One-dimensional sp3 carbon nanothreads derived from polycyclic aromatic hydrocarbon (PAH) molecules are proposed and investigated using ab-initio Density Functional Theory calculations and classical ...Molecular Dynamics simulations. These differ from nanothreads synthesized from benzene with respect to their diameter and surface morphology, due to variations in size and atomic structure of the precursor molecules. A series of possible atomic configurations analogous to those of conventional carbon nanothreads are proposed, and their stability and mechanical properties are evaluated. The PAH-based DNTs are as strong as conventional nanothreads under tensile strain, exhibiting higher 1D ultimate strength and bending modulus due to their larger diameters. Possible reaction pathways toward formation of naphthalene-derived nanothreads are investigated, indicating the feasibility of synthesizing such materials, which are potential candidates for use in reinforced nanocomposites, nanofibers, sensors and other applications.
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In this study, we propose two new 2D phosphorene allotropes, ϕ-P and σ-P, and use density functional theory calculations to explore their structural, electronic, and mechanical properties. The atomic ...structure of ϕ-P is derived from phagraphene, a 2D carbon allotrope recently discovered using evolutionary algorithms. The ϕ-P phase is converted into σ-P by a pair of Stone-Wales-like transformations, and both are thermally and mechanically stable, similarly to other predicted phosphorene allotropes. Nudged elastic band calculations show that the two materials can be interconverted by application of uniaxial strain under specific conditions. These materials are semiconductors, with band gaps controlled by strain and stacking of layers, and the corresponding bulk phases are either metallic or have a small band gap. The charge carrier mobilities and mechanical properties under uniaxial tensile strain are highly anisotropic because of the structural features of these new phases. The ϕ-P and σ-P allotropes are valuable additions to the phosphorene family because of their ability of being interconverted by mechanical deformation, enabling dynamic control of morphology and physical properties of the material and of the preferential direction for charge transport, a feature that can be explored toward the design of novel applications in nanoscale electronics.
Carbon nanothreads (NTs) are ultrathin materials synthesized by solid-state reaction of crystalline benzene or pyridine under high pressure. Recent experimental studies show that the sp2–sp3 ...conversion in C–C or C–N bonds toward NT formation is not always complete, typically resulting in samples constituted by a mixture of both partially and fully saturated structures. The objective of this study is to use density functional theory calculations to compute the mechanical and electronic properties of partially saturated carbon and carbon nitride nanothreads and analyze how they differ from those of conventional fully saturated NTs. The results show that partially saturated NTs have lower ideal strengths and stiffness compared to their fully saturated versions, but they are still remarkably strong. The electronic behavior varies from semiconducting to insulating, with band gaps in the range ∼1.8–4.0 eV, while fully saturated NTs usually have wider gaps (>4.0 eV). These results show that partially saturated nanothreads can be used for the same applications previously suggested for fully saturated NTs on the basis of their outstanding mechanical strength, and novel applications may be envisioned due to their wider range of possible band gaps.
Carbon nanothreads are one-dimensional materials obtained by controlled compression of aromatic molecules. Benzene and other six-membered ring molecules are normally used as precursors, but recent ...experiments have shown that carbon nanothreads can also be synthesized from five-membered ring heterocyclic compounds such as thiophene and furan, with an improved control of the structure of the final material and potentially easier scalability. In this work we use Density Functional Theory calculations to unveil the structural, electronic and mechanical properties of carbon nanothreads derived not only from thiophene and furan, but also from pyrrole, aiming to encourage experimental efforts towards the synthesis of equivalent 1D materials. Our results show that these new structures are remarkably stable when compared to similar nanothreads derived from benzene and pyridine. The presence of heteroatoms may lead to significant variations on the electronic band gap of these materials compared to conventional nanothreads, without compromising their mechanical properties. These findings suggest that nanothreads derived from five-membered rings are suitable for the same applications proposed for conventional NTs and potential candidates for new ones.
Structural, mechanical and electronic properties of carbon nanothreads derived from five-membered ring heterocyclic compounds are presented and discussed, demonstrating their enhanced stability and promising set of features.
Structural design of 2D conjugated porous organic polymer films (2D CPOPs), by tuning linkage chemistries and pore sizes, provides great adaptability for various applications, including membrane ...separation. Here, four free-standing 2D CPOP films of imine- or hydrazone-linked polymers (ILP/HLP) in combination with benzene (B-ILP/HLP) and triphenylbenzene (TPB-ILP/HLP) aromatic cores are synthesized. The anisotropic disordered films, composed of polymeric layered structures, can be exfoliated into ultrathin 2D-nanosheets with layer-dependent electrical properties. The bulk CPOP films exhibit structure-dependent optical properties, triboelectric nanogenerator output, and robust mechanical properties, rivaling previously reported 2D polymers and porous materials. The exfoliation energies of the 2D CPOPs and their mechanical behavior at the molecular level are investigated using density function theory (DFT) and molecular dynamics (MD) simulations, respectively. Exploiting the structural tunability, the comparative organic solvent nanofiltration (OSN) performance of six membranes having different pore sizes and linkages to yield valuable trends in molecular weight selectivity is investigated. Interestingly, the OSN performances follow the predicted transport modeling values based on theoretical pore size calculations, signifying the existence of permanent porosity in these materials. The membranes exhibit excellent stability in organic solvents at high pressures devoid of any structural deformations, revealing their potential in practical OSN applications.
The interface between two-dimensional (2D) materials and soft, stretchable polymeric substrates is a governing criterion in proposed 2D materials-based flexible devices. This interface is dominated ...by weak van der Waals forces and there is a large mismatch in elastic constants between the contact materials. Under dynamic loading, slippage, and decoupling of the 2D material is observed, which then leads to extensive damage propagation in the 2D lattice. Herein, graphene is functionalized through mild and controlled defect engineering for a fivefold increase in adhesion at the graphene-polymer interface. Adhesion is characterized experimentally using buckling-based metrology, while molecular dynamics simulations reveal the role of individual defects in the context of adhesion. Under in situ cyclic loading, the increased adhesion inhibits damage initiation and interfacial fatigue propagation within graphene. This work offers insight into achieving dynamically reliable and robust 2D material-polymer contacts, which can facilitate the development of 2D materials-based flexible devices.
The requirement of concentrated carbon dioxide (CO2) feedstock significantly limits the economic feasibility of electrochemical CO2 reduction (eCO2R) which often involves multiple intermediate ...processes, including CO2 capture, energy‐intensive regeneration, compression, and transportation. Herein, a bifunctional gas diffusion electrode (BGDE) for separation and eCO2R from a low‐concentration CO2 stream is reported. The BGDE is demonstrated for the selective production of ethylene (C2H4) by combining high‐density‐polyethylene‐derived porous carbon (HPC) as a physisorbent with polycrystalline copper as a conversion catalyst. The BGDE shows substantial tolerance to 10 vol% CO2 exhibiting a Faradaic efficiency of ≈45% toward C2H4 at a current density of 80 mA cm−2, outperforming previous reports that utilized such partial pressure (PCO2 = 0.1 atm and above) and unaltered polycrystalline copper. Molecular dynamics simulation and mixed gas permeability assessment reveal that such selective performance is ensured by high CO2 uptake of the microporous HPC as well as continuous desorption owing to the molecular diffusion and concentration gradient created by the binary flow of CO2 and nitrogen (CO2|N2) within the sorbent boundary. Based on detailed techno‐economic analysis, it is concluded that this in situ process can be economically compelling by precluding the C2H4 production cost associated with the energy‐intensive intermediate steps of the conventional decoupled process.
A bifunctional gas diffusion electrode is reported for integrated CO2 separation and electrochemical conversion to ethylene from low concentration CO2 stream (10 vol%), bypassing the prerequisite of energy‐intensive incumbent CO2 capture and regeneration, compression, and transportation steps.
The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike ...nanostructures of SrTiO3 have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO3, which is fundamental to the synthesis of perovskite-type materials with tailored properties.
The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike ...nanostructures of SrTiO
have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO
, which is fundamental to the synthesis of perovskite-type materials with tailored properties.
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