Coaxial Nanotubes Research Articles

Study on the dynamics responses of a transmission system made from carbon nanotubes

A rotational transmission system from coaxial carbon nanotubes (CNTs) is investigated using a computational molecular dynamics approach. The system consists of a motor from a single-walled carbon nanotube and a bearing from a double-walled carbon nanotube. The motor has a high fixed rotational frequency and the two ends of the outer tube in the bearing are fixed. The inner tube in the bearing works as a rotor. Because of the interlayer friction in the bearing, configurations of the joint between the adjacent ends of motor and rotor have significant effects on rotational transmission properties. Four factors are considered in simulation, i.e., the bonding types of atoms (sp1 and sp2) on the ends of motor and rotor, the difference between motor and rotor radii, the rotational speed of motor, and the environmental temperature. It is found that the synchronous transmission happens if the sp1 atoms on the jointed ends of motor and rotor are bonded each other and become new sp2 atoms. Therefore, the lower difference between radii of motor and rotor, higher temperature of environment leads to synchronous rotational transmission easily. If the environmental temperature is too low (e.g., <150 K), the end of motor adjacent to rotor is easily under buckling and new sp2 atoms appear, too. With capped CNTs or higher radii difference between rotor and motor at an appropriate temperature, a stable asynchronous rotation of rotor can be generated, and the rotor's frequency varying linearly with motor's frequency between 230 and 270 GHz. A multi-signal transmission device combined with oscillating and rotational motion is proposed for motor and stator shares a same size in radius.

Rational design of coaxial structured carbon nanotube–manganese oxide (CNT–MnO2) for energy storage application

Recently, there has been great research interest in the development of composites (core–shell structures) of carbon nanotubes (CNTs) with metal oxides for improved electrochemical energy storage, photonics, electronics, catalysis, etc. Currently, the synthetic strategies for metal oxides/hydroxides are well established, but the development of core–shell structures by robust, cost-effective chemical methods is still a challenge. The main drawbacks for obtaining such electrodes are the very complex synthesis methods which ultimately result in high production costs. Alternatively, the solution based method offers the advantages of simple and cost effective synthesis, as well as being easy to scale up. Here, we report on the development of multi-walled carbon nanotube–manganese oxide (CNT–MnO2) core–shell structures. These samples were directly utilized for asymmetric supercapacitor (ASC) applications, where the CNT–MnO2 composite was used as the positive electrode and ZIF-8 (zeolitic imidazolate framework, ZIF) derived nanoporous carbon was used as the negative electrode. This unconventional ASC shows a high energy density of 20.44 W h kg−1 and high power density of 16 kW kg−1. The results demonstrate that these are efficient electrodes for supercapacitor application.

Crystallography of Coaxial and Scroll Nanotubes of Arbitrary Composition

Crystallography of Coaxial and Scroll Nanotubes of Arbitrary Composition

Coaxial nanotubes of stimuli responsive polymers with tunable release kinetics.

Stimuli responsive polymeric (SRP) nanotubes have great potential as nanocarriers of macromolecules due to their large surface areas and release mechanisms that can be activated externally. In this work, we demonstrate vapor phase synthesis of coaxial nanotubes with layers of different SRP polymers for improved release kinetics. Temperature responsive poly(N-isopropylacrylamide) (pNIPAAm), pH responsive poly(methacrylic acid) (pMAA) and poly(hydroxyethyl methacrylate) (pHEMA) are used to fabricate the responsive coaxial nanotubes and the phloroglucinol dye is used as the model molecule to study the release kinetics. Fastest release is observed with single layer pNIPAAm nanotubes with rates of 0.134 min(-1), whereas introducing pHEMA or pMAA as inner layers slows down the release, enabling tuning of the response. Furthermore, repeating the release studies multiple times shows that the release rates remain similar after each run, confirming the stability of the nanotubes.

Strongly coupled 1D sandwich-like C@Fe3O4@C coaxial nanotubes with ultrastable and high capacity for lithium-ion batteries

A scalable and bottom-up synthesis method is successfully developed for fabricating 1D sandwich-like C@Fe3O4@C coaxial nanotubes, which exhibit excellent lithium storage properties.

Design, synthesis of uniform Au nanoparticles modified Fe2O3–TiO2 coaxial nanotubes and their enhanced thermal stability and photocatalytic activity

Au nanoparticles are loaded on Fe2O3/TiO2 nanotubes by a one-pot strategy using lysine as both a linker and a capping agent.

Temperature effects on a motion transmission device made from carbon nanotubes: a molecular dynamics study

Temperature effects on a motion transmission system made from coaxial carbon nanotubes ((5, 5) motor and (5, 5)/(10, 10)/(1, 15) converter) is studied. Changing the environmental temperature can induce mode conversion of the rotation of (5, 5) rotor.

Fabrication of TiO2/MS (M = Pb, Zn) core–shell coaxial nanotube arrays and their photocatalytic properties

TiO2/MS (M = Pb, Zn) core–shell coaxial nanotube arrays were prepared by a simple method of liquid deposition, where the template worked as a septum.

Translation of the assembling trajectory by preorganisation: a study of the magnetic properties of 1D polymeric unpaired electrons immobilised on a discrete nanoscopic scaffold.

A nitronyl nitroxide (NN)-appended hexabenzocoronene (HBC(NN)), when allowed to coassemble with bis(hexafluoroacetylacetonato)cobalt(II), forms a coaxial nanotubular architecture featuring NN-Co(II) coordinated copolymer chains immobilised on the outer and inner nanotube surfaces. Upon lowering the temperature, this nanotube has enhanced magnetic susceptibility below 10 K.

Coaxial conducting polymer nanotubes: polypyrrole nanotubes coated with polyaniline or poly(p-phenylenediamine) and products of their carbonisation

AbstractPolypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in a reaction mixture containing methyl orange. They were subsequently coated with polyaniline or poly(p-phenylenediamine) in situ during the oxidation of respective monomers in their presence. A part of the coaxial nanotubes was deprotonated using ammonia solution. The conductivity of polypyrrole nanotubes of 60 S cm

Rational design of coaxial mesoporous birnessite manganese dioxide/amorphous-carbon nanotubes arrays for advanced asymmetric supercapacitors

Coaxial mesoporous MnO2/amorphous-carbon nanotubes have been synthesized via a facile and cost-effective strategy at room temperature. The coaxial double nanotubes of inner (outer) MnO2 and outer (inner) amorphous carbon can be obtained via fine tuning the preparative factors (e.g., deposition order and processing temperature). Furthermore, the electrochemical properties of the coaxial nanotubes were evaluated by cycle voltammetric (CV) and galvanostatic charge–discharge (GC) measurements. The as-prepared coaxial double nanotubes of outer MnO2 and inner amorphous carbon exhibit the optimized pseudocapacitance performance (362 F g−1) with good cycling stability, and ideal rate capability owning to the unique nanostructures. When assembled into two-electrode asymmetric supercapacitor, an energy density of 22.56 W hkg−1 at a power density of 224.9 W kg−1 is obtained. These findings provide a new and facile approach to fabricate high-performance electrode for supercapacitors.

Porous poly(3,4-ethylenedioxythiophene) nanoarray used for flexible supercapacitor

Porous poly(3,4-ethylenedioxythiophene) (PEDOT) nanoarray used for flexible supercapacitor has been prepared to investigate its electrochemical capacitance performance. Well-aligned titania (TiO2) and titanium nitride (TiN) nanotube array was fabricated by an anodization, crystallization, nitridation processes. PEDOT-TiO2 and PEDOT-TiN nanoarray hybrid was fabricated by coating PEDOT on nanotube walls of TiO2 and TiN through a pulse voltammetry electrodeposition process. PEDOT nanopore array was fabricated through HF corrosion of TiN from PEDOT-TiN. The morphology and microstructure of PEDOT-TiO2, PEDOT-TiN and PEDOT were characterized by scanning electron microscopy and Raman spectroscopy. The electrochemical capacitance was investigated by cyclic voltammetry and galvanostatic charge–discharge measurements. PEDOT-TiO2 and PEDOT-TiN showed heterogeneous coaxial nanotube structure. PEDOT exhibited free-standing nanopore array structure. The specific capacitance of PEDOT-TiN nanoarray hybrid was determined to be 393.1Fg−1 at a current density of 1.0mAcm−2, presenting much higher capacitance than PEDOT-TiO2 nanoarray hybrid (128.7Fg−1) and PEDOT nanopore array (109.3Fg−1). All-solid-state flexible supercapacitor was constructed using supple electrode of PEDOT-TiN nanoarray hybrid and polyvinyl alcohol gel electrolyte of sulphuric acid. The volume specific capacitance, energy and power density were determined to be 4.08Fcm−3, 2.26mWhcm−3 and 250mWcm−3 at a high output voltage of 2.0V and a current density of 10mAcm−2. PEDOT-TiN nanoarray hybrid exhibited the effective energy storage in flexible supercapacitor application.

Photocatalytic reduction of carbon dioxide by hydrous hydrazine over Au-Cu alloy nanoparticles supported on SrTiO3/TiO2 coaxial nanotube arrays.

Efficient photocatalytic conversion of CO2 into CO and hydrocarbons by hydrous hydrazine (N2H4⋅H2O) is achieved on SrTiO3/TiO2 coaxial nanotube arrays loaded with Au-Cu bimetallic alloy nanoparticles. The synergetic catalytic effect by the Au-Cu alloy nanoparticles and the fast electron-transfer in SrTiO3/TiO2 coaxial nanoarchitecture are the main reasons for the efficiency, while N2H4⋅H2O as the H source and electron donor provides a reducing atmosphere to protect the surface Cu atoms from oxidation, therefore maintaining the alloying effect which is the basis for the high photocatalytic activity and stability. This approach opens a feasible route to enhance the photocatalytic efficiency, which also benefits the development of photocatalysts and co-catalysts.

Photocatalytic Reduction of Carbon Dioxide by Hydrous Hydrazine over Au–Cu Alloy Nanoparticles Supported on SrTiO3/TiO2 Coaxial Nanotube Arrays

AbstractEfficient photocatalytic conversion of CO2 into CO and hydrocarbons by hydrous hydrazine (N2H4⋅H2O) is achieved on SrTiO3/TiO2 coaxial nanotube arrays loaded with Au–Cu bimetallic alloy nanoparticles. The synergetic catalytic effect by the Au–Cu alloy nanoparticles and the fast electron‐transfer in SrTiO3/TiO2 coaxial nanoarchitecture are the main reasons for the efficiency, while N2H4⋅H2O as the H source and electron donor provides a reducing atmosphere to protect the surface Cu atoms from oxidation, therefore maintaining the alloying effect which is the basis for the high photocatalytic activity and stability. This approach opens a feasible route to enhance the photocatalytic efficiency, which also benefits the development of photocatalysts and co‐catalysts.

Supercapacitance of polypyrrole/titania/polyaniline coaxial nanotube hybrid

The polypyrrole/titania/polyaniline (PPy/TiO2/PANI) coaxial nanotube hybrid has been prepared through a stepwise electrodeposition process for an electrochemical energy storage. Independent TiO2 nanotube array was used as the framework, which was formed by anodizing titanium foil at 30V in fluoride-containing water and ethylene glycol mixture solution. The PPy was selectively coated on the outer surface of TiO2 nanotube walls to form PPy/TiO2 through a normal pulse voltammetry electrodeposition process. The PANI was then coated on the inner surface of TiO2 nanotube walls to form PPy/TiO2/PANI coaxial nanotube hybrid through a photoassisted cyclic voltammetry electrodeposition process. The morphology and microstructure feature of PPy/TiO2/PANI were characterized by field-emission scanning electron microscopy and Raman spectrum. The capacitance performance was conducted by cyclic voltammetry and galvanostatic charge–discharge measurements. PPy/TiO2/PANI coaxial nanotube hybrid with P/N-type doping properties exhibited a high specific capacitance of 497Fg−1 at a current density of 0.5Ag−1 and a potential window of −0.2 to 0.8V in 1.0M H2SO4 solution. The capacitance declined from 267.9 to 193.7Fg−1 after 500 cycles at a high current density of 2.0Ag−1, showing 72.3% capacitance retention and a good cycle stability for the promising supercapacitor application.

MnO2–TiO2/C nanocomposite arrays for high-performance supercapacitor electrodes

Coaxial TiO2 and carbon nanotube arrays (TiO2/C NTAs) are prepared by hydrothermal treatment of anatase TiO2 nanotube arrays (TiO2 NTAs) in a glucose solution and carbonized under N2 at 700 °C. The TiO2/C NTAs provide an extremely large, solvated, ion accessible surface area as well as a direct pathway for charge transport, thus yielding substantially improved areal capacitance of 26.1 mF/cm2 at a current density of 0.1 mA/cm2 that is 60 times larger than the capacitance of anatase TiO2 NTAs under the same conditions. The TiO2/C NTAs provide a good support for depositing highly pseudocapacitive materials such as MnO2 to form coaxial MnO2, C and TiO2 nanotube arrays (MnO2–TiO2/C NTAs), producing better capacitive properties. The MnO2–TiO2/C electrode shows a high specific capacitance (580 F/g at a current density of 2.6 A/g), an excellent rate capability and a good cycling stability.

Preparation of coaxial heterogeneous graphene quantum dot-sensitized TiO2 nanotube arrays via linker molecule binding and electrophoretic deposition

Coaxial heterogeneous graphene quantum dot-sensitized TiO2 nanotube arrays (GQDs/TNTs) are prepared by a coupling technique of linker molecule binding and electrophoretic deposition (EPD). The silane linker molecules act as a superb medium for integrating GQDs and TNTs by covalent amide linkage, thus preventing GQDs from clogging the tube entrances and forming a uniform GQD layer tightly attached to the inside tube walls during the following EPD process. By adjusting the time of EPD, appropriate thickness of the deposited GQDs in the internal tube walls of TNTs can be controlled. Compared to the pristine TNTs and GQDs/TNTs prepared by the conventional impregnation–precipitation method, the hybrids fabricated by EPD exhibit significantly enhanced photoelectrochemical water-splitting activity and photocatalytic organic dye decomposition performance for their broad photo-absorption range, fast separation of photogenerated charge, and stability.

Carbon-based nanorings sliding along inner coaxial nanotubes: Möbius topology effects in damping gigahertz oscillations

The axial sliding of carbon-based normal nanorings (NCNs) and one-turn Möbius nanorings (MCNs) along inner coaxial carbon nanotubes with hydrogen-terminated edges is described. Classical molecular dynamics simulations were carried out to investigate their sliding considering C300H100 NCN and MCN nanostructures and single wall armchair carbon nanotubes (SW CNTs) with chiralities (16, 16), (18, 18), and (20, 20). The NCN:CNT system exhibited an oscillatory movement with an initial frequency of about 10 gigahertz decaying slowly with time as the vibrational energy is transferred to radial and torsional modes of the nanoring, while the amplitude remained practically constant except for the (16, 16)-CNT. The MCN:CNT systems, on the other hand, initially oscillated as the NCN:CNT, but a strong damping regime ensued due to the strong interaction of the twisted nanoring with the CNT tips, effectively stopping the oscillation after 400 ps for all MCN:CNT structures investigated.

Rationally designed carbon-coated Fe3O4 coaxial nanotubes with hierarchical porosity as high-rate anodes for lithium ion batteries

Fe3O4 is a promising high-capacity anode material for lithium ion batteries, but challenges including short cycle life and low rate capability hinder its widespread implementation. In this work, a well-defined tubular structure constructed by carbon-coated Fe3O4 has been successfully fabricated with hierarchically porous structure, high surface area, and suitable thickness of carbon layer. Such purposely designed hybrid nanostructures have an enhanced electronic/ionic conductivity, stable electrode/electrolyte interface, and physical buffering effect arising from the nanoscale combination of carbon with Fe3O4, as well as the hollow, aligned and hierarchically porous architectures. When used as an anode material for a lithium-ion half cell, the carbon-coated hierarchical Fe3O4 nanotubes showed excellent cycling performance with a specific capacity of 1,020 mAh center dot g(-1) at 200 mA center dot g(-1) after 150 cycles, a capacity retention of ca. 103%. Even at a higher current density of 1,000 mA center dot g(-1), a capacity of 840 mAh center dot g(-1) is retained after 300 cycles with no capacity loss. In particular, a superior rate capability can be obtained with a stable capacity of 355 mAh center dot g(-1) at 8,000 mA center dot g(-1). The encouraging results indicate that hierarchically tubular hybrid nanostructures can have important implications for the development of high-rate electrodes for future rechargeable lithium ion batteries (LIBs).

Coaxial Nanotube Battery inside Single Nanopore

We report here a nanobattery comprised of nanotubular electrodes and electrolyte confined within an anodic aluminum oxide (AAO) nanopore. To construct confined electrically insulating electrolyte space in batteries with aligned nanoelectrodes, we have used atomic layer deposition (ALD) to synthesize nanotubular, heterogeneous coaxial electrodes at both ends of AAO nanopores. The nanoelectrodes include Ru nanotube current collectors with V2O5storage material on top of the Ru to form a symmetric full storage cell, with anode and cathode separated by an electrolyte region. The V2O5 is prelithiated at one end to serve as anode while pristine V2O5 at the other end serves as cathode, so that the battery can be asymmetrically cycling between 0.2V and 1.8V. Capacity retention at high power (relative to 1C values 178mAh/g) is 95% at 5C and 46% at 150C. At 5C rate (12 min charge-discharge cycle), 81.3% capacity remains after 1000 cycles. The importance of incorporating integrated current collectors is demonstrated by the rate performance of V2O5 cathode with Ru nanotube current collector as compared to a Au planar current collector. While both show similar capacity at low rate (1C), at high rates (150C) that demand fast electron transport the V2O5/Ru nanotube (78mAh/g) exhibits almost twice the capacity of the V2O5/planar Au (42mAh/g). This nanopore battery poses an extreme case of highly confined organic electrolyte environments in ultrasmall batteries. These promising results demonstrate the importance of integrating current collectors with storage nanoelectrodes, the benefit of electrolyte-accessible surface area of the nanotubular electrodes, and the cycling robustness of the nanostructures. At the same time, they provide a valuable data source for fundamental modeling to understand and quantify a science of “nanoionics” – a mesoscale phenomenon resulting from dense packing of ion storage nanostructures.