Carbon Nanotube Array Electrodes Research Articles

An Ingenious Strategy to Integrate Multiple Electrocatalytically Active Components within a Well-Aligned Nitrogen-Doped Carbon Nanotube Array Electrode for Electrocatalysis

In this paper, an ingenious strategy was developed to construct a well-aligned nitrogen-doped carbon nanotube (NCNT) array electrode integrated with multiple electrocatalytically active components ...

Hydrogel Cryo‐Microtomy Continuously Making Soft Electronic Devices

AbstractStandard fabrication of soft electronic devices with both high controllability and yield is highly desirable but remains a challenge due to the modulus mismatch of component materials through a one‐step process. Here, by mimicking the freeze‐section process of multicomponent biological tissues containing low‐modulus muscles and high‐modulus bones, for the first time, a hydrogel cryo‐microtomy method to continuously making soft electronic devices based on a sol‐solid‐gel transition mechanism is presented. Polyvinyl alcohol (PVA) electrolyte and aligned nitrogen‐doped multi‐walled carbon nanotube (N‐MWCNT) array electrode are demonstrated as low‐ and high‐modulus components to fabricate soft supercapacitors with high performances. Stable interfaces form between frozen PVA electrolyte and N‐MWCNT electrodes with matched moduli at subzero temperature and are well maintained during cryo‐microtomy process. The resulting soft supercapacitors realize controllable patterns, tunable thicknesses from 0.5 to 600 μm, high yields such as 20 devices per minute even at lab scale, and high reproducibility with over 75% devices in 15% performance fluctuation. This cryo‐microtomy method is further generalized to fabricate other soft devices such as sensors with high sensing properties.

Design of quadruple-layered metal oxides/nitrogen, oxygen-doped carbon nanotube arrays as binder-free electrodes for flexible lithium-ion batteries

Designing flexibly binder-free metal oxide electrodes, which could effectively alleviate the mechanical stress and maintain the structural integrity during the lithiation/delithiation process, is still a major challenge. Here we report a facile strategy for successfully synthesizing free-standing quadruple-layered metal oxides/nitrogen, oxygen-doped carbon nanotube array electrodes. In the quadruple-layered structure, metal oxides are protected by carbon layer to minimize the direct exposure to the electrolyte and accommodate the huge volume change during cycling, and thus form the solid-electrolyte interface layer. Besides that, the abundant oxygen and nitrogen-containing functional groups of carbon layer shows a strong interaction with metal oxides to prevent the electrode pulverization during charging and discharging. Meanwhile, carbon layer is introduced to facilitate the stable and fast electrons mobility. As a result, the as-prepared quadruple-layered electrodes show excellent electrochemical performance in terms of high reversible capacity, good rate capability, and stable cyclability. This work may pave the way for the construction of flexible binder-free lithium ion batteries with superior lithium storage properties.

Effective surface emissivity and heat dissipation among integrated bamboo-like super-black vertical carbon nanotube array electrodes in silicon via holes

Recently, carbon nanotube (CNT)-based micro-devices have attracted extensive attention at the frontiers of intelligent electronics, but the practical application of these devices are seriously limited by the low CNT package rates, poor heat dissipation, and intricate in-situ growth processes. Here, microelectrodes with low impedance based on in-situ-grown super-black vertical bamboo-like multi-walled CNT arrays (∼70 μm) were fabricated inside silicon via holes using face-down catalytic plasma enhanced chemical vapor deposition. Interestingly, the unique CNT array exhibited uniformly high absorption efficiency with a broad range of wavelength (exceeding 99.65% in the UV-NIR band and 99% in the mid-infrared region). Moreover, the excellent cooling performance of CNT array microelectrodes based on in-situ-grown bamboo-like CNT arrays within silicon via holes was demonstrated. Our study highlights the benefits of CNT-based micro functional devices, which indicates the integrated in-situ-grown bamboo-like CNT arrays will have potential applications in advanced microelectrodes, CNT-based field-effect transistors, and portable terahertz inspection devices.

An Entangled Cobalt–Nitrogen–Carbon Nanotube Array Electrode with Synergetic Confinement and Electrocatalysis of Polysulfides for Stable Li–S Batteries

The lithium–sulfur (Li–S) battery is considered as a promising battery chemistry for next-generation energy storage on the merits of low cost and high energy density. However, the sluggish redox ki...

Design and understanding of dendritic mixed-metal hydroxide nanosheets@N-doped carbon nanotube array electrode for high-performance asymmetric supercapacitors

Design and fabrication of supercapacitors (SCs) with high energy density, fast discharge rate, and long cycle life is of great importance; however, the performances of SCs depend critically on advances in materials development. Here we report the development of a high-performance electrode material composed of hierarchical, porous interlaced ultrathin Zn and Ni co-substituted Co carbonate hydroxides (ZnNiCo-CHs) nanosheets branched on N-doped carbon nanotube arrays (C@ZnNiCo-CHs), which were grown directly on a nickel foam current collector. The mesoporous features and large open spaces of the interlaced ultrathin ZnNiCo-CHs nanosheets provide more active sites for redox reactions and facilitate fast mass transport; the self-standing N-doped carbon nanotube arrays offer large surface area, promote fast electron transport, and enhance structure stability, resulting in outstanding rate capability and long-term stability. Density functional theory calculations suggest that the ZnNiCo-CHs nanosheets have low deprotonation energy, greatly facilitating the rate of redox reactions. Further, an asymmetric SC constructed from a C@ZnNiCo-CHs positive electrode and an N-, S-codoped rGOs negative electrode demonstrates a high energy density of 70.9 W h kg−1 at a power density of 966 W kg−1 while maintaining a capacity retention of 91% even after 20,000 cycles at 20 A g−1. The findings provide some important insight into rational design of transition metal compounds based materials for fast energy storage, which may be applicable to creating efficient and robust electrode materials for other energy-related devices.

Sticky-note supercapacitors

Novel sticky-note supercapacitors with repeated adhesive performance are fabricated from sticky carbon nanotube array electrodes. The supercapacitors can be repeatedly attached onto various substrates, and they can also be brought into direct contact with each other to power external electronic devices as their contacting layers are electrically conductive. They are flexible with high specific capacitances after attaching and removing.

Limits to the magnitude of capacitance in carbon nanotube array electrode based electrochemical capacitors

Nanostructured electrochemical capacitors (ECs) are advantageous for charge and energy storage due to their intrinsically large surface area, which contributes to a large electrostatic/double layer capacitor (Cdl). However, the intrinsically small density of states in nanostructures results in a quantum capacitor (CQ) in series with Cdl which could diminish the total device capacitance value (Ctot). We investigate, through comparison with experiment, the relative magnitudes of Cdl and CQ in electrodes constituted of carbon nanotube arrays. Consequently, we attribute the increase in Ctot resulting from ionizing radiation to an increase in CQ and suggest limits to the capacitance in ECs.

High-performance short channel organic transistors using densely aligned carbon nanotube array electrodes

We report high-performance short channel pentacene field effect transistor (FET) using carbon nanotube aligned array electrodes. The devices show field effect mobility of up to 0.65 cm2/Vs and current on-off ratio of up to 1.7 × 106, which is the best for sub-micron pentacene FETs. The calculated cutoff frequency (fc) of the devices is up to 211 MHz which is among the best reported fc for organic transistors. The high performance of our short channel FET is attributed to improved charge injections from the aligned array carbon nanotube electrodes into the pentacene.

Recording the Reaction Process of Loop‐Mediated Isothermal Amplification (LAMP) by Monitoring the Voltammetric Response of 2′‐Deoxyguanosine 5′‐Triphosphate

AbstractWe describe here a novel strategy for recording the reaction process of loop‐mediated isothermal amplification (LAMP) by monitoring the voltammetric response of 2′‐deoxyguanosine 5′‐triphosphate (dGTP). Unlike the other three kinds of reactive substrates for DNA synthesis in LAMP reaction, dGTP exhibits sensitive voltammetric response at the carbon nanotube array electrode. When the LAMP reaction occurs, the concentration of dGTP decreases accordingly, bringing forth the decrease of the anodic peak current (ipa). In inversion, the decrease of the ipa of dGTP was used to characterize the reaction process of LAMP. The relationships among the LAMP reaction time, the initial quantity of template DNA and the value change of the ipa were studied. The results indicate that the protocol integrated LAMP and voltammetric techniques can be used for not only qualitative gene discrimination but also quantitative gene assay in a wide range. The malB gene extracted from common strains of Escherichia coli cells was tested as a model. The detecting results of LAMPs obtained by voltammetric method were in good agreement with those by optical‐based methods (gel electrophoresis and fluorescent dye).

Ambipolar copper phthalocyanine transistors with carbon nanotube array electrodes

We report on organic thin film transistors (OTFTs) based on copper phthalocyanine (CuPc) having electrodes consisting of isolated carbon nanotube (CNT) arrays embedded in the organic layer. CuPc OTFT with CNT array electrodes show p-type behavior with Ohmic hole injection, high hole mobility, and enhanced switching characteristics at low voltage. The p-type devices are converted to ambipolar OTFT by vacuum annealing. Despite the large offset between the CNT work function and the CuPc energy levels, electron injection characteristics are also Ohmic. The extension of CNT electrodes to the phthalocyanine family confirms the validity of this contact approach for organic electronic devices.

Fabrication of Aligned Carbon Nanotube Array Electrodes for Organic Electronic Devices

Fabrication of Aligned Carbon Nanotube Array Electrodes for Organic Electronic Devices

Making Contacts to n-Type Organic Transistors Using Carbon Nanotube Arrays

We investigated the performance of carbon nanotube (CNT) array electrodes applied to n-type and ambipolar phenyl-C61-butyric acid methyl ester (PCBM) thin film transistors on a SiO(2) dielectric substrate. Compared to conventional Au electrodes, CNT arrays provide better injection efficiency, improved switching behavior, higher electron mobility, and lower contact resistance. Experiments on ambipolar PCBM transistors indicate that the injection performance is enhanced by the electrostatics of the CNT contacts, which promotes electron and hole tunneling across Schottky barriers at the PCBM/nanotube interface. The use of CNT arrays is a valid replacement to low workfunction metals, which are often reactive in air and difficult to process. Our work paves the way for a widespread use of carbon nanotube array electrodes in high-performance n-type and p-type organic thin film transistors.

Dense and long carbon nanotube arrays decorated with Mn 3O 4 nanoparticles for electrodes of electrochemical supercapacitors

Mn 3O 4 nanoparticles have been homogenously deposited within highly dense, millimeter-long carbon nanotube array (CNTA) by dip-casting method from non-aqueous solutions. After modified with Mn 3O 4 nanoparticles, CNTAs have been changed from hydrophobic to hydrophilic without their alignment and integrity being destroyed. The hydrophilic Mn 3O 4/CNTA composite electrodes present improved performance for supercapacitors, compared with as-grown CNTA electrodes. The maximum specific capacitance of the Mn 3O 4/CNTA composite electrode was found to be 143 F/g, leading to an exceptionally high area-normalized capacitance (Faraday per geometric area of the electrode) of 1.70 F/cm 2, while the specific capacitance for as-grown CNTA electrode is only 1–2 F/g. When normalized to the deposited Mn 3O 4 nanoparticles, the specific capacitance was estimated to be as high as 292 F/g. The method is promising for producing high performance area-limited electrochemical supercapacitors and provides a new route of decorating highly dense CNTAs with active materials.

Carbon nanotube array anodes for high-rate Li-ion batteries

The electrochemical performance of carbon nanotube array (CNTA) and entangled carbon nanotube (ECNT) electrodes are studied as anodes for Li-ion batteries. CNTA anodes display higher capacity (373 mAh g −1) and much better rate and cycle performances than ECNT anodes. The performance of CNTA electrode shows length dependencies, i.e., shorter CNTA electrodes present higher specific capacity and better rate performance. The energy storage characteristics of CNTA electrodes are discussed on the basis of experimental results of SEM, TEM, and Raman spectra. The inner graphene layers of CNTs in CNTA electrode, which can form electron conductive paths and ensure a high conductivity, are retained during Li-ion insertion/extraction. These mechanically robust inner graphene layers can avoid the loss of outer active materials during Li-ion insertion/extraction, which, in turn, results in a good cycle performance.

Electrochemical Characteristics of Well‐aligned MWCNT Array Electrodes

Capacitive and electron transfer (faradaic) characteristics of well‐aligned multi‐walled carbon nanotube (MWCNT) array electrodes as determined by cyclic voltammetry and impedance spectroscopy were reported. The characteristics were discussed in dependence on the specific deposit mass of the MWCNT arrays, which linearly increased with the deposit thickness of the arrays.

Co(OH) 2-combined carbon-nanotube array electrodes for high-performance micro-electrochemical capacitors

We have investigated binder-free Co(OH) 2-combined carbon-nanotube (CNT) array electrodes using anodized aluminum oxide (AAO) templates for micro-electrochemical capacitors. It is shown that compared to the capacitors fabricated with CNT only electrodes (6.3 F/cm 3 at 100 mV/s), those with the Co(OH) 2-combined CNT array electrodes produce much higher capacitance (12.74 F/cm 3 at 100 mV/s) together with superior high-rate capacitance. The improved electrochemical behavior is explained in terms of high capacitance of amorphous Co(OH) 2 electrode and the use of CNT arrays as effective current collector.

Ruthenium Porphyrin Functionalized Single-Walled Carbon Nanotube Arrays—A Step Toward Light Harvesting Antenna and Multibit Information Storage

Ruthenium porphyrin functionalized single-walled carbon nanotube arrays have been prepared using coordination of the axial position of the metal ion onto 4-aminopyridine preassembled single-walled carbon nanotubes directly anchored to a silicon(100) surface (SWCNTs-Si). The formation of these ruthenium porphyrin functionalized single-walled carbon nanotube array electrodes (RuTPP-SWCNTs-Si) has been monitored using infrared spectroscopy (IR), differential pulse voltammetry (DPV), atomic force microscopy (AFM), laser desorption time-of-flight mass spectroscopy (LDI-TOF-MS), UV-vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. Electrochemical results show two successive one-electron reversible redox waves. The surface concentration of the ruthenium porphyrin molecules is 3.44 x 10 (-8) mol cm (-2). Optical results indicate that the immobilization of ruthenium porphyrin enhances the light absorption of SWCNTs-Si surfaces in the visible light region. Moreover mixed assembly of ferrocene/porphyrin onto carbon nanotube arrays has been achieved by altering the ratio of two redox-active species in the deposition solution. These results suggest the ruthenium porphyrin modified electrodes are excellent candidates for molecular memory devices and light harvesting antennae.

Carbon Nanotube Array Electrodes based Supercapacitors with 3.5V Working Voltage

Carbon Nanotube Array Electrodes based Supercapacitors with 3.5V Working Voltage

Fabrication and characterization of carbon nanotube array electrodes with gold nanoparticle tips

Abstract In this work we fabricated 8 mm long aligned multi-walled carbon nanotube array electrodes and electrochemically deposited gold nanoparticles in a controlled manner onto the nanotube tips at the top of the array. A soldering technique was also developed to provide reliable electrical contact between the carbon nanotubes at the bottom of the array and copper on a patterned printed circuit board. The top surfaces of the nanotube tower electrodes were activated using a reactive ion etcher prior to gold deposition. Electrodeposition of Au particles on the plasma-treated tower electrodes was performed over a range of deposition times and potentials. Cyclic voltammetry and electrochemical impedance spectroscopy analyses showed that the Au-deposited carbon nanotube array electrodes were successfully fabricated. The new electrodes will be the foundation for further biosensor development using self-assembled monolayers and bio-conjugation of antibodies for novel label-free immunosensing.