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A 2D metastable carbon allotrope, penta-graphene, composed entirely of carbon pentagons and resembling the Cairo pentagonal tiling, is proposed. State-of-the-art theoretical calculations confirm that the new carbon polymorph is not only dynamically and mechanically stable, but also can withstand temperatures as high as 1000 K. Due to its unique atomic configuration, penta-graphene has an unusual negative Poisson’s ratio and ultrahigh ideal strength that can even outperform graphene. Furthermore, unlike graphene that needs to be functionalized for opening a band gap, penta-graphene possesses an intrinsic quasi-direct band gap as large as 3.25 eV, close to that of ZnO and GaN. Equally important, penta-graphene can be exfoliated from T12-carbon. When rolled up, it can form pentagon-based nanotubes which are semiconducting, regardless of their chirality. When stacked in different patterns, stable 3D twin structures of T12-carbon are generated with band gaps even larger than that of T12-carbon. The versatility of penta-graphene and its derivatives are expected to have broad applications in nanoelectronics and nanomechanics. Significance Carbon has many faces––from diamond and graphite to graphene, nanotube, and fullerenes. Whereas hexagons are the primary building blocks of many of these materials, except for C ₂₀ fullerene, carbon structures made exclusively of pentagons are not known. Because many of the exotic properties of carbon are associated with their unique structures, some fundamental questions arise: Is it possible to have materials made exclusively of carbon pentagons and if so will they be stable and have unusual properties? Based on extensive analyses and simulations we show that penta-graphene, composed of only carbon pentagons and resembling Cairo pentagonal tiling, is dynamically, thermally, and mechanically stable. It exhibits negative Poisson's ratio, a large band gap, and an ultrahigh mechanical strength.

MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti ₃C ₂T ₓ MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti ₃C ₂T ₓ/polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10 ⁴ S/m in the case of the Ti ₃C ₂T ₓ/PVA composite film and 2.4 × 10 ⁵ S/m for pure Ti ₃C ₂T ₓ films. The tensile strength of the Ti ₃C ₂T ₓ/PVA composites was significantly enhanced compared with pure Ti ₃C ₂T ₓ or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm ³ for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few. Significance Two-dimensional transition metal carbides (MXenes) offer a quite unique combination of excellent mechanical properties, hydrophilic surfaces, and metallic conductivity. In this first report (to our knowledge) on MXene composites of any kind, we show that adding polymer binders/spacers between atomically thin MXenes layers or reinforcing polymers with MXenes results in composite films that have excellent flexibility, good tensile and compressive strengths, and electrical conductivity that can be adjusted over a wide range. The volumetric capacitances of freestanding Ti ₃C ₂T ₓ MXene and its composite films exceed all previously published results. Owing to their mechanical strength and impressive capacitive performance, these films have the potential to be used for structural energy storage devices, electrochemical actuators, radiofrequency shielding, among other applications.

The effect of the grain size on the mechanical properties of metallic materials has been a topic of significant interest for researchers and industry. For many decades, a relationship defining the mechanical strength proportional to the inverse of the square root of the grain size has been widely accepted despite some reports of deviations from this behavior. Nevertheless, the initial explanations for this relationship, based mainly on the activation of slip systems by dislocation pileups at grain boundaries, have provided essentially no predictive capability. Here, we show that a physically based model for grain boundary sliding predicts, in excellent agreement with experimental data, the flow stress for plastic deformation for a broad range of materials using the fundamental properties of each material over a wide range of grain sizes and testing conditions. This mechanism also successfully predicts the reported enhanced strain rate sensitivity in ultrafine and nanocrystalline materials at different temperatures.

Edible packaging is a thin layer formed on food surface, which can be eaten as an integral part of the food product. While an edible coating is formed as thin layer directly on the food surface for improving shelf life of fruits and vegetables, the edible film is formed as thin layer separately and wrapped on food surface later. The edible films have attracted much interest as it has potential to overcome the problems associated with plastic packaging. However, their film properties are not as good as the conventional packaging materials, such as plastics. The food and beverage industry is showing much interest to incorporate the benefits of nanotechnology. The nanomaterials have unique characteristics (such as, large surface area-to-volume ratio, distinct optical behaviour and high mechanical strength), which, when incorporated with the edible films, could improve the film properties of the edible films. Therefore, the right selection and incorporation of nanomaterials can improve the film properties. Most of the previous review articles on food packaging summarized the research findings of synthetic and/or biodegradable films and coatings. Only few review articles were devoted for edible films and coatings. Among them, very few review articles had discussion about the use of nanotechnology for all kinds of food packaging applications. However, there is no comprehensive review on nanoedible films. The objective of this review article is to cover the recent works on nanoedible films prepared incorporating the nanofillers (such as, nanostarch, nanocellulose, nanochitosan/nanochitin, nanoproteins and nanolipids), the film properties (such as, the mechanical properties, WVP and film colour of some of the recent nanoedible films), and the challenges and opportunities for future research.

Carboxymethyl cellulose (CMC) is one of the most promising cellulose derivatives. Due to its characteristic surface properties, mechanical strength, tunable hydrophilicity, viscous properties, availability and abundance of raw materials, low-cost synthesis process, and likewise many contrasting aspects, it is now widely used in various advanced application fields, for example, food, paper, textile, and pharmaceutical industries, biomedical engineering, wastewater treatment, energy production, and storage energy production, and storage and so on. Many research articles have been reported on CMC, depending on their sources and application fields. Thus, a comprehensive and well-organized review is in great demand that can provide an up-to-date and in-depth review on CMC. Herein, this review aims to provide compact information of the synthesis to the advanced applications of this material in various fields. Finally, this article covers the insights of future CMC research that could guide researchers working in this prominent field.

In 2004, Geim and Novoselov discovered two-dimensional graphene comprised of sp2 carbon atoms. Graphene is a thin layer of carbon consisting of excellent surface area, thermal conductivity, high electron mobility, greater mechanical strength, high electrical conductivity, and current density. Graphene attained significant attention among the research community. The properties and attributes of graphene make this material sufficiently promising to be utilized in different sectors. Based on this, researchers' interest in exploring innovative methods to develop quality graphene for the industrial purpose have increased. Therefore, this review presents a current research development on the synthesis methods of graphene and its composites and their structure and properties. Furthermore, the practical aspects of graphene and its derivatives that are fabricated via these techniques for different graphene-based applications in the development of biosensors, water treatment, solar energy systems, fuel cells, catalysis engineering, food package engineering, and various other applications are also discussed. Based on the literature published over the years, it has been observed that the synthesis approaches, namely liquid-phase exfoliation, chemical vapor deposition (CVD), and oxidative exfoliation reduction, can be commercialized to produce high-quality graphene. Overall, graphene-based nanomaterials have opened glorious opportunities for future applications.

A key molecular link between cells and the extracellular matrix is the binding between fibronectin and integrins α₅β₁ and αvβ₃. However, the roles of these different integrins in establishing adhesion remain unclear. We tested the adhesion strength of fibronectin-integrin-cytoskeleton linkages by applying physiological nanonewton forces to fibronectin-coated magnetic beads bound to cells. We report that the clustering of fibronectin domains within 40 nm led to integrin α₅β₁ recruitment, and increased the ability to sustain force by over six-fold. This force was supported by α₅β₁ integrin clusters. Importantly, we did not detect a role of either integrin αvβ₃ or talin 1 or 2 in maintaining adhesion strength. Instead, these molecules enabled the connection to the cytoskeleton and reinforcement in response to an applied force. Thus, high matrix forces are primarily supported by clustered α₅β₁ integrins, while less stable links to αvβ₃ integrins initiate mechanotransduction, resulting in reinforcement of integrin-cytoskeleton linkages through talin-dependent bonds.

Polymer–clay nanocomposites are the most remarkable nanomaterials of the current decade with broad range of applications, because they attempt a great competence to impart outstanding properties when compared to pure polymers even at a very less percentage of nanofiller inclusion. Montmorillonite, vermiculite, halloysite, sepiolite, laponite, bentonite, and attapulgite are the dominant classes of clay used as reinforcement in polymer–clay nanocomposites. Clay is easily accessible, easily processed, inexpensive, and non-toxic, and clay nanocomposites have seen significant commercial interest due to improvements in processing. Clay nanocomposites show distinctive properties of outstanding thermal stability, enhanced flame retardancy, high dimensional stability, decreased gas permeability, and enhanced anticorrosive and improved mechanical properties. This review reveals the polymer-based nanocomposites reinforced with halloysite nanotubes, for high-performance promising applications. The qualities of the nanofiller can be changed by chemically modifying exterior surface and interior lumen. Chemical alteration of the halloysite nanotube surface, in particular, results in nanoarchitecture with targeted affinity through functionalization of the outer surface and potential for drug transport through functionalization of the nanotube lumen. The various functionalization techniques of altering the nanofillers to allow interaction with polymers are discussed. The significance of filler dispersion in the polymeric matrix is also featured. The consequences of functionalized nanofillers on the microstructure and morphology, mechanical strength, thermal stability, drug encapsulation and sustained release abilities, and flame retardancy as well as barrier properties can be summarized. Subsequently, the challenges, key problems, future prospects, and feasible mechanism for polymeric clay nanocomposites are also reviewed. Graphical Abstract