Structural Versatility Research Articles

Targeted regulation and optimization of multifunctional phase transition materials by novel void occupancy engineering.

As an innovative form of stimulus-response materials, organic-inorganic hybrid phase transition materials have become a wonderful contender in the field of functional electronic equipment due to their versatile structure, intensive functions and straightforward preparation. However, the targeted regulation and optimization of the electrical/optical response, along with the establishment of regular structure-performance relationships, pose significant challenges in meeting the diverse demands of practical applications over an extended period. Herein, we conducted a systematic investigation into the role of lattice void occupancy in regulating phase transition temperature (Tp) and related optical/electrical bistability. By taking hybrid material [TMEA][Cd(SCN)3] featuring a flexible ammonium cation [TMEA]+ (TMEA = ethyltrimethylammonium) as the prototype, we successfully synthesized three phase transition materials, namely [DEDMA][Cd(SCN)3], [TEMA][Cd(SCN)3] and [TEA][Cd(SCN)3] (DEDMA = diethyldimethylammonium, TEMA = triethylmethylammonium, and TEA = tetraethylammonium), and the excellent regulation of the physical properties of these compounds was achieved through subtle engineering of void occupancy. More strikingly, [TEA][Cd(SCN)3] exhibits remarkable bistable properties in terms of dielectric and nonlinear optical responses (with second-harmonic generation intensity reaching 2.5 times that of KDP). This work provides a feasible avenue to reasonably customise organic-inorganic hybrid phase transition materials and finely adjust their intriguing functionalities.

Reconstruction of Adaptive Leaky Integrate-and-Fire Neuron to Enhance the Spiking Neural Networks Performance by Establishing Complex Dynamics.

Since digital spiking signals can carry rich information and propagate with low computational consumption, spiking neural networks (SNNs) have received great attention from neuroscientists and are regarded as the future development object of neural networks. However, generating the appropriate spiking signals remains challenging, which is related to the dynamics property of neurons. Most existing studies imitate the biological neurons based on the correlation of synaptic input and output, but these models have only one time constant, thus ignoring the structural differentiation and versatility in biological neurons. In this article, we propose the reconstruction of adaptive leaky integrate-and-fire (R-ALIF) neuron to perform complex behaviors similar to real neurons. First, a synaptic cleft time constant is introduced into the membrane voltage charging equation to distinguish the leakage degree between the neuron membrane and the synaptic cleft, which can expand the representation space of spiking neurons to facilitate SNNs to obtain better information expression way. Second, R-ALIF constructs a voltage threshold adjustment equation to balance the firing rate of output signals. Third, three time constants are transformed into learnable parameters, enabling the adaptive adjustment of dynamics equation and enhancing the information expression ability of SNNs. Fourth, the computational graph of R-ALIF is optimized to improve the performance of SNNs. Moreover, we adopt a temporal dropout (TemDrop) method to solve the overfitting problem in SNNs and propose a data augmentation method for neuromorphic datasets. Finally, we evaluate our method on CIFAR10-DVS, ASL-DVS, and CIFAR-100, and achieve top1 accuracy of 81.0% , 99.8% , and 67.83% , respectively, with few time steps. We believe that our method will further promote the development of SNNs trained by spatiotemporal backpropagation (STBP).

3D ceramic structure fabrication by Stereolithography and physicochemical characterization

In this study, a methodology for 3D printing of Silica (SiO2) structures for potential gas separation applications (either as membranes or as substrates for selective layers deposition) utilizing Stereolithography (SLA) is presented. The porosity, morphology and crystallinity of the 3D printed samples structure were optimized by the parametric study of the calcination profile of the printed ceramic SiO2 resin; the printed material was calcined at 450, 600 and 1250 °C by different residence times at different temperature steps. The microstructure of the 3D printed samples was characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Structural characterization (crystallinity and average crystal size) was performed by X-Ray Diffraction (XRD). The porosity and the specific surface area of the 3D printed samples were determined through the Brunauer–Emmett–Teller (BET) technique, which revealed that the surface area was gradually increased by increasing final calcination temperature. Permeability tests with flat sheet printed samples were performed in a constant pressure (isobaric) gas permeation system to quantify pure gases’ (e.g., CO2, N2, O2, Ar) permeances. Permselectivities of binary gaseous mixtures were obtained for printed samples calcined under different temperature profiles. The outcomes open new opportunities in 3D printing of versatile ceramic structures which can be exploited either as substrates for gas separation ceramic membranes or as membrane contactors for gas–liquid applications.

Multivariate metal-organic frameworks generated through post-synthetic modification: impact and future directions.

Reticular chemistry has proven to be invaluable over time, thanks to the structural versatility, and tailored porosity observed in structures like metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and metal-organic polyhedra (MOPs). Despite the wide array of ligands and metals available for synthesizing MOFs, they are still somewhat constrained by the reliance on de novo conditions and the focus on generating MOFs with single ligand and metal. To surpass these limitations, researchers have established strategies to generate multivariate (MTV) MOF structures incorporating more than one ligand/metal into the crystal lattice. MTV-MOFs have demonstrated enhanced properties by virtue of the additional functionalities incorporated within their structures. One approach to developing MTV-MOFs is through post-synthetic modification (PSM), where new functionalities are introduced after the initial synthesis, thereby achieving the enhanced properties of MTV-MOFs even in cases where the new functionalities are incompatible with MOF synthesis.

Hybrid exosomes, exosome-like nanovesicles and engineered exosomes for therapeutic applications.

Exosomes are endosome-derived nanovesicles involved in cellular communication. They are natural nanocarriers secreted by various cells, making them suitable candidates for diverse drug delivery and therapeutic applications from a material standpoint. They have a phospholipid bilayer decorated with functional molecules and an enclosed parental matrix, which has attracted interest in developing designer/hybrid engineered exosome nanocarriers. The structural versatility of exosomes allows the modification of their original configuration using various methods, including genetic engineering, chemical procedures, physical techniques, and microfluidic technology, to load exosomes with additional cargo for expanded biomedical applications. Exosomes show enormous potential for overcoming the limitations of conventional nanoparticle-based techniques in targeted therapy. This review highlights the exosome sources, characteristics, state of the art in the field of hybrid exosomes, exosome-like nanovesicles and engineered exosomes as potential cargo delivery vehicles for therapeutic applications.

Polyoxometalates immobilized on MIL-100 (Fe) as an emerging platform for eliminating breast cancer tumor cells

Polyoxometalates (POMs) have shown promising antitumor activities attributed to their virtue of incomparable structural versatility and interesting redox properties. However, the clinical application of POM drugs is limited by their poor stability and low anticancer specificity. To overcome these shortcomings, a multifunctional platform based on POMs (the tetrabutylammonium salts of [PW12O40]3−, [V10O28H3]3− and [Mo6O19]2−) and MIL-100 (Fe) was successfully developed for combined chemical and chemodynamic therapy, ultimately inducing cancer cell apoptosis. The prepared POMs@MIL-100 (Fe) composites showed great efficiency in killing MCF-7 and 4T1 cells while with a low toxicity to normal MCF-10A and C2C12 cells.

Switchable metallacycles and metallacages.

Two-dimensional metallacycles and three-dimensional metallacages constructed by coordination-driven self-assembly have attracted much attention because they exhibit unique structures and properties and are highly efficient to synthesize. Introduction of switching into supramolecular chemistry systems is a popular strategy, as switching can endow systems with reversible features that are triggered by different stimuli. Through this strategy, novel switchable metallacycles and metallacages were generated, which can be reversibly switched into different stable states with distinct characteristics by external stimuli. Switchable metallacycles and metallacages exhibit versatile structures and reversible properties and are inherently dynamic and respond to artificial signals; thus, these structures have many promising applications in a wide range of fields, such as drug delivery, data processing, pollutant removal, switchable catalysis, smart functional materials, etc. This review focuses on the design of switchable metallacycles and metallacages, their switching behaviours and mechanisms triggered by external stimuli, and the corresponding structural changes and resultant properties and functions.

Tidying up the conformational ensemble of a disordered peptide by computational prediction of spectroscopic fingerprints.

The most advanced structure prediction methods are powerless in exploring the conformational ensemble of disordered peptides and proteins and for this reason the "protein folding problem" remains unsolved. We present a novel methodology that enables the accurate prediction of spectroscopic fingerprints (circular dichroism, infrared, Raman, and Raman optical activity), and by this allows for "tidying up" the conformational ensembles of disordered peptides and disordered regions in proteins. This concept is elaborated for and applied to a dodecapeptide, whose spectroscopic fingerprint is measured and theoretically predicted by means of enhanced-sampling molecular dynamics coupled with quantum mechanical calculations. Following this approach, we demonstrate that peptides lacking a clear propensity for ordered secondary-structure motifs are not randomly, but only conditionally disordered. This means that their conformational landscape, or phase-space, can be well represented by a basis-set of conformers including about 10 to 100 structures. The implications of this finding have profound consequences both for the interpretation of experimental electronic and vibrational spectral features of peptides in solution and for the theoretical prediction of these features using accurate and computationally expensive techniques. The here-derived methods and conclusions are expected to fundamentally impact the rationalization of so-far elusive structure-spectra relationships for disordered peptides and proteins, towards improved and versatile structure prediction methods.

Progress and perspectives on two-dimensional silicon anodes for lithium-ion batteries

Silicon (Si) anodes with extremely high theoretical capacities are considered indispensable for next-generation high-energy lithium-ion batteries (LIBs). However, several intractable problems, including pulverization, poor electrical contact, and continuous side reactions caused by the large volume change of Si during lithiation/delithiation, lead to a short cycle life and poor rate capability, thus hindering the commercial use of Si anodes in LIBs. Two-dimensional (2D) Si with a unique graphene-like structure has a short ion diffusion pathway, small volume change during lithiation, and efficient redox site utilization, making it more promising than bulk Si or Si with other versatile structures for use in LIBs. Theoretical analysis demonstrated that the low energy barrier on the surface of 2D Si accelerates the transport of Li + . However, the issues surrounding 2D Si, including the tedious and user-unfriendly synthesis, ease of restacking, and atmospheric sensitivity, limit its practical applications, which are discussed in this review. Furthermore, possible solutions to these remaining challenges and new directions are provided, with the aim of designing practical and high-performance 2D Si anodes for next-generation LIBs.

SiC Takviyeli Cu-Al-Ni Kompozitlerinin Üretiminde Toz Metalurjisi Yönteminin Kullanımı ve Üretim Sonucunun Karakterizasyonu

Powder metallurgy (PM) is an important production route of alloys and is also important in terms of its properties and economy. This method is suitable for the production of complex and versatile shapes and structures. In this study, it was tried to improve the microstructure and mechanical properties of CuAlNi and CuAlNi-SiC alloys sintered at constant pressing and constant temperature. Composite samples were manufactured by the PM method by supplementing the CuAlNi powder mixture with SiC powders at different weight ratios (2.5%, 5, 7.5 and 10%) at the micron level. Scanning electron microscope (SEM) and optical microscope were used to determine the microstructures of the manufatured samples, and X-Ray Fluorescence (XRF) and X-Ray Diffraction method (XRD) analyzes were used to determine the phases formed in their internal structures. Micro hardness (HV5) was taken to determine the hardness effect. According to the micro structure results, SiC particles were homogeneously dispersed in the structure. Depending on the increasing SiC reinforcement, an increase in hardness values was observed.

A cyclopolymer incorporating tetraphenylethene groups in its cyclic repeating units

Although incorporating AIEgens in versatile polymer topological structures is of high interest, cyclopolymers incorporating AIEgens have rarely been reported yet. In this work, a cyclopolymer incorporating tetraphenylethene groups in its cyclic repeating units (pTPE-dMMA) is synthesized in comparison with a linear polymer with tetraphenylethene pendant side groups (pTPE-MMA). The PLQY of pTPE-dMMA in the solid state is 50.35%, higher than that of pTPE-MMA (32.06%) in the solid state. The AIE behaviors of both pTPE-dMMA and pTPE-MMA in solutions are investigated. Because of the ring-constraint, the PL color of AIE cyclopolymer is not dependent on aggregation, while the PL intensity increases as the increased cyclopolymer concentration or aggregation. Even in an ultra-dilute solution (0.002 mg/mL), pTPE-dMMA exhibits significant AIE performance as the water fraction is increased. The enhanced AIE properties of pTPE-dMMA are ascribed to the ring constraint in the side groups and dense intra-/inter-molecular stacking. This work is useful not only for the designing novel AIE materials or fluorescent dyes, but also for understanding the structure–property–function relationships of a cyclopolymer.

A secretory system for extracellular production of spider neurotoxin huwentoxin-I in Escherichia coli

Due to their advantages in structural stability and versatility, cysteine-rich peptides, which are secreted from the venom glands of venomous animals, constitute a naturally occurring pharmaceutical arsenal. However, the correct folding of disulfide bonds is a challenging task in the prokaryotic expression system like Escherichia coli due to the reducing environment. Here, a secretory expression plasmid pSE-G1M5-SUMO-HWTX-I for the spider neurotoxin huwentoxin-I (HWTX-I) with three disulfides as a model of cysteine-rich peptides was constructed. By utilizing the signal peptide G1M5, the fusion protein 6 × His-SUMO-HWTX-I was successfully secreted into extracellular medium of BL21(DE3). After enrichment using cation-exchange chromatography and purification utilizing the Ni-NTA column, 6 × His-SUMO-HWTX-I was digested via Ulp1 kinase to release recombinant HWTX-I (rHWTX-I), which was further purified utilizing RP-HPLC. Finally, both impurities with low and high molecular weights were completely removed. The molecular mass of rHWTX-I was identified as being 3750.8 Da, which was identical to natural HWTX-I with three disulfide bridges. Furthermore, by utilizing whole-cell patch clamp, the sodium currents of hNav1.7 could be inhibited by rHWTX-I and the IC50 value was 419 nmol/L.

Engineering quantum states and electronic landscapes through surface molecular nanoarchitectures

Surfaces are at the frontier of every known solid. They provide versatile supports for functional nanostructures and mediate essential physicochemical processes. Being intimately related with 2D materials, interfaces and atomically thin films often feature distinct electronic states with respect to the bulk, which are key for many relevant properties, such as catalytic activity, interfacial charge-transfer, or crystal growth mechanisms. Of particular interest is reducing the surface electrons' dimensionality and spread with atomic precision, to induce novel quantum properties via lateral scattering and confinement. Both atomic manipulation and supramolecular principles provide access to custom-designed molecular superlattices, which tailor the surface electronic landscape and influence fundamental chemical and physical properties at the nanoscale. Herein, we review the confinement of surface state electrons focusing on their interaction with molecule-based scaffolds created by molecular manipulation and self-assembly protocols under ultrahigh vacuum conditions. Starting from the quasi-free 2D electron gas present at the (111)-terminated surface planes of noble metals, we illustrate the enhanced molecule-based structural complexity and versatility compared to simple atoms. We survey low-dimensional confining structures in the form of artificial lattices, molecular nanogratings or quantum dot arrays, which are constructed upon appropriate choice of their building constituents. Whenever the realized (metal-)organic networks exhibit long-range order, modified surface band structures with characteristic features emerge, revealing intriguing physical properties, such as discretization, quantum coupling or energy and effective mass renormalization. Such collective electronic states can be additionally modified by positioning guest species at the voids of open nanoarchitectures [...].

Tunneling magnetoresistance and spin-valley polarization of aperiodic magnetic silicene superlattices

Magnetic silicene superlattices (MSSLs) are versatile structures with spin-valley polarization and tunneling magnetoresistance (TMR) capabilities. However, the oscillating transport properties related to the superlattice periodicity impede stable spin-valley polarization states reachable by reversing the magnetization direction. Here, we show that aperiodicity can be used to improve the spin-valley polarization and TMR by reducing the characteristic conductance oscillations of periodic MSSLs (P-MSSLs). Using the Landauer–Büttiker formalism and the transfer matrix method, we investigate the spin-valley polarization and the TMR of Fibonacci (F-) and Thue–Morse (TM-) MSSLs as typical aperiodic superlattices. Our findings indicate that aperiodic superlattices with higher disorder provide better spin-valley polarization and TMR values. In particular, TM-MSSLs reduce considerably the conductance oscillations giving rise to two well-defined spin-valley polarization states and a better TMR than F- and P-MSSLs. F-MSSLs also improve the spin-valley polarization and TMR, however they depend strongly on the parity of the superlattice generation.

Multifunctional Architectures of Cyclic Dipeptide Copolymers and Composites, and Modulation of Multifaceted Amyloid-β Toxicity.

Alzheimer's disease (AD) is a major neurodegenerative disorder primarily characterized by the β-amyloid (Aβ42) misfolding and aggregation-associated multifaceted amyloid toxicity encompassing oxidative stress, neuronal death, and severe cognitive impairment. Modulation of Aβ42 aggregation via various structurally anisotropic macromolecular systems is considered effective in protecting neuronal cells. In this regard, we have developed a cyclic dipeptide (CDP)-based copolymer (CP) and explored its material and biomedical properties. Owing to the structural versatility, CDP-CP forms solvent-dependent anisotropic architectures ranging from dense fibers and mesosheets to vesicles, which are shown to interact with dyes and nanoparticles and mimic synthetic protocells, providing a conceptually new approach to achieve advanced functional materials with the hierarchical organization. CP upon interaction with gold nanoparticles (GNP) and polyoxometalate (POM) generated faceted architectures (CP-GNP) and the nanocomposite (CP-POM), respectively. CP-GNP and CP-POM have shown remarkable ability to inhibit Aβ42 aggregation, dissolve the preformed aggregates, and scavenge reactive oxygen species (ROS) to ameliorate multifaceted amyloid toxicity. In cellulo studies show that CP-GNP and CP-POM protect neuronal cells from Aβ42-induced toxicity and reduce lipopolysaccharide (LPS)-activated neuroinflammation at sub-micromolar concentration. To our knowledge, this is the first report on the hierarchical organization of CDP-CP into 1D-to-2D architectures and their organic-inorganic hybrid nanocomposites to combat the multifaceted amyloid toxicity.

Recent Advances of Ti/Zr-Substituted Polyoxometalates: From Structural Diversity to Functional Applications.

Polyoxometalates (POMs), a large family of anionic polynuclear metal-oxo clusters, have received considerable research attention due to their structural versatility and diverse physicochemical properties. Lacunary POMs are key building blocks for the syntheses of functional POMs due to their highly active multidentate O-donor sites. In this review, we have addressed the structural diversities of Ti/Zr-substituted POMs based on the polymerization number of POM building blocks and the number of Ti and Zr centers. The synthetic strategies and relevant catalytic applications of some representative Ti/Zr-substituted POMs have been discussed in detail. Finally, the outlook on the future development of this area is also prospected.

Unraveling the roles of single transition metal atom anchored on equivalent stoichiometry graphitic carbon nitride (gC6N6) for carbon dioxide reduction: a density functional theory study

CO2 photoreduction into hydrocarbon fuels is a promising strategy in closing the carbon cycle to realize a sustainable energy economy. Among the many photocatalysts that have been developed thus far, porous graphitic carbon nitride (gC6N6) has emerged as a potential photocatalyst candidate in view of its unique optoelectronic properties, metal-free nature and two-dimensional versatile structure that can be easily modified. In this work, the enhancement of equivalent stoichiometry carbon nitride (gC6N6) through single transition metal atom modification was systematically studied from first principles density functional theory calculations. The formation energy calculations revealed that incorporating single Co, Cu, Ni or Pd atom into gC6N6 is energetically favorable, with the exception of Pt. The computed density of states plot indicates that a greater degree of hybridization of the transition metal atom d-orbitals with the p-orbitals of O atom from CO2 will lead to stronger adsorption interaction. The optical absorption spectra show that Cu, Pd, and Pt promotes greater light absorption by extending the optical absorption to the NIR region. The presence of additional dopant states near the Fermi surface was found to have affected the optical absorption. The band structures of the Co,Cu,Pd,Pt@gC6N6 show bandgap narrowing due to the shifting of conduction band edge closer to the Fermi level. Contrastingly, Ni@gC6N6 exhibits bandgap narrowing through the shifting of the valence band edge to the Fermi level. The band edge positions suggest that anchoring gC6N6 with single Co, Cu, Ni, Pd and Pt atom dopants possesses the capability to reduce CO2 into C1 products. Among all the transition metals studied, Pd@gC6N6 and Cu@gC6N6 are identified as the most promising single-atom photocatalysts for CO2 reduction due to their energetically favorable formation energy, stable CO2 adsorption configuration, narrow bandgap, low charge carrier recombination, extended light absorption range and suitable band edge positions.

Effects of Cl/Br substitution of antimony octahedra on photoluminescence and a new engineering strategy for performance optimization

Organic-inorganic metal halides have garnered extensive attention due to their versatile structures as well as fascinating optical properties, among which especially antimony halides are the focus of recent research. Herein, we design a series of novel zero-dimensional (0D) antimony halides of (C13H14N3)3SbCl6–xBrx (x = 0, 3, 6) with bright and tunable broadband emissions from yellow (576 nm) to orange (600 nm), which are attributed to the triplet self-trapped excitons (STEs) of the six-coordinated [SbX6]3– (X = Cl− or Br−) units. The role of halogens on their specific 3P1→1S0 transition is determined, wherein Cl/Br transmutation reveals a common law modulating photoluminescence behaviors. Furthermore, a new two-step compound technology is innovatively developed for performance optimization, enabling by incorporating the pristine antimony halides into polymethyl methacrylate (PMMA) with high transparency and strong moisture resistance. The composites (C13H14N3)3SbCl6–xBrx/PMMA (x = 0, 3, 6) were fabricated through a demanding technology that significantly improve the processability and water stability of antimony halides while maintaining high photoluminescence quantum yields. This work not only proposes a method for halogen substitutions to tune emission, but also opens up a feasible research avenue for performance optimization in the multifunctional luminescence materials.

The Progress of Metal-Organic Framework for Boosting CO2 Conversion

With the rapid development of modern society, environmental problems, including excessive amounts of CO2 released in the atmosphere, are becoming more and more serious. It is necessary to develop new materials and technologies to reduce pollution. Among them, metal–organic frameworks (MOFs) have shown potential for application in the area of catalysis due to their ultra-high specific surface area, structural versatility, and designability as well as ease of modification and post-synthesis. Herein, we summarize recent research advances by use of MOFs for boosting CO2 conversion. Furthermore, challenges and possible research directions related to further exploration are also discussed.

Washability and abrasion resistance of illuminative knitted e-textiles with POFs and silver-coated conductive yarns

For the integration of conductive yarns in e-textiles, knitting offers structural versatility and malleability for wider product applications in the contexts of wearables and interiors. To enable mass adoption of conductive materials, it is imperative for users to be able to launder these materials as part of product maintenance. Interactive textiles knitted from polymeric optical fibres (POFs) and silver-coated conductive yarns are able to illuminate and change colours via integrated touch sensor systems. Current research only focuses on the washability and abrasion resistance of conductive yarns solely and not both POF and conductive yarn within the same fabric structure. This study is novel as it investigates the washability and abrasion resistance of POF and silver-coated conductive yarn integrated knitted textiles with different loop structures and the impact to their illuminative function. POFs were knitted within the same fabric structure by the inlay method using a 7-gauge industrial hand-operated flatbed knitting machine. This study examined how washing and abrasion affect POFs and silver-coated conductive yarn in five different knit structures, and the illuminative function of the knitted textiles. Washing and abrasion affected the resistance of conductive yarns. Scratches and bent POFs were observed after 20 gentle washing cycles. However, washing had minimal impact on the illuminative function of the knitted e-textiles examined in this study. The experiments provide evidence that e-textiles knitted with POFs and conductive yarns in the same fabric structure withstand washing and abrasion and thus have the potential for mass market adoption in fashion and interior applications.