Performance Of Single-walled Carbon Nanotube Research Articles

Mechanical Interlocking to Unlock the Reinforcing Potential of Carbon Nanotubes.

Single-walled carbon nanotubes (SWNTs) present extraordinary mechanical properties, with Youngs' modulus>1 TPa and tensile strength>50 GPa; this makes them ideal candidates as fillers for the reinforcement of polymers. However, the performance of SWNTs in this field has fallen behind expectations. This is due to a combination of imperfect individualization of the SWNTs and poor load transfer from the polymer to the SWNTs. Here, we study the reinforcement of polymers of different chemical nature using mechanically interlocked derivatives of single-walled carbon nanotubes (MINTs). We compare the mechanical properties of fibers made of poly (methyl methacrylate) (PMMA) and polysulfone (PSU) and their composites made with pristine SWNTs, MINTs, and the corresponding supramolecular models. With very low loading of MINTs (0.01 % w/w), improvements of more than 100 % on Youngs Modulus and the tensile strength are observed for both the nonpolar aliphatic PMMA and the very polar aromatic PSU polymers, while pristine carbon nanotubes and the supramolecular nanofillers showed smaller reinforcement. These data, together with our previous report on the reinforcement of polystyrene (nonpolar and aromatic), indicate that derivatization of SWNTs as MINTs is a valid general strategy to optimize the interaction between SWNT fillers and the polymer matrix.

High-performance g-C3N4 coated single-walled carbon nanotube composite films for flexible thermoelectric generators

Thermoelectric (TE) devices consisting of p-type and n-type single-walled carbon nanotubes (SWCNTs) based films, which can gather waste heat and turn it into electrical power, show potential application in supplying power for wearable electronic devices. In this study, graphitic carbon nitride (g-C3N4) has been prepared by high temperature pyrolysis of melamine and confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction pattern (XRD), respectively. Then the prepared g-C3N4 is composited with SWCNTs via mechanical mixing and vacuum-filtering method to obtain free-standing flexible g-C3N4/SWCNT thermoelectric composite films. The results demonstrate that g-C3N4 is efficiently covered on the surface of SWCNTs via interfacial π-π interaction, and g-C3N4 layer with several nanometers coated on SWCNTs simultaneously improves the electrical conductivity (σ) and the Seebeck coefficient (S) of g-C3N4/SWCNT. At a mass ratio of 2.5 % for g-C3N4/SWCNT, an optimal power factor value of 163.0 ± 1.0 μW m−1 K−2 is obtained for g-C3N4/SWCNT with the σ of 702.6 ± 1.6 S cm−1 and the S of 48.2 ± 0.2 μV K−1 at room temperature. Finally, a self-powering TE device composed of three pairs of p-n junctions is manufactured, and the actual output power is about 1.13 μW at the temperature difference of 50 K. As a result, this study offers a straightforward way to enhance the thermoelectric performance of single-walled carbon nanotubes, which can be utilized in flexible power generators.

Organic borate doped carbon nanotube for enhancement of thermoelectric performance

Molecular doping is vital to control the charge transport in organic/inorganic semiconductors, which provides an important technique to optimize the thermoelectric (TE) performance. Here, two organic borates with designed molecular structures, Ph3C+[B(C6F5)4]- and Ph2I+[B(C6F5)4]-, were employed as p-type dopants to enhance the TE performance of single-walled carbon nanotubes (SWCNTs). The electrons are transferred from SWCNTs to the electron-deficient cations of the borates, resulting in charge-transfer complexes stabilized by [B(C6F5)4]-. Specifically, compared to the pristine SWCNTs, the borate-doped SWCNT films reveal enhanced power factors of 135.5 ± 8.4 μW m−1 K−2 for SWCNT/Ph3C+[B(C6F5)4]-, and 156.6 ± 7.2 μW m−1 K−2 for SWCNT/Ph2I+[B(C6F5)4]-. Moreover, the p-doped SWCNTs display good air and thermal stabilities due to the chemical inertness and thermal stability of the organic [B(C6F5)4]- anions. In addition, by immersion in organic solvent, the TE performance can be further increased. This work provides a novel strategy to achieve stable p-doped SWCNT films with excellent TE performance via rational molecular design of organic borate dopants.

Enhancement of the Electrical Conductivity and Thermoelectric Performance of Single-Walled Carbon Nanotubes by the Introduction of Conjugated Small Molecules with Cation Groups

Organic conjugated small molecules (OCSMs)-based single-walled carbon nanotube (SWCNT) composites have received great attention as potential thermoelectric (TE) materials. The studies show that both π–π and cation−π interactions between OCSMs and SWCNTs obviously improve the TE performance. However, up to now, few OCSMs containing both cation groups and π structures have been combined with SWCNTs as TE materials. In this work, an organic conjugated small molecule with a cation group, (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP), was applied to combine with SWCNTs for the first time due to π–π and cation−π interactions between PyBOP and SWCNTs, which are beneficial to improving the electrical conductivity and thermoelectric (TE) performance. The highest electrical conductivity of 3731.5 S cm–1 was achieved for SWCNT/PyBOP, which was 6.59 times larger than that of the pristine SWCNTs, and also one of the highest values for OCSM-based SWCNT composites reported up to date. Among all of the composites, SWCNT/PyBOP displays the maximum power factor of 279.5 μW m–1 K–2 at 403 K. The results demonstrate that the electrical conductivity of SWCNT composites can be dramatically improved by tuning the structure of the OCSMs, which points out a new direction for the rapid development of high-performance TE composite materials.

Procarbazine adsorption on the surface of single walled carbon nanotube: DFT studies

In this research, the performance of single-walled carbon nanotube (SWCN) as a sensor and nanocarrier for procarbazine (PC) was investigated by infra-red (IR), natural bond orbital (NBO), frontier molecular orbital (FMO) computations. All of the computations were done using the density functional theory method in the B3LYP/6-31G (d) level of theory The calculated negative values of adsorption energy, enthalpy changes, Gibbs free energy changes showed the PC interaction with SWCN is exothermic, spontaneous and experimentally possible. The increasing of specific heat capacity (CV) of SWCN after adsorption of PC showed the thermal conductivity improved during the interaction process and this nanostructure is an excellent sensing material for the detection of PC. The NBO results demonstrate in all of the evaluated conformers a chemical bond with SP3 hybridization is formed between the medicine and SWCN. The great values of thermodynamic constants showed the adsorption process is irreversible and SWCN is not a suitable nanocarrier for delivery of PC. The density of states (DOS) spectrums showed the bandgap of SWCN decreased sharply after the adsorption of PC and this nanomaterial can be used as a sensor for electrochemical detection of PC.

Enhanced Microwave Absorption Performance of SWCNT/SiC Composites

The present work emphasizes the microwave absorption performance of single-walled carbon nanotube (SWCNT)/SiC composites prepared by mechanically mixing the components, i.e., SWCNT and SiC in desired weight fractions using a cost-effective and simple ball-milling route. The microwave absorption results reveal that the integration of SiC with a small weight fraction of SWCNT exhibited an improved absorption performance in the Ku band compared to pristine SiC. The SWCNT/SiC composite with 2.5 wt.% SWCNT exhibited a superior microwave absorption behavior with a minimum reflection loss of − 37.11 dB and < − 10 dB absorption bandwidth of 4.38 GHz for the absorber thickness of 2 mm. The microwave absorption efficiency of SWCNT/SiC composites was also measured corresponding to − 10 dB, which is equivalent to 90% microwave absorption when evaluating the absorption performance. A maximum microwave absorption efficiency of 18.95 dB GHz/mm was observed for the composite with 2.5 wt.% SWCNT dispersion compared to 3.4 dB GHz/mm for pristine SiC. Enhanced microwave absorption characteristics for SWCNT/SiC composites may be attributed to various absorption mechanisms, such as dipole polarization, multiple scatterings, multiple reflections, conductive loss, interfacial polarization, and defect-induced dipole polarization. The microwave absorption results of SWCNT/SiC composites indicate that they may serve as encouraging thin thickness candidates with superior microwave absorption for application in the Ku band.

Electrochemical enhancement of optoelectronic performance of transparent and conducting single-walled carbon nanotube films

We propose a novel approach to enhance optoelectronic performance of single-walled carbon nanotubes (SWCNTs) for transparent conducting film applications. The method provides fine and reversible tuning of optoelectrical properties of SWCNT films over a wide range of parameters. Using imidazolium-based ionic liquid with a wide electrochemical window (BMIM-PF6), we achieved the film sheet resistance as low as 53 Ω/sq at the 90% transmittance, thereby shifting the SWCNT Fermi level up to 1.4 eV. We believe the results to promote collateral research of adjustable tuning of the electronic structure of carbon nanomaterials as promising components for future electronics, electrochromic devices, and ionotronics.

On the Thermal Performance of a Fractal Microchannel Subjected to Water and Kerosene Carbon Nanotube Nanofluid

Using single layer microchannels accompanied by nanofluids is one of the most practical solutions in thermal management of high power density devices. The main challenge in cooling systems of electronic devices is to provide a uniform temperature distribution. In the present study, fluid flow and heat transfer in a fractal microchannel heatsink have been simulated employing the computational fluid dynamics (CFD) method. The fractal microchannel is used to achieve uniform temperature distribution. Thermal performance of single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) dispersed in the two base fluids of water and kerosene in a fractal microchannel at Reynolds (Re) numbers of 1500 to 3000 are investigated. It should be noted that the nanofluids have been simulated by the two-phase mixture model. The results indicated that the use of fractals silicon microchannel leads to having a uniform temperature distribution. Based on the results, at maximum Re number when the working fluid is water, Nu number and pumping power are 20.9 and 0.033 W whereas, in kerosene flow at the same condition, Nu number and pumping power are 6 and 0.054 W, respectively. According to the obtained results, using the SWCNT nanoparticle compared with the MWCNT nanoparticle leads to a significant enhancement in the Nusselt (Nu) number. This difference is more pronounced by increasing the Re number and nanoparticle volume fraction. In addition, the results indicated that at the same Re number and nanoparticle volume fraction, the performance evaluation criterion of the water-based nanofluid is 4 times higher than that of the kerosene-based nanofluid. So the use of the water as the working fluid with the SWCNT nanoparticle for cooling in the fractal silicon microchannel is recommended.

Self-assembly of single-walled carbon nanotubes arrays with different line width

Single-walled carbon nanotubes (SWNTs) are one of the most promising nanoelectronic materials, However, there are still some application challenges, including purification, regular arrangement, interconnection, and so on. There is evidence that the array assembly can improve the performance of SWNTs. In this work, we develop a line-width controllable large-scale assembly of SWNTs based on aqueous solution, using electron beam (E-beam) lithography to construct self-assembled templates. The results show that SWNTs arrays of different line-width are obtained, which is possible to design the structure of SWNTs assembly to meet different functions.

ZnO Nanocluster-Functionalized Single-Walled Carbon Nanotubes Synthesized by Microwave Irradiation for Highly Sensitive NO2 Detection at Room Temperature

To improve the NO2-sensing performance of single-walled carbon nanotube (SWCNT)-based sensors, zinc oxide (ZnO) nanoclusters (NCs) were functionalized by a microwave (MW)-assisted synthesis technique. Gas sensors based on pristine SWCNTs and ZnO NC–SWCNT composites synthesized using different weight ratios (ZnO/SWCNTs = 0.5:1, 1:1, 2:1, and 3:1) were fabricated, and their ability to sense various gases at room temperature (25 °C) was investigated. The results showed that the sensing performance of the ZnO NC–SWCNT composite synthesized with a weight ratio of 1:1 (denoted as Z-SWCNTs) was significantly enhanced with respect to NO2 response and selectivity. This enhanced sensing performance is thought to be a result of both the modulation of the conduction channel at the ZnO NC–SWCNT heterointerfaces and the generation of defects (or holes) by MW irradiation that act as active sites for the target gases. The results obtained in this work provide not only a facile method of cofunctionalizing oxide NCs and defects but also a new methodology for improving the sensing capabilities of SWCNT-based gas sensors.

Adsorbate-enhanced field-emission from single-walled carbon nanotubes: a comparative first-principles study

We report a comparative ab initio study of different types of adsorbates and their adsorption mechanism on the field-emission performance of single-walled carbon nanotubes by analyzing electrical properties and transport characteristics and considering the thermal stability of the adsorbed structure. Adsorbates were found to reduce the work function by up to 1.3 eV, enhance tunneling near the carbon nanotube tip, and increase the field-emission current by as much as two orders of magnitude. A significant localization of the electron cloud was also observed near the adsorbates under a high applied electric field.

Significant Enhancement of Single-Walled Carbon Nanotube Based Infrared Photodetector Using PbS Quantum Dots

We show that the performance of single-walled carbon nanotubes (SWCNTs) based infrared photodetector can be greatly enhanced through the combination with colloidal PbS quantum dots (QDs). To improve the photo-induced charge transport efficiency and the carrier mobility, the colloidal PbS QDs are modified by short-chain inorganic. Under illumination, the light-induced electron-hole pairs can be effectively separated by the internal electric field formed at the interfaces between SWCNTS and PbS QDs, which will lead to the increase of both conductivities in them. Photocurrent is formed under the driving of source-drain voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> ) applied by the interdigital finger electrodes. Our hybrid phototransistor achieves a responsivity of 7.2 A/W, a specific detectivity (defined below) of 7.1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> Jones, and a response time of 1.58 ms at the same time under 1550-nm illumination with low intensity. Through gate voltage tuning, the responsivity can be increased to 353.4 A/W. In addition, our hybrid phototransistor is stable, low-cost, and compatible with complementary metal oxide semiconductor, which benefits a lot in real applications.

Improvement of thermoelectric performance of single-wall carbon nanotubes by heavy doping: Effect of one-dimensional band multiplicity

Doped single-wall carbon nanotube (SWCNT) films were prepared and their Seebeck coefficient (S) and electrical resistivity (ρ) were investigated as functions of carrier density. For heavy doping, a second maximum of S (S = 35 µV/K) was discovered, with its corresponding power factor, P = 85 µW/(m·K2), 6 times that of the first maximum for lightly doped films. Calculations for zigzag SWCNTs suggest that the thermoelectric performance can be effectively improved by controlling the multiplicity of the one-dimensional band and tuning the carrier density. This provides a new strategy for achieving higher performance at a lower cost than using high-purity semiconducting SWCNTs.

Rippling effect on the structural response of electrostatically actuated single-walled carbon nanotube based NEMS actuators

Several nonlinear phenomena have shown to have significant effect on the electromechanical performance of single-walled carbon nanotube (SWCNT) based nanoelectromechanical (NEMS) devices. To name few: the van der Waals forces, the Casimir forces, the tip charge concentration and the rippling phenomenon. Some of these effects have been take care of in previous investigation; however, some have been disregarded in the mechanical models suggested for simulation of the SWCNT based structures. In this paper, the influence of rippling deformation on the vibration characteristics of SWCNT based actuators is investigated using a nonlinear Euler-Bernoulli beam theory that incorporates the effect of rippling deformation using an improved function including some correcting terms for the SWCNT curvature (rippling deformation). The influence of the Casimir and the van der Waals attraction forces are considered in the proposed model as well as the size-dependent behavior assuming the so-called Eringen nonlocal elasticity theory. The dynamic response of CNT is investigated based on time history and phase portrait plots of the CNT based nano-actuator. It is shown that the rippling deformation can significantly decrease the static as well as the dynamic pull-in voltage of the SWCNT based actuator. The rippling deformation of SWCNT decreases the dynamic pull-in time as well. Effect of various factors such as the DC actuation load and the Casimir attractive forces on the dynamic stability and the pull-in characteristics of the nano-actuator are examined. Results of the present study are beneficial to accurate design and fabrication of electromechanical CNT based actuators. Comparison between the obtained results and those reported in the literature by experiments and molecular dynamics, verifies the integrity of the present numerical analysis.

Analysis of propagation delay and repeater insertion in single-walled carbon nanotube bundle interconnects

A new closed-form expression of 50% propagation delay for distributed RLC interconnects is proposed using the multivariable curve fitting method, with a maximum error of 4% with respect to SPICE results. Then accurate closed-form solutions for the optimum repeater number and size to minimize the propagation delay are further derived. The performance of single-walled carbon nanotube (SWCNT) bundle interconnects is evaluated using the proposed models in the intermediate and global levels at the 22- and 32-nm technology nodes, and compared against traditional Cu interconnects. It is shown that the performance of SWCNT bundle interconnects in propagation delay can outperform Cu interconnects, and the improvement will be enhanced with technology scaling and wire length increasing. On the other hand, the propagation delay of SWCNT bundle interconnects is super-linearly dependent on the wire length similar to Cu interconnects, indicating that the method of repeater insertion to reduce the propagation delay can also apply to SWCNT bundle interconnects. The results shown that repeater insertion can really reduce the propagation delay of SWCNT bundle interconnects effectively, and the optimum repeater number is much smaller than that of Cu interconnects.

Enhanced dispersion and electronic performance of single-walled carbon nanotube thin films without surfactant: A comprehensive study of various treatment processes

A method for enhancing electronic performance of single-walled carbon nanotube (SWCNT) thin films through enhanced dispersion of SWCNTs in aqueous solutions is presented. The best dispersion enhancement is obtained by covalent attachment of urea to the acid functionalized SWCNTs. Dispersion properties of urea treatment are compared to conventional chemical and physical treatment techniques, such as surfactants. The treatment type and time significantly influence SWCNT surface functionalization, which determines the dispersion effectiveness as described by the SWCNT aggregate size, morphology and stability. The findings suggest that urea-SWCNTs, as compared to surfactant dispersed-SWCNTs, resulted in the most effective dispersion method among chemical treatments, yielding the smallest monodispersed aggregates with the most rod-like morphology that were stable over the greatest range in pH. Thin films prepared with SWCNT samples were evaluated for their transparency and resistance, two metrics that are important for electronics device applications. The urea-SWCNT films exhibited superior optoelectrical properties compared to SWCNT films prepared with conventional chemicals as well as surfactants. This indicates a correlation between degree of dispersibility and optoelectrical properties.

The influences of preparation methods on the structure and catalytic performance of single-wall carbon nanotubes supported palladium catalysts in nitrocyclohexane hydrogenation

Preparation methods on the structure and catalytic performance of single-wall carbon nanotubes supported palladium catalysts.

Adsorption of acid red18 dye from aqueous solution using single-wall carbon nanotubes: kinetic and equilibrium

ABSTRACTDyes or colors are one of the most important chemicals used in textile industries. It is necessary that dye-contaminated wastewater before discharging to environment treated by an appropriate and effective method. In this study, the performance of single-wall carbon nanotubes (SWCNTs) as an adsorbent for the removal of dye from aqueous solution was evaluated. The effect of operational parameters, such as contact time, solution pH, adsorbent dosage, and initial dye concentration was studied. Adsorption data were analyzed using Langmuir, Freundlich, and Temkin adsorption isotherms. The Langmuir isotherm (R2 = 0.9844) was the best fitted graph for experimental data with maximum adsorption capacity (qm) of 166.667 mg/g. The kinetic data were tested using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The results of this study indicate that SWCNTs can be used as an effective adsorbent for the removal of azo dyes.

Study on Antifouling Performance of Single-walled Carbon Nanotubes Modified Electrode and Its Application in Determination of 5-Hydroxytryptamine

A carbon fiber microelectrode(CFME) modified with single-walled carbon nanotubes(SWNTs) was prepared,the surface morphology and electrochemical behavior of modified electrode was characterized by transmission electron microscope(TEM),cyclic voltammetry(CV),differential pulse voltammetry(DPV) and chronoamperometry.The experimental results showed that the SWNTs could significantly alleviate electrode fouling caused by 5-hydroxytryptamine(5-HT).In 0.2 mol/L Tris-HCl(pH 7.4) buffer,the amperomatric method was used for the determination of three consecutive injections of 1.0×104 mol/L 5-HT,the peak current decreased significantly successively at a CFME,and the third peak current was 43.4% of the first one.The peak current decrease slightly at a SWNTs-CFME and the third peak current was 97.3% of the first one,the peak current change was significantly less with the rising of test times,the results indicated that the SWNTs-CFME possessed stable electrochemical performance.The detection limit of 5-HT improved from 1.2×107 mol/L to 6.8×107 mol/L after SWNTs coating.The modified electrode-based microchip capillary electrophoresis system was successfully applied to detect 5-HT in rat blood plasma and the concentration of 5-HT was(6.96±0.24) ×107 mol/L(n=5),the recovery of standard addition was between 96.8% and 103.9%.

Label-Free Detection of DNA Hybridization Using Pyrene-Functionalized Single-Walled Carbon Nanotubes: Effect of Chemical Structures of Pyrene Molecules on DNA Sensing Performance

We investigate the effect of functional groups of pyrene molecules on the electrical sensing performance of single-walled carbon nanotubes (SWNTs) based DNA biosensor, in which pyrenes with three different functional groups of carboxylic acid (Py-COOH), aldehyde (Py-CHO) and amine (Py-NH2) are used as linker molecules to immobilize DNA on the SWNT films. UV/Visible absorption spectra results show that all of the pyrene molecules are successfully immobilized on the SWNT surface via pi-pi stacking interaction. Based on fluorescence analysis, we show that the amide bonding of amine terminated DNA via pyrene containing carboxylic groups is the most efficient to immobilize DNA on the nanotube film. The electrical detection results show that the conductance of Py-COOH modified SWNT film is increased upon DNA immobilization, followed by further increase after hybridization of target DNAs. It indicates that the pyrene molecules with carboxylic acid groups play an important role to achieve highly efficient label-free detection by nondestructive and specific immobilization of DNAs.