Single Carbon Nanotubes Research Articles

Solar radiation synthesis of functional carbonaceous materials using Al2O3/TiO2-Cu-HA doped catalyst

Single carbon nanotubes were synthesized through a physical vapor deposition method, using concentrated solar radiation as means of vaporization and promoting the formation of carbonaceous plasma plume. A novel catalyst, containing multiple hybrid ceramic/metal phases has been obtained through flame spraying. In conjunction with this catalyst, good quality nanomaterials, such as long single-walled nanotubes and nanoparticles have been obtained and characterized by both morphological (SEM, TEM) as well as structural means on analysis (XRD, FTIR). A mild oxidation of the carbonaceous phase has been reported, which could prove useful in applications in conjunction with metals or hydrophilic polymers as potential matrices for nanocomposites obtaining.

Field emission properties of a DWCNT bundle and a single MWCNT

The field emission properties of a bundle of double-walled carbon nanotubes (DWCNTs) and a single multiwalled carbon nanotube (MWCNT) were investigated. A DWCNT bundle or a single MWCNT was attached to the head of sharpened tip of tungsten by electrophoresis; the tungsten tip was dipped into a drop of a carbon nanotube/1,2-dichloroethane suspension on a stainless plate, and a high-frequency AC voltage (20 V peak to peak with a frequency of 15 MHz) was applied between the tungsten tip and the stainless steel plate. The turn-on fields of the DWCNT and MWCNT tips for 1 nA/cm2 were 0.05 and 0.48 V/μm, respectively. From the Fowler-Nordheim plots, the field enhancement factor (β) of the tips was estimated to be 109,600 (DWCNT) and 6780 (MWCNT). The present DWCNT emitter is characterized by a very small turn-on field and large β. The field emission performance is discussed in terms of the sizes of the bundle of DWCNTs and a single MWCNT.

A terahertz performance of hybrid single walled CNT based amplifier with analytical approach

This work is focuses on terahertz performance of hybrid single walled carbon nanotube (CNT) based amplifier and proposed for measurement of soil parameters application. The proposed circuit topology provides hybrid structure which achieves wide impedance bandwidth of 0.33 THz within range of 1.07-THz to 1.42-THz with fractional amount of 28%. The single walled RF CNT network executes proposed ambition and proves its ability to resonant at 1.25-THz with analytical approach. Moreover, a RF based microstrip transmission line radiator used as compensator in the circuit topology which achieves more than 30 dB of gain. A proper methodology is chosen for achieves stability at circuit level in order to obtain desired optimal conditions. The fundamental approach optimizes matched impedance condition at (50+j0) Ω and noise variation with impact of series resistances for the proposed hybrid circuit topology and demonstrates the accuracy of performance parameters at the circuit level. The chip fabrication of the proposed circuit by using RF based commercial CMOS process of 45 nm which reveals promising results with simulation one. Additionally, power measurement analysis achieves highest output power of 26 dBm with power added efficiency of 78%. The succeed minimum noise figure from 0.6 dB to 0.4 dB is outstanding achievement for circuit topology at terahertz range. The chip area of hybrid circuit is 0.65 mm2 and power consumption of 9.6 mW.

Trends in Adsorption Energies of the Oxygenated Species on Single Platinum Atom Embedded in Carbon Nanotubes

Herein we study the effect of strain on the catalytic activity of different Pt-doped single wall metallic carbon nanotubes (SWCNT) towards the oxygen reduction reaction (ORR). We consider the possibility of the Pt-doped at single vacancy inside the SWCNT to investigate the effect of confinement on the reaction mechanism. Density functional theory calculations indicate that for the SWCNTs with tube diameters below 7 A, the strain energy varies significantly influencing the adsorption energies of the key intermediates of the ORR reaction. For the SWCNTs with tube diameters above 7 A, on the other hand, both the calculated strain and the adsorption energies are almost constant. We furthermore find that the adsorption energies are strongly affected by confinement effects as shown for Pt-doped systems that are located inside the SWCNT. We show that the Pt-doped at single vacancy of the SWCNT strongly binds the oxygenated species under ORR potentials and therefore the active species is covered by oxo- or hydroxo group. Because the presence of Pt atoms doped at the single and double vacancies of the SWCNT is equivalently probable we also studied the Pt-doped at double vacancy. We find that the most active motif is the Pt-doped at double vacancy of SWCNT with 0.24V overpotenital.

Ultrathin Beta-Nickel hydroxide nanosheets grown along multi-walled carbon nanotubes: A novel nanohybrid for enhancing flame retardancy and smoke toxicity suppression of unsaturated polyester resin

Novel nanohybrid (β-Ni(OH)2-CNTs) obtained by ultrathin Beta-Nickel hydroxide (β-Ni(OH)2) nanosheets grown along multi-walled carbon nanotubes (CNTs) was successfully synthesized and then incorporated into UPR to prepare UPR/β-Ni(OH)2-CNTs nanocomposites. Structure of β-Ni(OH)2-CNTs nanohybrid was confirmed by X-ray diffraction, scanning electron microscopy measurements. Compared with single CNTs or β-Ni(OH)2, the dispersion of β-Ni(OH)2-CNTs in UPR was improved greatly. And the UPR/β-Ni(OH)2-CNTs nanocomposites exhibited significant improvements in flame retardancy, smoke suppression, and mechanical properties, including decreased peak heat release rate by 39.79%, decreased total heat release by 44.87%, decreased smoke release rate by 29.86%, and increased tensile strength by 12.1%. Moreover, the amount of toxic volatile from UPR nanocomposites decomposition was dramatically reduced, and smoke generation was effectively inhibited during combustion. The dramatical reduction of fire hazards can be ascribed to the good dispersion, the catalytic charring effect of β-Ni(OH)2 nanosheets and physical barrier effect of stable network structure consisted of β-Ni(OH)2 and CNTs.

Fabrication and Properties of Magnesium Matrix Composite Reinforced by Carbon Nanotubes-Alumina Hybrid Reinforcements

Magnesium matrix composite reinforced by carbon nanotubes (CNTs)-Al2O3 hybrid reinforcements was successfully fabricated by a novel process. CNTs-Al2O3 in-situ mixture was synthesized by directly growing CNTs on Al2O3 particles acting as the carrier of Ni catalysts via chemical vapour deposition. The influences of Ni catalyst content on the morphology, structure and yield of CNTs were investigated. By powder metallurgy process, the CNTs-Al2O3 in-situ mixture was dispersed in Mg powder to fabricate the CNTs-Al2O3 synergistically reinforced Mg matrix composite. The performance test results showed that, the Mg matrix composite possessed improved mechanical properties, and the strengthening effects of CNTs-Al2O3 in-situ mixture were prior to those of single CNTs or Al2O3 reinforcement. The improvement of mechanical properties was due to that the introduction of Al2O3 can promote the dispersion of CNTs in Mg matrix and improve the interfacial bonding between CNTs and Mg.

Effect of single and multi-wall carbon nanotubes on the mechanical properties of Gd-123 superconducting phase

The influence of single wall carbon nanotubes SWCNTs and multi wall carbon nanotubes MWCNTs on Vickers microhardness of Gd-123 superconducting phase is studied. Samples of type (SWCNTs)x and (MWCNTs)xGdBa2Cu3O7−δ, composite where, 0.0≤x≤0.1wt.%, are prepared by solid-state reaction technique. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM). Moreover the samples are examined by measuring electrical resistivity and Vickers microhardness. The obtained results showed an enhancement in the phase formation and grains connectivity up to 0.06 and 0.08wt.% for SWCNTs and MWCNTs added samples, respectively. Likewise the superconducting transition temperature Tc was improved at a low content of CNTs but it suppressed for higher concentrations. In addition, the analysis of Vickers microhardness measurements suggests that the most suitable model that describes the behavior of our sample is proportional specimen resistance PSR model.

A molecular dynamics approach of the role of carbon nanotube diameter on thermal interfacial resistance through vibrational mismatch analysis

Carbon nanotubes (CNT) have been known to increase the heat transfer at the solid-liquid interfaces, but have a limitation due to the thermal interfacial resistance. Vibrational mismatch at the interface leads to this thermal interfacial resistance, which plays an important role in energy transfer at the boundary. Negligible work has been reported on the influence of CNT diameter on the resistance through the vibrational mismatch study. Molecular dynamics simulations have been performed to investigate the effect of single walled armchair CNT diameter on interfacial resistance between CNT and water molecules. This work is an effort to understand the heat transfer phenomenon at the interface of armchair CNT and water molecules. Vibrational mismatch at the interface is quantified by analyzing the vibrational spectra of CNT and water molecules. The thermal interfacial resistance is observed to be relatively higher for the larger diameter nanotube. This is attributed to the higher vibrational mismatch existing for larger diameter CNT due to low overlapping region between vibrational density states of CNT and water molecules. For smaller diameter CNT, the thermal interfacial resistance is low which results in the efficient heat transfer at the interface thus, emphasizing the indispensable role of smaller diameter CNTs in the cooling applications.

Electromagneto squeezing rotational flow of Carbon (C)-Water (H2O) kerosene oil nanofluid past a Riga plate: A numerical study.

This article predicts the electromagneto squeezing rotational flow of carbon-water nanofluid between two stretchable Riga plates. Riga plate is known as electromagnetic actuator which is the combination of permanent magnets and a span wise aligned array of alternating electrodes mounted on a plane surface. Mathematical model is developed for the flow problem with the phenomena of melting heat transfer, viscous dissipation and heat generation/absorption. Water and kerosene oil are utilized as the base fluids whereas single and multi-wall carbon nanotubes as the nanomaterials. Numerical solutions of the dimensionless problems are constructed by using built in shooting method. The correlation expressions for Nusselt number and skin friction coefficient are developed and examined through numerical data. Characteristics of numerous relevant parameters on the dimensionless temperature and velocity are sketched and discussed. Horizontal velocity is found to enhance for higher modified Hartman number.

Improving Single-Carbon-Nanotube-Electrode Contacts Using Molecular Electronics.

We report the use of an electroactive species, acetaminophen, to modify the electrical connection between a carbon nanotube (CNT) and an electrode. By applying a potential across two electrodes, some of the CNTs in solution occasionally contact the electrified interface and bridge between two electrodes. By observing a single CNT contact between two microbands of an interdigitated Au electrode in the presence and absence of acetaminophen, the role of the molecular species at the electronic junction is revealed. As compared with the pure CNT, the current magnitude of the acetaminophen-modified CNTs significantly increases with the applied potentials, indicating that the molecule species improves the junction properties probably via redox shuttling.

Modulation of thermal and thermoelectric transport in individual carbon nanotubes by fullerene encapsulation.

The potential impact of encapsulated molecules on the thermal properties of individual carbon nanotubes (CNTs) has been an important open question since the first reports of the strong modulation of electrical properties in 2002. However, thermal property modulation has not been demonstrated experimentally because of the difficulty of realizing CNT-encapsulated molecules as part of thermal transport microstructures. Here we develop a nanofabrication strategy that enables measurement of the impact of encapsulation on the thermal conductivity (κ) and thermopower (S) of single CNT bundles that encapsulate C 60, Gd@C 82 and Er 2@C 82. Encapsulation causes 35-55% suppression in κ and approximately 40% enhancement in S compared with the properties of hollow CNTs at room temperature. Measurements of temperature dependence from 40 to 320 K demonstrate a shift of the peak in the κ to lower temperature. The data are consistent with simulations accounting for the interaction between CNTs and encapsulated fullerenes.

Schottky Diode Based on a Single Carbon–Nanotube–ZnO Hybrid Tetrapod for Selective Sensing Applications

AbstractIn this work, a general strategy to change the selectivity of individual ZnO tetrapod (ZnO‐T)‐Schottky diode‐based devices by hybridization with carbon nanotubes (CNT) is presented. A microscale Schottky diode based on Pt‐nanocontacts to a single ZnO‐T covered/hybridized with CNT, designated as ZnO‐T−CNT, is fabricated and the temperature‐dependent UV and gas sensing properties are investigated. The gas sensing investigations indicate that due to the presence of CNTs on the surface of the ZnO‐T a higher NH3 response (factor of ≈90) at room temperature is observed, compared to H2 gas response (≈14). This effect is attributed to the excellent charge transfer between the CNTs and ZnO‐T as well as NH3 molecule adsorption on the surface of the CNTs, which can efficiently reduce the Schottky barrier height. By increasing the operating temperature up to 150 °C (starting from 50 °C) the NH3 response is considerably reduced, leading to an excellent H2 gas selectivity. In the case of H2 gas, an increase in temperature up to 150 °C shows a considerably increase in gas response of about 140 (≈10 times). Thus, this device offers the possibility to be used for selective detection of NH3 and H2 by only changing the operating temperature. Furthermore, by using the developed strategy/approach other materials can be used for the fabrication of gas sensors with selectivity to other gases.

Positive synergistic effect of graphene oxide/carbon nanotube hybrid coating on glass fiber/epoxy interfacial normal bond strength

As coating material for micro-sized fibers, carbon nanotubes (CNTs) are effective in enhancing interfacial bonding due to their anchoring role while are easy to strip off from fiber surfaces; comparatively, graphene oxide (GO) is less effective in enhancing interfacial bonding but can be tightly adhered on fiber surfaces due to its encapsulating role. In this work, simultaneous grafting of CNTs and GO onto glass fibers (GFs) is conducted to combine their advantages and examine their synergistic effect. The contact angle measurement on fiber surfaces indicates that the GO/CNT hybrid coating leads to a significant increase in wetting property of GF surfaces with epoxy resin. As a result, the transverse tensile strength as an indication of interfacial normal bond property of glass fiber/epoxy composites is greatly enhanced by the GO/CNT hybrid coating. As a comparison, GO and CNTs are also coated separately on GFs. The enhancement in the interfacial normal property is in the order of GO/CNT > CNT > GO coating. Furthermore, the interfacial bond property by the GO/CNT hybrid coating layer is shown to be significantly higher (128%) than the calculated value in terms of the rule of mixtures from the results of single GO and CNT coatings, indicating that the GO/CNT hybrid coating displays a great positive synergistic effect on glass fiber/epoxy interfacial normal bond strength. Consequently, the present methodology is a promising approach for effectively improving fiber-matrix interfacial bond property in multi-scale composites.

Effects of single and multi-walled carbon nano tubes on water and engine oil based rotating fluids with internal heating

Three dimensional (3D) flow of a rotating Water and Engine Oil Based fluid is analyzed. Effects of nanometer (nm) sized Single (SWCNT) and multiwalled carbon nanotubes (MWCNT) are examined on flow and heat transfer characteristics. Thermofluid performance within Water and Engine Oil base fluid are investigated using thermal conductivity and viscosity of both single and multiple wall carbon nanotubes (CNTs) of similar volume. The governing partial differential equations are converted into nonlinear, coupled, ordinary differential equations which are solved numerically using a combination of Quasi-linearization and Chebyshev pseudo-spectral methods. Effects of relevant parameters on physical quantities are examined. The obtained results revealed an enhancement in temperature as well as corresponding thermal boundary layer thickness with volume fraction of both types of carbon nanotubes. Due to higher density and thermal conductivity, SWCNTs offer higher skin friction and Nusselt number. Engine oil base fluid depicted higher heat transfer rate and local skin friction than water based fluid for both type of carbon nanotubes. Residual error are plotted to check the accuracy of obtained results. Comparison with previously published literature is made and an excellent agreement is observed which validate our applied numerical scheme.

Synthesis, characterization and application of magnetic carbon materials as electron shuttles for the biological and chemical reduction of the azo dye Acid Orange 10

A set of core(ferrite, FeO)-shell(carbon, C) composites, C@FeO, C@MnFeO, C@CoFeO, and carbon nanotubes (CNT) impregnated with 2% of Fe (CNT@2%Fe) were prepared. The different composites were tested as redox mediators (RM) in the biological reduction of the azo dye Acid Orange 10 (AO10). Materials were tested at different concentrations from 0.1 to 1.0gL−1. In the absence of RM, the AO10 decolourisation after 24h of reaction was only 30% at a rate of 0.2d−1. In the presence of the core-shell composites, better results were obtained with C@FeO materials at the amount of 1.0gL−1. The extent of AO10 decolourisation was above 90% and rate improved circa 29-fold. With CNT@2%Fe, the best efficiency (98±3%) was achieved with 0.5gL−1 leading to a 79-fold rate increase. In abiotic controls, though at lower extent, the reduction of the dyes also occurred likely due to the electron transfer from Fe2+ to carbon and then to the dye. To prove this, assays combining single CNT and FeO materials were performed, and FeO had effect in the reaction only when combined with CNT. In the biological assay, the rate was the double and the percentage of decolourisation increased from (88±6)% to (97±1)%, when both materials were present in solution as compared with results in the presence of CNT alone. Under abiotic conditions, decolourisation occurred only in the presence of both materials, with a final percentage of (54±2)%. Owing to their magnetic character, materials were removed from the media and successfully applied in successive cycles.

(Invited) Single Carbon Nanotube Tracking Reveals Nanoscale Organization of the Extracellular Space in Live Brain Tissue

Sub-wavelength localizations of single molecules allows super-resolution imaging and a subtle probing of spatio temporal nano-environments in cells [1]. By using biocompatible luminescent single wall carbon nanotubes (SWCNTs) in the near-IR emission [2,3], here we show an approach to directly observe local structures and rheology of the extracellular space in a brain tissue using super-resolution imaging. Upon injection in live rat cerebroventricles [4], individual SWCNTs are followed for tens of minutes in acute slices as they diffuse inside the extracellular space. Because of the interplay between the nanotube geometry and the extracellular space local environment [5], we can extract information about the extracellular space dimension and local viscosity. We find a striking diversity of extracellular space dimensions down to 40 nm, and as well as of local viscosity values. Moreover, by chemically altering the brain extracellular matrix of the live animals before nanotube injection, we reveal that ECS rheology properties are affected, but that extracellular space alterations are local and inhomogeneous at nanoscale dimensions [6].

(Keynote) Carbon Nanotubes ~Controllability of Nanostructure and Applications~

Carbon nanotubes (CNTs) have been attracting lots of attention from various fields of science and technology because of their extraordinary physical and chemical performances owing to their intrinsic nano-sized and one-dimensional nature. The most common process to synthesize carbon nanotubes is CCVD(Catalytic Chemical Vapor Deposition) method, because this technique is very powerful for large scale production and controlling the nanostructure. The CCVD method uses most commonly the nano-sized iron particles that are either dispersed on the substrate or floating reactant technique [1]. By using CCVD process, single, double and multi wall CNTs have been successfully grown, and based on the characteristic structure of CNTs various kinds of applications have been proposed and developed. We are facing many environmental problems such as global warming and pollution, constant shortage of water and processing of agricultural wastes, etc. Therefore, finding measures for the resolution of such urgent issues is required. In this account, since we believe that CNTs and other nanocarbons have the ideal properties to solve such problems, some applications aiming toward resolving the environmental issues will be introduced. At first, the current usage of CNTs in energy storage devices as one of the important component of high performance lithium ion secondary batteries is shown. Mainly, the effectiveness of the addition of CNTs to both cathode and anode electrode materials of lithium ion secondary batteries will be demonstrated[1]. The usage of CNTs as multi-functional filler in polymeric composites such as functional rubber[2], water desalination membranes [3] will be summarized. The water desalination and purification using reverse osmosis (RO) membrane prepared from polyamide/CNT nanocomposite is very promissing. We have successfully developed a high-concentration CNT dispersion method which was applied to the formation of PA/CNT RO membrane by interfacial polymerization. PA/CNT RO membrane has superior anti-fouling characteristics and high chroline resistance [3]. Desalination property and the science behind the high-performance PA/CNT RO membrane will be discussed. For successful developments of CNT’s, the CNT’s safety is the most important issue [4,5,6]. By openly sharing all the information on toxicity risks and benefits of the carbon nanomaterials including CNTs with all the stakeholders, and by the responsible productions and uses through the designing safer nanostructure based on accumulated CNTs science and technology, CNTs can contribute to the sustainability of the 21st century.

Quantum Near-Field Effects in Hybrid Carbon Nanotube Systems

Physical understanding of near-field processes in complex hybrid nanostructures of reduced dimensionality is a natural prerequisite for the development of future generation advanced nanomaterials and devices. I present two examples of how the near-field processes can drastically affect optical and transport properties of hybrid carbon nanotube structures. First is the Surface Enhanced Raman Scattering (SERS) effect for a two-level atomic system (TLS) coupled to a low-energy interband plasmon resonance of a carbon nanotube (CN) [1]. Here, the SERS comes about as a strong-coupling near-field effect in which the local-field enhancement occurs due to the interband plasmon excitation when the TLS is located near the CN surface and its transition energy matches a CN local photonic DOS resonance. Previously, most of the applications of CNs to enhance the Raman scattering have been to decorate them with metallic nanoparticles, to use metal plasmons as spectroscopic enhancers with CNs only serving as their supporters [2,3]. Here, individual CNs are shown to result in the SERS effect due to their intrinsic interband plasmon modes [1]. The effect may be used to detect individual atomic type objects trapped near nanotubes. More advanced applications may include highly efficient CN based SERS substrates for single molecule/atom/ion detection, precision spontaneous emission control, and quantum optical manipulation. Second is the plasmon mediated electron transport in hybrid metal-semiconductor CN systems composed of single wall semiconducting CNs with encapsulated metallic atomic wires (AWs) [4]. Encapsulating metallic wires of just one atom thick into a single wall CN, metallic or semiconducting, is known to drastically alter the transport properties of the compound hybrid system [5]. Our theory and numerical simulations predict generic Fano resonances in charge transfer through the hybrid metal-semiconductor CN system, whereby the strong plasmon mediated AW-CN near-field interaction blocks some of the pristine AW transmission band channels to open up new coherent channels in the CN bandgap outside the AW transmission band [4]. This effect can be used to optimize charge transfer in hybrid nanodevices built on metal-semiconductor nanotube systems. I.V.B. acknowledges the US DOE grant support (DE-SC0007117). Part of this work (electron transport) was done in collaboration with M.F.Gelin of TU-Munich, Germany, whose visit to North Carolina Central University was sponsored by the US NSF grant ECCS-1306871.

A Vision-Based Automated Manipulation System for the Pick-Up of Carbon Nanotubes

The ability to pick up a single carbon nanotube (CNT) from a bundle of CNTs is of great importance for nanodevice fabrication. In this study, we propose a nanorobotic manipulation system allowing automated pick-up of CNTs based on visual feedback. We used histogram thresholding for automatic binarization, and it clearly distinguished CNTs from the substrate and other impurities under various image brightnesses and contrasts. Furthermore, the CNT tip was successfully extracted by making use of the geometrical characteristics of the CNT. We designed a segment detection method to separate the CNT and atomic force microscope cantilever during overlapping. The contact detection between them was identified by evaluating the linearity of the fitted CNT curve. We also further analyzed the specific properties of point contact and linear contact, significantly improving the success rate of pick-up. Finally, the experimental results show that our method is highly promising for realistic fabrication of nanodevices.

Negative differential resistance and switching behavior in single wall bamboo-shape carbon nanotubes based molecular device: A first-principles study nanoscale device design

By using the first-principles density functional theory and a nonequilibrium Green’s function, the quantum electronic transport properties of single wall bamboo-shape carbon nanotubes created by partitioning in C(12,0) zigzag single wall carbon nanotubes based molecular devices are investigated. In the present work, we designed and simulated C(12,0) bamboo-shape single wall carbon nanotubes (BS-SWCNTs) by connecting the coronene (C24H12) molecule as interface of two pure zigzag C(12,0) nanotubes by chemical bonds and interface regions, thus obtained six pentagons and six hexagons on both sides of the tube. We observed that this BS-SWCNTs device exhibits the negative differential resistance (NDR) with certain bias voltage 1.1V. The current voltage characteristics of the BS-SWCNTs show a switching behavior at bias region 1.1–1.6V and very high peak-to-valley current ratio of the order of 106. A detailed analysis of the origin of NDR was carried out with transmission pathways, MPSH with various external bias voltages.