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Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties.

The recent expansion of multidrug-resistant (MDR) pathogens poses significant challenges in treating healthcare-associated infections. Although antibacterial resistance occurs by numerous mechanisms, active efflux of the drugs is a critical concern. A single species of efflux pump can produce a simultaneous resistance to several drugs. One of the best-studied efflux pumps is the TtgABC: a tripartite resistance-nodulation-division (RND) efflux pump implicated in the intrinsic antibiotic resistance in Pseudomonas putida DOT-T1E. The expression of the TtgABC gene is down-regulated by the HTH-type transcriptional repressor TtgR. In this context, by employing quantum chemistry methods based on the Density Functional Theory (DFT) within the Molecular Fragmentation with Conjugate Caps (MFCC) approach, we investigate the coupling profiles of the transcriptional regulator TtgR in complex with quercetin (QUE), a natural polyphenolic flavonoid, tetracycline (TAC), and chloramphenicol (CLM), two broad-spectrum antimicrobial agents. Our quantum biochemical computational results show the: [i] convergence radius, [ii] total binding energy, [iii] relevance (energetically) of the ligands regions, and [iv] most relevant amino acids residues of the TtgR-QUE/TAC/CLM complexes, pointing out distinctions and similarities among them. These findings improve the understanding of the binding mechanism of effectors and facilitate the development of new chemicals targeting TtgR, helping in the battle against the rise of resistance to antimicrobial drugs. These advances are crucial in the ongoing fight against rising antimicrobial drug resistance, providing hope for a future where healthcare-associated infections can be more beneficially treated.

Research into nanostructured materials frequently relates to pure substances. This contrasts with industrial applications, where chemical doping or alloying is often used to enhance the electrical or mechanical properties of materials 1 . However, the controlled preparation of doped nanomaterials has been much more difficult than expected because the increased surface-area-to-volume ratio can, for instance, lead to the expulsion of impurities (self-purification) 2 . For nanostructured alloys, the influence of growth methods and the atomic structure on self-purification is still open to investigation 2 , 3 . Here, we explore, experimentally and with molecular dynamics simulations, to what extent alloying persists in the limit that a binary metal is mechanically stretched to a linear chain of atoms. Our results reveal a gradual evolution of the arrangement of the different atomic elements in the narrowest region of the chain, where impurities may be expelled to the surface or enclosed during elongation.

Understanding the mechanical properties of nanoscale systems requires a range of measurement techniques and theoretical approaches to gather the relevant physical and chemical information. The arrangements of atoms in nanostructures and macroscopic matter can be different, principally due to the role of surface energy, but the interplay between atomic and electronic structure in association with applied mechanical stress can also lead to surprising differences. For example, metastable structures such as suspended chains of atoms 1 , 2 , 3 and helical wires 4 , 5 have been produced by stretching metal junctions. Here, we report the spontaneous formation of the smallest possible metal nanotube with a square cross-section during the elongation of silver nanocontacts. Ab initio calculations and molecular simulations indicate that the hollow wire forms because this configuration allows the surface energy to be minimized, and also generates a soft structure capable of absorbing a huge tensile deformation. The interplay between atomic and electronic structure, in association with applied mechanical stress, can lead to surprising differences between the atomic arrangements found in nanoscale and macroscopic structures. The spontaneous formation of the smallest possible metal nanotube with a square cross-section has now been observed during the elongation of silver nanocontacts.

Metallic nanowires (NWs) have been the object of intense theoretical and experimental investigations in the last years. In this work we present and review a new methodology we developed to study NW formation from mechanical stretching. This methodology is based on tight-binding molecular dynamics techniques using second-moment approximations. This methodology had been proven to be very effective in the study of NWs, reliably reproducing the main experimentally observed structural features. We have also investigated the problem of determining from what regions the atoms composing the linear atomic chains come. Our results show that ∼90% of these atoms come from outmost external layers.

Crystalline microporous materials are solids formed by interconnected pores of less than 2 nm in size. Typically, they possess large surface areas desirable for versatile applications such as catalysis, gas adsorption, and energy storage. In the present work, we propose a new porphyrin-based 2D nanoporous crystal, named 2D Porphyrazine (2DP), which is formed by topological assembling H\\(_5\\)C\\(_13\\)N\\(_4\\) porphyrins. We have considered its monolayer, bi-layer, and molecular crystal (bulk) arrangements. We carried out DFT calculations to investigate 2DP structural and electronic properties. Results show that 2DP is a very stable structure with a direct bandgap of 0.65 eV and significant optical absorption in the visible range. 2DP exhibited satisfactory affinity to lithium atoms. Simulations also showed the existence of proton transfer between nitrogen atoms. It is the first report on the site-specific hydrogen exchange process in 2D crystals.

Pentahexoctite (PH) is a pure sp\\(^2\\) hybridized planar carbon allotrope whose structure consists of a symmetric combination of pentagons, hexagons, and octagons. The proposed PH structure was shown to be an intrinsically metallic material exhibiting good mechanical and thermal stability. PH nanotubes (PHNTs) have also been proposed, and their properties were obtained from first principles calculations. Here, we carried out fully-atomistic simulations, combining reactive (ReaxFF) molecular dynamics (MD) and density functional theory (DFT) methods, to study the PHNTs elastic properties and fracture patterns. We have investigated the mechanical properties behavior as a function of the tube diameter and temperature regimes. Our results showed that the PHNTs, when subjected to large tensile strains, undergo abrupt structural transitions exhibiting brittle fracture patterns without a plastic regime.

In this work, we investigated the mechanical response and fracture dynamics of boron nitride nanotubes (BNNTs)-peapods under ultrasonic velocity impacts (from 1 km/s to 6 km/s) against a solid target. BNNT-peapods are BNNTs containing an encapsulated linear arrangement of C60 molecules. We carried out fully atomistic reactive (ReaxFF) molecular dynamics simulations. We have considered the case of horizontal and vertical shootings. Depending on the velocity values we observed tube bending, tube fracture, and C60 ejection. One interesting result was tube unzipping with the formation of bilayer nanoribbons 'incrusted' with C60 molecules.

Studies aimed at designing new allotropic forms of carbon have received much attention. Recently, a new 2D graphene-like allotrope named Pentahexoctite was theoretically proposed. Pentahexoctite has a metallic signature, and its structure consists of continuous 5-6-8 rings of carbon atoms with sp2 hybridization. Here, we carried out fully-atomistic computational simulations, combining reactive (ReaxFF) molecular dynamics (MD) and density functional theory (DFT) methods, to study the elastic properties and fracture patterns of Pentahexoctite monolayer. Results revealed a Young's Modulus of 0.74 TPa, smaller than the graphene one (about 1.0 TPa). The Pentahexoctite monolayer, when subjected to a critical strain, goes directly from elastic to completely fractured regimes. This process occurs with no plasticity stages between these two regimes. Importantly, graphene presents a similar fracture process. The elastic properties calculated with both DFT and MD are in good agreement. Keywords: Reactive Molecular Dynamics, DFT, Mechanical Properties, Carbon Allotrope,

Phagraphene (PhaG) is a quasi-planar 2D structure composed of \\(5-6-7\\) ring sequence. We have investigated the structural and mechanical properties of phagraphene nanotubes (PhaNTs) through fully atomistic reactive molecular dynamics (MD) simulations. For comparison purposes, the results were also contrasted to similar carbon nanotubes (CNTs). Results showed that PhaNTs and CNTs present similar brittle fracture mechanisms. The Young's modulus values obtained for PhaNTs were smaller than the corresponding ones for CNTs. Both, PhaNTs and CNTs, present equivalent fracture strains ranging between 15\\%-20\\%. For the ultimate strength values, CNTs present values about 30\\% higher than the corresponding ones for PhaNTs.