Shape-Persistent Dendrimers.

Dendrimers have a diverse and versatile morphology, frequently consisting of core, linking, and peripheral moieties. Dendrimers with flexible linkers, such as PAMAM, cannot retain the persistent shape of molecules, and this has been widely explored and reviewed previously; nevertheless, dendrimers with stiff linkers can preserve the persistent shape of the dendrimers, which has been reported considerably less. This review thus focuses on addressing shape-persistent dendrimers with rigid linking moieties discovered in recent years, i.e., from 2012 to 2023. Shape-persistent dendrimers with an interstitial gap between the dendritic frames in the solid state may or may not let the intramolecular void space be accessible for guest molecules, which largely depends on whether their peripheral groups are flexible or non-flexible. In this paper, eight articles on shape-persistent dendrimers with a flexible alkyl periphery, which may exhibit mesogenic phases upon thermal treatment, and eight articles on shape-persistent dendrimers with a non-flexible periphery, which may allow external ions, gases, or volatile organic compounds to access the interstitial gaps between dendritic frames, are reviewed.

Dendrimers with Tetraphenylmethane Moiety as a Central Core: Synthesis, a Pore Study and the Adsorption of Volatile Organic Compounds.

Reasonable yields of two dendrimers with central tetraphenylmethane and peripheral 3,5-di-(tert-butanoylamino)benzoylpiperazine moieties are prepared. These dendrimers have a void space in the solid state so they adsorb guest molecules. Their BET values vary, depending on the H-bond interaction between the peripheral moiety and the gas molecules, and the dendritic framework that fabricates the void space is flexible. In the presence of polar gas molecules such as CO2, the BET increases significantly and is about 4-8 times the BET under N2. One dendrimer adsorbs cyanobenzene to a level of 436 mg/g, which, to the authors' best knowledge, is almost equivalent to the highest reported value in the literature.

Void Space versus Surface Functionalization for Proton Conduction in Metal-Organic Frameworks.

Void space and functionality of the pore surface are important structural factors for proton-conductive metal-organic frameworks (MOFs) impregnated with conducting media. However, no clear study has compared their priority factors, which need to be considered when designing proton-conductive MOFs. Herein, we demonstrate the effects of void space and pore-surface modification on proton conduction in MOFs through the surface-modified isoreticular MOF-74(Ni) series [Ni2 (dobdc or dobpdc), dobdc=2,5-dihydroxy-1,4-benzenedicarboxylate and dobpdc=4,4'-dihydroxy-(1,1'-biphenyl)-3,3'-dicarboxylate]. The MOF with lower porosity with the same surface functionality showed higher proton conductivity than that with higher porosity despite including a smaller amount of conducting medium. Density functional theory calculations suggest that strong hydrogen bonding between molecules of the conducting medium at high porosity is inefficient in inducing high proton conductivity.

Native Void Space for Maximum Volumetric Capacity in Silicon-Based Anodes.

Volumetric energy density is considered a primary factor in developing high-energy batteries. Despite its significance, less efforts have been devoted to its improvement. Silicon-based materials have emerged as next-generation anodes for lithium-ion batteries due to their high specific capacity. However, their volumetric capacities are limited by the volume expansion rate of silicon, which restricts mass loading in the electrodes. To address this challenge, we introduce porous silicon templated from earth-abundant minerals with native internal voids, capable of alleviating volumetric expansion during repeated cycles. In situ transmission electron microscopy analysis allows the precise determination of the expansion rate of silicon, thus presenting an analytical model for finding the optimal content in silicon/graphite composites. The inner pores in silicon reduce problems associated with its expansion and allow higher silicon loading of 42% beyond the conventional limitations of 13-14%. Consequently, the anode designed in this work can deliver a volumetric capacity of 978 mAh cc-1. Thus, suppressing volume expansion with natural abundant template-assisted materials opens new avenues for cost-effective fabrication of high volumetric capacity batteries.

Exploring the Mechanism of Viral Peptide-Induced Membrane Fusion.

Membrane fusion is essential in several cellular processes in the existence of eukaryotic cells such as cellular trafficking, compartmentalization, intercellular communication, sexual reproduction, cell division, and endo- and exocytosis. Membrane fusion proceeds in model membranes as well as biological membranes through the rearrangement of lipids. The stalk hypothesis provides a picture of the general nature of lipid rearrangement based on mechanical properties and phase behavior of water-lipid mesomorphic systems. In spite of extensive research on exploring the mechanism of membrane fusion, a clear molecular understanding of intermediate and pore formation is lacking. In addition, the mechanism by which proteins and peptides reduce the activation energy for stalk and pore formation is not yet clear though there are several propositions on how they catalyze membrane fusion. In this review, we have discussed about various putative functions of fusion peptides by which they reduce activation barrier and thus promote membrane fusion. A careful analysis of the discussed effects of fusion peptides on membranes might open up new possibilities for better understanding of the membrane fusion mechanism.

PCB plug-in solder joint defect detection method based on coordinated attention-guided information fusion.

Printed Circuit Boards (PCBs) are the foundational component of electronic devices, and the detection of PCB defects is essential for ensuring the quality control of electronic products. Aiming at the problem that the existing PCB plug-in solder defect detection algorithms cannot meet the requirements of high precision, low false alarm rate, and high speed at the same time, this paper proposes a method based on spatial convolution pooling and information fusion. Firstly, on the basis of YOLOv3, an attention-guided pyramid structure is used to fuse context information, and multiple convolutions of different size are used to explore richer high-level semantic information; Secondly, a coordinated attention network structure is introduced to calibrate the fused pyramidal feature information, highlighting the important feature channels, and reducing the adverse impact of redundant parameters generated by feature fusion; Finally, the ASPP (Atrous Spatial Pyramid Pooling) structure is implemented in the original Darknet53 backbone feature extraction network to acquire multi-scale feature information of the detection targets. With these improvements, the average detection accuracy of the enhanced network has been elevated from 94.45 to 96.43%. This experiments shows that the improved network is more suitable for PCB plug-in solder defect detection applications.

Application of Polyacrylic Hydrogel in Durability and Reduction of Environmental Impacts of Concrete through ANN.

While adding superabsorbent polymer hydrogel particles to fresh concrete admixtures, they act as internal curing agents that absorb and then release large amounts of water and reduce self-desiccation and volumetric shrinkage of cement that finally result in hardened concrete with increased durability and strength. The entrainment of microscopic air bubbles in the concrete paste can substantially improve the resistance of concrete. When the volume and distribution of entrained air are adequately managed, the microstructure is protected from the pressure produced by freezing water. This study addresses the design and application of hydrogel nanoparticles as internal curing agents in concrete, as well as new findings on crucial hydrogel-ion interactions. When mixed into concrete, hydrogel particles produce their stored water to power the curing reaction, resulting in less volumetric shrinkage and cracking and thereby prolonging the service life of concrete. The mechanical and swelling performance qualities of the hydrogel are very sensitive to multivalent cations found naturally in concrete mixes, such as aluminum and calcium. The interactions between hydrogel nanoparticles and alkaline cementitious mixes are described in this study, while emphasizing how the chemical structure and shape of the hydrogel particles regulate swelling behavior and internal curing efficiency to eliminate voids in the admixture. Moreover, in this study, an artificial neural network (ANN) was utilized to precisely and quickly analyze the test results of the compressive strength and durability of concrete. The addition of multivalent cations reduced swelling capacity and changed swelling kinetics, resulting in fast deswelling behavior and the creation of a mechanically stiff shell in certain hydrogel compositions. Notably, when hydrogel particles were added to a mixture, they reduced shrinkage while encouraged the creation of particular inorganic phases within the void area formerly held by the swelled particle.

The Numerical Analysis of Replenishment of Hydrogel Void Space Concrete Using Hydrogels Containing Nano-Silica Particles through ELM-ANFIS.

Currently, Nano-materials are gaining popularity in the building industry due to their high performance in terms of sustainability and smart functionality. In order to reduce cement production and CO2 emissions, nano-silica (NS) has been frequently utilized as a cement alternative and concrete addition. The influence of Nano-silica-containing hydrogels on the mechanical strength, electrical resistivity, and autogenous shrinkage of cement pastes was investigated. The goal of this study was to identify the main structure-property relationships of water-swollen polymer hydrogel particles used as internal curing agents in cementitious admixtures, as well as to report a unique synthesis process to combine pozzolanic materials with hydrogel particles and determine the replenishment of hydrogel void space. Experiments were designed to measure the absorption capacity and kinetics of hydrogel particles immersed in pure water and cementitious pore solution, as well as to precisely analyze the data derived from the tests using hybridized soft computing models such as Extreme learning machine (ELM) and Adaptive neuro-fuzzy inference system (ANFIS). The models were developed, and the findings were measured using regression indices (RMSE and R2). The findings indicated that combining nano-silica with polymeric hydrogel particles creates a favorable environment for the pozzolanic reaction to occur, and that nano-silica assists in the refilling of hydrogel void space with hydrated cement phases.

Tailoring the Void Space Using Nanoreactors on Carbon Fibers to Confine SnS2 Nanosheets for Ultrastable Lithium/Sodium-Ion Batteries.

Herein, a rational design of SnS2 nanosheets confined into bubble-like carbon nanoreactors anchored on N,S doped carbon nanofibers (SnS2 @C/CNF) is proposed to prepare the self-standing electrodes, which provides tunable void space on carbon fibers for the first time by introducing hollow carbon nanoreactors. The SnS2 @C/CNF provides the stable support with greatly enhanced ion and electron transport, alleviates aggregation and volume expansion of SnS2 nanosheets, and promotes the formation of abundant exposed edges and active sites. The volume balance between SnS2 nanosheets and hollow carbon nanoreactors is reached to accommodate the expansion of SnS2 during cycles by controlling the thickness of SnO2 shells, which achieves the best space utilization. The doping of N,S elements enhances the wettability of the carbon nanofiber matrix to electrolyte and Li ions and further improves the electrical conductivity of the whole electrode. Thus, the SnS2 @C/CNF benefits greatly in structural stability and pseudocapacitive capacity for improved lithium/sodium storage performance. As a result of these improvements, the self-standing SnS2 @C/CNF film electrodes exhibit the highly stable capacity of 964.8 and 767.6 mAh g-1 at 0.2 A g-1 , and excellent capacity retention of 87.4% and 82.4% after 1000 cycles at high current density for lithium-ion batteries and sodium-ion batteries, respectively.

In situ construction of ball-in-ball structured porous vanadium pentoxide intertwined with carbon fibers induces superior electronic/ionic transport dynamics for aqueous zinc-ion batteries.

HYPOTHESIS: Using V2O5 as an aqueous zinc-ion battery (ZIB) cathode has major drawbacks, including inferior electrode/electrolyte contact interfaces, morphological and structural deterioration, and unsatisfactory conductivity. Purposeful construction of ball-in-ball structured V2O5 with porous and void architectures wrapped with carbon fibers is expected to overcome the drawbacks, thus bringing the electrochemical performance of V2O5 into full play. EXPERIMENTS: In situ construction of ball-in-ball structured porous V2O5 wrapped by intertwined carbon fibers (V2O5@void@V2O5@CFs) is implemented through a simple combined hydrothermal and calcination route. A combination of in/ex situ analytical methods and density functional theoretical calculations are performed to clarify the energy storage mechanism of the material for aqueous ZIBs. FINDINGS: The reversible reaction to generate ZnxV2O5·nH2O executes during the zinc ion insertion/extraction procedure in V2O5@void@V2O5@CFs. Benefitting from the synergistic effect of the porous ball-in-ball structure with void space and the wrapped CFs, the material exhibits boosted specific capacity (455 mAh g-1 after 100 cycles and 149 mAh g-1 after 2000 cycles at 4 and 25 A g-1, respectively), cyclic stability, rate ability and energy density (355 Wh kg-1 at 739 W kg-1) when used for aqueous ZIBs due to improved capacitive contribution, fast zinc ion transport dynamics, and enhanced conductivity.

Controlling Void Space in Crumpled Graphene-Encapsulated Silicon Anodes using Sacrificial Polystyrene Nanoparticles.

Silicon anodes have a theoretical capacity of 3590 mAh g-1 (for Li15 Si4 , at room temperature), which is tenfold higher than the graphite anodes used in current Li-ion batteries. This, and silicon's natural abundance, makes it one of the most promising materials for next-generation batteries. Encapsulating silicon nanoparticles (Si NPs) in a crumpled graphene shell by spray drying or spray pyrolysis are promising and scalable methods to produce core-shell structures, which buffer the extreme volume change (>300 vol %) caused by (de)lithiaton of silicon. However, capillary forces cause the graphene-based materials to tightly wrap around Si NP clusters, and there is little control over the void space required to further improve cycle life. Herein, a simple strategy is developed to engineer void-space within the core by incorporating varying amounts of similarly sized polystyrene (PS) nanospheres in the spray drier feed mixture. The PS completely decomposes during thermal reduction of the graphene oxide shell and results in Si cores of varying porosity. The best performance is achieved at a 1 : 1 ratio (PS/Si), leading to high capacities of 1638, 1468, and 1179 mAh g-1 Si+rGO at 0.1, 1, and 4 A g-1 , respectively. Moreover, at 1 A g-1 , the capacity retention is 80.6 % after 200 cycles. At a practical active material loading of 2.4 mg cm-2 , the electrodes achieve an areal capacity of 2.26 mAh cm-2 at 1 A g-1 .

A new approach for quantifying localized bone loss by measuring void spaces.

The application of high resolution peripheral quantitative computed tomography (HR-pQCT) for the study of bone health has provided valuable insight into the role bone microarchitecture has in determining bone strength and fracture risk. However, conventional density and morphological parameters struggle to distinguish whether localized bone loss is present, visible as heterogeneous deterioration in the trabecular network. This is because current HR-pQCT parameters quantify a global average of properties in the cortical or trabecular compartment. This study proposes a new metric we term "void space" that segments volumes of localized deterioration in the trabecular bone network from HR-pQCT scans and quantifies void space as the void space to total volume ratio (VS/TV, %). A simple and fully automated protocol for segmenting and quantifying void space in HR-pQCT scans is presented, along with the assessment of accuracy, precision, and cross-calibration between generations of HR-pQCT systems. Finally, prevalence of void space and the association with standard HR-pQCT parameters is demonstrated using a large population-based cohort (n = 1236). Void space detection was found to be highly reproducible (accuracy >95%, least significant change <1.76% VS/TV) and correlation between scanner generations was strong (R2 = 0.87), although the first generation system struggled to identify small voids. Assessment of void space prevalence in the population-based cohort revealed that void spaces were more common in females than males, prevalence increased with age, and void spaces were typically systemic (occurring at both scan sites rather than only one). A comparison of group-wise differences between participants with and without void space demonstrated that individuals with void spaces had significantly worse trabecular properties for both sexes and at both scan sites. Specifically, the median trabecular bone mineral density, bone volume fraction, and trabecular number were below the 25th percentile of the population, while trabecular separation and inhomogeneity were above the 75th percentile of the population in participants with void spaces. Cortical bone characteristics did not differ between participants with and without void spaces. When the void space region was excluded from morphological analysis so that only the remaining "functional bone" was considered, trabecular properties of participants with void spaces were greatly improved, especially for those who were the greatest outliers. Void space is an intuitive morphological parameter that captures localized deterioration in the trabecular bone network, and has the potential to provide valuable insight into the assessment of bone fragility.

Selenacalix[4]dithienothiophene: Synthesis, Structure, and Complexation of a Cyclic Tetramer of Selenide-Bridging Dithienothiophene.

An efficient cyclization toward a cyclic tetramer of dithienothiophene (DTT) linked by divalent selenium atoms has been developed via palladium-catalyzed coupling reaction of (nBu3 Sn)2 Se. X-ray analysis revealed its highly symmetrical structure had an alternate arrangement of DTT units. There are several Se⋅⋅⋅π interactions forming a supramolecular network leading to large void channel space. The cyclic tetramer possesses moderate electron-donating ability. Furthermore, the cyclic tetramer undergoes complexation with C60 in a 1:2 ratio in the solid state to give a highly symmetrical three-dimensional array of C60 .

A potential Cu/V-organophosphonate platform for tailored void spaces via terpyridine mold casting.

The reaction of appropriate copper and vanadium salts with tetratopic methane tetra-p-phenylphosphonic acid (MTPPA) in the presence of 2,2':6':2''-terpyridine (terpy) yielded the three-dimensional bimetallic copper vanadium phosphonate framework [{Cu(terpy)}4Cu(VO2)4(MTPPA-H)2]·4H2O (1). Terpy has no net contribution to the three-dimensional structure providing a potential platform for void space formation via mold-casting. The structure was characterized by single-crystal X-ray diffraction and thermogravimetric analysis (TGA). Magnetic measurements were performed using a SQUID magnetometer. The crystal structure of the methanol solvate of the free ligand, MTPPA·MeOH, was analysed using Hirshfeld surfaces and fingerprint plots.

Heterogeneous Double-Shelled Constructed Fe3O4 Yolk-Shell Magnetite Nanoboxes with Superior Lithium Storage Performances.

Among the numerous candidate materials for lithium ion batteries, ferroferric oxide (Fe3O4) has been extensively concerned as a prospective anode material because of its high theoretical specific capacity, abundant resources, low cost, and nontoxicity. Here, we designed and fabricated a unique yolk-shell construction by generating heterogeneous double-shelled SnO2 and nitrogen-doped carbon on Fe3O4 yolk (denoted as Fe3O4@SnO2@C-N nanoboxes). The yolk-shell structured Fe3O4@SnO2@C-N nanoboxes have the adjustable void space, which permits the free expansion of Fe3O4 yolks without breaking the double shells during the lithiation/delithiation processes, avoiding the structural pulverization. Moreover, the heterogeneous double-shelled SnO2@C-N can meaningfully improve the electronic conductivity and enhance the lithium storage performance. Two metal oxides also show the specific synergistic effect, promoting the electrochemistry reaction. As a result, this yolk-shell structured Fe3O4@SnO2@C-N exhibits high specific capacity (870 mA h g-1 at 0.5 A g-1 after 200 cycles), superior rate capability, and long cycle life (670 mA h g-1 at 3 A g-1 after 600 cycles). This design and construction method can be extended to synthesize other yolk-shell nanostructured anode materials with improved electrochemistry performance.

Tailored Synthesis of Porous TiO2 Nanocubes and Nanoparallelepipeds with Exposed {111} Facets and Mesoscopic Void Space: A Superior Candidate for Efficient Dye-Sensitized Solar Cells.

Anatase TiO2 nanocubes and nanoparallelepipeds, with highly reactive {111} facets exposed, were developed for the first time through a modified one pot hydrothermal method, through the hydrolysis of tetrabutyltitanate in the presence of oleylamine as the morphology-controlling capping-agent and using ammonia/hydrofluoric acid for stabilizing the {111} faceted surfaces. These nanocubes/nanoparallelepipeds were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and high angle annular dark-field scanning TEM (HAADF-STEM). Accordingly, a possible growth mechanism for the nanostructures is elucidated. The morphology, surface area and the pore size distribution of the TiO2 nanostructures can be tuned simply by altering the HF and ammonia dosage in the precursor solution. More importantly, optimization of the reaction system leads to the assembly of highly crystalline, high surface area, {111} faceted anatase TiO2 nanocubes/nanoparallelepipeds to form uniform mesoscopic void space. We report the development of a novel double layered photoanode for dye sensitized solar cells (DSSCs) made of highly crystalline, self-assembled faceted TiO2 nanocrystals as upper layer and commercial titania nanoparticles paste as under layer. The bilayered DSSC made from TiO2 nanostructures with exposed {111} facets as upper layer shows a much higher power conversion efficiency (9.60%), than DSSCs fabricated with commercial (P25) titania powder (4.67%) or with anatase TiO2 nanostructures having exposed {101} facets (7.59%) as the upper layer. The improved performance in bilayered DSSC made from TiO2 nanostructures with exposed {111} facets as the upper layer is attributed to high dye adsorption and fast electron transport dynamics owing to the unique structural features of the {111} facets in TiO2. Electrochemical impedance spectroscopy (EIS) measurements conducted on the cells supported these conclusions, which showed that the bilayered DSSC made from TiO2 nanostructures with exposed {111} facets as the upper layer possessed lower charge transfer resistance, higher electron recombination resistance, longer electron lifetime and higher collector efficiency characteristics, compared to DSSCs fabricated with commercial (P25) titania powder or with anatase TiO2 nanostructures having exposed {101} facets as the upper layer.