. This communication reports a metal-organic framework (MOF) material as a new type of electrically bistable material. Taking advantage of the flexible structure of MOF materials, the electrically bistable states of the MOF were reversibly modulated between its crystalline and amorphous phases. Interestingly, the material's amorphous phase exhibited anomalously higher conductivity than the crystalline phase. Our results illustrated a convenient method to develop electrically bistable materials from MOFs.

Role of molecular conformations in rubrene polycrystalline films growth from vacuum deposition at various substrate temperatures.

We report on the optical and structural characterization of rubrene polycrystalline films fabricated from vacuum deposition with various substrate temperatures (Tsub). Depending on Tsub, the role of twisted and planar rubrene conformational isomers on the properties of rubrene films is focused. The temperature (T)-dependent inverse optical transmission (IOT) and photoluminescence (PL) spectra were performed on these rubrene films. The origins of these IOT and PL peaks are explained in terms of the features from twisted and planar rubrene molecules and of the band characteristics from rubrene molecular solid films. Here, two rarely reported weak-peaks at 2.431 and 2.605 eV were observed from IOT spectra, which are associated with planar rubrene. Besides, the T-dependence of optical bandgap deduced from IOT spectra is discussed with respect to Tsub. Together with IOT and PL spectra, for Tsub > 170 °C, the changes in surface morphology and unit cell volume were observed for the first time, and are attributed to the isomeric transformation from twisted to planar rubrenes during the deposition processes. Furthermore, a unified schematic diagram in terms of Frenkel exciton recombination is suggested to explain the origins of the dominant PL peaks performed on these rubrene films at 15 K.

Novel trypsin-FITC@MOF bioreactor efficiently catalyzes protein digestion.

A simple nanoporous metal organic framework (MOF) bioreactor preparation via a low energy 30 minute vortex as driving force to immobilize trypsin enzyme is presented. No chemical modifications were employed thus organic wastes were eliminated. The digestion efficiency of this trypsin bioreactor is exceptionally high, even when reused. This "green" synthesis procedure produced a "green" bioreactor.

Two-dimensional single-crystalline Zn hexagonal nanoplates: size-controllable synthesis and X-ray diffraction study.

We synthesized two-dimensional (2D) Zn hexagonal nanoplates using the thermal metal-vapor deposition technique. An increase and decrease in the surface area and thickness of the 2D Zn hexagonal nanoplates were shown with elevated annealing temperatures, indicating their sizes to be controlled using the annealing treatment. X-Ray diffractometry (XRD) studies revealed the crystalline nature of the 2D Zn hexagonal nanoplates and the diffraction intensity of the (002) lattice plane, which increased parabolically with elevated annealing temperatures.

Growth mechanism and magnon excitation in NiO nanowalls.

The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed. The energy dispersive spectroscopy mapping technique was used to characterize the growth mechanism, and confocal Raman scattering was used to probe the antiferromagnetic exchange energy J2 between next-nearest-neighboring Ni ions in NiO nanowalls at various growth temperatures below the Neel temperature. This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation. Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature.PACS: 75.47.Lx; 61.82.Rx; 75.50.Tt; 74.25.nd; 72.10.Di.

Interplay between the crystalline and magnetic structures in lightly Cr-doped Bi(0.37)Ca(0.63)Mn(0.96)Cr(0.04)O(2.99).

The interplay between the crystalline and magnetic structures of a 4% Cr-doped Bi(0.37)Ca(0.63)Mn(0.96)Cr(0.04)O(2.99) has been investigated by alternating current (ac) magnetic susceptibility, electrical resistivity, and neutron diffraction measurements. The compound crystallizes into a monoclinic P2(1)/m symmetry. A Jahn-Teller distortion occurs at 280 K. The thermal behavior of charge transport may be described by a three-dimensional variable range hopping conduction. Strong interplay between the localized magnetic electrons and the itinerant electrons are clearly revealed as the localization length increases by 20% when the Mn spins become ordered below 85 K. Short range magnetic correlations persist up to 160 K. The collinear magnetic structure can be viewed as consisting of ferromagnetic spin-trimers antiferromagnetically embedded in a ferromagnetic environment. Cr-doping reduces the charge ordering temperature and the magnetic ordering temperature. It nevertheless introduces long-range ferromagnetism.