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Glassy carbon (GC) is usually considered the prototypical super-elastic material, which can almost fully recover its shape after compression of several gigapascals (GPa). In this work, nanoindentation is used to study the mechanical response of GC, which was subjected to a range of high pressures using a diamond anvil cell (DAC). We show that GC starts to lose its elasticity after compression to 6 GPa and becomes clearly mechanically anisotropic after being compressed beyond ∼30 GPa. Molecular dynamics (MD) simulations are used to calculate Young's modulus before and after compression. Through our experimental results and MD simulations, we show that the elasticity of GC is at a minimum around 30 GPa but recovers after compression to higher pressures along the DAC compression axis. [ABSTRACT FROM AUTHOR]

Central nervous system (CNS) injuries and neurodegenerative diseases have markedly poor prognoses and can result in permanent dysfunction due to the general inability of CNS neurons to regenerate. Differentiation of transplanted stem cells has emerged as a therapeutic avenue to regenerate tissue architecture in damaged areas. Electrical stimulation is a promising approach for directing the differentiation outcomes and pattern of outgrowth of transplanted stem cells, however traditional inorganic bio-electrodes can induce adverse effects such as inflammation. This study demonstrates the implementation of two organic thin films, a polymer/reduced graphene oxide nanocomposite (P(rGO)) and PEDOT:PSS, that have favorable properties for implementation as conductive materials for electrical stimulation, as well as an inorganic indium tin oxide (ITO) conductive film. Transcriptomic analysis reveals that electrical stimulation improves neuronal differentiation of SH-SY5Y cells on all three films, with the greatest effect for P(rGO). Unique material- and electrical stimuli-mediated effects are observed, associated with differentiation, cell-substrate adhesion, and translation. The work demonstrates that P(rGO) and PEDOT:PSS are highly promising organic materials for the development of biocompatible, conductive scaffolds that will enhance electrically-aided stem cell therapeutics for CNS injuries and neurodegenerative diseases., (© 2024 The Author(s). Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

Isotopes of heavier gases including carbon ( 13 C/ 14 C), nitrogen ( 13 N), and oxygen ( 18 O) are highly important because they can be substituted for naturally occurring atoms without significantly perturbing the biochemical properties of the radiolabelled parent molecules. These labelled molecules are employed in clinical radiopharmaceuticals, in studies of brain disease and as imaging probes for advanced medical imaging techniques such as positron-emission tomography (PET). Established distillation-based isotope gas separation methods have a separation factor (S) below 1.05 and incur very high operating costs due to high energy consumption and long processing times, highlighting the need for new separation technologies. Here, we show a rapid and highly selective adsorption-based separation of 18 O 2 from 16 O 2 with S above 60 using nanoporous adsorbents operating near the boiling point of methane (112 K), which is accessible through cryogenic liquefied-natural-gas technology. A collective-nuclear-quantum effect difference between the ordered 18 O 2 and 16 O 2 molecular assemblies confined in subnanometer pores can explain the observed equilibrium separation and is applicable to other isotopic gases.

Arterial networks enlarge in response to increase in tissue metabolism to facilitate flow and nutrient delivery. Typically, the transition of a growing artery with a small diameter into a large caliber artery with a sizeable diameter occurs upon the blood flow driven change in number and shape of endothelial cells lining the arterial lumen. Here, using zebrafish embryos and endothelial cell models, we describe an alternative, flow independent model, involving enlargement of arterial endothelial cells, which results in the formation of large diameter arteries. Endothelial enlargement requires the GEF1 domain of the guanine nucleotide exchange factor Trio and activation of Rho-GTPases Rac1 and RhoG in the cell periphery, inducing F-actin cytoskeleton remodeling, myosin based tension at junction regions and focal adhesions. Activation of Trio in developing arteries in vivo involves precise titration of the Vegf signaling strength in the arterial wall, which is controlled by the soluble Vegf receptor Flt1.

The relatively weak London dispersion forces are the only interactions that could cause aggregation between simple aromatic molecules. The use of molecular dynamics and high-level ab initio computer simulations has been used to describe the aggregation and interactions between molecular systems containing benzene, naphthalene and anthracene. Mixtures containing one type of molecule (homogenous) and more than one type of molecule (heterogenous) were considered. Our results indicate that as molecular weight increases so does the temperature at which aggregation will occur. In all simulations, the mechanism of aggregation is through small clusters coalescing into larger clusters. The structural analysis of the molecules within the clusters reveals that benzene will orient itself in T-shaped and parallel displaced configurations. Molecules of anthracene prefer to orient themselves in a similar manner to a bulk crystal with no T-shaped configuration observed. The aggregation of these aromatic molecules is discussed in the context of astrochemistry with particular reference to the dust formation region around stars.

Disordered carbons comprise graphene fragments assembled into three-dimensional networks. It has long been debated whether these networks contain positive curvature, as seen in fullerenes, negative curvature, as proposed for the schwarzite structures, or zero curvature, as in ribbons. We present a mesh-based approach to analyze the topology of a set of nanoporous and glassy carbon models that accurately reproduce experimental properties. Although all three topological elements are present, negatively curved structures dominate. At the atomic level, analysis of local environments shows that sp- and sp^{3}-bonded atoms are associated with line defects and screw dislocations that resolve topological complexities such as termination of free edges and stacking of low curvature regions into ribbons. These results provide insight into the synthesis of porous carbon materials, glassy carbon and the graphitizability of carbon materials.

Two-dimensional graphene has remarkable properties that are revolutionary in many applications. Scrolling monolayer graphene with precise tunability would create further potential for niche applications but this has proved challenging. We have now established the ability to fabricate monolayer graphene scrolls in high yield directly from graphite flakes under non-equilibrium conditions at room temperature in dynamic thin films of liquid. Using conductive atomic force microscopy we demonstrate that the graphene scrolls form highly conducting electrical contacts to highly oriented pyrolytic graphite (HOPG). These highly conducting graphite-graphene contacts are attractive for the fabrication of interconnects in microcircuits and align with the increasing interest in building all sp 2 -carbon circuits. Above a temperature of 450 °C the scrolls unravel into buckled graphene sheets, and this process is understood on a theoretical basis. These findings augur well for new applications, in particular for incorporating the scrolls into miniaturized electronic devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Junctions between carbon nanotubes and flat or curved graphene structures are fascinating for a number of reasons. It has been suggested that such junctions could be used in nanoelectronic devices, or as the basis of three-dimensional carbon materials, with many potential applications. However, there have been few detailed experimental analyses of nanotube-graphene connections. Here we describe junctions between nanotubes and graphene shells in a material produced by passing a current through graphite. Transmission electron micrographs show that the junction angles are not random but fall close to multiples of 30°. We show that connections with these angles are the only ones which are consistent with the symmetry of the hexagonal lattice, and molecular models show that a continuous lattice requires the presence of large carbon rings at the junction. Some of the configurations we propose have not been previously considered, and could be used to construct new kinds of three-dimensional carbon architecture. We also discuss the possible formation mechanism of the junctions.

Carbon nanohorns (sometimes also known as nanocones) are conical carbon nanostructures constructed from an sp(2) carbon sheet. Nanohorns require no metal catalyst in their synthesis, and can be produced in industrial quantities. They provide a realistic and useful alternative to carbon nanotubes, and possibly graphene, in a wide range of applications. They also have their own unique behavior due to their specific conical morphology. However, their research and development has been slowed by several factors, notably during synthesis, they aggregate into spherical clusters ∼100 nm in diameter, blocking functionalization and treatment of individual nanocones. This limitation has recently been overcome with a new approach to separating these "dahlia-like" clusters into individual nanocones. In this review, we describe the structure, synthesis, and topology of carbon nanohorns, and provide a detailed review of nanohorn chemistry.

Lateral slicing of micron length carbon nanotubes (CNTs) is effective on laser irradiation of the materials suspended within dynamic liquid thin films in a microfluidic vortex fluidic device (VFD). The method produces sliced CNTs with minimal defects in the absence of any chemical stabilizers, having broad length distributions centred at ca 190, 160 nm and 171 nm for single, double and multi walled CNTs respectively, as established using atomic force microscopy and supported by small angle neutron scattering solution data. Molecular dynamics simulations on a bent single walled carbon nanotube (SWCNT) with a radius of curvature of order 10 nm results in tearing across the tube upon heating, highlighting the role of shear forces which bend the tube forming strained bonds which are ruptured by the laser irradiation. CNT slicing occurs with the VFD operating in both the confined mode for a finite volume of liquid and continuous flow for scalability purposes.

The breakdown of the diamond lattice is explored by ion implantation and molecular dynamics simulations. We show that lattice breakdown is strain-driven, rather than damage-driven, and that the lattice persists until 16% of the atoms have been removed from their lattice sites. The figure shows the transition between amorphous carbon and diamond, with the interfaces highlighted with dashed lines., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

X-ray photoelectron spectroscopy at 3.5 keV photon energy, in combination with high-resolution transmission electron microscopy, is used to follow the formation of the interface between rhodium and carbon nanotubes. Rh nucleates at defect sites, whether initially present or induced by oxygen-plasma treatment. More uniform Rh cluster dispersion is observed on plasma-treated CNTs. Experimental results are compared to DFT calculations of small Rh clusters on pristine and defective graphene. While Rh interacts as strongly with the carbon as Ti, it is less sensitive to the presence of oxygen, suggesting it as a good candidate for nanotube contacts.

We present a combined theoretical and experimental comparative study of the deposition of five different metals on perfect and defective graphene and multi-walled carbon nanotubes (MWNTs): Ti, Ni, Pd, Pt and Au. Atomistic modelling successfully provides a comprehensive picture of surface binding, diffusion and aggregation properties for these metals, highlighting some fundamental differences in their surface chemical and electronic behaviour. We correlate these theoretical results with experimental TEM images of metal deposited MWCNTs.

We explore early stage oxygen addition to C60 buckminsterfullerene, and compare its oxygenation behavior to that of both pristine and defective metallic carbon nanotubes, using ab initio theoretical modeling. For fullerene oxygen addition up to C60O4, in general oxygenation preferentially occurs at the pentagon-hexagon bonds ([5,6] type addition), leading to open annulene structures, as opposed to the closed [6, 6] epoxide isomers. For carbon nanotubes the preference for annulene structures is significantly more pronounced as all epoxide addition is endothermic. Higher reaction enthalpies are found for oxidation in the proximity of defects as compared to the pristine sidewalls. In most cases higher reaction enthalpies are found for fullerene oxygenation as compared to carbon nanotubes.

The interaction between carbon buckminsterfullerene (C60) and carbon nanohorns (also referred to as nanocones) with different tip angles is investigated theoretically. Attachment of C60 to both the interior and the exterior of the horns are considered. Calculations cover a range of cone angles from flat graphene, through 114 degrees, 84 degrees, 60 degrees, 39 degrees and 20 degrees to fullerene pair interaction. Full DFT/LDA calculations are performed and the influence of dispersion forces are considered independently using a numerical potential. Fullerenes bind weakly to the external nanocone wall with approximately 2.9 angstroms spacing (0.5-0.9 eV binding energy), showing no discernable trend with cone tip angle. Fullerene binding inside cones is significantly stronger (> 3 eV), primarily due to strong dispersion force interactions, with higher (approximately 3.1 angstroms) fullerene-nanohorn spacing. In this case, the binding energy increases with number of pentagons in the tip. In all cases the fullerenes will be freely rotating below liquid nitrogen temperatures. For pristine cones and fullerenes, the fullerenes will experience a driving force towards (away) from the nanohorn tip when inside (outside) the nanohorn.