Nanotube Research Papers - Academia.edu (original) (raw)

Carbon nanotube paper, sometimes referred to as bucky paper, is a random arrangement of carbon nanotubes meshed into a single robust structure, which can be manipulated with relative ease. Multi-walled carbon nanotubes were used to make... more

Carbon nanotube paper, sometimes referred to as bucky paper, is a random arrangement of carbon nanotubes meshed into a single robust structure, which can be manipulated with relative ease. Multi-walled carbon nanotubes were used to make the nanotube paper, and were subsequently modified with platinum using an electroless deposition method based on substrate enhanced electroless deposition. This involves the use of a sacrificial metal substrate that undergoes electro-dissolution while the platinum metal deposits out of solution onto the nanotube paper via a galvanic displacement reaction. The samples were characterized using SEM/EDS, and Hall-effect measurements. The SEM/EDS analysis clearly revealed deposits of platinum (Pt) distributed over the nanotube paper surface, and the qualitative elemental analysis revealed co-deposition of other elements from the metal substrates used. When stainless steel was used as sacrificial metal a large degree of Pt contamination with various other metals was observed. Whereas when pure sacrificial metals were used bimetallic Pt clusters resulted. The co-deposition of a bimetallic system upon carbon nanotubes was a function of the metal type and the time of exposure. Halleffect measurements revealed some interesting fluctuations in sheet carrier density and the dominant carrier switched from N-to P-type when Pt was deposited onto the nanotube paper. Perspectives on the use of the nanotube paper as a replacement to traditional carbon cloth in water electrolysis systems are also discussed.

ABSTRACT：The term ' Piezoresistive effect ' describes a change in the electrical resistance of the material from deformed to its original shape by the external pressure, e.g., elongation, compression, etc. This phenomenon has various... more

ABSTRACT：The term ' Piezoresistive effect ' describes a change in the electrical resistance of the material from deformed to its original shape by the external pressure, e.g., elongation, compression, etc. This phenomenon has various applications of sensors for monitoring pressure, vibration, and acceleration. Although there are many materials which have the piezoresistive effect, rubber (nano)composites with conductive fillers have attracted a great deal of attention because the piezoresistive effect appears at the various range of pressure by controlling the type of filler, particle size, particle shape, aspect ratio of particles, and filler content. Especially one can obtain the composites with elasticity and flexibility by using the rubber as a matrix. This paper aims to review the piezoresistive effect itself, their basic principles, and the various conductive rubber-composites with piezoresistive effect.

Water-mediated interactions (WMIs) play diverse roles in molecular biology. They are particularly relevant in geometrically confined spaces such as the interior of the chaperonin, at the interface between ligands and their binding... more

Water-mediated interactions (WMIs) play diverse roles in molecular biology. They are particularly relevant in geometrically confined spaces such as the interior of the chaperonin, at the interface between ligands and their binding partners, and in the ribosome tunnel. Inspired in part by the geometry of the ribosome tunnel, we consider confinement effects on the stability of peptides. We describe results from replica exchange molecular dynamics simulations of a system containing a 23-alanine or 23-serine polypeptide confined to non-polar and polar nanotubes in the gas phase and when open to a water reservoir. We quantify the effect of water in determining the preferred conformational states of these polypeptides by calculating the difference in the solvation free energy for the helix and coil states in the open nanotube in the two phases. Our simulations reveal several possibilities. We find that nanoscopic confinement preferentially stabilizes the helical state of polypeptides with...

Nanostructures with any external dimensions in the nanoscale (size range approximately from 1 to 100 nm) or having internal or surface structure in the nanoscale are defined by the catalytic reaction model in conductive nanomaterial... more

Nanostructures with any external dimensions in the nanoscale (size range approximately from 1 to 100 nm) or having internal or surface structure in the nanoscale are defined by the catalytic reaction model in conductive nanomaterial particles. " Nanostructures " means a natural, accidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where for 50% or more of the particles in the number size distribution, one or more external dimensions are in the size range 1 nm - 100 nm. In special cases and where, the size distribution threshold may be replaced by a threshold between nanomaterial particles. Inferring from the above, nanostructures with one or more external dimensions less than 1 nm should be considered as vital devices in nanoelectronics. Nanostructures that react naturally. Or are produced as a combustion by-product (unintentional) from combustion processes. They are usually physically and chemically heterogeneous and are often referred to as porous particles. " On the other hand, nanostructures are produced and designed from multiple structures with physical and electronic goals for a specific purpose or function.

Metallic single wall carbon nanotube devices were characterized using low temperature transport measurements to study how the growth conditions affect defect formation in carbon nanotubes. Suspended carbon nanotube devices were grown in... more

Metallic single wall carbon nanotube devices were characterized using low temperature transport measurements to study how the growth conditions affect defect formation in carbon nanotubes. Suspended carbon nanotube devices were grown in situ by a molecular beam growth method on a pair of catalyst islands located on opposing Au electrodes fabricated by electron beam lithography. The authors present experimental evidence that defect formation in carbon nanotubes, in addition to the well known growth temperature dependence, is also affected by the nature and the composition of the carbon growth gases.

We report the direct measurements on the bulk morphology of vertically aligned multiwalled carbon nanotube (CNT) arrays using small angle neutron scattering (SANS). SANS measurements at different heights of CNT arrays corresponding to... more

We report the direct measurements on the bulk morphology of vertically aligned multiwalled carbon nanotube (CNT) arrays using small angle neutron scattering (SANS). SANS measurements at different heights of CNT arrays corresponding to different stages of the growth reveal increasing alignment order along the thickness and two distinctly different CNT morphologies. The observations suggest that the evolution of the macroscopic CNT morphologies be driven by competing collective growth and spatial constraints.

In the present work, multi-walled carbon nanotube (MWCNT)-doped TiO2 nanocomposite films were synthesized by sol–gel method. The influence of nanotube concentration on the structural, electrical and optical properties of the films was... more

In the present work, multi-walled carbon nanotube (MWCNT)-doped TiO2 nanocomposite films were synthesized by sol–gel method. The influence of nanotube concentration on the structural, electrical and optical properties of the films was investigated. The beneficial effects of the addition of carbon nanotubes into a TiO2 film and titania-coated MWCNTs have much in common. On the other hand, this work contributes to the previous studies in terms of the optical and electrical properties of MWCNT. For this reason, MWCNT/rare brookite-phased TiO2 matrix as simple sol–gel deposited composite films were investigated in our study. The XRD studies showed that the composite film has a brookite crystal structure at the annealing temperature of 450∘C. According to the surface morphology investigations, SEM image of nanocomposite film shows that composite film has a granular and rod-like structure. The absorbance measurements of the films were carried out by the UV–Vis spectrophotometer to investi...

Nanostructures and nanomaterials intrinsically can interact with biological systems at the fundamental molecular levels with high specificity, which has held great potential for developing methods of controlling cell behaviors such as... more

Nanostructures and nanomaterials intrinsically can interact with biological systems at the fundamental molecular levels with high specificity, which has held great potential for developing methods of controlling cell behaviors such as adhesion, proliferation, and differentiation. For instance, carbon nanotubes (CNTs), as extracellular scaffolds, have been used to guide neural cell growth and regulate cell polarity. However, in order to harness

It is well established that pristine multiwalled carbon nanotubes offer poor structural reinforcement in epoxy-based composites. There are several reasons for this which include reduced interfacial contact area since the outermost... more

It is well established that pristine multiwalled carbon nanotubes offer poor structural reinforcement in epoxy-based composites. There are several reasons for this which include reduced interfacial contact area since the outermost nanotube shields the internal tubes from the matrix, poor wetting and interfacial adhesion with the heavily cross-linked epoxy chains, and intertube slip within the concentric nanotube cylinders leading to a sword-in-sheath type failure. Here we demonstrate that unzipping such multiwalled carbon nanotubes into graphene nanoribbons results in a significant improvement in load transfer effectiveness. For example, at ϳ0.3% weight fraction of nanofillers, the Young's modulus of the epoxy composite with graphene nanoribbons shows ϳ30% increase compared to its multiwalled carbon nanotube counterpart. Similarly the ultimate tensile strength for graphene nanoribbons at ϳ0.3% weight fraction showed ϳ22% improvement compared to multiwalled carbon nanotubes at the same weight fraction of nanofillers in the composite. These results demonstrate that unzipping multiwalled carbon nanotubes into graphene nanoribbons can enable their utilization as high-performance additives for mechanical properties enhancement in composites that rival the properties of singlewalled carbon nanotube composites yet at an order of magnitude lower cost.

It is well established that pristine multiwalled carbon nanotubes offer poor structural reinforcement in epoxy-based composites. There are several reasons for this which include reduced interfacial contact area since the outermost... more

It is well established that pristine multiwalled carbon nanotubes offer poor structural reinforcement in epoxy-based composites. There are several reasons for this which include reduced interfacial contact area since the outermost nanotube shields the internal tubes from the matrix, poor wetting and interfacial adhesion with the heavily cross-linked epoxy chains, and intertube slip within the concentric nanotube cylinders leading to a sword-in-sheath type failure. Here we demonstrate that unzipping such multiwalled carbon nanotubes into graphene nanoribbons results in a significant improvement in load transfer effectiveness. For example, at ϳ0.3% weight fraction of nanofillers, the Young's modulus of the epoxy composite with graphene nanoribbons shows ϳ30% increase compared to its multiwalled carbon nanotube counterpart. Similarly the ultimate tensile strength for graphene nanoribbons at ϳ0.3% weight fraction showed ϳ22% improvement compared to multiwalled carbon nanotubes at the same weight fraction of nanofillers in the composite. These results demonstrate that unzipping multiwalled carbon nanotubes into graphene nanoribbons can enable their utilization as high-performance additives for mechanical properties enhancement in composites that rival the properties of singlewalled carbon nanotube composites yet at an order of magnitude lower cost.

] reported the experimental realization of carbon nanotube S-like shaped nanostructures, the so-called carbon nanotube serpentines. We report here results from multimillion fully atomistic molecular dynamics simulations of their... more

] reported the experimental realization of carbon nanotube S-like shaped nanostructures, the so-called carbon nanotube serpentines. We report here results from multimillion fully atomistic molecular dynamics simulations of their formation. We consider one-m-long carbon nanotubes placed on stepped substrates with and without a catalyst nanoparticle on the top free end of the tube. A force is applied to the upper part of the tube during a short period of time and turned off; then the system is set free to evolve in time. Our results show that these conditions are sufficient to form robust serpentines and validates the general features of the ''falling spaghetti model'' proposed to explain their formation.

In this study, platinum particles were fabricated on flexible, transparent, single-walled carbon nanotube films without the addition of reducing or protecting agents using a facile and controllable electrochemical method. Spherical... more

In this study, platinum particles were fabricated on flexible, transparent, single-walled carbon nanotube films without the addition of reducing or protecting agents using a facile and controllable electrochemical method. Spherical platinum particles (SPPs) were transformed into flower-like platinum particles (FPPs) by varying the applied potential, the pattern size of the photoresist polymer, and the deposition time. An analysis of the X-ray diffraction data revealed that the FPPs possessed a face centered cubic structure. The intensity ratio of ( ) to (200) diffraction lines for the FPPs (2.15) was greater than that of the SPPs (1.44), indicating that the as-prepared FPPs were dominated by the lowest-energy (111) facets. The electrocatalytic activities of the synthesized particles with regard to methanol and formic acid oxidation were investigated. The FPPs exhibited higher catalytic performance for the electrochemical oxidation of methanol and formic acid than the SPPs. The high oxidation current of the FPP-based electrode was directly related to the morphologies of the platinum particles. The simple approach employed in this study will be useful for fabricating particles of other noble metals with different morphologies.

Boron nitride nanoribbons (BNNRs) are strips of thin BN sheets with widths on the nanometer scale. BNNRs have unique edge states and width-related properties. First-principle calculations reveal that the bandgaps of zigzag BNNRs relate to... more

Boron nitride nanoribbons (BNNRs) are strips of thin BN sheets with widths on the nanometer scale. BNNRs have unique edge states and width-related properties. First-principle calculations reveal that the bandgaps of zigzag BNNRs relate to nanoribbon width and are tunable by external electric fields and different levels of edge hydrogenation. Though bulk hexagonal boron nitride (hBN) crystals are electrically insulating, BNNRs can be made half-metallic through edge hydrogenation, fluorination, and oxygen functionalization. 3] Intriguing edge magnetism has also been proposed in BNNRs. [3b, 4] An experimental study has shown that BNNRs are much more electrically conductive than boron nitride nanotubes (BNNTs). BNNRs are chemically more reactive than bulk BN owing to the high number of unsaturated edge atoms, which makes them ideal gas-sensing materials. Compared to BN nanotubes and nanosheets, BNNRs could be better composite fillers for improved mechanical enhancement because of stronger interface bindings between BNNR edges and matrix. Therefore, BNNRs are of great interest for nanoscale electronic, spintronic, optoelectronic, sensor, and composite applications. All of these applications require BNNRs in large amounts and high quality. However, the synthesis of nanoribbons is quite challenging. BNNRs have been produced by unzipping BNNTs by postsynthesis treatment, that is, plasma etching and alkali metal intercalation, similar to the methods [

We are developing a compact two-cavity amplifier that uses a rugged carbon-nanotube cold-cathode to produce microwave radiation with very high efficiency. The entire RF circuit and electron gun have already been built and are currently... more

We are developing a compact two-cavity amplifier that uses a rugged carbon-nanotube cold-cathode to produce microwave radiation with very high efficiency. The entire RF circuit and electron gun have already been built and are currently under testing. We will present ...

This paper describes the electrochemical investigation of two multi-walled carbon nanotube-based electrodes using potassium ferricyanide as a benchmark redox system. Carbon nanotubes were fabricated by chemical vapor deposition on silicon... more

This paper describes the electrochemical investigation of two multi-walled carbon nanotube-based electrodes using potassium ferricyanide as a benchmark redox system. Carbon nanotubes were fabricated by chemical vapor deposition on silicon wafer with camphor and ferrocene as precursors. Vertically-aligned as well as islands of horizontally-randomly-oriented carbon nanotubes were obtained by varying the growth parameters. Cyclic voltammetry was the employed method for this electrochemical study. Vertical nanotubes showed a slightly higher kinetic. Regarding the sensing parameters we found a sensitivity for vertical nanotubes almost equal to the sensitivity obtained with horizontally/randomly oriented nanotubes (71.5 ± 0.3 μA/(mM cm 2) and 62.8± 0.3 μA/(mM cm 2), respectively). In addition, values of detection limit are of the same order of magnitude. Although tip contribution to electron emission has been shown to be greatly larger than the lateral contribution on single carbon nanotubes per unit area, the new findings reported in this paper demonstrate that the global effects of nanotube surface on potassium ferricyanide electrochemistry are comparable for these two types of nanostructured surfaces.

This study is an attempt to perform equilibrium molecular dynamics and non-equilibrium molecular dynamics (NEMD) to evaluate the stability and thermal behavior of molybdenum disulfide nanotubes (MoS2NTs) by reactive empirical bond order... more

This study is an attempt to perform equilibrium molecular dynamics and non-equilibrium molecular dynamics (NEMD) to evaluate the stability and thermal behavior of molybdenum disulfide nanotubes (MoS2NTs) by reactive empirical bond order potential. The stability of nanotubes, cohesive energy, isobaric heat capacity, and enthalpies of fusion in armchair and zigzag structures with different radii were calculated. The observed results illustrate that SWMoS2NTs, which have larger diameters, are more stable with more negative energy than the smaller ones. Moreover, it was found that the melting point is increased with an increase in the nanotube's radius. During the melting process, the structural transformation of nanotubes was investigated using a mean-square displacement and radial distribution function diagrams. Afterwards, using a NEMD simulation, the thermal conductivity of nanotubes with various diameters was calculated at a constant nanotube length. The obtained results show t...

The effect of opposite sign of interactions in a single-walled Ising nanotube is investigated using the Wang-Landau algorithm. The thermodynamic observables are calculated from the estimated density of states (DOS) with and without the... more

The effect of opposite sign of interactions in a single-walled Ising nanotube is investigated using the Wang-Landau algorithm. The thermodynamic observables are calculated from the estimated density of states (DOS) with and without the presence of an external magnetic field. Irrespective of the applied magnetic field, a symmetric trend of DOS is observed for opposite sign of interactions which is in contrast to the asymmetric trend for same sign of interactions. Further, two types of anti-ferromagnetic (AFM) orderings, namely A-type and C-type anti-ferromagnetic order, are observed for opposite sign of interactions. These AFM spin orientations are switched to ferromagnetic (FM) phase by increasing the applied magnetic field (B). However, the spin ordering changes from the ordered AFM/FM phase to a disordered paramagnetic phase by increasing the temperature. Phase diagram shows that these three phases coexist around B = 2.0. This study indicates that, by properly tuning the magnetic properties, the single-walled nanotube can be used for fabrication of new types of magnetic storage nano materials.

We present the Monte-Carlo analysis report for the magnetic response of the single-walled nanotube using the Metropolis and Wang Landau algorithms. Our nanotube architecture uses the spin half Ising model with nearest neighbors... more

We present the Monte-Carlo analysis report for the magnetic response of the single-walled nanotube using the Metropolis and Wang Landau algorithms. Our nanotube architecture uses the spin half Ising model with nearest neighbors interaction. We find the phase changes from ferromagnetic/anti ferromagnetic to paramagnetic by modifying the system interaction parameters. We determine the transition temperatures for varying interaction strength in the absence of the magnetic field. We find the transition temperature changes with the external magnetic field for a fixed interaction strength. Our study confirmed that the transition from ferromagnetic/anti ferromagnetic to paramagnetic is second order.