Length Of Multi-walled Carbon Nanotubes Research Articles

Investigating the potential of multiwalled carbon nanotubes based zinc nanocomposite as a recognition interface towards plant pathogen detection

The emergence of nanotechnology has opened new horizons for constructing efficient recognition interfaces. This is the first report where the potential of a multiwalled carbon nanotube based zinc nanocomposite (MWCNTs-Zn NPs) investigated for the detection of an agricultural pathogen i.e. Chili leaf curl betasatellite (ChLCB). Atomic force microscope analyses revealed the presence of multiwalled carbon nanotubes (MWCNTs) having a diameter of 50–100nm with zinc nanoparticles (Zn-NPs) of 25–500nm. In this system, these bunches of Zn-NPs anchored along the whole lengths of MWCNTs were used for the immobilization of probe DNA strands. The electrochemical performance of DNA biosensor was assessed in the absence and presence of the complementary DNA during cyclic and differential pulse voltammetry scans. Target binding events occurring on the interface surface patterned with single-stranded DNA was quantitatively translated into electrochemical signals due to hybridization process. In the presence of complementary target DNA, as the result of duplex formation, there was a decrease in the peak current from 1.89×10−04 to 5.84×10−05A. The specificity of this electrochemical DNA biosensor was found to be three times as compared to non-complementary DNA. This material structuring technique can be extended to design interfaces for the recognition of the other plant viruses and biomolecules.

The effect of multi-wall carbon nanotube morphology on electrical and mechanical properties of polyurethane nanocomposites

In this study, we examine the effect of multi-wall carbon nanotubes (MWCNT) morphology on electrical and mechanical properties of MWCNT-filled polyurethane (PU) nanocomposites. The main objective of this study is to understand the role of aspect ratio and length of MWCNTs in determining the performance of nanocomposites. Highly aligned MWCNTs were prepared by aerosol-assisted chemical vapour deposition method and compared to commercially available MWCNTs in PU matrix for ease of dispersibility and performance. We observed opposing influence of the MWCNT on electrical and mechanical behaviour of the nanocomposites. The electrical properties were proportional to length of the MWCNTs whereas the mechanical properties were dependent on the aspect ratio of the MWCNTs. Moreover, thicker nanotubes (approximately 40nm) with a higher aspect ratio (approximately 225) are less prone to shortening and impart better tensile and storage modulus along with improved electrical and therefore are more suitable for the MWCNT nanocomposites.

CNT network modeling and simulation of the electrical properties of CNT/PNN-PZT/epoxy paint sensor

In this study, the electrical properties of Carbon nanotubes (CNT)/PNN-PZT/epoxy paint sensor, a kind of piezoelectric composites, were simulated to explain the effect of the dispersion state of Multiwalled CNT (MWCNT) in the paint sensor on sensor characteristics. The conductivity of the CNT/PNN-PZT/epoxy paint was calculated by the 3D resistor network simulation in consideration of the length, dispersion state, and volume fraction of MWCNT. The electrical property of the paint sensor was predicted efficiently by a simple simulation method. Both the conductivity of the piezoelectric composite and the percolation threshold of MWCNT in the piezoelectric composite were simulated according to the dispersion state of MWCNT in the composite. Finally, the simulation results were compared and verified with experimental data.

Homogenization for Dispersion and Reduction in Length of Carbon Nanotubes

An important aspect that limits the use of carbon nanotubes (CNTs) is the difficulty in obtaining homogeneously dispersed CNTs of uniform length. Hence, homogenization of multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) was carried out using bullet blender and the dispersion behavior was compared with that of ultrasonication. 1% sodium dodecyl sulphate (SDS), Triton-x-100 and polyethylene glycol 4000 were used as dispersing agents during homogenization. The dispersed CNTs were studied using transmission electron microscopy, ImageJ and Raman spectroscopy. Though dispersion and reduction in length of MWCNTs were observed both with ultrasonication and homogenization, lowest length range with about 75% reduction in polydispersity index was obtained on homogenization. Longer time of ultrasonication resulted in damage to small MWCNTs. Well dispersed and shorter MWCNTs were obtained with Triton-x-100 while reduction in length was minimum with SDS. SWCNTs of less than 1 μm length could be obtained by homogenization with Triton-x-100.

Multi-walled carbon nanotube-physicochemical properties predict the systemic acute phase response following pulmonary exposure in mice.

Pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) has been linked to an increased risk of developing cardiovascular disease in addition to the well-documented physicochemical-dependent adverse lung effects. A proposed mechanism is through a strong and sustained pulmonary secretion of acute phase proteins to the blood. We identified physicochemical determinants of MWCNT-induced systemic acute phase response by analyzing effects of pulmonary exposure to 14 commercial, well-characterized MWCNTs in female C57BL/6J mice pulmonary exposed to 0, 6, 18 or 54 μg MWCNT/mouse. Plasma levels of acute phase response proteins serum amyloid A1/2 (SAA1/2) and SAA3 were determined on day 1, 28 or 92. Expression levels of hepatic Saa1 and pulmonary Saa3 mRNA levels were assessed to determine the origin of the acute phase response proteins. Pulmonary Saa3 mRNA expression levels were greater and lasted longer than hepatic Saa1 mRNA expression. Plasma SAA1/2 and SAA3 protein levels were related to time and physicochemical properties using adjusted, multiple regression analyses. SAA3 and SAA1/2 plasma protein levels were increased after exposure to almost all of the MWCNTs on day 1, whereas limited changes were observed on day 28 and 92. SAA1/2 and SAA3 protein levels did not correlate and only SAA3 protein levels correlated with neutrophil influx. The multiple regression analyses revealed a protective effect of MWCNT length on SAA1/2 protein level on day 1, such that a longer length resulted in lowered SAA1/2 plasma levels. Increased SAA3 protein levels were positively related to dose and content of Mn, Mg and Co on day 1, whereas oxidation and diameter of the MWCNTs were protective on day 28 and 92, respectively. The results of this study reveal very differently controlled pulmonary and hepatic acute phase responses after MWCNT exposure. As the responses were influenced by the physicochemical properties of the MWCNTs, this study provides the first step towards designing MWCNT that induce less SAA.

Carbon nanotubes length optimization for preparation of improved transparent and conducting thin film substrates

Abstract Transparent and conductive thin films of multiwalled carbon nanotubes (MWCNTs) with different lengths were prepared on glass substrates by the spin coating method. In order to reduce the MWCNTs length, they were functionalized. The initial length of MWCNTs (10–15 μm) was reduced to 1200, 205 and 168 nm after 30, 60 and 120 min refluxing time, respectively. After post annealing at 285 °C for 24 h, the electrical and optical properties were greatly improved for functionalized MWCNT thin films. They strongly depend on the length of CNTs. The optical transmittance of the film prepared using 30 min reflux CNTs was 2.6% and 6.6% higher than that of the 60 min and 120 min refluxed samples respectively. The sheet resistance of this film showed reductions of 45% and 80% as well. The film also exhibited the least roughness. The percolative figure of merit, which is proportional to the transparency and disproportional to the sheet resistance, was found to be higher for the sample with 30 min refluxed MWCNTs.

The effects of MWCNT length on the mechanical, crystallization and electromagnetic interference shielding effectiveness of PP/MWCNT composites

The length of multi-walled carbon nanotubes (MWCNT) has an important influence on the properties of polymer/MWCNT composites. This study aims to examine the influence of the length of MWCNT on the mechanical properties, distribution, melting and crystallization behavior, and electromagnetic interference shielding effectiveness (EMI SE) of PP/MWCNT composites. The test results show that MWCNT of a short length contribute to better mechanical properties and have a better dispersion in the matrix. MWCNT also serve as a nucleating agent for PP, thereby increasing the crystallization temperature (Tc). In particular, short MWCNT provide PP/MWCNT composites with a greater degree of cyrstallinity. The conjunction of 8 wt% long MWCNT in PP/MWCNT composites results in an optimal electrical resistivity of 65.02 Ω-cm, and an average EMI SE of −29.47 dB. The polymer/MWCNT composites have properties that can be adjusted by using different lengths of MWCNT, which is advantageous for application in diverse products.

Effect of Nanotube Morphologies on Multi-Walled Carbon Nanotubes Based Counter Electrode for Dye-Sensitized Solar Cell.

Multi-walled carbon nanotubes (MWCNTs) with different morphologies were introduced into dyesensitized solar cell (DSSC) as low-cost substitutes for Pt counter electrode (CE). The effect of length and orientation of MWCNTs on the power conversion efficiency (PCE) of DSSC with MWCNTs CE were studied by measuring electrochemical impedance spectroscopy of MWCNTs and the photocurrent density–voltage (J–V ) characteristics of DSSC in this study. Results revealed that the long MWCNTs showed better electrocatalytic activity of reducing triiodide ions than short MWCNTs and yielded the power conversion efficiency of 2.42%. When the aligned multi-walled carbon nanotubes (AMWCNTs) with the same length as the long MWCNTs were used to prepare the CE, the power conversion efficiency of the DSSC reaches 2.95%. In order to further improve the performance of the DSSC, the processing of photoanode and counter electrode were adjusted. The power conversion efficiency of the cell with AMWCNTs as CE prepared by adjusted processing achieved 3.95% and the short circuit current density is superior to the DSSC with Pt as CEs, and it indicated the adjusted processing is beneficial to increase the overall performance of the dye-sensitized solar cell.

A probabilistic micromechanical modeling for electrical properties of nanocomposites with multi-walled carbon nanotube morphology

The nanoscopic characteristics of the multi-walled carbon nanotubes (MWCNTs) used in composites are crucial for attempting to understand and design nanocomposites of a novel class. We investigate the correlations between the nanofiller properties and effective electrical properties of MWCNT-embedded polycarbonate composites by theoretical and experimental approaches. A probabilistic computational model is proposed to predict the influence of MWCNT morphology on the electrical behaviors of MWCNTs-embedded polymer composites. A parameter optimization method in accordance with a genetic algorithm is then applied to the model, resulting that the ideal sets of model constant for the simulation are computationally estimated. For the experimental validation purpose, a comparison between the present theoretical and experimental results is made to assess the capability of the proposed methods. In overall, good agreement between the predictions and experimental results can be observed and the electrical performance of the composites can be improved as the MWCNT length increases.

Mechanical properties of polyimide/multi-walled carbon nanotube composite fibers

A series of polyimide (PI)/multi-walled carbon nanotube (MWCNT) composite fibers were prepared by copolymerizing a mixture of monomers and carboxylic-functionalized MWCNTs, followed by dry-jet wet spinning, thermal imidization, and hot-drawing process. The content of the carboxylic groups of MWCNTs significantly increased when treated with mixed acid, whereas their length decreased with treatment time. Both the carboxylic content and length of MWCNTs influenced the mechanical properties of the composite fibers. Fiber added with 0.1 wt% MWCNTs treated for 4 h exhibited the best mechanical properties, i.e., 1.4 GPa tensile strength and 14.30% elongation at break, which were 51% and 32% higher than those of pure PI fibers, respectively. These results indicated that a suitable MWCNT content strengthened and toughened the resultant PI composite fibers, simultaneously. Moreover, raising draw ratio resulted in the increase of tensile strength and tensile modulus of the composite fibers.

Experimental validation of the Burgio–Rojac model of planetary ball milling by the length control of multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) were used as a model system to verify the applicability of the Burgio–Rojac milling map for describing top-down attrition phenomena in the submicrometer range. The nanotubes were milled using several different operation parameter sets in a planetary ball mill. Transmission electron micrographs of the products were analyzed to assess length reduction and Raman spectra were recorded to evaluate the extent of milling-induced amorphization from the intensity ratio of the D and G lines. A simple statistical model describing MWCNT length reduction was established and different data representations were compared against the predictions of this model. While it was not possible to fully interpret the resulting data as functions of the typically considered primary milling parameters, the derivative parameter space defined by the individual ball impact energy and cumulative transferred energy variables calculated from the Burgio–Rojac model provided a satisfactory reference frame. The single hit threshold energy for successful MWCNT attrition was determined to be approx. 35 mJ/hit.

Amperometric biosensor based on glassy carbon electrode modified with long-length carbon nanotube and enzyme

An amperometric biosensor based on a glassy carbon electrode modified with long-length multiwalled carbon nanotubes (MWCNTs) and enzyme nicotinamide-adenine-dinucleotide-dependent glucose dehydrogenase (GDH) is presented. We demonstrate the effect of the MWCNT length on the amperometric response of the enzyme biosensor. The long length of MWCNT is 200 µm (average), whereas the normal length of MWCNT is 1 µm (average). The response of the long MWCNT–GDH electrode is 2 times more sensitive than that of the normal-length MWCNT–GDH electrode in the concentration range from 0.25–35 mM. The result of electrochemical impedance spectroscopy measurements suggest that the long-length MWCNT–GDH electrode formed a better electron transfer network than the normal-length one.

In situ process monitoring of hierarchical micro-/nano-composites using percolated carbon nanotube networks

We report a method to monitor the manufacturing process of hierarchical micro-/nano-composites that uses integrated and percolated multi-walled carbon nanotube (MWCNT) networks with the aim of reducing part-to-part variability. Composites were fabricated by VARTM. Fiber textiles were spray-coated with MWCNTs, electrodes were embedded prior to vacuum bagging. In situ process monitoring was achieved by measurement of the electrical resistance of electrode pairs. The effects of MWCNT density and length on the ability to monitor the manufacturing process were evaluated. Experiments showed that monitoring the changes in resistance between electrode pairs on the conductive MWCNT network allowed various events during the manufacturing process, including part infusion, onset of crosslinking, and gel point of the resin, which are necessary for accurate evaluation of part quality. Our simple yet effective method to monitor the manufacturing processes and predict the final-part quality of multiscale composites can be integrated into existing processes with minimal modifications.

Significance of the Length of Carbon Nanotubes on the Bioelectrocatalytic Activity of Bilirubin Oxidase for Dioxygen Reduction

Bilirubin oxidase (BOD) catalyzes 4e−-reduction of O2 into H2O and is one of the enzymes allowing direct electron transfer (DET)-type bioelectrocatalysis. Mesoporous carbon materials are often used for constructing BOD-modified DET-type biocathodes. We have examined the performance of several multi-walled carbon nanotubes (MWCNTs) as cathode platforms for BOD-catalyzed bioelectrocatalytic O2 reduction. It has been found that the length of MWCNTs is a very important factor to control the performance. The π-π conjugated system with the carboxy groups on the surface of MWCNTs plays an important role in enhancing the DET-type bioelectrocatalytic activity of BOD. Water-soluble MWCNT with the length of as short as 1−4μm is the most suitable material among the MWCNTs examined, and they have been used to construct a mesoporous carbon electrode without any binder. The catalytic current density has reached a diffusion-controlled level for the first time for BOD at an electrode rotating rate of 4000rpm and at 25°C (8mAcm−2).

Multi-walled carbon nanotubes change morpho-functional and GABA characteristics of mouse cortical astrocytes

BackgroundMulti-walled carbon nanotubes (MW-CNTs) have been extensively explored for their possible beneficial use in the nervous system. CNTs have shown to modulate neuronal growth and electrical properties, but its effect that varying length of MW-CNTs on primary astrocyte roles have not been clearly demonstrated yet.ResultsWe investigate here the effect of MW-CNTs on astrocytic morphology, cell–cell interaction and the distribution of intracellular GABA (gamma-amino butyric acid). Primary cultured cortical astrocytes on MW-CNT-coated glass coverslips grow rounder and make more cell–cell interactions, with many cell processes, compared to astrocytes on poly-d-lysine (PDL) coverslips. In addition, intracellular GABA spreads into the cell processes of astrocytes on MW-CNT coverslips. When this GABA spreads into cell processes from the cell body GABA can be released more easily and in larger quantities compared to astrocytes on PDL coverslips.ConclusionsOur result confirm that MW-CNTs modulate astrocytic morphology, the distribution of astrocytic GABA, cell–cell interactions and the extension of cell processes. CNTs look to be a promising material for use neuroprosthetics such as brain-machine interface technologies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-015-0152-y) contains supplementary material, which is available to authorized users.

In English

The effect of acid treatment on the structure and properties of suspensions of multiwalled carbon nanotubes (MWCNTs) in glycerol has been investigated. The concentrations of MWCNTs were within 0–2% by weight. Suspensions were treated during 5–60 min at T = 343 K by a mixture of concentrated nitric and sulphuric acids with the volume ratio of 1:3. The degree of acid treatment influence on the structure of suspension was analyzed using methods of thermal analysis and infrared spectroscopy. Oxidation of MWCNTs could affect significantly their thermal stability and degree of destruction. The changes in the structure of MWCNT clusters in glycerol, electrical conductivity and percolation behaviour of the systems are discussed. The acid treatment is shown to cause significant decrease in conductivity of suspension and enhancement of its temperature dependence. Reduction of the length of MWCNTs after acid treatment is reported.

Dispersion stability of multi-walled carbon nanotubes in refrigerant with addition of surfactant

In order to apply surfactant for improving the stability of multi-walled carbon nanotubes (MWCNTs) nanorefrigerant in refrigeration system, the effects of surfactant type, ultrasonication time, surfactant concentration, initial MWCNT concentration and MWCNT structure on the dispersion stability of MWCNTs in refrigerant with surfactant are investigated in the present study. In the experiments, R141b was selected as host refrigerant for the preparation of nanorefrigerant, UV–vis spectrophotometer method was used to quantitatively evaluate the dispersion stability of MWCNTs, and Fourier transform infrared spectroscopy (FTIR) as well as dynamic light scattering (DLS) analysis were performed to understand the dispersion stability mechanism. The experimental results show that the good dispersion stability of MWCNTs is obtained with addition of sodium dodecylbenzene sulfonate (SDBS) as a surfactant, and the increase of ultrasonication time improves the dispersion stability. The relative concentration increases with the increase of SDBS concentration and then decreases, while increases with the decrease of initial MWCNT concentration at the optimal SDBS concentration. It is also found that the decrease of MWCNT length or outer diameter leads to the increase of relative concentration.

Preparation of Multiwalled Carbon Nanotubes Embedded in Copper Composite Powders

High energy milling (HEM) was used for preparation of multiwalled carbon nanotubes (MWCNTs) embedded in copper composite powders and cut off MWCNTs. The results show that, the MWCNTs can be cut off, the length of MWCNTs is 0.1–2 μm after wet ball milling for 1 h and the structure of the MWCNTs isn’t damaged. The MWCNTs/Cu composite powders could also be prepared by HEM. MWCNTs are uniformly dispersed in composite powders under the milling parameters as follows: ball/powder weight ratio 10:1, rotational speed 700/900 rpm, milling time 2 h, MWCNTs content 3 wt%. A good adhesion of CNTs in copper matrix was obtained and revealed by means of transmission electron microscope (TEM).

Thermal conductivity of polymer composites based on the length of multi-walled carbon nanotubes

The anisotropic development of thermal conductivity in polymer composites was evaluated by measuring the isotropic, in-plane and through-plane thermal conductivities of composites containing length-adjusted short and long multi-walled CNTs (MWCNTs). The thermal conductivities of the composites were relatively low irrespective of the MWCNT length due to their high contact resistance and high interfacial resistance to polymer resins, considering the high thermal conductivity of MWCNTs. The isotropic and in-plane thermal conductivities of long-MWCNT-based composites were higher than those of short-MWCNT-based ones and the trend can accurately be calculated using the modified Mori-Tanaka theory. The in-plane thermal conductivity of composites with 2 wt% long MWCNTs was increased to 1.27 W/m·K. The length of MWCNTs in polymer composites is an important physical factor in determining the anisotropic thermal conductivity and must be considered for theoretical simulations. The thermal conductivity of MWCNT polymer composites can be effectively controlled in the processing direction by adjusting the length of the MWCNT filler.

Optical resonance in far-infrared spectra of multiwalled carbon nanotubes

We have studied the plasmon resonance behaviors of various multiwalled carbon nanotubes (MWCNTs) using far-infrared (FIR) spectroscopy. MWCNTs having high crystallinity showed clear FIR peak structures, the same as those observed in single-walled carbon nanotubes (SWCNTs). However, the FIR peak structures in defective MWCNTs were severely suppressed. The observed FIR peak positions apparently depend on the inverse of the MWCNT length. These results are consistent with the one-dimensional plasmon resonance model, which is sensitive to the geometrical structure of a CNT channel and the disturbance of the plasmon motion in the channels.