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Single-walled carbon nanotubes can be classified as either metallic or semiconducting, depending on their conductivity, which is determined by their chirality. Existing synthesis methods cannot controllably grow nanotubes with a specific type of conductivity. By varying the noble gas ambient during thermal annealing of the catalyst, and in combination with oxidative and reductive species, we altered the fraction of tubes with metallic conductivity from one-third of the population to a maximum of 91%. In situ transmission electron microscopy studies reveal that this variation leads to differences in both morphology and coarsening behavior of the nanoparticles that we used to nucleate nanotubes. These catalyst rearrangements demonstrate that there are correlations between catalyst morphology and resulting nanotube electronic structure and indicate that chiral-selective growth may be possible.

In the present work, a new concept of x-ray source was developed. The conventional thermionic tungsten filament tube is commonly available in various fields of application, such as, medical diagnostic and therapy system, microwave amplifier, non-destructive testing (NDT) technology, and so on. However, it has intrinsic problems such as high power consumption, very low x-ray efficiency, and out-gassing problems. Therefore, in the present study a new carbon nanotube (CNT) based x-ray source was developed as a substitute for the conventional one. The new x-ray source consists of three major parts. The CNT electron field emitter was employed as a cathode, a very thin metal mesh as a grid to extract electrons from the CNT, and finally a molybdenum embedded copper target as an anode to accelerate electrons. A supplementary electrostatic focusing lens was employed in the tube to focus the electron beam on the anode target. A detailed description of the tube structure as well as electron beam characteristics is presented in this study. In addition, preliminary x-ray images obtained by using the CNT x-ray tube are presented. Index Terms--Carbon nanotube (CNT), field emission, high resolution imaging, inspection system, X-ray source.

Development of materials that deliver more energy at high rates is important for high-power applications, including portable electronic devices and hybrid electric vehicles. For lithium-ion ([Li.sup.+]) batteries, reducing material dimensions can boost [Li.sup.+] ion and electron transfer in nanostructured electrodes. By manipulating two genes, we equipped viruses with peptide groups having affinity for single-wailed carbon nanotubes (SWNTs) on one end and peptides capable of nucleating amorphous iron phosphate (a-FeP[O.sub.4]) fused to the viral major coat protein. The virus done with the greatest affinity toward SWNTs enabled power performance of a-FeP[O.sub.4] comparable to that of crystalline lithium iron phosphate (c-LiFeP[O.sub.4]) and showed excellent capacity retention upon cycling at 1C. This environmentally benign low-temperature biological scaffold could facilitate fabrication of electrodes from materials previously excluded because of extremely low electronic conductivity.

Improved electrically powered artificial muscles are needed for generating force, moving objects, and accomplishing work. Carbon nanotube aerogel sheets are the sole component of new artificial muscles that provide giant elongations and elongation rates of 220% and (3.7 x [10.sup.4])% per second, respectively, at operating temperatures from 80 to 1900 kelvin. These solid-state--fabricated sheets are enthalpic rubbers having gaslike density and specific strength in one direction higher than those of steel plate. Actuation decreases nanotube aerogel density and can be permanently frozen for such device applications as transparent electrodes. Poisson's ratios reach 15, a factor of 30 higher than for conventional rubbers. These giant Poisson's ratios explain the observed opposite sign of width and Length actuation and result in rare properties: negative Linear compressibility and stretch densification.

A novel modified carbon nanotube paste electrode of 2-(4-oxo-3-phenyl-3, 4-dihydro-quinazolinyl)-N'-phenyl-hydrazinecarbothioamide (2PHC) was fabricated, and the electrooxidation of epinephrine (EP), norepinephrine (NE), and their mixture has been studied using electrochemical methods. The modified electrode displayed strong catalyric function for the oxidation of EP and NE and resolved the overlap voltammetric response of EP and NE into two well-defined voltammetric peaks of about 240 mV with square wave voltammetry (SWV). A linear response in the range of (5 x [10.sup.-8])-(5.5 x [10.sup.-4]) M with a detection limit (S/N = 3) of 9.4 nM for EP was obtained.

Comprehensive modeling and design methods for carbon nanotube (CNT)-based interconnects are developed, which are used for examining the performance, reliability and fabrication requirements for future nanotube-based interconnect solutions. The large diameter MWCNT bundles are more susceptible to process variations than SWCNT bundles, which have important implications for their utilization in future nanoscale integrated circuits.

This paper presents a comparative analysis of the electromagnetic properties of new composite materials that are of interest to future aircraft/aerospace structures. The fabrication process of single-phase and new multiphase micro/nanocomposites is described. Carbon black, carbon fibers, and multiwall carbon nanotubes are randomly mixed into an epoxy resin matrix at various weight fractions and compositions. The experimental characterization in the frequency range 8-18 GHz shows that the dispersion characteristics of short-carbon-fiber-reinforced composites can be properly controlled by the addition of nanopowders and nanotubes into the mixture. Numerical simulations demonstrate the feasibility of the fabricated materials for the design of new electromagnetic micro/nanostructured shields and radar-absorbing laminates. Thin dielectric Salisbury screens are especially designed to exhibit minimum reflection coefficient at 15 GHz. It shows that the total thickness of the screen can be reduced below 2 mm by using a lossy sheet made of three-phase composites. Index Terms--Advanced composite materials, aircraft, multiwall carbon nanotubes, radar-absorbing materials, shielding.

We report for the first time to our knowledge large-signal measurements performed at 600 MHz and in time domain on carbon nanotube field-effect transistors (CNFETs) using a large-signal network analyzer. To overcome the very high mismatch between the high CNFET impedance and the basic 50-[ohm] configuration of the setup, the output impedance was matched with the help of an experimental active load-pull configuration. Hence, we were able to observe under large-signal conditions the nonlinear behavior of CNFETs. Static measurements and continuous-wave S/j-parameter measurements were made for many different biases. They were used in order to determine a nonlinear electrical model that has been validated thanks to the nonlinear measurements. The developed model opens the way for electrical CNFET circuit simulation and nonlinear applications of these devices. Index Terms--Carbon nanotube field-effect transistor (CNFET), large-signal network analyzer (LSNA), neuronal modeler, non-linear model.

The fabrication and functional characterization of a thin-film bulk-acoustic resonator (TFBAR) gas sensor onto a silicon substrate are discussed. A nanocomposite layer of carbon nanotubes, prepared by the Langmuir-Blodgett technique has been shown to be used for the functionalization of the sensor.

We report on the accuracy of the pseudo-rigid-body model (PRBM) in predicting the behavior of a nanoscale parallel-guiding mechanism (nPGM) that uses two single-walled (5,5) carbon nanotubes (CNTs) as the flexural guiding elements. The nPGM has two regions of behavior: region 1 is governed by the bulk deformation of the nanotubes, and region 2 is characterized by hingelike flexing of four 'kinks' that occur due to buckling of the nanotube walls. PRBM parameters for (5,5) CNTs are proposed. Molecular simulation results of region 1 behavior match PRBM predictions of (1) kinematic behavior with less than 7.3% error and (2) elastomechanic behavior with less than 5.7% error. Although region 1 is of more interest because of its well-defined and stable nature, region 2 motion is also investigated. We show that the PRBM parameters are dependent on the selection of the effective tube thickness and moment of inertia, the lesson being that designers must take care to consider the thickness and moment of inertia values when deriving PRBM constants. [DOI: 10.1115/1.2885192] Keywords: compliant mechanism, pseudo-rigid-body, flexure, carbon nanotube, molecular simulations, nanomechanical, nanoelectromechanical

Nanofibrils of ultrahigh molecular weight syndiotactic polystyrene (sPS) are prepared in a silica nanotube reactor (SNTR) by using a metallocene catalyst in conjunction with methylaluminoxane cocatalyst. The sPS synthesized in the SNTR has ultrahigh molecular weight with a large fraction of molecular weight polymers.

We demonstrate a method for generating discretely structured protein nanotubes from the simple ring-shaped building block, homohexameric Hcpl from Pseudomonas aeruginosa. Our design exploited the observation that the crystal lattice of Hcpl contains rings stacked in a repeating head-to-tail pattern. High-resolution detail of the ring-ring interface allowed the selection of sites for specific cysteine mutations capable of engaging in disulfide bond formation across rings, thereby generating stable Hcp1 nanotubes. Protein nanotubes containing up to 25 subunits ([approximately equal to] 100 nm in length) were self-assembled under simple conditions. Furthermore, we demonstrate that the tube ends and interior can be independently and specifically functionalized to generate nanocapsules. nanocapsule | protein engineering | dendrimer | disulfide | drug delivery

Free vibrations of a double-walled carbon nanotube (DWNT) are studied. The inner and outer carbon nanotubes are modeled as two individual elastic beams interacting each other by van der Waals forces. An original method is proposed to calculate the first seven order resonant frequencies and relative vibrational modes. Detailed results are demonstrated for DWNTs according to the different boundary conditions between inner and outer tubes, such as fixed-free, canthever-free, fixed-simple and fixed-fixed (reduced form) supported ends. Our results indicate that there is a special invariable frequency for a DWNT that is not affected by different combinations of boundary conditions. All vibrational modes of the DWNT must be coaxial when the resonant frequency is smaller than this frequency. Some noncoaxial vibrations will occur when their resonant frequencies exceed the frequency. Especially, the first noncoaxial resonant frequency is still invariable for. all different boundary conditions. A change of resonant frequency for various lengths of DWNTs is discussed in detail. In addition, our model predicts a new coaxialnoncoaxial vibrational mode in fixed-simple supports for inner and outer tubes of a DWNT. [DOI: 10.1115/1.2793133] Keywords: carbon nanotube, vibration, resonant frequency, vibrational mode, boundary condition

The improvement of the interpixel uniformity by individually controlling the luminance of all subpixels in a display panel is discussed. The correction method has ensured the improvement of the interpixel uniformity in large-size carbon nanotube field emission display (CNT-FED).

This paper reports the molecular imprinting at the walls of highly uniform silica nanotubes for the recognition of 2,4,6-trinitrotoluene (TNT). It has been demonstrated that TNT templates were efficiently imprinted into the matrix of silica through the strong acid-base pairing interaction between TNT and 3-aminopropyltriethoxysilane (APTS). TNT-imprinted silica nanotubes were synthesized by the gelation reaction between APTS and tetraethylorthosilicate (TEOS), selectively occurring at the porous walls of APTS-modified alumina membranes. The removal of the original TNT templates leaves the imprinted cavities with covalently anchored amine groups at the cavity walls. A high density of recognition sites with molecular selectivity to the TNT analyte was created at the wall of silica nanotubes. Furthermore, most of these recognition sites are situated at the inside and outside surfaces of tubular walls and in the proximity of the two surfaces due to the ultrathin wall thickness of only 15 nm, providing a better site accessibility and lower mass-transfer resistance. Therefore, greater capacity and faster kinetics of uptaking target species were achieved. The silica nanotube reported herein is an ideal form of material for imprinting various organic or biological molecules toward applications in chemical/biological sensors and bioassay.

Scaling of Silicon transistors continue ill the sub 100-nm regime amidst severe roadblocks. Increased short-channel effects, rising leakage currents, severe process parameter variations are only a few of the overwhelming challenges that the device and circuit designers are laced with. In an attempt to alleviate the problems associated with the scaling of silicon transistors, researchers have began a quest for novel alternate materials in a post-Si nanoelectronics era. Of the different materials investigated so far, carbon nanotubes with their superior transport properties, excellent thermal conductivities and high current handling capacities have proved to be a potential heir to St. This paper reviews the promise of carbon nanotube field-effect transistors as future devices for high-performance as well as low-power electronics. Index Terms--Carbon nanotubes, high-speed logic, low-power circuits, subthreshold logic.

Crossbar switching networks formed by nanowires are promising future data storage devices. This work addresses the fundamental question: What is the information storage capacity of a crossbar switching network? The two major classes of nanowire crossbar switching networks are considered, those with ohmic and those with semiconductive switches. The focus is on the first class which is in the center of current nanotechnology research. Exact, simple approximate, and asymptotic expressions of the information storage capacity are provided as functions of the network size. The derivations indicate technological and geometrical considerations in the design of efficient nanowire devices. Index Terms--Array, capacity, crossbar, device, information, memory, nanotechnology, nanotube, nanowire, network, storage, switching.

In this paper, a nonlinear theory applicable to the design of nanotube based devices is presented. The role of finite kinematics for a doubly clamped nanotube device is investigated. In particular, we analyze the continuous deformation and instability (pull in) of a clamped-clamped nanotube suspended over an electrode from which a potential differential is imposed. The transformation of an applied voltage into a nanomechanical deformation indeed represents a key step toward the design of innovative nanodevices. Likewise, accurate prediction of pull-in/pull-out voltages is highly needed. We show that an energy-based method can be conveniently used to predict the structural behavior and instability corresponding to the ON/OFF states of the device at the so-called pull-in voltage. The analysis reveals that finite kinematics effects can result in a significant increase of the pull-in voltage. This increase results from a ropelike behavior of the nanotube as a consequence of the stretching imposed by the actuation. [DOI: 10.1115/1.1875452]

Many routes have been developed for the synthesis of carbon nanotubes, but their assembly into continuous fibers has been achieved only through postprocessing methods. We spun fibers and ribbons of carbon nanotubes directly from the chemical vapor deposition (CVD) synthesis zone of a furnace using a liquid source of carbon and an iron nanocatalyst. This process was realized through the appropriate choice of reactants, control of the reaction conditions, and continuous withdrawal of the product with a rotating spindle used in various geometries. This direct spinning from a CVD reaction zone is extendable to other types of fiber and to the spin coating of rotating objects in general., Macroscopic assemblies of carbon nanotubes are desired for a wide range of applications, including composites, micromechanical actuators, power cables, electrodes, and catalyst supports (1, 2). Considerable research has been directed [...]

The scope of various types of two-dimensional carbon nanostructures including graphene and free-standing carbon nanowalls/nanosheets are discussed. The synthesis, characterization and potential applications of the carbon nanostructures are presented.

The article presents a new shell model and a general hypothesis, which can be employed for the growth and synthesis of various different semiconductor nanotubes. It also explains the different conditions that can be created for the formation of different carbon nanotubes with varying characteristics and properties.

Byline: Peiman Keshavarzian, Keivan Navi Multiple-valued logic circuits can reduce the number of operations necessary to implement a particular mathematical function and further have an advantage in terms of reduced area. Implementable CNTFET circuits have operational characteristics to approach the advantage of using MVL. Conventional nanotube diameters and using CNTFET characteristics has attracted considerable attention in the ternary logic family designs. In order to describe all ternary functions, we have achieved a new CNTFET circuit design in the universal form. In this design we have neither exclusive design problems nor mathematical equations to achieve the appropriate combination of the basic operations in the MVL fields.

Byline: Ting Xu, Zhihong Wang, Jianmin Miao This paper reports on a carbon-nanotube (CNT) enhanced piezoelectric membrane for the possible application as a mass sensitive biosensor. CNT possesses a hollow core and large specific surface area that could be used for bio-molecular binding. A larger number of probe molecules on the surfaces of CNT could capture more target molecules and therefore increase the detection sensitivity of the biosensor. Based on this idea, we have fabricated the piezoelectric membrane incorporated with CNT. The piezoelectric membrane with a thickness of 0.8 [micro]m was fabricated by micro-machining technique and its Q factor in air was characterised to be as high as 219 at a frequency of about 122 kHz. The fabricated PZT membrane was then loaded into quartz tube under a pressure of 12 Torr to grow CNTs by using thermal chemical vapour deposition (TCVD) at a temperature of 700[degrees]C. CNTs were successfully synthesised on the backside of the membrane and the average length was about 10 [micro]m. Raman spectrum showed the intensity ratio (IG/ID) of the grown CNTs in this work was 1.18. The detailed fabrication process has been reported.

The bound state in a current-carrying nanotube is discussed on the basis of the Landau quantization which includes the finite length effect, induced magnetic field, and electric field. The results obtained shed light on significant role of Landau mode in the electrical breakdown and thinning phenomena and the spread of wave function in the outer side in the radial direction which activates the air and triggers the destruction of atomic bonds.

Two device models of outer-wall disordered carbon nanotube with lead contacts of multi- and single-wall nanotubes are described for both measurement and control of carrier mobility in multiwall carbon nanotubes. The results have presented a new method for the design and application of the nanotube molecular devices and device wiring.

A dense nest of carbon nanotube (CNT) onto the surface of carbonyl ion (CI) particles is constructed by using 4-aminobenzoic acid as a grafting agent. Magnetorheological (MR) characteristics of CI/SNT particles in a parallel plate geometry equipped with a magnetic field supplied is shown to be similar with that of pristine CI suspension, while the sedimentation ratio has also improved.

Polarized Raman spectroscopy is used for deriving the orientation distribution function (ODF) for a uniaxial-axially symmetric system. The ODF results have shown that the higher electric field frequencies have produced a good alignment of the single wall nanotube (SWNT) inclusions.

The fabrication and magnetic properties of the Ni-Cu nanowires and the Ni nanotubes are reported. The finite size effect in nucleation and growth could be exploited for the formation of core/shell nanowires for pore diameters in the range of 100-220 nm.

Lanthanum atoms are introduced into carbon nanotubes with the help of fullerene cages as carry bags and are further transformed into atomic wires. Since the lanthanoid metals are encapsulated in the fullerene cage to form metallofullerene, this method can be used for all the metallofullerenes, generating atomic wires of transition or lanthanoid series metals inside carbon nanotubes (CNTs).

A first principle computational study about the water confined between prototypical nonpolar substrates like single-wall carbon nanotubes and graphene sheets is reported. The findings reveal that the perturbation induced by the presence of confining media is extremely local in liquid water and is determined by subtle electronic structure rearrangements occurring at the interface with the confining medium.

The fabrication of two kinds of Ce[O.sub.2] nanotubes with unique structures and morphologies by using Ce(OH)C[O.sub.3] nanorods as precursors is demonstrated.

Tellurium-filled double-walled carbon nanotubes (Te@DWNTs) are analyzed by using Raman spectroscopy. The comparison of the main Raman bands and their temperature coefficients of pristine and filled carbon nanotubes have shown a decreased interaction between the carbon atoms in the nanotubes, which is due to the additional van der Waals interaction between the Te atoms and the carbon nanotube inner wall.

A large number of studies are conducted to demonstrate and fabricate the highly ordered silicon (Si) nanotube (SiNT) arrays, which act as attractive matrix to accommodate macromolecules and help in direct electrochemistry of cytochrome c without any pretreatment. The result indicates that the SiNT arrays exhibit good biocompatibility, as well as a nanoscale hollow structure and hence can be used in the preparation of various Si-based biosensors and protein characterizations.

A new method that makes use of colloidal silica templates is demonstrated to fabricate porous three-dimensional architectures of carbon nanotubes (CNTs). Porous CNT membranes and three-dimensional carbon nanotube foams are obtained by treating these silica-CNTs structures with HF.

New capabilities for creating arrangements of single-walled carbon nanotubes SWNTs that could be useful for applications in thin-film electronics are introduced. It is stated that these techniques complement other reported approaches and may facilitate the use of SWNTs in practical devices.

Byline: Yu.E. Lozovik, A.G. Nikolaev, A.M. Popov The structures of double wall carbon nanotubes (DWNTs) with atomic scale defects that can operate as bolt and nut pairs are analysed. The barriers and threshold forces for the relative motion of walls along the thread line and for twistoff are calculated for various types of defects. It is found that a type of defect does not influence the qualitative characteristics of a thread. The possibility of producing of the DWNT (which can operate as bolt and nut pair) by selforganisation is proposed.

A simple method to decorate that multiwalled carbon nanotubes (MWCNTs) with zinc sulfide nanospheres is developed. The method involves ultrasonic pretreatment and heat treatments of MWCNTs, zinc chloride, and thiourea in ethanol.

The template technique was used for the successful preparation of the double coaxial carbon nanotubes (CNT) composed of N-doped and B-doped multiwalls. By changing the CVD conditions it was shown that is possible to adjust the N or B fraction and respective thickness of N-doped and B-doped multiwalls.

The synthesis of shell-cross-linked organometallic nanotubes of silver that contain a polyferrocenylsilane (PFS) inner wall covered by a cross-linked network of polymethylvinylsiloxane chains is reported. The result showed that pretreatment of PFS with organic oxidants such as dichloromethane is the key step to obtain silver particles within the tubes in high yields and the resulting soluble peapod-like hybrid nanostructures may ultimately be useful for the fabrication of nanodevices.

Byline: A.M. Benito, W.K. Maser, M.T. Martinez In this paper, we present our work on carbon nanotubes, including our most recent results, in two important fields: production of carbon nanotubes itself and fabrication of carbon nanotube based composites with enhanced functionality. Firstly, we focus on the three main carbon nanotube production techniques, namely electric arc, laser evaporation and CVD. Based on our results, for each method the importance of the key parameters is highlighted. A comparison of production possibilities towards commercialisation concludes this section. Secondly, we report on the synthesis of a soluble and highly functional polyaniline/carbon nanotube composite and emphasise the general importance of conformational changes in order to achieve proper carbon nanotubematrix interactions.