We found out the promising catalyst materials(NiPd). The NiPd not only has the low melting point but also has the Pd enhancing the surface diffusion at low temperatures(<500'c ). With the Pd film thickness increasing, we could control the CNT density and synthesize more aligned and uniform CNTs. We also obtained the better electrical properties including lower turn-on field (3.4 V/um) and higher current density (34.3 mA/cm2) for NiPd as catalyst. For the advantages described above, we believe that the difficulty of low temperature on FED can be overcome. Further, the large area field emission display might be fabricated in the future.

A capillary-enforced template-based method is described for the preparation of InVO4 nanotube arrays. Nanotube arrays of InVO4 were prepared by filling the InVO4 sol into pores of polycarbonate membranes and pyrolyzing through sintering. Another type of InVO4 nanotube arrays (InVO4/acac) are obtained from the sol with the addition of acetylene acetone (acac). For comparison purposes, InVO4 films were prepared by drop casting from InVO4 same sol. Films and the two types of nanotube arrays of InVO4 annealed at 500°C consist of mixed monoclinic (InVO4-I) and orthorhombic (InVO4-III) phases. Scanning electron microscopy (SEM) characterizations indicate that the nanotubes are well-aligned, perpendicular to substrate surface with the outer diameter of ~200 nm for short InVO4 nanotubes and ~170 nm for long InVO4 nanotubes. Chronopotentiometry results reveal that InVO4/acac nanotube array has the highest charge capacity (790 mAh/g), followed by InVO4 nanotube array (600 mAh/g) then InVO4 film (290 mAh/g). Such enhanced lithium-ion intercalation properties are ascribed to the large surface area and short diffusion distance offered by nanostructures and amorphisation caused by acetylene acetone in the case of InVO4/acac nanotube arrays.

Silver nanowires were coated with a silica shell through an indirect approach. Incorporation of the fluorescent ion Eu(III) into the silica shell in situ was achieved. Subsequent chemical dissolution of the inner metal core resulted in fluorescent silica nanotubes. Transmission electron microscopy (TEM), electron dispersive X-ray microanalysis (EDAX), fluorescence spectroscopy, and zeta potential measurements were used to characterize the materials.

We report on the basic characteristics and gas sensing operation of density controlled single-walled carbon nanotube (SWCNT) thin films on poly(dimethyl siloxane) (PDMS) substrates The vacuum filteration and PDMS mold transfer method allowed the density of SWCNT distributed to have non-local uniformity. The optical transparency of the SWCNT thin films was inversely proportional to SWCNT density and conductivity. The flexible SWCNT thin film showed high mechanical stability with negligible change in conductance after being bent by 180o. We evaluated its gas sensing operation depending on SWCNT density and bias voltage. It was shown that lower SWCNT density thin films had higher sensitivity to NH3 gas, which may be due to higher exposed surface area for lower density SWCNT thin films. Also, we found that lower bias voltage devices showed faster recovery times. The results show that vacuum filteration and mold transfer method produced flexible SWCNT thin films that have stable mechanical and electrical characteristics and also stable gas sensing capabilities making them applicable to future flexible integrated sensors.

Carbon Nanotube (CNT) morphologies with a self-contained gate, such as Y-junctions, offer a new way of exploiting features unique to the nanoscale, such as quantum ballistic transport. The advantages of low power and high frequency operation can then be applied to the fabrication of novel devices. Several other novel functionalities in Y- CNTs, including rectification, switching, high-frequency performance, and logic gates have been experimentally verified1. Y-CNT geometry dependent current blocking behavior, as a function of annealing temperature has also been observed. In view of the above observations, we propose that Y-CNTs can be used as prototypical nanoelectronic components.

The goal of this study is to compare operation and performance of the piezoelectric and carbon nanotube actuators, by focusing on the conditions that such piezoelectric device can be replaced by carbon nanotube actuators in a near future. For many years piezoelectric (PZT) and electrostrictors devices have been the key elements for the construction of actuator systems such as positioners, miniature ultrasonic motors, and adaptive mechanical motors. However, in recent years major advances and accomplishments have been reported in the field of nanotube materials, which promise a breakthrough in the field of nanosensors and nanoactuators. The aim here is to make a comparison between the PZT- and CNT-based actuator/sensor devices in terms of the actuator materials, designs, and device control techniques. First, a model is established for the operation of a typical PZT actuator and the related electromechanical coupling relations and equations governing the actuation process are described. In the second study actuation behavior of carbon nanotube materials is modeled and the results concerning a similar parameter to that of PZT are reported.

HgSe nanotubes have been prepared by spray deposition of solvothermally synthesized HgSe: Iodine nanoparticles on glass substrates at low temperature (200°C). Spray deposition was done without voltage and with an externally applied voltage (700V) to the nozzle and it is found from TEM studies that the average length of the nanotubes increases in case of the films deposited with applied voltage compared to that of without voltage. But there is no change in the average diameter (~ 35 nm). The nanotubes are found to have cubic crystal structure. Iodine is found to act as a catalyst and helps in the growth of nanotubes. The growth mechanism of the nanotubes is analogous to the well known solution-liquid-solid/vapor-liquid-solid (SLS/VLS) mechanism. The EDAX analysis of the tip of the nanotube reveals the presence of Hg, Se and Iodine in the ratio of 73:2:24 for the spot size of <1μm.

The rolling of lipid bilayer sheets into hollow cylindrical tubules have emerged as a group of interesting supramolecular nanostructures. Here, we image the self-assembled tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphochloline (DC8,9PC) with atomic force microscopy. Nanoscale ripple structures with a periodicity of ~ 200nm in the cylindrical lipid tubules are observed. We develop two simple methods based on microfluidic networks and surface patterning to produce two dimensional ordered arrays of parallel aligned lipid tubules on substrates.

Poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) were used to tailor the microstructure of single-walled carbon nanotubes (SWNTs) in both aqueous solutions and dry composite films. Microstructural changes were achieved as the pH of aqueous suspensions were changed, as evidenced by elevated suspension viscosity, scanning electron microscopy and electrical conductivity measurements. The ability to tailor microstructure is useful for aqueous SWNT processing and solid polymer nanocomposites.

We report on electron transport characteristics for semiconducting, single wall, chiral carbon nanotubes. The Boltzmann transport equation is solved indirectly by the Ensemble Monte Carlo method. The basis for the transport calculations is provided by electronic structure calculations within the framework of a simple tight binding model. Scattering mechanisms considered are due to the electron-phonon interactions involving longitudinal acoustic, longitudinal optic, and radial breathing mode phonons. Results show significantly increased Umklapp scattering processes due to the reduced Brillouin zone compared to zigzag nanotubes. This results in increased transient velocity oscillation and negative differential mobility.

Large-scale, high-density, and patterned carbon nanotubes (CNTs) on both pure Si and quartz (SiO2) substrates have been produced using different approaches. The CNTs were synthesized by pyrolysis of the ball-milled iron phthalocyanine (FePc) in a tube furnace under a Ar-5% H2 gas flow. Because patterned CNTs are difficult to grow directly on smooth and perfect single-crystalline Si wafer surface, mechanical scratches were created to help the selective deposition and growth of CNTs on the scratched areas. This simple process does not require pre-deposition of any metal catalysts. For SiO2 substrates, which can be readily covered by a CNT film, patterned CNTs are produced using a TEM grid as mask to cover the areas where CNTs are not needed. The growth temperature and vapor density have strong influence on the patterned CNT formation. The scratch areas with a special structure and a higher surface energy help the selective nucleation of CNTs.

Size exclusion chromatography (SEC) has been used to separate single wall carbon nanotubes (SWNT) dispersed by chemical modification in organic solvents and by DNA in aqueous solution. The chromatographic detection includes size sensitive detectors, multi-angle light scattering (MALS) and intrinsic viscosity (IV), which can provide information on the size and shape of the SEC fractions. The dispersions were also characterized by small angle neutron scattering (SANS) and atomic force microscopy (AFM). Chemical modification was accomplished by covalent attachment of octadecyl amine to acid treated SWNT and by covalent attachment of butyl groups through free radical grafting. Both covalent attachment methods produced dispersions that contained impurities or clusters of SWNT. The DNA dispersions produced the best dispersions, being predominately single nanotubes.

A newly designed module was synthesized and found to self-assemble into rosette nanotubes (RN) in both water and methanol. Characterization using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) established the formation of analogous RNs in both solvents. However, the chiroptical outcome of the assemblies, observed by circular dichrosim (CD) spectroscopy, was found to be mirror image based solely on the solvent used. Preliminary molecular modeling studies indicated the formation of M and P helical rosette nanotubes, in agreement with the experimental observations. This work represents the first example of solvent-controlled helicity in a self-assembling supramolecular system.

A highly efficient one-step technique was developed in order to obtain long and aligned carbon nanotubes with or without Fe filling. The aligned carbon nanotubes (CNTs) were synthesized by heating ferrocene Fe(C5H5)2 using microwave (MW) irradiation. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to study the growth process of the aligned multi-layer carbon nanotubes. It was found that CNTs have a metal particle at the tip of each tube. This carbon nanostructures promise to become important in fuel cells and in nanoscale engineering of other systems.

Supramolecular nanotube hosts with precisely controlled inner or outer diameters have been synthesized by self-assembly of cardanol-based glycolipids, glucopyranosylamide lipids, or glucose-based unsymmetrical bolaamphiphiles. Time-resolved fluorescent measurement using 8-anilinonaphtahalene-1-sulfonate (ANS) as a probe revealed that the water confined in a cardanol-based glycolipid nanotube has relatively lower solvent polarity than bulk water, which corresponds to that of 1-propanol. Extensively developed hydrogen bond networks also characterize the confined water in comparison to the case in bulk water. Encapsulation ability of the glucopyranosylamide lipid nanotube, which depends on capillary action, has been examined by filling the lyophilized lipid nanotubes with aqueous dispersions of gold or silver nanocrystals, ferritin, or magnetic crystals. We have also succeeded in filling the unsymmetrical bolaamphiphile nanotube, which possesses positively charged inner surfaces, with negatively charged polymer beads or ferritin without depending on capillary action.

A secondary ammonium hydrochloride of the peptidic lipid, in which an L-prolyl-L-prolyl-L-proline fragment is coupled with an L-glutamate derivative carrying two long alkyl chains, self-assembles in water to form nanotube structures consisting of a single bilayer wall. Using this lipid nanotube as a template, we carried out the sol—gel transcription to metal oxide nanotubes from aqueous lipid nanotubes without solution catalysts. TEM analysis of the aqueous gel phase, coupled with electron energy-loss spectroscopy (EELS) revealed the presence of a high population of hybrid nanotube architectures with a well-defined lipid/silica interface and thus proved the success of structural transcription from the lipid nanotube template. Besides silica, when changing the lipid nanotube in aqueous solutions to an iced lipid nanotube as a template, we also succeeded in the transcription to transition metal oxide nanotubes (titanium oxide, tantalum oxide, vanadium oxide) was also succeeded. The weakly acidic and mildly catalytic headgroup of the lipid is responsible for the formation of the metal oxide on the surface of the lipid nanotube template.