Nanotube Core Research Articles

Epitaxial pyrolytic carbon coatings templated with defective carbon nanotube cores for structural annealing and tensile property improvement

Epitaxial pyrolytic carbon coatings templated with defective carbon nanotube cores for structural annealing and tensile property improvement

A Facile and Rapid Approach to Lotus‐Seedpod‐Structured Electronic Skin for Monitoring Diverse Physical Stimuli

AbstractAlthough the burgeoning Internet of Things has created soaring demand for electronic skin (e‐skin), a facile and eco‐friendly approach towards the scalable fabrication of the hierarchical active layer for such a system is still limited in the stage of development. Herein a sensing layer with lotus‐seedpod‐like structures is reported that is readily prepared by multi‐melt multi‐injection molding (M3IM). Because of the shear flow and thermodynamic factors in M3IM, silica microspheres in the core layer of the polyethylene/silica composite are inclined to migrate to the interface between the skin layer of ethylene‐α‐octene block copolymer/carbon nanotube composite and core layer, resulting in lotus‐seedpod‐like structures consisting of micro‐pits and asperities formed on the surface of the peeled skin layer. The sensitivity of the fabricated e‐skin is significantly affected by the number of micro‐pits on the lotus‐seedpod‐like structure, which mainly depend on the silica mass fraction in the composites. For instance, the e‐skin made from the composites with 66.67 wt% silica exhibits a sensitivity of 19.87 kPa−1 over a wide linear range of 0.017–11.5 kPa and demonstrates excellent durability and reproducibility, enabling multiple signal detection. This work sheds light on the rapid and scalable fabrication of sensors using a polymer melt processing strategy.

The partially unzipped carbon nanotubes supported molybdenum carbide composite for enchanced hydrogen evolution reaction

The substrate effect of electrocatalyst on the hydrogen evolution reaction (HER) was explored in present work, and the multiwall carbon nanotube (MWCNT) with different unzipped extent was used as the model substrate to support molybdenum carbide nanoparticles. The partially unzipped MWCNT which contained the carbon nanotube core and graphene nanoribbon shells was important for the high HER performance. The final molybdenum carbide/reduced graphene oxide nanoribbon catalyst showed a lower overpotential of 135 mV at 10 mA cm−2 and a small Tafel slope of 59 mV decade−1 in 0.5 M H2SO4.

Isotopic Labelling of Confined Carbyne

AbstractCarbyne is a one‐dimensional allotrope of carbon consisting of a linear chain of carbon atoms bonded to each other with exceptional strength. Its outstanding mechanical, optical, and electronic properties have been theoretically predicted, but its stability has only been achieved when grown encapsulated in the hollow core of carbon nanotubes. One of the advantages of this confinement is that its properties can be controlled by the chain's length and surrounding environment. We investigated an alternative way of gaining control of its properties is using isotope labelling as tuning mechanism. The optimized liquid precursor was first chosen among several options, which can greatly enhance the yield of the confined carbyne. Then isotopic labelled liquid precursor was encapsulated for further synthesis of isotopic labelled confined carbyne. This allowed us to obtain pioneering results on isotope engineered carbyne with around 11.9 % of 13C‐labelling using 13C‐methanol as precursor.

Isotopic Labelling of Confined Carbyne.

Carbyne is a one-dimensional allotrope of carbon consisting of a linear chain of carbon atoms bonded to each other with exceptional strength. Its outstanding mechanical, optical, and electronic properties have been theoretically predicted, but its stability has only been achieved when grown encapsulated in the hollow core of carbon nanotubes. One of the advantages of this confinement is that its properties can be controlled by the chain's length and surrounding environment. We investigated an alternative way of gaining control of its properties is using isotope labelling as tuning mechanism. The optimized liquid precursor was first chosen among several options, which can greatly enhance the yield of the confined carbyne. Then isotopic labelled liquid precursor was encapsulated for further synthesis of isotopic labelled confined carbyne. This allowed us to obtain pioneering results on isotope engineered carbyne with around 11.9 % of 13 C-labelling using 13 C-methanol as precursor.

Designing an Interlayer-Widened MoS2-Packed Nitrogen-Rich Carbon Nanotube Core–Shell Structure for Redox-Mediated Quasi-Solid-State Supercapacitors

Herein, we present a hierarchical structure consisting of an expanded interlayer, which comprises MoS2 dispersed onto and diffused into nitrogen-doped carbon nanotubes (MoS2-CNTPPys), as an electro...

One-Dimensional van der Waals Heterostructures as Efficient Metal-Free Oxygen Electrocatalysts.

Two-dimensional covalent organic frameworks (2D-COFs) may serve as an emerging family of catalysts with well-defined atomic structures. However, the severe stacking of 2D nanosheets and large intrinsic bandgaps significantly impair their catalytic performance. Here, we report coaxial one-dimensional van der Waals heterostructures (1D vdWHs) comprised of a carbon nanotube (CNT) core and a thickness tunable thienothiophene-pyrene COF shell using a solution-based in situ wrapping method. Density functional theory calculations and operando and ex situ spectroscopic analysis indicate that carbon-sulfur regions in thienothiophene groups in the COF serve as an active catalytic site for oxygen reduction and evolution reactions. The coaxial structure enables n-doping from the CNT core to the COF shell, which is controllable by varying COF shell thickness. The charge transfer from CNTs lowers COF's bandgap and work function, which reduces the charge transfer barrier between the active catalytic sites and adsorbed oxygen intermediates, resulting in dramatically enhanced catalytic activity. The 1D vdWHs were applied as a bifunctional oxygen electrocatalyst in rechargeable zinc-air batteries, delivering a high specific capacity of 696 mAh gZn-1 under a high current density of 40 mA cm-2 and excellent cycling stability. The 1D vdWHs based on the coaxial structure of 2D COF wrapped around CNT cores may be further used as versatile building units to create multidimensional vdWHs for exploring fundamental physics and chemistry as well as practical applications in electrochemistry, electronics, photonics, and beyond.

Core–Sheath Fiber‐Based Wearable Strain Sensor with High Stretchability and Sensitivity for Detecting Human Motion

AbstractFiber‐based strain sensors are considered to be an important part of smart wearables due to their flexible performance, lightness, and easily processing into various structures. However, the low sensitivity of fiber‐based strain sensors has limited their real‐life applications for detecting human movements. In this work, a poly(styrene‐butadiene‐styrene) (SBS)/multi‐walled carbon nanotube (MWCNTs) core–sheath fiber (SSCCSF) strain sensor is fabricated via a simple and facile coaxial wet‐spinning method. The cross‐sectional morphology, the mechanical properties, and the electromechanical performance of the SSCCSFs are investigated. Scanning electron microcopy results show that SSCCSFs have a bean‐like cross‐section with SBS as the core and SBS/MWCNTs as the sheath. Electromechanical performance evaluation confirms that the SSCCSF show a high sensitivity in a broad working range (gauge factor = 25832.77 at 41.5% strain) and excellent durability (5000 cycles at 10% strain). Furthermore, the SSCCSF displays outstanding sensing performance for detecting large motions in human movements including hand joint bending (such as knuckles and wrists) and subtle motions in physiological activities, involved in swallowing behavior, breathing, and pulse beat. This study demonstrates the potential application of SSCCSFs for wearable electronics with activity monitoring sensors.

Wettability and confinement size effects on stability of water conveying nanotubes

This study investigates the wettability and confinement size effects on vibration and stability of water conveying nanotubes. We present an accurate assessment of nanotube stability by considering the exact mechanics of the fluid that is confined in the nanotube. Information on the stability of nanotubes in relation to the fluid viscosity, the driving force of the fluid flow, the surface wettability of the nanotube, and the nanotube size is missing in the literature. For the first time, we explore the surface wettability dependence of the nanotube natural frequencies and stability. By means of hybrid continuum-molecular mechanics (HCMM), we determined water viscosity variations inside the nanotube. Nanotubes with different surface wettability varying from super-hydrophobic to super-hydrophilic nanotubes were studied. We demonstrated a multiphase structure of nanoconfined water in nanotubes. Water was seen as vapor at the interface with the nanotube, ice shell in the middle, and liquid water in the nanotube core. The average velocity of water flow in the nanotube was obtained strongly depend on the surface wettability and the confinement size. In addition, we report the natural frequencies of the nanotube as functions of the applied pressure and the nanotube size. Mode divergence and flutter instabilities were observed, and the activation of these instabilities strongly depended on the nanotube surface wettability and size. This work gives important insights into understanding the stability of nanotubes conveying fluids depending on the operating pressures and the wettability and size of confinement. We revealed that hydrophilic nanotubes are generally more stable than hydrophobic nanotubes when conveying fluids.

Stress distribution of a sector of cylindrical sandwich shell with FG-CNT core and piezoelectric face sheets subjected to blast pressure

ABSTRACT A novel layerwise theory along with higher-order shear deformation theory is studied to determine the stress distribution in a three-layer simply supported sector of cylindrical sandwich shell with piezoelectric face sheets and functionally graded carbon nanotube (FG-CNT) core. The out-of-shell displacement of the sandwich shell at each layer is assumed to be a quadratic polynomial function of the radial component in addition to a function of the coordinate components within the shell. The sandwich shell is subjected to the internal blast pressure so that the positive and negative phases of the pressure are considered. The 19 equations of motion have been derived by Hamilton’s principle and Maxwell’s static equations. The results indicate that the thickness, length and opening angle of the cylindrical shell have more effect on the stress distribution. In addition, the type of FG-CNT core has an effect on stress components in terms of time.

Time-depended stress analysis of a sector of the spherical sandwich shell with piezoelectric face sheets and FG-CNT core subjected to blast pressure

A novel Layerwise theory (LT) along with the higher-order shear deformation theory (HSDT) is investigated to determine the stress distribution in a three-layer sector of the spherical sandwich shell with piezoelectric face sheets and functionally graded carbon nanotube (FG-CNT) core. The simply-supported sandwich shell is subjected to the internal blast pressure so that the positive and the negative phases of the pressure are considered. The blast pressure is generated by a 1 Kg TNT hemispherical surface burst detonated. The out-of-shell displacement of the sandwich spherical shell at each layer is assumed to be a quadratic polynomial function of the radial component in addition to a function of the coordinate components within the shell. The nineteen equations of motion are derived by Hamilton's principle and Maxwell's static equations. By solving these nineteen equations, the stress distribution is calculated in the spherical sandwich shell in terms of time.

Nanocable with thick active intermediate layer for stable and high-areal-capacity sodium storage

Developing electrodes cycling stably at high areal mass loadings is critical for sodium ion batteries (SIB) to reach practical applications, but remains challenging due to the larger ionic radius of Na + and generally sluggish electrochemical kinetics in thick electrodes. Consequently, most of the reported SIB electrodes exhibit low mass loadings (<1 mg cm −2 ) and thereby limited areal capacities. Here, we develop a hybrid network structure with orthorhombic Nb 2 O 5 coatings sandwiched between three-dimensional carbon nanotube (CNT) underlayers and outer carbon shells. By thickening Nb 2 O 5 intermediate layers, we can effectively raise the mass loadings of the sponge anodes with the electron and ion transport kinetics well maintained, owing to the highly conductive CNT substrate, porous network and carbon shell-enabled robust nanocable structures. As a result, the sponge anodes exhibit reversible areal capacities of 2.7 mAh cm −2 after 200 cycles at mass loadings up to 16.6 mg cm −2 , exceeding 9 times those of previous Nb 2 O 5 -based structures, and the achieved cycling stability is also among the best of the high-areal-capacity SIB anodes reported so far. Our work shows that thickening intermediate active coatings in rationally designed nanocable structures represents an effective way to promote their areal sodium storage performance for practical use. • Three-dimensional network structured electrode composed of interconnected nanocables. • Nanocable comprises carbon nanotube core, Nb 2 O 5 intermediate layer and carbon shell. • Thickening intermediate layer to raise electrodes mass loadings and areal capacities. • Robust hierarchical structure enables stable cycling performance for sodium storage.

Fabrication of Light‐Weight and Highly Conductive Copper–Carbon Nanotube Core–Shell Fibers Through Interface Design

AbstractMetal‐carbon nanotube (CNT) hybrid fibers are emerging materials for light‐weight conductors that can replace common metallic conductors. One of the main challenges to their development is the poor affinity between CNT and metals. In this work, a new approach for fabrication of CNT/Cu core‐shell fibers is demonstrated that outperforms the commercial Cu wires in terms of specific conductivity, ampacity, and strength. By introducing thiol groups to the surface of CNT fibers, a dense Cu coating with enhanced adhesion is obtained. Consequently, CNT/Cu core‐shell fibers with specific conductivity of 3.6 × 107 S m−1 and tensile strength of 1 GPa, which is almost five times higher than commercial Cu wires, are produced. Due to strong interaction of thiol functional groups and Cu atoms, the fiber can preserve its integrity and conductivity after &gt;500 fatigue bending cycles. Furthermore, the ampacity of the composite wire reaches to 1.04 × 105 A cm−2, which corresponds to a specific ampacity two times higher than that of commercial Cu wires. The interfacial design between Cu and CNT presented here is versatile and can be implemented in other processing and deposition methods.

Performance optimization of a nanotube core–shell semi-junctionless p+p+n heterojunction tunnel field effect transistor

In this paper, the electrical characteristics of a heterojunction nanotube semi-junctionless tunnel field effect transistor (NSJTFET) with germanium in the source and GaAs in the drain channel regions are thoroughly investigated. The proposed n-channel NSJTFET is a p+p+n structure, employing internal core gate and external shell gate. The device under study provides a superior gate control over the channel by amplifying the band-to-band tunneling rate. The results imply that an increased on-state drive current of nearly 100 times as compared to the conventional nanowire tunnel field effect transistor (TFET) is achieved. In addition, the steep slope NSJTFET structure exhibits subthreshold swing of approximately 7.6 mV/dec in comparison with 25 mV/dec for the conventional TFET. Sensitivity analysis of main electrical parameters demonstrates that source-channel doping concentration and metal gate workfunction are critical design parameters that may affect the device performance. Moreover, a framework of core–shell gate workfunction engineering is utilized via calculating 2D variation matrix of the on-state current, threshold voltage and off-state current for optimizing the device performance.

Characterization of a TiO₂/Multi-Wall Carbon Nanotube Core-Shell Nanocomposite Synthesized by a Hydrothermal Method.

TiO₂ is a significant n-type semiconducting material because of its superior electric and photocatalytic properties. Although this material has been extensively studied as a semiconductor electrode for dye-sensitized solar cells for its inherent bandgap and its excellent electrical and chemical properties, the photoelectric efficiency is nevertheless lower than that of the Si-based solar cells, which is generally reported as 13-27%. On the other hand, various carbon structures have been studied to increase the overall charge transport efficiency by reducing the charge transport resistance in the cell while having high electric conductivity. These results are expected to improve the photoelectric conversion efficiency when applied to dye-sensitized solar cells. We fabricated a TiO₂/multi-wall carbon nanotube (MWCNT) core-shell structure by a hydrothermal method. The TiO₂ anatase phase in the TiO₂/MWCNT core-shell structure was confirmed by X-ray diffraction (XRD). The core-shell nanostructure with a diameter of 127 nm to 211 nm was observed by field emission scanning electron microscope (FE-SEM). The morphology of the TiO₂/MWCNT core-shell nanocomposite was also analyzed by transmission electron microscope (TEM). The Fourier-Transform Infrared Spectrometer (FT-IR) and Brunauer Emmett and Teller (BET) method were used to observe the chemical bonding and specific surface area of the TiO₂/MWCNT core-shell nanocomposite, respectively. The TiO₂/MWCNT core-shell composites had a larger specific surface area of 92.00 m²/g, a larger pore volume of 0.33 cm³/g, and a larger pore size of 65.21 nm than commercial TiO₂ nanoparticles (P25). The TiO₂/MWCNT core-shell structure may provide a high-speed path for photoelectrons to pass quickly and will be useful for various applications, such as solar cells and photocatalysts.

Emergence of Topologically Nontrivial Spin-Polarized States in a Segmented Linear Chain.

The synthesis of new materials with novel or useful properties is one of the most important drivers in the fields of condensed matter physics and materials science. Discoveries of this kind are especially significant when they point to promising future basic research and applications. van der Waals bonded materials comprised of lower-dimensional building blocks have been shown to exhibit emergent properties when isolated in an atomically thin form [1-8]. Here, we report the discovery of a transition metal chalcogenide in a heretofore unknown segmented linear chain form, where basic building blocks each consisting of two hafnium atoms and nine tellurium atoms (Hf_{2}Te_{9}) are van der Waals bonded end to end. First-principle calculations based on density functional theory reveal striking crystal-symmetry-related features in the electronic structure of the segmented chain, including giant spin splitting and nontrivial topological phases of selected energy band states. Atomic-resolution scanning transmission electron microscopy reveals single segmented Hf_{2}Te_{9} chains isolated within the hollow cores of carbon nanotubes, with a structure consistent with theoretical predictions. van der Waals bonded segmented linear chain transition metal chalcogenide materials could open up new opportunities in low-dimensional, gate-tunable, magnetic, and topological crystalline systems.

A One-Dimensional Carbon Nanotube‒Metalloporphyrin Hybrid Material for Lithium Storage

Multi-redox organic and organometallic electrode materials have been emerging alternatives to the widespread inorganic counterparts in advanced power sources due to their design diversity, light weight, flexibility, and environmental benignity.1 However, their electrically insulating nature, limited capacity, and poor durability should be resolved for the practical application.Here, we present a one-dimensional (1D) nanohybrid composed of a multiwalled carbon nanotube (MWCNT) core and a cobalt porphyrin shell (Figure) as a new class of electrode materials for rechargeable lithium batteries.2 Highly π-conjugated and multielectron redox-active meso-tetrakis(4-carboxyphenyl) porphyrinato cobalt (CoTCPP) shows strong noncovalent interactions with the MWCNT, leading to the successful formation of the 1D nanohybrid. The resultant nanohybrid, due to its structural uniqueness and maximal use of active areas, facilitates electron transport and electrolyte accessibility, which thus contribute to exhibiting a high specific capacity and improving redox kinetics. Furthermore, intrigued by the 1D structure of the nanohybrid, an all-fibrous nanomat electrode was fabricated through concurrent electro-spraying/-spinning processes. The nanomat electrode provides bicontinuous electron and ion conduction pathways, which eventually reveals the well-distinguishable lithiation behavior of CoTCPP and exceptional electrochemical performances with a long-term stability (ca. 226 mAh g ‒1 based on the electrode sheet weight at a current density of 5 C for over 1500 electrochemical cycles).We hope that the material design strategy described in this study offers new insight into the development of high-performance electrode materials for next-generation power sources and energy storage systems.

Hierarchical core-shell hollow CoMoS4@Ni–Co–S nanotubes hybrid arrays as advanced electrode material for supercapacitors

Despite cobalt molybdenum sulfide (CoMoS4)-based materials are a prospective class of electrode material for supercapacitors, their relatively inferior rate capability and cyclic stability have severely restricted practical applications. Engineering multicomponent binder-free electrode material is deemed an effective approach to fulfill the demand of high-performance supercapacitors. Herein, the hierarchical core-shell hollow CoMoS4@Ni–Co–S nanotubes supported on flexible carbon cloth are designed through a scalable hydrothermal method combined with electrodeposition process. Due to the synergistic contribution of highly conductive CoMoS4 nanotubes core and highly active nickel cobalt sulfide nanosheets shell, the 3D hierarchical CoMoS4@Ni–Co–S nanotubes electrode achieves a remarkable specific capacitance of 2208.5 F g−1 at a rate of 1 A g−1 and extraordinary cycling life (91.3% capacitance retention over 5000 cycles at 3 A g−1). Moreover, the assembled CoMoS4@Ni–Co–S//activated carbon (AC) asymmetric supercapacitor presents satisfactory electrochemical performance, delivering an energy density of 49.1 W h kg−1 at a high power density of 800 W kg−1 and competitive cyclic stability (90.3% retention of initial capacity after 10000 cycles). This work designs an effective synthetic route and validates the potential prospects of binder-free 3D hierarchical architecture for developing high-performance and advanced energy storage devices.

Hierarchical Nanorods Constructed by Vertical WS2 Nanosheets on Carbon Nanotube Cores with Enhanced Lithium Storage Properties

AbstractA nanorod hybrid constructed by vertical WS2 nanosheets on multi‐walled carbon nanotubes (MWCNTs) core is synthesized by a facile solvothermal method. The WS2 nanorod is difficult to form compared to its MoS2 counterpart because of the relatively sluggish dynamics of W4+. Herein, multi‐site nucleation of WS2 are initiated by the acid‐ and heat‐treated MWCNT bundles with high concentration of defects and functional groups, forming nanorods with high aspect ratio, and inducing strong interface interaction between MWCNTs and WS2. WS2 nanosheets are vertically assembled on the surfaces of MWCNT bundles without agglomeration, exposing abundant active sites for Li+ storage. A three‐dimensional electron conductive network is formed by the nanorods to improve the charge transport efficiency and alleviate the structure change/restacking of WS2 during lithium‐ion batteries cycling. A specific capacity of 963 mAh g−1 at 0.5 A g−1 after 500 cycles is retained by the nanorod hybrid anode, showing excellent electrochemical performances.

Self-assembled N-doped carbon with a tube-in-tube nanostructure for lithium-sulfur batteries

Lithium-sulfur batteries hold broad prospects as the low-cost and high-energy storage system. However, the practical application is limited by the intrinsic insulating nature of sulfur and severe shuttle effect of soluble polysulfide intermediates. Herein, we demonstrate a convenient self-assembly strategy for encapsulating carbon nanotubes in nitrogen-doped hollow carbon shells, to construct a nitrogen-doped tube-in-tube carbon nanostructure (NTTC) as a host material of sulfur. In this peculiar structure, the highly conductive carbon nanotube cores facilitate the electron transfer while the hollow porous structure is capable of accommodating high sulfur content of 70 wt% in the composites. Moreover, the nitrogen doping helps to alleviate the shuttle effect owing to enhanced chemisorption towards polysulfides. Benefiting from these merits, the NTTC/S composite with the high areal mass loading of ~2.5 mg cm−2 presents a high reversible capacity (1346.9 mAh g−1 at 0.05 C) and excellent rate capability (533.5 mAh g−1 at 3C). More impressively, NTTC/S electrode exhibits good cycling stability at a high rate of 2 C corresponding to slight capacity decay of 0.055% per cycle over 500 discharge/charge cycles.