Void Channels Research Articles

Luminescent yttrium organic frameworks: Cell imaging, gas adsorption and nitro sensing applications

The flexibility of ligand (L) yield, two different yttrium organic frameworks, denoted as {[Y(L)2(H2O)4]·Cl3·DMF·(H2O)3·(S)}n (MOF-1) and {[Y(L)3/2(H2O)2]·(NO3)3·(S)}n (MOF-2), where L denotes 9,10-bis((4-carboxylatopyridinium-1-methylene)anthracene and S denotes the disordered solvent molecules. Detailed single crystal X-ray study established a one dimensional (1D) chain for MOF-1 and a three dimensional (3D) frameworks with one channel voids structure for MOF-2, respectively, due to different conformation of the ligand. In both MOFs, Y(III) have bicapped trigonal prismatic geometry. The phase purity of both MOFs has been confirmed by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and IR spectroscopic studies. MOF-1, with its particle size in nano range, good fluorescence property and solubility in water, is a suitable candidate for cell imaging study. In contrast, three dimensional framework of MOF-2, with small voids, makes it well suited for gas adsorption and sensing of nitro aromatic compounds.

Impact of the blockage ratio and void fraction of porous obstacle on gas explosion characteristics in semi-confined channel

This study conducted various explosion experiments under different porous obstacle conditions of blockage ratio (BR) and void fraction (Φf). The impact of porous obstacle on flame propagation velocity (v) and peak overpressure (Pop) were analyzed. The results indicate that an increase in the BR enhances explosion pressure near the blockage area for both porous and non-porous obstacles. However, it also increases the downstream pressure decline gradient. An increase in the Φf weakens the hindrance of porous obstacle on the flame propagation, allowing more flame to pass through the internal void channels of obstacles, thus delaying the downstream pressure decay. Compared to non-porous obstacles, gas explosions disturbed by porous obstacles with both high BR (BR＞75%) and high Φf (Φf＞0.55) exhibit a lower downstream pressure decline gradient and a longer positive pressure duration. As a result, the explosion can produce a broader range of destruction.

Porphyrin/Fullerene Porous Molecular Cocrystal Featuring a Robust One-Dimensional Channel.

Microporous molecular crystals are promising materials because of their designable porosity as well as their resistance to chemical and other stimuli. Here, we developed microporous molecular cocrystals by taking advantage of the specific interactions between porphyrins and fullerene molecules. Single-crystal X-ray diffraction analysis revealed that one nickel(II) porphyrin interacts with two fullerene molecules to form a two-dimensional honeycomb network with an eclipsed stacking mode, providing one-dimensional void channels. After the pores were activated by heat treatment or mechanical grinding, the prepared cocrystal can incorporate gas and solvent molecules reversibly while maintaining its single-crystallinity. Also, it retained its single-crystallinity in the presence of water, acid-base, or high pressure. These findings in this study expand the availability of molecular crystals based on intermolecular interactions as porous materials, which are expected to work under conditions that have not been applicable to other molecule-based porous materials.

Ni–Co spinel based oxide as new type of additive to glass seal for solid oxide fuel cells

Glass seals utilized in Solid Oxide Fuel Cells (SOFCs) can be subject to modification through the incorporation of oxide additives to bolster their mechanical strength. This research focuses on a novel class of additives, specifically protective coating materials designed for alloy interconnects. It is crucial to emphasize that the glass seal interfaces directly with the protective coating, bypassing direct contact with the alloy itself. The efficacy of this approach is exemplified through the utilization of Ni–Co spinel-based oxide, established as an effective protective substance for stainless steel interconnects. The introduction of a minute quantity of Ni–Co oxides does not induce alterations in the glass seal properties, encompassing phase structure, microstructure, thermal expansion coefficient (CTE), and softening behavior. The Ni–Co oxide additive serves to mitigate the glass devitrification tendency, leading to a substantial augmentation in shear strength at the seal-interconnect interface and a marked enhancement in sealing properties. The composite seal, enriched with 3.0 wt% Ni–Co oxide, showcases superior sealing performance, demonstrating exceptional stability throughout a rigorous 1200-h test. The average leakage rate during this test period stands at 0.0024 sccm⋅cm−1. The incorporation of Ni–Co oxide triggers the formation of needle-shaped crystals, playing a pivotal role in averting channel void formation and augmenting the bonding strength between the seal and interconnect. Consequently, this fortifies gas tightness, ensuring the maintenance of outstanding sealing performance over an extended duration.

DNA Cryogels with Anisotropic Mechanical and Responsive Properties for Specific Cell Capture and Release.

Due to their programmable stimuli-responsiveness, excellent biocompatibility, and water-rich and soft structures similar to biological tissues, smart DNA hydrogels hold great promise for biosensing and biomedical applications. However, most DNA hydrogels developed to date are composed of randomly oriented and isotropic polymer networks, and the resulting slow response to biotargets and lack of anisotropic properties similar to those of biological tissues have limited their extensive applications. Herein, anisotropic DNA hydrogels consisting of unidirectional void channels internally oriented up to macroscopic length scales were constructed by a directional cryopolymerization method, as exemplified by a DNA-incorporated covalently cross-linked DNA cryogel and a DNA duplex structure noncovalently cross-linked DNA cryogel. Results showed that the formation of unidirectional channels significantly improved the responsiveness of the gel matrix to biomacromolecular substances and further endowed the DNA cryogels with anisotropic properties, including anisotropic mechanical properties, anisotropic swelling/shrinking behaviors, and anisotropic responsiveness to specific biotargets. Moreover, the abundant oriented and long macroporous channels in the gel matrix facilitated the migration of cells, and through the introduction of aptamer structures and thermosensitive polymers, an anisotropic DNA cryogel-based platform was further constructed to achieve the highly efficient capture and release of specific cells. These anisotropic DNA hydrogels may provide new opportunities for the development of anisotropic separation and biosensing systems.

Research on Flexible Transparent Conductive Electrodes Based on Ultra-Thin Ag in the Form of Grain Boundary with IZO Layer

In this paper, we investigated a transparent conductive electrode (TCE) that satisfies electrical, optical, and mechanical properties, formed by depositing ultra-thin Ag metal in the form of a random grain boundary with an indium zinc oxide (IZO) layer on a PET substrate. Commonly used ITO electrodes are brittle and difficult to apply to flexible devices. In contrast, IZO-based electrodes are mechanically flexible and can be used as flexible TCE, and have high electrical and optical properties. A 90 nm thick IZO electrode has a transmittance of 90.2% at a wavelength of 460 nm and a sheet resistance of 29.5 ohm/sq. In particular, Ag metal was deposited in the form of an atypical metal island using an RF magnetron sputtering system. At 3 nm there were few metal clusters in the form of islands, and many void channels were formed, resulting in high sheet resistance as well as a decrease in optical transmittance. However, about 5 nm thickness, the number of void channels decreased and the optical path changed, improving the electrical and optical properties. Results showed that the sheet resistance was reduced to 19.8 ohm/sq, and the transmittance was also increased to 91.1%. The mechanical properties were also found to be the same for conventional IZO and Ag/IZO TCE.

Highly oriented hydrogels for tissue regeneration: design strategies, cellular mechanisms, and biomedical applications.

Many human tissues exhibit a highly oriented architecture that confers them with distinct mechanical properties, enabling adaptation to diverse and challenging environments. Hydrogels, with their water-rich "soft and wet" structure, have emerged as promising biomimetic materials in tissue engineering for repairing and replacing damaged tissues and organs. Highly oriented hydrogels can especially emulate the structural orientation found in human tissue, exhibiting unique physiological functions and properties absent in traditional homogeneous isotropic hydrogels. The design and preparation of highly oriented hydrogels involve strategies like including hydrogels with highly oriented nanofillers, polymer-chain networks, void channels, and microfabricated structures. Understanding the specific mechanism of action of how these highly oriented hydrogels affect cell behavior and their biological applications for repairing highly oriented tissues such as the cornea, skin, skeletal muscle, tendon, ligament, cartilage, bone, blood vessels, heart, etc., requires further exploration and generalization. Therefore, this review aims to fill that gap by focusing on the design strategy of highly oriented hydrogels and their application in the field of tissue engineering. Furthermore, we provide a detailed discussion on the application of highly oriented hydrogels in various tissues and organs and the mechanisms through which highly oriented structures influence cell behavior.

Dual-Objective Mechanobiological Growth Optimization for Heterogenous Lattice Structures

Abstract Computational design is growing in necessity for advancing biomedical technologies, particularly for complex systems with numerous trade-offs. For instance, in tissue scaffolds constructed from repeating unit cells, the structure’s porosity and topology affect biological tissue and vasculature growth. Here, we adapt curvature-based tissue growth and agent-based vasculature models for predicting scaffold mechanobiological growth. A non-dominated sorting genetic algorithm (NSGA-II) is used for dual-objective optimization of scaffold tissue and blood vessel growth with heterogeneous unit cell placement. Design inputs consist of unit cells of two different topologies, void unit cells, and beam diameters from 64 to 313 µm. Findings demonstrate a design heuristic for optimizing scaffolds by placing two selected unit cells, one that favors high tissue growth density and one that favors blood vessel growth, throughout the scaffold. The pareto front of solutions demonstrates that scaffolds with large porous areas termed channel voids or small voids improve vasculature growth while lattices with no larger void areas result in higher tissue growth. Results demonstrate the merit in computational investigations for characterizing tissue scaffold design trade-offs and provide a foundation for future design multi-objective optimization for complex biomedical systems.

Experimental Study on the Diffusion Law of Coal-Based Solid Waste Slurry with Grouting Filling in the Gangue Voids of the Caving Zone.

Due to the concealment of the caving zone, it is difficult to detect and grasp the diffusion law of the slurry in the voids of the gangue pile. On the preparation of reasonable grouting filling materials, a large-scale three-dimensional gangue grouting filling test system has been established to detect the slurry pressure and resistivity inside the gangue pile and analyze the flow pattern of the slurry in the voids of the gangue pile. The research results show that the slump and bleeding rate of the filling slurry are significantly reduced with the increase of the fly ash content. The optimal ratio of fly ash, coal gangue, and gasification slag is 7:2:1, with a mass fraction of 72%. In the process of grouting, the internal pressure of the gangue pile can be divided into the initial stable stage, the step growth stage, and the pressure stability stage, and the change curve of the pressure sensor at the lower level is similar. The resistance value of the original broken gangue in the experiment is approximately 1600 Ω. Grouting filling forms a slurry-rock mixture, and its resistance continuously decreases with the stable injection of the slurry (minimum value 150 Ω). It is determined that the slurry near the grouting hole mainly diffuses longitudinally with a good void filling effect. The void channels of slurry diffusion are randomly distributed and have different shapes, which hinder slurry flow and diffusion. Slurry particles accumulate and settle at local small voids. Meanwhile, the surface of the gangue blocks is dry, and the slurry absorbs part of the water during diffusion, resulting in the increase of the slurry concentration and the weakening of the lateral diffusion ability. Secondary or multiple grouting can effectively fill the void of the broken gangue and further improve the filling effect.

Experimental study on the thermal evolution of silicon defects with zonal characteristics induced by precisely localized irradiation of focused helium ion beams

The thermal evolution of defects introduced in silicon by line scanning with helium ion microscopy was investigated, confirming that the evolution of the defective structure after annealing at 650 °C for 1 h results in a central void channel and a sector ring of cavities surrounding it, located in the amorphous and transition regions of the unannealed pre-irradiated sample, respectively. The variation of defective structures with annealing temperature and ion dose indicates that high temperature is favorable for the formation of void channels and cavities, and the coarsening and recrystallization processes compete in the shaping of a void channel. The total volume of the defective structure is linearly related to the ion dose, while the zoning phenomenon is attributed to the differences in the vacancy amounts within their locations. These results provide direct experimental evidence for the thermal evolution of defects with zonal characteristics induced by precisely localized helium irradiation.

Effect of void space arrangement on wind power potential and pressure coefficient distributions for high-rise void buildings

High-rise void building complexes can augment the permeation of airflows over buildings, and thereby strengthen urban wind energy harvesting for realization of the sustainable development goals (SDGs). This paper considers the wind over a typical 2×2 compact high-rise building array with the openings to analyze the wind power potential at varying void sizes, locations of voids, and direction of incoming wind. The predicted mean wind speeds and turbulence intensities are compared against the measured data with 4 generic high-rise building models having voids in an atmospheric boundary layer wind tunnel for validation of the computational model. Based on the comparative results from four common Reynolds-averaged Navier-Stokes (RANS) turbulence models including the standard, realizable, renormalization group (RNG) k-ε, and shear-stress transport (SST) k-ω models as well as the Reynolds stress model (RSM), the RSM approach can provide the most accurate predictions of streamwise mean velocity and turbulence intensity. The present study then conducts CFD simulations to explore the effects of opening configuration and wind direction on the wind field around high-rise void buildings. Considering the variations of void sizes of 10 × 10 m2, 12.5 × 12.5 m2, 15 × 15 m2, void heights of z/H = 0.25, 0.5, 0.75 and wind directions of 0°, 45°, respectively, the simulated results indicate elevated wind power densities with acceptable turbulence intensities over the upstream gap passage and void channels to achieve prospective urban wind power harvest and mitigate wind load on structures of high-rise void buildings.

Assessment of mechanical properties of fiber reinforced cementitious system exposed to high temperature

AbstractIn this study, it was aimed to determine the optimum fiber type and usage ratio by examining the effect of fiber type and usage rate on the properties of mortar mixtures exposed to high temperatures such as 300°C, 450°C, and 600°C. For this purpose, mixtures were prepared by substituting polypropylene (PP), polyamide (PA) and basalt (B) fibers in proportions as 0.25%, 0.50%, 0.75%, and 1% instead of aggregate. Unit weight, compressive‐flexural strength, ultrasonic pulse velocity (UPV), and permeability properties of mixtures were determined. Regardless of fiber type, flexural strength and permeability increased, UPV decreased with the addition of fiber. Basalt fiber mixtures exhibited the highest performance in terms of flexural strength. PP fiber mixtures exhibited the best performance in terms of permeability, ultrasonic pulse velocity and dynamic modulus of elasticity. SEM analyzes showed that PP fibers exposed to 600°C melted, leading to the formation of channel voids. According to TGA result, approximately 15% mass loss was observed in the control sample at 600°C.

Ultralight PPy@PVA/BC/MXene composite aerogels for high-performance supercapacitor eltrodes and pressure sensors

Directional freezing is an efficient approach to design anisotropic materials with surface void and well-defined aligned channels along the freezing direction for charge transmission and ion diffusion. Herein, poly(vinyl alcohol) (PVA)/bacterial cellulose (BC)/MXene (PBM) composite aerogels are prepared via directional freezing. The aligned porous architecture of PBM not only enables uniform loading and high accessibility of PPy through the aerogel network, but also ensures efficient penetration and fast transport of electrolytes. The as-prepared PPy@PVA/BC/MXene (PPy@PBM) aerogel based supercapacitors show a high areal specific capacitance of 3948 mF cm−2 at 0.47 mA cm−2, a desirable energy density 178 μWh cm−2 at a power density of 951 μW cm−2 and excellent cycling stability (120% capacitance retention after 10,000 cycles). In addition, the PPy@PBM aerogels demonstrate high sensitivity (313.2 kPa−1 in 200 to 3000 Pa pressure range), ultralow detection limit (<1 Pa) and fast response (79 ms) as pressure sensors. This study proposes an efficient approach to prepare porous composite aerogels for supercapacitor electrodes and pressure sensors.

An ionic Fe-based metal-organic-framework with 4'-pyridyl-2,2':6',2''-terpyridine for catalytic hydroboration of alkynes.

An ionic metal-organic-framework (MOF) containing nanoscale channels was readily assembled from ditopic 4'-pyridyl-2,2':6',2''-terpyridine (pytpy) and a simple iron(ii) salt. X-ray structural analysis revealed a two-dimensional grid-like framework assembled by classic octahedral (pytpy)2FeII cations as linkers (with pytpy as a new ditopic pyridyl ligand) and octa-coordinate FeCl2 centers as nodes. The layer-by-layer assembly of the 2-D framework resulted in the formation of 3-D porous materials consisting of nano-scale channels. The charges of the cationic framework were balanced with anionic Cl3FeOFeCl3 in its void channels. The new Fe-based MOF material was employed as a precatalyst for syn-selective hydroboration of alkynes under mild, solvent-free conditions in the presence of an activator, leading to the synthesis of a range of trans-alkenylboronates in good yields. The larger scale applicability and recyclability of the new MOF catalyst was further explored. This represents a rare example of an ionic MOF material that can be utilized in hydroboration catalysis.

Crystal Structure and Twisted Aggregates of Oxcarbazepine Form III.

Polymorphism and crystal habit play vital roles in dictating the properties of crystalline materials. Here, the structure and properties of oxcarbazepine (OXCBZ) form III are reported along with the occurrence of twisted crystalline aggregates of this metastable polymorph. OXCBZ III can be produced by crystallization from the vapor phase and by recrystallization from solution. The crystallization process used to obtain OXCBZ III is found to affect the pitch, with the most prominent effect observed from the sublimation-grown OXCBZ III material where the pitch increases as the length of aggregates increases. Sublimation-grown OXCBZ III follows an unconventional mechanism of formation with condensed droplet formation and coalescence preceding nucleation and growth of aggregates. A crystal structure determination of OXCBZ III from powder X-ray diffraction methods, assisted by crystal structure prediction (CSP), reveals that OXCBZ III, similar to carbamazepine form II, contains void channels in its structure with the channels, aligned along the c crystallographic axis, oriented parallel to the twist axis of the aggregates. The likely role of structural misalignment at the lattice or nanoscale is explored by considering the role of molecular and closely related structural impurities informed by crystal structure prediction.

Asymptotically exact photonic approximations of chiral symmetric topological tight-binding models

Topological photonic edge states, protected by chiral symmetry, are attractive for guiding wave energy as they can allow for more robust guiding and greater control of light than alternatives; however, for photonics, chiral symmetry is often broken by long-range interactions. We look to overcome this difficulty by exploiting the topology of networks, consisting of voids and narrow connecting channels, formed by the spaces between closely spaced perfect conductors. In the limit of low frequencies and narrow channels, these void–channel systems have a direct mapping to analogous discrete mass–spring systems in an asymptotically rigorous manner and therefore only have short-range interactions. We demonstrate that topological tight-binding models that are protected by chiral symmetries, such as the SSH model and square-root semimetals, are reproduced for these void–channel networks with appropriate boundary conditions. We anticipate, moving forward, that this paper provides a basis from which to explore continuum photonic topological systems, in an asymptotically exact manner, through the lens of a simplified tight-binding model.

First-principles simulations to understand the structural and electrolyte properties of idealized Li7.5B10S18X1.5 (X=Cl, Br, I)

Recently, researchers at the University of Waterloo (Canada) and Oak Ridge National Laboratory (Oak Ridge, TN) reported a new family of lithium thioborate halide electrolytes with the composition ${\mathrm{Li}}_{7.5}{\mathrm{B}}_{10}{\mathrm{S}}_{18}{X}_{1.5}$ $(X=\mathrm{Cl}, \mathrm{Br}, \mathrm{I})$ having very impressive ionic room-temperature conductivity of magnitude $\ensuremath{\sigma}=1 \mathrm{mS}/\mathrm{cm}$. The researchers characterized the structures of the three materials in terms of a well-defined thioborate framework with a void structure containing fractionally occupied Li and X sites. The space group of the materials was identified to be monoclinic ($C2/c$, No. 15). We report the results of first-principles simulations of these materials focusing on understanding the idealized ground-state structures, the mechanisms of Li ion migration, and the overall stability of the materials. A systematic search of many possible stoichiometric crystalline configurations found ordered ground-state realizations of the materials for each of the three halides, $X=\mathrm{Cl}, \mathrm{Br}, \mathrm{I}$. Molecular dynamics simulations based on the initially ordered structures at various temperatures show significant Li ion hopping within the void channels of the structures at temperatures as low as T = 400 K. Simulations of possible decomposition products suggest that these electrolytes are also chemically stable. Overall, the simulations are consistent with the experimentally reported findings indicating that these materials are very promising solid electrolytes for possible use in solid-state Li ion batteries.

Crystal structure of a trigonal polymorph of aqua-dioxidobis(pentane-2,4-dionato-κ2 O,O')uranium(VI).

The title compound, [UO2(acac)2(H2O)] consists of a uran-yl(VI) unit ([O=U=O]2+) coordinated to two monoanionic acetyl-acetonate (acac, C5H7O2) ligands and one water mol-ecule. The asymmetric unit includes a one-half of a uranium atom, one oxido ion, one-half of a water mol-ecule and one acac ligand. The coordination about the uranium atom is distorted penta-gonal-bipyramidal. The acac ligands and Ow atom comprise the equatorial plane, while the uranyl O atoms occupy the axial positions. Inter-molecular hydrogen bonding between complexes results in the formation of two-dimensional hexa-gonal void channels along the c-axis direction with a diameter of 6.7 Å. The monoclinic (P21/c space group) polymorph was reported by Alcock & Flanders [(1987). Acta Cryst. C43, 1480-1483].

High Aspect Ratio Structuring of Glass with Ultrafast Bessel Beams.

Controlling the formation of high aspect ratio void channels inside glass is important for applications like the high-speed dicing of glass. Here, we investigate void formation using ultrafast Bessel beams in the single shot illumination regime. We characterize the morphology of the damages as a function of pulse energy, pulse duration, and position of the beam inside fused silica, Corning Eagle XG, and Corning Gorilla glass. While a large set of parameters allow for void formation inside fused silica, the operating window is much more restricted for Eagle XG and Gorilla glass. The transient formation of a molten layer around voids enables us interpreting the evolution of the morphology with pulse energy and duration.

First Principles Simulations to Understand the Structural and Electrolyte Properties of Idealized Li7.5B10S18X1.5 (X = Cl, Br, I) Li Superionic Conductors Recently Identified in the Experimental Literature

Recently, researchers at the University of Waterloo (Canada) and Oak Ridge National Laboratory (USA) reported a new family of lithium thioborate halide electrolytes which have the composition Li7.5B10S18X1.5 (X = Cl, Br, I) and which are very impressive ionic conductors with \U0001d782=10-3 S/cm measured at room temperature [1]. The researchers identified the crystal structure of the three materials with the monoclinic space group C2/c (No. 15) having highly disordered Li and X sites. In this presentation, we report the results of first-principles simulations of these materials, focusing on understanding the mechanisms of Li ion migration and the overall stability of the materials. By optimizing many possible stoichiometric crystalline configurations, we found ordered ground state realizations of the materials for the three halides X = Cl, Br, and I. Molecular dynamics simulations based on the initially ordered structures at various temperatures show significant Li ion hopping within the void channels of the structures at temperatures as low as T = 600 K. Simulations of possible decomposition products suggest that these electrolytes are also chemically stable. Overall, the preliminary simulations are consistent with the experimental findings of Ref. [1], indicating that these materials are very promising solid electrolytes for possible use in solid state Li ion batteries.------------------------------------------[1] K. Kaup, A. Assoud, J. Liu, and L. F. Nazar, Fast Li-ion conductivity in superadamantanoid lithium thioborate halides, Angewandte Chimie, 133, 7051-7056 (2020) doi.org/10.002/anie.202013339.------------------------------------------Acknowledgements -- This work was supported by NSF grant DMR-1940324. Computations were performed on the Wake Forest University DEAC cluster, a centrally managed resource with support provided in part by the university.