Addition Of Single-walled Carbon Nanotubes Research Articles

Effect of Single Walled Carbon Nanotube Addition to thePhysical Properties of Monolithic Alumina

The effect of single-wall carbon nanotube (SWCNT) addition on the physical properties of alumina (Al2O3) ceramic composite were studied in this paper. The SWCNT and Al2O3 nanocomposite samples were prepared using wet mixing with 5 different compositions of SWCNT. The nanocomposite samples were confined inside alumina sagger with high purity graphite packing powder and were sintered using pressureless sintering at 1600°C. The hardness shows an optimum values at 0.1 wt% of SWCNT, 20.13 GPa. However, further addition of SWCNT then reduced the properties values of the Al2O3.

Anomalous fluorescence enhancement and fluorescence quenching of graphene quantum dots by single walled carbon nanotubes.

We explore the mechanism of the fluorescence enhancement and fluorescence quenching effect of single walled carbon nanotubes (SWCNTs) on highly fluorescent graphene quantum dots (GQDs) over a wide range of concentrations of SWCNTs. At very low concentrations of SWCNTs, the fluorescence intensity of the GQDs is enhanced, while at higher concentrations, systematic quenching of fluorescence is observed. The nature of the Stern-Volmer plot for the latter case was found to be non-linear indicating a combined effect of dynamic and static quenching. The contribution of the dynamic quenching component was assessed through the fluorescence lifetime measurements. The contribution of static quenching is confirmed from the red shift of the fluorescence spectra of the GQDs after addition of SWCNTs. The fluorescence intensity is first enhanced at very low concentration due to improved dispersion and higher absorption by GQDs, while at higher concentration, the fluorescence of GQDs is quenched due to the complex formation and associated reduction of the radiative sites of the GQDs, which is confirmed from time-resolved fluorescence measurements. Laser confocal microscopy imaging provides direct evidence of the enhancement and quenching of fluorescence at low and high concentrations of SWCNTs, respectively. This study provides an important insight into tuning the fluorescence of GQDs and understanding the interaction between GQDs and different CNTs, which is important for bio-imaging and drug delivery applications.

Dielectric properties of (SWCNTs)x GdBa2CuO7−δ superconductor nanocomposites

Gd-123 superconducting phase was prepared by solid-state reaction technique. Single-walled carbon nanotubes (SWCNTs) were added in Gd-123 superconducting matrix with different concentrations during the final sintering process to obtain (SWCNTs)[Formula: see text] GdBa2Cu3O[Formula: see text] (x = 0.0–0.1 wt.%) nanoparticles–superconductor composite. The influence of SWCNTs addition on the phase formation, structural, morphological, superconducting and dielectric properties of Gd-123 phase was investigated. It was found that SWCNTs addition enhance the phase formation and does not change the crystal structure of the host Gd-123 superconducting phase. The superconducting properties of Gd-123 samples were improved after the addition of SWCNTs up to x = 0.06 wt.% due to the enhancement in intergrain connectivity by healing up of micro-cracks and reduction of defects, while these properties were retarded with further increase in x. The dielectric response of (SWCNTs)[Formula: see text] Gd-123 superconducting phase with x = 0.0, 0.01, 0.04, 0.05, 0.06 and 0.1 wt.% was measured from 100 KHz to 5 MHz at 77 K. The results reveal that for both real ([Formula: see text]) and imaginary ([Formula: see text]) parts of dielectric constant, the frequency of dispersion increased by increasing SWCNTs amount up to 0.06 wt.%, then this frequency shifted to lower values for x [Formula: see text] 0.06 wt.%. The results were discussed according to the presence and interference of both interfacial and dipolar polarizations.

Biosensor Based on Screen-Printed Electrode and Glucose-Oxidase Modified with the Addition of Single-Walled Carbon Nanotubes and Thermoexpanded Graphite

The modification of an electrode produced by a matrix printing head with the use of glucose oxidase (GOD), single-walled carbon nanotubes (SWCNTs), and thermoexpanded graphite (TEG) has been studied. During glucose oxidation, modification by SWCNTs leads to the effect of direct electron transfer. Both nanomaterials increase the magnitude of the sensitivity coefficient (SC) from 0.11 to 0.24 mA M–1 in the case of glucose oxidase–and ferrocene-based electrodes when modification is done with the addition of TEG and up to 0.62 mA M–1 when modification is done with the addition of SWCNTs. A comparison of the characteristics of the biosensors with ferrocene and nanomaterials with those of the mediator-free biosensors based on SWCNTs and GOD shows that the biosensor provides higher sensitivity detection; the magnitude of sensitivity coefficient is 1.5 mA M–1. The higher magnitude of the SC can be explained by the occurrence of more effective electron transfer from active centers of the enzyme to the electrode. Voltammetric measurements demonstrate that electron transfer in a mediator-free biosensor is not complicated by a chemical reaction and is carried out under the control of diffusion factors. After testing the mediator-free biosensor in practice, it is possible to talk about the applicability of such a biosensor in detecting glucose in different environments, including the fermentation industry.

Dielectric behavior and electrical conductivity of PVDF filled with functionalized single-walled carbon nanotubes

Polyvinylidene fluoride (PVDF)/single-walled carbon nanotube (SWCNT) composites are characterized by X-ray diffraction and scanning calorimetry, and studied by dielectric relaxation spectroscopy (DRS) in the temperature range of −75 to 150 °C. The effects of SWCNTs and SWCNT functionalization are analyzed in terms of α and αc relaxation, dielectric permittivity, loss tangent, and AC electrical conductivity. Some small changes are detected in α relaxation with the addition of SWCNTs, and a strong influence of SWCNTs is observed in the other relaxation αc. Below the percolation threshold, the dielectric permittivity of functionalized SWCNT composites increases compared to blank PVDF, without notable changes in the dielectric loss. All the composite systems show an electrical percolation behavior with different thresholds depending on SWCNT functionalization. Threshold concentrations remain nearly unchanged in the whole temperature and frequency ranges. The base PVDF conductivity strongly depends on temperature and frequency, while the maximum conductivity above the percolation remains nearly unchanged (∼10−2 S/m) for all the systems, temperatures and frequencies.

A New Dimension for Low-Dimensional Carbon Nanostructures

In this issue of Chem , Martin, Guldi, and colleagues describe the preparation and study of one of the first examples of near-infrared-absorbing donor-acceptor materials based on carbon nanotubes and graphene. These materials show charge-transfer interactions in both the ground and excited states.

Low-Dimensional Carbon Allotropes: Ground- and Excited-State Charge Transfer with NIR-Absorbing Heptamethine Cyanine

Summary At the focal point of our studies are mutual interactions between an anionic heptamethine cyanine and individualized single-walled carbon nanotubes (SWCNTs) or exfoliated nanographene (NG). Here, we report the distinct near-infrared absorption of the heptamethine cyanine, which assists in visualizing the electronic interactions in the ground state with ease and precision. In statistical Raman assays, we conclude from downshifted 2D- and G-modes for SWCNTs, as well as upshifted 2D- and downshifted G-modes for NG, that these electronic interactions result in stable n-doping of SWCNTs and NG. Key to this shift of charge density is the electron-donating character of the heptamethine cyanine. In the excited state, a complete but metastable transfer of charges is accompanied by a radical-ion-pair state that lives for several nanoseconds. Such a time domain has not yet been realized, for example, in NG to date.

Improvement in thermal durability of fluorinated rubber by the addition of single-walled carbon nanotubes as a thermally stable radical scavenger

Rubber is an excellent material, but its usage has been limited due to its low heat-resistance. In a high-temperature environment, rubber decomposes due to the heat radicals generated by the bond cleavage reaction. In order to improve the heat-resistivity of rubber, it is necessary to stabilize the radicals. Therefore, carbon nanotubes (CNTs), which are known for their excellent radical scavenging ability, were added to fluorinated rubber. The upper limit of the temperature for continuous use was increased from approximately 200 to 340 °C with the addition of the small amount of CNTs. This technology would make it possible to easily improve the heat resistivity of rubber and would expand their use in a variety of applications that were previously limited due to the issues of heat-resistivity.

Molecular simulation and experimental analysis on thermal and mechanical properties of carbon nanotube/epoxy resin composites with different curing agents at high‐low temperature

The performance variation and its associated factors of a polymer composites over a wide temperature range need to be particularly concerned in engineering application. In this article, on the basis of molecular dynamics simulation analysis and experimental verification of glass transition temperature (Tg) of neat epoxy resins and single‐walled carbon nanotube (SWCNT)/epoxy composites with two structures of aromatic diamines curing agents, the elastic modulus of systems were studied from cryogenic temperature (100 K) until near the Tg in depth. Both simulation and experimental results showed that the thermal and mechanical performance of amine‐epoxy systems were enhanced obviously after incorporating SWCNTs of 1 wt% and stiffer amine curing agent molecules, and the elastic modulus was declining as the temperature rising. Further, some microstructure parameters of resin molecules influencing the elastic modulus of amine‐epoxy systems were analyzed, including the cohesive energy density (CED), free volume fraction (FFV), and mean square displacement. Among them, both CED and FFV can be significantly affected by addition of SWCNTs and different amine curing agent, and were closely related to the temperature, which can act as novel criteria to predict and optimize some thermal and mechanical performances of crosslinked resin systems and their composites for serving under different temperature. POLYM. COMPOS., 39:E945–E954, 2018. © 2017 Society of Plastics Engineers

Reduction in thermal conductivity of BiSbTe lump

In this work, systematic investigations on the thermal conductivities of BiSbTe lump, microstructured pristine BiSbTe bulk and single wall carbon nanotubes (SWCNTs)/BiSbTe bulk nanocomposites were performed. BiSbTe lumps were crushed to form a coarse powder (200 µm) and effect of particle size reduction on the effective thermal conductivity of BiSbTe (200 µm) bulk were analyzed. For further reduction in the conductivity, a two pronged strategy has been employed. First, additional refinement of BiSbTe (200 µm) were performed through ball milling in an inert environment. Second, SWCNTs in 0.75, and 1.0 vol% were distributed uniformly in the fine BiSbTe ball milled powder. The results showed that the effective thermal conductivities decrease with the reduction in the particle size from lump to BiSbTe (200 µm) bulk as well as with the addition of SWCNTs accompanied by further refinement of BiSbTe particles. The significant reduction in thermal conductivities of the lump was achieved for pure BiSbTe (200 µm) bulk and 0.75 vol% of SWCNTs/BiSbTe composite. This can be ascribed to the enhanced phonon scattering by the grain boundaries between the nanostructured BiSbTe particles as well as the interfaces between BiSbTe and the low dimensional carbon nanotubes.

Single-Wall Carbon Nanotube Doping in Lead-Acid Batteries: A New Horizon.

The addition of single-wall carbon nanotubes (SWCNT) to lead-acid battery electrodes is the most efficient suppresser of uncontrolled sulfation processes. Due to the cost of SWCNT, we studied the optimization loading of SWCNT in lead-acid battery electrodes. We optimized the SWCNT loading concentrations in both the positive and negative plates, separately. Loadings of 0.01% and 0.001% in the positive and negative active masses were studied, respectively. Two volts of lead-acid laboratory cells with sulfuric acid, containing silica gel-type electrolytes, were cycled in a 25% and 50% depth-of-discharge (DOD) cycling with a charging rate of C and 2C, respectively, and discharge rates of C/2 and C, respectively. All tests successfully demonstrated an excellent service life up to about 1700 and 1400 cycles for 25% and 50% DOD operations, respectively, at a low loading level of SWCNT. This performance was compared with CNT-free cells and cells with a multiwall carbon nanotube (MWCNT) additive. The outstanding performance of the lead-acid cells with the SWCNT additive is due to the oxidative stability of the positive plates during charging and the efficient reduction in sulfation in both plates while forming conducting active-material matrices.

Single-walled carbon nanotubes as stabilizing agents in red phosphorus Li-ion battery anodes

Structural breakdown and capacity loss of a red phosphorus-based anode material for lithium-ion batteries have been considerably attenuated with the addition of single-walled carbon nanotubes.

Totally embedded hybrid thin films of carbon nanotubes and silver nanowires as flat homogenous flexible transparent conductors.

There is a great need for viable alternatives to today’s transparent conductive film using largely indium tin oxide. We report the fabrication of a new type of flexible transparent conductive film using silver nanowires (AgNW) and single-walled carbon nanotube (SWCNT) networks which are fully embedded in a UV curable resin substrate. The hybrid SWCNTs-AgNWs film is relatively flat so that the RMS roughness of the top surface of the film is 3 nm. Addition of SWCNTs networks make the film resistance uniform; without SWCNTs, sheet resistance of the surface composed of just AgNWs in resin varies from 20 Ω/sq to 107 Ω/sq. With addition of SWCNTs embedded in the resin, sheet resistance of the hybrid film is 29 ± 5 Ω/sq and uniform across the 47 mm diameter film discs; further, the optimized film has 85% transparency. Our lamination-transfer UV process doesn’t need solvent for sacrificial substrate removal and leads to good mechanical interlocking of the nano-material networks. Additionally, electrochemical study of the film for supercapacitors application showed an impressive 10 times higher current in cyclic voltammograms compared to the control without SWCNTs. Our fabrication method is simple, cost effective and enables the large-scale fabrication of flat and flexible transparent conductive films.

Effect of Uniform Dispersion of Single-Wall Carbon Nanotubes on the Thermoelectric Properties of BiSbTe-Based Nanocomposites

Thermoelectric properties of BiSbTe-based bulk nanocomposites by incorporation of single-wall carbon nanotubes (SWCNTs) in different (0.0, 0.5, 1.0 and 1.5) vol.% were investigated from 300 K to 500 K. SWCNTs were uniformly dispersed in BiSbTe via a combination of ultra-sonication, magnetic stirring and mild ball milling. Fine BiSbTe powder was formed by crushing and ball milling the lumps in an inert environment. The composites demonstrate grain boundary structures exhibiting a three-dimensional network of one-dimensional flexible SWCNTs in BiSbTe bulks. The homogenous distribution of SWCNTs in BiSbTe drastically changes the transport properties of the composites. At 0.5 vol.% of SWCNTs, the effective thermal conductivity decreases suggesting the increased phonon scattering. Meanwhile, at 1.0 vol.% and 1.5 vol.%, the conductivities of the composites somehow increases attributed to homogenous distribution of SWCNTs in the BiSbTe matrix. The increased electrical resistivity with the addition of SWCNTs implies the enhanced scattering of carriers at the grain boundaries and SWCNTs/BiSbTe interfaces. The dimensionless figure of merit somewhat decreases with the addition of 0.5 vol.% SWCNTs. The results suggest that the figure of merit can be improved by optimizing the SWCNT composition below 0.5 vol.% by adequately tailoring the thermoelectric transport.

Exploration of single wall carbon nanotubes for the peristaltic motion in a curved channel with variable viscosity

In the present paper, we have investigated peristaltic flow of single wall carbon nanotubes (SWCNTs) in a curved channel with variable viscosity. The present problem is modeled and exact solutions for non-dimensional differential equation are achieved under long wavelength and low Reynolds number approximation. The features of the peristaltic motion are examined by plotting graphs and discussed in detail. Velocity tables are also incorporated for different values of volume fraction of the nano particle material and for viscosity parameter. Results showed that addition of SWCNTs decreases nano particle temperature and velocity profile near the left wall. It is found that for pure blood case, velocity for the variable viscosity fluid is greater as compared to the constant viscosity fluid. It is also found that for the case of SWCNTs, velocity for the variable viscosity fluid near the left wall decreases whereas it gets opposite behavior near the right wall.

Improvement of photovoltaic performance of inverted hybrid solar cells by adding single-wall carbon nanotubes in poly(3-hexylthiophene)

Solution prepared hybrid solar cells show promising low cost technology for electricity generation from sun light, although their power conversion efficiency has to be improved. One of the approaches is to increase the absorbance or charge carrier mobility of organic semiconductors. In this work, pristine single walled carbon nanotubes (SWCNT) were added into poly(3-hexylthiophene) (P3HT) solution to form P3HT:SWCNT composite films with different weight percent (wt%) of SWCNT. It is observed that optical absorbance spectra as well as the morphology of the composite films were modified by the addition of SWCNTs. This phenomenon could be explained by the π-π interaction between the conjugated polymer and carbon nanotubes. Most importantly, the electrical conductivities of the composite films increased with the SWCNT wt%. When these films were used as hole conductor layers in inverted planar hybrid solar cell, with CdS thin films as electron acceptor layers, the fill factor (FF) and open-circuit voltage (Voc) of the corresponding cells were decreased with the increase of the wt% of SWCNT. However, the short-circuit current density (Jsc) and the power conversion efficiency (PCE) showed a maximum value at about 0.4wt% of SWCNT in P3HT. The transient photovoltage measurements (TPV) revealed that the presence of SWNCT promoted the charge recombination process at P3HT/CdS interface, and as a result, reduced the Voc. The photovoltaic performance of the hybrid solar cells could be optimized by choosing an adequate weight percentage of SWCNT in P3HT to balance the charge carrier transport and charge recombination processes at the donor-acceptor interface.

Preparation of a Single‐Walled Carbon Nanotube/Cd0.8Zn0.2S Nanocomposite and Its Enhanced Photocatalytic Hydrogen Production Activity

Single‐walled carbon nanotube (SWCNT) and Cd0.8Zn0.2S nanocomposites were fabricated by a coprecipitation process with prefunctionalized SWCNTs as the starting material. The resultant SWCNT/Cd0.8Zn0.2S composites were characterized by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), high‐resolution transmission electron microscopy (HRTEM), Fourier transform IR (FTIR) spectroscopy, Raman spectroscopy, UV/Vis diffuse reflectance absorption spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The addition of SWCNTs improve both the visible‐light‐induced activity and stability for H2 production of Cd0.8Zn0.2S, and 10 wt.‐% SWCNT/Cd0.8Zn0.2S exhibits a maximum activity (632 mmol h–1) for H2 production that is ca. 1.40 times higher than that (451 mmol h–1) of Cd0.8Zn0.2S alone. This enhanced photoactivity of Cd0.8Zn0.2S through the incorporation of SWCNTs can be attributed to the synergetic effects of the intrinsic properties of its components; the functionalized SWCNTs act as the supporting matrix and electron acceptor of Cd0.8Zn0.2S and cause an effective charge separation at the SWCNT/Cd0.8Zn0.2S interfaces and an improvement in the photoactivity and stability for H2 production.

Properties of polyurethane nanocomposite filaments for conductive textile applications

Composite filaments of thermoplastic polyurethane (TPU) and single-walled carbon nanotubes (SWCNTs) have been fabricated via extrusion process and their properties were studied using various characterization techniques. Twin-screw extruder has been used for making the composite filaments and the processing parameters like temperature, screw speed, and pressure were optimized. Thermal, morphological, mechanical, and electrical properties were studied by varying the weight percentage of SWCNTs. Raman shift of SWCNTs is observed for the CNTs dispersed in TPU matrix. Thermal analysis shows that there is an increase in the degradation and melting temperature of the TPU/SWCNTs blends. With the addition of SWCNTs as small filler loadings of 1 wt%, the tensile strength of the blended materials increased from 13 MPa to 21.6 MPa. The electrical conductivity of the composite filaments starts with the addition of 0.01% of SWCNTs. The highest value of electrical conductivity (3.7 × 10−7 S cm−1) obtained with 2 wt% of SWCNTs. This melt extrusion process method could open up for the preparation of new high-performance nanotube composite materials.

Fabrication of CuSbS2 Solar Cells by Sulfurization of Thermally Evaporated Metal Stacks

We report on the deposition of thin films of chalcostibite (CuSbS2) created by sulfurization of thermally evaporated metal stacks. We found by X-ray diffraction that thermally evaporated copper and antimony metal films, which were annealed for 1.5 hours at 400°C followed by rapid sulfurization at 400°C for 15 minutes, exhibit the CuSbS2 crystalline phase. The films have high optical absorption with a band gap of ~1.6 eV. Our CuSbS2- based thin film solar cells had low conversion efficiency, due to the formation of a layer of molybdenum disulfide (MoS2) and/or secondary phases at the molybdenum back contact layer–CuSbS2 interface. To negate this problem, we applied a layer of single-walled carbon nanotubes (SWCNT) on the molybdenum back contact. This arrangement allowed for a better junction between the molybdenum and CuSbS2 layers. With the addition of SWCNT, our best cell under AM 1.5 illumination exhibited an open circuit voltage (Voc) of 321 mV, a short circuit current density (Jsc) of 3.76 mA/cm2, and a fill factor of 27%, resulting in a conversion efficiency of 0.33%. This work shows that for effective solar devices, it is critical that device layers are electrically aligned to allow for better electron passage. In the case presented here, we increased the efficiency by creating a passageway for electrons through the device by eliminating the formation of MoS2. This can be achieved by inserting single-walled carbon nanotubes (SWCNTs) that allow a better junction between the molybdenum and CuSbS2 layers. An alternative may include changing sulfur quantity, sulfurization time, or temperature.

Modification of conductive polymer PEDOT:PSS layer by SWCNT

In this study, the effect of addition of single-walled carbon nanotubes (SWCNTs) on the morphological properties of poly(3,4-ethylenedioxythiophene/poly(4-styrenesulfonate) (PEDOT:PSS) has been investigated using scanning electron microscope (SEM) as well as the surface roughness evaluation by atomic force microscopy (AFM). The spin-coated films of PEDOT:PSS and PEDOT:PSS with addition of SWNTs (0.5 % by wt.) on glass were compared in our study. Experimental results show that surface roughness of PEDOT:PSS layers increases after addition SWNTs to the solution - from 3.50 nm for the samples without SWNTs to 4.65 nm for the samples with SWNTs. The analysis of SEM images showed that there are some agglomerations of SWNTs on the surface of PEDOT:PSS/SWCNT composite film.