Electrochemical characterization of parylene-embedded carbon nanotube nanoelectrode arrays

A novel parylene-embedded carbon nanotube nanoelectrode array is presented for use as an electrochemical detector working electrode material. The fabrication process is compatible with standard microfluidic and other MEMS processing without requiring chemical mechanical polishing. Electrochemical studies of the nanoelectrodes showed that they perform comparably to platinum. Electrochemical pretreatment for short periods of time was found to further improve performance as measured by cathodic and anodic peak separation of K(3)Fe(CN)(6). A lower detection limit below 0.1?μM was measured and with further fabrication improvements detection limits between 100?pM and 10?nM are possible. This makes the nanoelectrode arrays particularly suitable for trace electrochemical analysis.     

Synthesis and characterization of polythiophene-modified TiO<Subscript>2</Subscript> nanotube arrays

The highly ordered and uniform TiO₂ nanotube arrays were fabricated by anodic oxidation method and PTh(polythiophene)/TiO₂ nanotube arrays electrode were obtained by electrochemical polymerization. X-ray powder diffraction (XRD) analysis confirmed the formation of TiO₂ phase. The morphologies and optical characteristics of the TiO₂ nanotube arrays were studied by scanning electron microscope (SEM), UV-Vis absorption spectra and Raman spectra. The results demonstrate that the PTh/TiO₂ electrode could enlarge the visible light absorption region and increase the photocurrent in visible region. The modified TiO₂ electrode with light-to-electric energy conversion efficiency of 1·46%, the short-circuit current density of 4·52 mAcm^− 2, open-circuit voltage of 0·74 V and fill factor of 0·44, were obtained.     

纳米碳管阵列

在概括纳米碳管阵列特异的场发射效应及在场发射器方面应用前景的基础上，介绍了合成纳米碳管阵列的研究历程以及化学气相沉积法在纳米碳管阵列合成方面的重要意义，就当前纳米碳管阵列的快速合成与低温合成两个发展方向进行了概述，并指出等离子体化学气相沉积法能有效地用于纳米碳管阵列的低温合成。     

Synthesis and characterization of polyaniline-camphorsulphonic acid nanotube film

Polyaniline (PANI) nanotubes were prepared in the bulk solution and as films using the aniline oxidation with ammonium peroxydisulfate in aqueous solutions of camphorsulfonic acid (CSA). The in situ PANI films produced during the oxidation of aniline in CSA and also in hydrochloric acid solutions were followed by monitoring the frequency changes of quartz crystal microbalance (QCM). The kinetics of the film formation were discussed. The scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) showed PANI nanotubes. In addition, nanorods and nanoflowers composed from nanofibers and nanoflakes are also present to some extent. The nanotubes were characterized using UV-Vis spectroscopy.     

Photocatalytic microreactor using anodized TiO2 nanotube array

Photocatalytic microreactor using an anodized TiO₂ nanotube/Ti bi-layered plate was fabricated. The inner diameter and length of TiO₂ nanotube were controllable by the anodization voltage and time. The photocatalytic reduction of p-nitrophenol was conducted in the microreactor. The experimental results were well fitted by a model assuming parabolic velocity profile and zero-order kinetics of surface reaction. The photocatalytic activity of TiO₂ nanotube was enhanced as the surface area was increased by anodization voltage and time.     

Synthesis and characterization of new polyaniline/nanotube composites

New polyaniline/nanotube (PANI/NT) composites have been synthesized by “in situ” polymerization processes using both multi-wall carbon nanotubes (MWNTs) and single-wall carbon nanotubes (SWNTs) in concentrations ranging from 2 to 50 wt.%. Although no structural changes are observed using MWNTs above a concentration of 20 wt.%, the in situ synthesis results in electronic interactions between nanotubes and the quinoid ring of PANI leading to enhanced electronic properties and thus to the formation of a genuine PANI/MWNT composite material. On the other hand, using SWNTs favors the formation of inhomogeneous mixtures rather than of a homogeneous composite materials, independent of the SWNT concentration. X-ray diffraction, Raman and transport measurements show the different behavior of both classes of nanotubes in PANI/NT materials. The difficulties in the formation of a true PANI/SWNT composite are related to the far more complex structure of the SWNT material itself, i.e. to the presence of entangled bundles of SWNTs, amorphous carbon and even catalytic metal particles.     

Synthesis and characterization of highly ordered cobalt-magnetite nanocable arrays

Magnetically tunable, high-density arrays of coaxial nanocables within anodic aluminum oxide (AAO) membranes have been synthesized. The nanocables consist of magnetite nanowires surrounded by cobalt nanotube sheaths and cobalt nanowires surrounded by magnetite nanotube sheaths. These materials are a combination of separate hard (Co) and soft (Fe3O4) magnetic materials in a single nanocable structure. The combination of two or more magnetic materials in such a radial structure is seen as a very powerful tool for the future fabrication of magnetoresistive, spin-valve and ultrafast spin-injection devices with nonplanar geometries. The nanocable arrays were prepared using a supercritical-fluid inclusion process, whereby the nanotube was first deposited onto the pore walls of the nanoporous membranes and subsequently filled with core material to form coaxial nanocables. In essence, this paper describes a technique for placing novel magnetic technologies into well-defined building blocks that may ultimately lead to new multifunctional devices, such as spin valves and high-density magnetic storage devices.     

Synthesis and characterization of single crystalline selenium nanowire arrays

Ordered selenium nanowire arrays with diameters about 40 nm have been fabricated by electrodeposition using anodic porous alumina templates. As determined by X-ray diffraction, Raman spectra, electron diffraction and high-resolution transmission electron microscopy, selenium nanowires have uniform diameters, which are fully controllable. Single crystalline trigonal selenium nanowires have been obtained after postannealing at 180 °C. These nanowires are perfect with a c-axis growth orientation. The optical absorption spectra reveal two types of electron transition activity.     

Self-assembled-monolayers (SAMs) modified template synthesis and characterization of SrTiO3 nanotube arrays

A self-assembled-monolayers (SAMs) modified anodic aluminum oxide (AAO) membranes were used to generate crystalline strontium titanate (SrTiO3) nanotube arrays, which have been characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), coupled with electron diffraction analysis. The possible formation mechanism can be explained by the induced nucleation effect of the functional headgroups in the SAMs.     

银改性阳极氧化TiO2纳米管及光催化性能研究

利用电化学阳极氧化法在钛片表面制备了TiO2纳米管,以SEM、XRD对其形貌结构进行表征,采用光还原沉积法在硝酸银溶液中得到了Ag/TiO2纳米管,并研究了改性前后TiO2纳米管对甲基橙溶液的光降解能力.结果表明,最佳氧化电压为25V、氧化时间为20min、煅烧温度为500℃.最佳硝酸银溶液浓度为0.2mol/L,最佳光还原时间为60min,光降解率为99％.沉积Ag颗粒大小在10～20nm间,且改性后的光催化性能有很大提高,30min时降解率达到改性前的两倍.     

Synthesis of vertically aligned carbon nanotube arrays by injection method in CVD

The well aligned multiwalled carbon nanotube arrays were synthesized by injecting the acetonitrile-ferrocene solution at regular intervals of time. The carbon nanotube arrays were deposited on quartz substrate which is placed at the centre of the CVD reactor in quartz tube. The injection method in chemical vapor deposition allows-excellent control of the catalyst to carbon ratio which facilitates the better growth of aligned carbon nanotubes. The effect of various reaction parameters such as growth temperature, catalyst concentration, gas flow rate, growth time and substrate surface on growth of carbon nanotubes have been studied. It was observed that the diameter of carbon nanotubes increases with increase in catalyst concentration and temperature of the synthesis. The SEM analysis reveals that the average growth rate of carbon nanotube film synthesis was about 1.1 microm/min when the synthesis time was one hour.     

Synthesis and characterization of multiwalled carbon nanotube/FeCo nanocomposites

Multiwalled carbon nanotube/FeCo nanocomposites were produced by Catalytic Chemical Vapour Deposition using highly porous FeCo-SiO2 aerogels with different loadings and dimensions of FeCo nanoparticles as catalysts. Multiwalled carbon nanotubes with average number of walls depending on the size of the catalyst nanoparticles were obtained. Inside the nanotubes spherical or elliptical FeCo nanoparticles are retained, and the magnetic properties of the resulting nanocomposites were characterized in detail.     

Synthesis of ZnO nanotube arrays and heterostructures of Cu-ZnO coaxial nanotubes by electrodeposition-oxidation method

Semiconductor ZnO nanotube arrays and heterostructures of Cu-ZnO coaxial nanotubes have been synthesized by electrodeposition into porous anodic alumina membranes and subsequent oxidation. Scanning electron microscopy and transmission electron microscopy indicate that the ZnO nanotubular arrays and Cu-ZnO coaxial nanotubular arrays are of large-area and highly ordered. X-ray diffraction patterns show that the nanotubes are polycrystalline. Photoluminescence spectra of the Cu-ZnO nanotubes show that a violet peak, a blue peak and a green peak are centered at 422 nm, 480 nm and 537 nm, respectively. The ordered ZnO nanotube arrays and heterostructures of Cu-ZnO coaxial nanotubes may have promising potential applications in nanodevices.     

Orthogonally-oriented nanotube arrays: theory

A novel surface involving ordered arrays of partially-embedded carbon nanotubes is developed theoretically. Analysis indicates it should exhibit ultra-low values for friction, adhesion and wear, and also possess superior thermal and electrical properties. The surface consists of orthogonally-oriented, self-assembling arrays of carbon nanotubes, partially embedded lengthwise in a solid substrate. Calculations indicate that stiction forces due to van der Waals interactions can be made small, perhaps more than an order of magnitude less than for Teflon and other advanced perfluorocarbons. Static and kinetic frictional forces could be three orders of magnitude less than for conventional solids.     

Harmonic oscillators of carbon nanotube arrays

The harmonic properties of single-walled carbon nanotube (10, 10) arrays in cantilever geometry of lengths, L = 1,000 to 10,000 nm and diameters, D = 15 to 70 nm have been measured recently, and a linear relationship between the first natural frequency and the ratio of array diameter and the square of the span length, D/L2 was postulated. In the present work the authors show that this relationship is highly nonlinear, especially for large values of the ratio, D/L2. In addition, for a given array length, L = 1000 nm, the first natural frequency of the cantilever is shown to vary little with diameters more than 30 nm and to become asymptotic to a value of 22 MHz as it is further increased. The present study is based on earlier work of the authors wherein the flexural stiffness of the single-walled carbon nanotube (CNT) array of hexagonal symmetry and of non-covalent bonding, due to van der Waals interactions, was predicted in terms of the chirality of the nanotubes and the shearing transfer efficiency between nanotubes when subjected to flexural deformation. In addition, predictions are shown to be in agreement with the experimental evidence wherein the flexural modulus of the CNT array decreases with an increase in array diameter.     

Synthesis and characterization of TiO2 nanotube/hydroquinone hybrid structure

It is shown that 1,4-benzenediol (hydroquinone) and TiO2 nanotubes can form a hybrid structure that is stable in aqueous environment. The incorporation of hydroquinone restores the local structure of nanotubes to anatase-like as evidenced by Raman spectroscopy. Subtle overall structural changes take place upon annealing of the hybrid structure contributing to its stability. The hybrid system shows a broad optical absorption peak extending significantly beyond 700 nm with potential applications in photocatalysis and photoelectrochemistry.     

碳纳米管/导电聚苯胺纳米复合纤维的合成与表征

为实现碳纳米管在树脂内形成一体化导电网络，从而制备出透明导电性能最优的有机透明导电涂层，必须把导电性的碳纳米管纤维在树脂内有效地组装成一体化导电结构网络。本文报道运用在树脂内可以自组装的导电苯胺来实现碳纳米管纤维自组装的方法．合成出了导电聚苯胺纳米薄膜均匀包覆的碳纳米管/导电聚苯胺纳米复合纤维．并运用透射电镜、傅立叶红外光谱以及四探针法表面电阻测试仪对合成出的具有精细微观结构的纳米复合纤维进行了表征．发现合成出了理想的碳纳米管/导电聚苯胺纳米复合纤维，并且其导电性较碳纳米管和导电聚苯胺自身都有大幅度的提高。这种特殊结构的纳米复合纤维的制备为组装高性能的聚合物基透明导电涂层奠定了坚实基础，而且这种自组装方法为各种纳米纤维的组装提供了可能。     

Synthesis and characterization of nano-scale alumina on single walled carbon nanotube

In this study, nano-scale crystalline alumina was synthesized on single walled carbon nanotube by sol-gel method for using as a sorbent for solid phase extraction of trace metals. The characterization of the synthesized nanocomposite material was performed by scanning electron microscope, transmission electron microscope and X-ray diffractometer methods. It was proved that the obtained composite material was mainly nano-scale Al₂O₃, and partly Mg₂Al₂O₄ and Zn₂Al₂O₄ on single walled carbon nanotube. In addition, the specific surface area of the material was determined and found as 165 m²/g. The adsorption capacity of the nanomaterial was also determined for cadmium(II) ions and found as 2.18 mg/g at pH 8.     

碳纳米管阵列研究进展

在介绍CNT阵列性能的基础上,对国内外直接合成CNT阵列的方法进行了评述,重点阐述了各种方法的基本特点及CNT阵列的生长机理、结构控制和批量制备问题。进而探讨了CNT原生阵列、抽丝形成的CNT丝、以及CNT阵列分散后得到的CNTs在复合材料、力学增强、功能器件等方面的初步应用,展望了CNT阵列的发展趋势,指出低成本、大批量可控制备CNT阵列仍然是未来一段时间内国际研究热点。     

Synthesis and characterization of extremely uniform Fe-Co-Ni ternary alloy nanowire arrays

We have fabricated extremely uniform arrays of polycrystalline Fe-Co-Ni ternary alloy nanowires having composition Fe 12.3 wt.%, Co 43.9 wt.% and Ni 43.8 wt.%. The wires are made by electrodeposition into nanoporous alumina templates, using an electrodeposition voltage of 15 V at 1000 Hz. Nanowires have been fabricated having diameters ranging from 43 nm to 120 nm, and lengths of 3 microm to 7 microm, as dependent upon template topology. The magnetization easy axis lies along the nanowire length, with an easy axis coercivity of 72 kA/m.