Multiwalled Carbon Nanotube Arrays Research Articles

Electrophysical properties of laser-structured carbon nanomaterials functionalized with LaB6 nanoparticles

In this paper, we perform density functional theory (DFT)-calculations to study the effect of LaB6 nanoparticles on the electrophysical properties of carbon nanomaterial based on laser-structured multi-walled carbon nanotubes (MWCNTs). Based on the calculation results, the most energetically favorable landing sites for LaB6 nanoparticles on the surface of the carbon framework are determined. It is found that during the functionalization with LaB6 nanoparticles, the carbon framework takes on a charge from the atoms of lanthanum and boron, which leads to an increase in the density of electronic states of the MWCNT nanostructure. It is shown that even at low concentrations of LaB6 nanoparticles (4.5 %), the work function of the carbon nanomaterial decreases by 0.5 eV. The results of the calculations are verified in the course of a real experiment. To carry it out, using the original technology of laser irradiation, a hybrid nanomaterial was created from a vertical array of MWCNTs functionalized with LaB6 nanoparticles. Pulsed laser action on an array of MWCNTs with an adjusted energy density of 0.15 J/cm2 made it possible to shorten, align, and orient the upper ends of the nanotubes perpendicular to the substrate. The effect of binding of LaB6 nanoparticles to a carbon surface has been experimentally established. Laser exposure of the MWCNT array coated with LaB6 nanoparticles resulted in a ∼ 5 by times increase in electrical conductivity compared to the original MWCNT array. Recording the emission current-voltage characteristics of hybrid nanomaterials demonstrated a decrease in the total work function of the carbon nanomaterial after functionalization with LaB6 nanoparticles by 16 %. Field emission current density values were calculated for all samples based on their measured field emission CVC characteristics. The MWCNT array exhibited the highest current density of 0.37 A/cm2 after LaB6 deposition and laser exposure. It is predicted that the carbon nanomaterial based on laser-structured MWCNTs coated with LaB6 nanoparticles will be an excellent nanomaterial for field emission electronics.

Comparison of Synchrotron and Laboratory X-ray Sources in Photoelectron Spectroscopy Experiments for the Study of Nitrogen-Doped Carbon Nanotubes

The chemical composition and stoichiometry of vertically aligned arrays of nitrogen-doped multi-walled carbon nanotubes (N-CNTs) were studied by photoelectron spectroscopy using laboratory and synchrotron X-ray sources. We performed careful deconvolution of high-resolution core-level spectra to quantify pyridine/pyrrole-like defects in N-CNTs, which are a key factor in the efficiency of the piezoelectric response for this material. It is shown that the XPS method makes it possible to estimate the concentration and type of nitrogen incorporation (qualitatively and quantitatively) in the “N-CNT/Mo electrode” system using both synchrotron and laboratory sources. The obtained results allow us to study the effect of the nickel catalytic layer thickness on the concentration of pyridine/pyrrole-like nitrogen and piezoelectric response in the nanotubes.

Multi-Walled Carbon Nanotube Array Modified Electrode with 3D Sensing Interface as Electrochemical DNA Biosensor for Multidrug-Resistant Gene Detection.

Drug resistance in cancer is associated with overexpression of the multidrug resistance (MDR1) gene, leading to the failure of cancer chemotherapy treatment. Therefore, the establishment of an effective method for the detection of the MDR1 gene is extremely crucial in cancer clinical therapy. Here, we report a novel DNA biosensor based on an aligned multi-walled carbon nanotube (MWCNT) array modified electrode with 3D nanostructure for the determination of the MDR1 gene. The microstructure of the modified electrode was observed by an atomic force microscope (AFM), which demonstrated that the electrode interface was arranged in orderly needle-shaped protrusion arrays. The electrochemical properties of the biosensor were characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Chronocoulometry (CC) was used for the quantitative detection of the MDR1 gene. Taking advantage of the good conductivity and large electrode area of the MWCNT arrays, this electrochemical DNA sensor achieved a dynamic range from 1.0 × 10-12 M to 1.0 × 10-8 M with a minimal detection limit of 6.4 × 10-13 M. In addition, this proposed DNA biosensor exhibited high sensitivity, selectivity, and stability, which may be useful for the trace analysis of the MDR1 gene in complex samples.

New oil derivative refractive index sensor using ribbon of multi-walled carbon nanotubes

In this work, we propose a new liquid refractive index (RI) sensor based on one-dimensional (1D) regular array of multi-walled carbon nanotubes (MWCNTs) for sensing oil derivatives (ODs), for the first time. The proposed sensor is a ribbon consisting of 10 MWCNTs grown inside an AAO (Al2O3) template as the host material, which can sense the change of host material RI with high precision up to △n = 0.0015 corresponding to the sensitivity S = 930 nm/RIU. Replacing the host material with ODs changes the reflection in the range of visible wavelengths. The reflection spectrum of sensor is calculated for the RI range of 1.3888–1.5306 belonging to various ODs. The RI difference △n = 0.1418 between Butanol (C4H10O) and Nitrobenzene (C6H5NO2) host materials results in 130 nm wavelength shift. By removing one or two cylinders of MWCNTs and creating a point defect within the sensor structure, whereas ODs are injected into the defect area, we achieved a sensitivity up to 430 nm/RIU. The proposed sensor with un-reactive nature of MWCNTs can be used in environments with high temperature and pressure such as oil refinery industry.

Thermoelectric properties of a vertically aligned carbon nanotube array with embedded bismuth telluride

Recently, thermoelectric (TE) devices have attracted much attention because they have no moving parts, simple structures, high reliability, and environmental friendly, when compared to other green energy techniques. In this paper, we report a novel thermoelectric composite constructed one with a self-assembled highly oriented Sb doped Bi2Te3 and one without doping nanoflake layer deposited on regular vertically aligned checkerboard-patterned multi-walled carbon nanotube (MWCNT) arrays (500 nm squares and 1 µm pitch) on insulated SiO2/Si substrates. The height of Bi2Te3/Bi0.4Sb1.6Te3, MWCNTs and volumetric ratio of MWCNT to Bi2Te3/ Bi0.4Sb1.6Te3 are about 3 μm, 1.5 μm, and 25%, respectively. The blending of regular vertically aligned MWCNT patterns into Bi0.4Sb1.6Te3 results in a dramatically enhancement of Seebeck coefficient and electrical conductivity. The Seebeck coefficient and power factor of Bi0.4Sb1.6Te3-MWCNTs show a maximum value of 600 μV/K and 60 μW/cm-K2 at 160 K and gradually decrease to 409 μV/K, and about 14.1 μW/cm-K2 at 300 K, respectively. The significant records of the low temperature Seebeck coefficients and relative electrical properties are extremely important for the fundamental understanding of vertically aligned MWCNT embedded thermoelectric composites.

Effect of catalyst support layers on emissivity of carbon nanotubes grown via floating catalyst chemical vapor deposition

We propose an efficient method of growing carbon nanotube (CNT) arrays on a variety of metals using chemical vapor deposition (CVD) assisted by a simple surface treatment of the substrate materials. The main feature of this method is the application of shot blasting with fine alumina shot to create the catalyst support layer that is required for the effective growth of CNTs on the various conductive materials, including the ultrahard metal tungsten. Energy dispersive X-ray spectroscopy shows that the shot blasting forms a noncontinuous layer where alumina nanoparticles are embedded as residue from the blasting media on the treated surfaces. Such a noncontinuous alumina layer can behave as the catalyst support layer, which is normally prepared via sputtering or a vacuum evaporation coating process. The influence of shot size on the characteristics of the nonuniform alumina buffer layer as well as the resultant multiwalled CNT arrays grown via CVD in conjunction with a floating iron catalyst are investigated. The results show that the morphology, crystallinity, and spectral emissivity of CNTs depend on the size of alumina shot used in the shot blasting treatment. The characteristics of the CNTs grown on various metal substrates with a discontinuous and continuous alumina buffer layers are compared with each other. These comparisons indicate that the degrees of hardness and the redox property of the substrates moderately affect the characteristics of CNTs on the discontinuous layer in contrast to the continuous layer.

Distribution of Iron Nanoparticles in Arrays of Vertically Aligned Carbon Nanotubes Grown by Chemical Vapor Deposition.

Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sources is fed into the hot zone of the reactor. Metal nanoparticles catalyze the growth of CNTs and, during synthesis, are partially captured into the internal cavity of CNTs. In this work, we considered various stages of multi-walled CNT (MWCNT) growth on silicon substrates from a ferrocene–toluene mixture and estimated the amount of iron in the array. The study showed that although the mixture of precursors supplies evenly to the reactor, the iron content in the upper part of the array is lower and increases toward the substrate. The size of carbon-encapsulated iron-based nanoparticles is 20–30 nm, and, according to X-ray diffraction data, most of them are iron carbide Fe3C. The reasons for the gradient distribution of iron nanoparticles in MWCNT arrays were considered, and the possibilities of controlling their distribution were evaluated.

Thermally responsive ionic transport system reinforced by aligned functional carbon nanotubes backbone

Ion transport plays an important role in energy conversion, biosensors, and a variety of biological processes. Carbon nanotubes, especially for the carbon nanotubes arrays with controlled vertically aligned structures, have displayed great potential as a promising material for regulating ion transport behaviors in the applications of the nanofluidic devices and osmotic energy conversion. Herein, we demonstrate the thermo-controlled ion transport system through the vertically aligned multiwall carbon nanotubes arrays membrane modified by the thermo-responsive hydrogel in a simple and reliable way. The functional carbon nanotubes backbone with the inherent surface charge and interstitial channels structure renders the system improved ion transport behaviors and well controlled switching property by thermo. Based on the integrated properties, the energy output from osmotic power in this system could be regulated by the reversible temperature switches. Moreover, it can realize a higher osmotic energy conversion property regulated by the thermos, which may extend the practical application in the future. The system that combines intelligent response with controlled ion transport behaviors and potential osmotic energy utilizations presents a valuable paradigm for the use of carbon nanotubes and hydrogel composite materials and provides a promising way for applications of nanofluidic devices.

Laser synthesis of iron nanoparticles as effective catalysts for the growth of vertically aligned MWCNTs with amorphous shell

Vertically aligned multi-walled carbon nanotubes (MWCNTs) are attractive for use in nanoelectronics, nanosensors, electrodes for energy storage and harvesting devices, composites, weaving yarns and many other devices. However, in order to reach practical relevance in these applications, the vertically aligned MWCNTs must be dense and sufficient height. Fulfilling those requirements is often challenging. Herein, we report production of high density vertically aligned MWCNTs with amorphous shell on iron nanoparticles by the modified CVD method in the tube flow reactor via catalytic pyrolysis of acetylene. The iron thin films of thickness from 0.5 to 68 nm were obtained by the pulsed laser deposition in droplet-free mode on single crystal silicon substrates (100). The obtained films of the thickness from 0.5 to 20 nm were arrays of nanoparticles with a size from 5 to 17 nm as a result of thermal annealing. These nanoparticles were used as catalysts for the growth of MWCNTs. SEM investigations have shown that height of the obtained vertically aligned MWCNTs depends on the thickness of the initial iron film. The height of the MWCNTs array of 42 µm was achieved on the iron nanoparticles obtained after annealing the metal film of 5 nm thickness. The growth temperature of the obtained MWCNTs array was 700 °C at the volume flow ratio of the C2H2 and H2(5 %)/Ar gas mixture was 1:4. TEM investigations have shown that the diameter of the obtained MWCNTs reached 15–20 nm with amorphous shell thickness of 5–10 nm. Four distinguished Raman peaks at 1360, 1603, 2711, and 2932 cm− 1 correspond to the D-band, G-band, 2D-band, and (D + G)-band, respectively and confirm the formation MWCNTs with good graphitization.

Terahertz and infrared transmission properties of super-thin periodic multi-walled carbon nanotube gratings

Super-aligned multi-walled carbon nanotube arrays on Si wafer were synthesized by low press chemical vapor deposition. The super-thin multi-walled carbon nanotube films were obtained by a drawing process on the side of the vertically aligned carbon nanotubes. The as-synthesized samples were characterized by scanning electron microscopy and optical microscopy. Terahertz time-domain measurements showed that anisotropic transmission properties were observed. The multi-walled carbon nanotube films with various two-dimensional periods and thicknesses displayed remarkably enhanced transmission at the terahertz range. Comparing experimental results with theoretical calculations revealed that the excitation of surface plasmon polaritons on the carbon nanotubes/Si interface was the key mechanism responsible for the enhanced transmission. The resonance peaks were red shifted with increasing period. In the infrared region, no obvious resonance peaks were observed.

Laser synthesis of iron nanoparticles as effective catalysts for the growth of vertically aligned MWCNTs with amorphous shell

Vertically aligned multi-walled carbon nanotubes (MWCNTs) are attractive for use in nanoelectronics, nanosensors, electrodes for energy storage and harvesting devices, composites, weaving yarns and many other devices. However, in order to reach practical relevance in these applications, the vertically aligned MWCNTs must be dense and sufficient height. Fulfilling those requirements is often challenging. Herein, we report production of high density vertically aligned MWCNTs with amorphous shell on iron nanoparticles by the modified CVD method in the tube flow reactor via catalytic pyrolysis of acetylene. The iron thin films of thickness from 0.5 to 68 nm were obtained by the pulsed laser deposition in droplet-free mode on single crystal silicon substrates (100). The obtained films of the thickness from 0.5 to 20 nm were arrays of nanoparticles with a size from 5 to 17 nm as a result of thermal annealing. These nanoparticles were used as catalysts for the growth of MWCNTs. SEM investigations have shown that height of the obtained vertically aligned MWCNTs depends on the thickness of the initial iron film. The height of the MWCNTs array of 42 µm was achieved on the iron nanoparticles obtained after annealing the metal film of 5 nm thickness. The growth temperature of the obtained MWCNTs array was 700 °C at the volume flow ratio of the C2H2 and H2(5%)/Ar gas mixture was 1:4. TEM investigations have shown that the diameter of the obtained MWCNTs reached 15–20 nm with amorphous shell thickness of 5–10 nm. Four distinguished Raman peaks at 1360, 1603, 2711, and 2932 cm− 1 correspond to the D-band, G-band, 2D-band, and (D + G)-band, respectively and confirm the formation MWCNTs with good graphitization.

Interfaces Based on Laser-Structured Arrays of Carbon Nanotubes with Albumin for Electrical Stimulation of Heart Cell Growth.

Successful formation of electronic interfaces between living cells and electronic components requires both good cell viability and performance level. This paper presents a technology for the formation of nanostructured arrays of multi-walled carbon nanotubes (MWCNT) in biopolymer (albumin) layer for higher biocompatibility. The layer of liquid albumin dispersion was sprayed on synthesized MWCNT arrays by deposition system. These nanostructures were engineered using the nanosecond pulsed laser radiation mapping in the near-IR spectral range (λ = 1064 nm). It was determined that the energy density of 0.015 J/cm2 provided a sufficient structuring of MWCNT. The structuring effect occurred during the formation of C–C bonds simultaneously with the formation of a cellular structure of nanotubes in the albumin matrix. It led to a decrease in the nanotube defectiveness, which was observed during the Raman spectroscopy. In addition, laser structuring led to a more than twofold increase in the electrical conductivity of MWCNT arrays with albumin (215.8 ± 10 S/m). Successful electric stimulation of cells on the interfaces with the system based on a culture plate was performed, resulting in the enhanced cell proliferation. Overall, the MWCNT laser-structured arrays with biopolymers might be a promising material for extended biomedical applications.

Excitation of Ultraslow High‐q Surface Plasmon Polariton Modes in Dense Arrays of Double‐Walled Carbon Nanotubes

AbstractThis work explores the plasmonic properties of parallel double‐walled carbon nanotube arrays. It is shown that ultraslow surface plasmon polariton (SPP) modes possessing a phase velocity some orders of magnitude lower than the speed of light in vacuum and high Q‐factor can be generated in such arrays. It is demonstrated that nonrelativistic electron beams with the velocity less than 106 m s−1 can be used to excite SPPs in arrays of double‐walled carbon nanotubes. For the SPP modes excited by an electron beam, the frequency range of SPP waves and electron beam velocities corresponding to the phase matching within a wide frequency range are determined. It opens the way to design slow‐wave structures based on the dense arrays of multiwalled carbon nanotubes employing an efficient energy transfer from the pump to the SPPs.

Lithography-free synthesis of periodic, vertically-aligned, multi-walled carbon nanotube arrays

Until now, the growth of periodic vertically aligned multi-walled carbon nanotube (VA-MWCNT) arrays was dependent on at least one lithography step during fabrication. Here, we demonstrate a lithography-free fabrication method to grow hexagonal arrays of self-standing VA-MWCNTs with tunable pitch and MWCNT size. The MWCNTs are synthesized by plasma enhanced chemical vapor deposition (PECVD) from Ni catalyst particles. Template guided dewetting of a thin Ni film on a hexagonally close-packed silica particle monolayer provides periodically distributed Ni catalyst particles as seeds for the growth of the periodic MWCNT arrays. The diameter of the silica particles directly controls the pitch of the periodic VA-MWCNT arrays from 600 nm to as small as 160 nm. The diameter and length of the individual MWCNTs can also be readily adjusted and are a function of the Ni particle size and PECVD time. This unique method of lithography-free growth of periodic VA-MWCNT arrays can be utilized for the fabrication of large-scale biomimetic materials.

Preparation of carbon nanotube arrays nanocomposites filled with Prussian blue and electrochemical sensing of hydrogen peroxide

In this work, A nanocomposite film composed of multi-walled carbon nanotube arrays (MWCNTA) filled with Prussian Blue (PB) was prepared, and it was successfully applied in the electrochemical Sensing of H2O2. The nanostructure of MWCNTA/PB was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The electrochemical behavior was investigated by cyclic voltammetry (CV). The excellent catalytic reduction performance of H2O2 by MWCNTA/PB was observed and applied as a H2O2 electrochemical sensor. It is found that the linear detection range of the sensor is 10 μM to 110 μM and the sensitivity is 0.407 μA μM–1, as well as the detection limit is 0.21 μM. The interference experiment results showed that uric acid, dopamine, glucose and ascorbic acid could not affect the electrochemical detection of H2O2, indicating that the sensor has good stability and anti-interference.

Study of Vertically Aligned Multi-Walled Carbon Nanotubes Array for an Absolutely Black Body

Study of Vertically Aligned Multi-Walled Carbon Nanotubes Array for an Absolutely Black Body

Kinetics of Oxidation of Composites Based on Arrays of Multiwalled Carbon Nanotubes and Tin Oxide Obtained by the Magnetron Sputtering Method

Kinetics of Oxidation of Composites Based on Arrays of Multiwalled Carbon Nanotubes and Tin Oxide Obtained by the Magnetron Sputtering Method

Laser Patterning of Aligned Carbon Nanotubes Arrays: Morphology, Surface Structure, and Interaction with Terahertz Radiation.

The patterning of arrays of aligned multi-walled carbon nanotubes (MWCNTs) allows creating metastructures for terahertz (THz) applications. Here, the strips and columns from MWCNTs vertically grown on silicon substrates are prepared using CO2 laser treatment. The tops of the patterned arrays are flat when the laser power is between 15 and 22 W, and craters appear there with increasing power. Laser treatment does not destroy the alignment of MWCNTs while removing their poorly ordered external layers. The products of oxidative destruction of these layers deposit on the surfaces of newly produced arrays. The oxygen groups resulting from the CO2 laser treatment improve the wettability of nanotube arrays with an epoxy resin. We show that the patterned MWCNT arrays absorb the THz radiation more strongly than the as-synthesized arrays. Moreover, the pattern influences the frequency behavior of the absorbance.

High-performance refractive index sensor for oil derivatives based on MWCNT photonic crystal microcavity

In this paper, we propose a new all-optical sensor based on a two-dimensional (2D) regular array of multi-walled carbon nanotubes (MWCNTs) for the refractive index sensing of oil derivatives, for the first time. The interaction of optical wave with the desirable oil derivatives is enhanced using the slow light effect that makes the group velocity go down. We consider the geometric feature for the proposed sensor structure as a photonic crystal (PhC) with a line defect formed by missing some rows of MWCNT elements. The difference of refractive index △n = 0.1418 between Butanol (C4H10O) and Nitrobenzene (C6H5NO2) host materials results in a wavelength shift of 149 nm, and indicates a sensitivity of 1050 nm/RIU, which can be widely used for the bio/chemical detection and environmental monitoring. To achieve the physical stability of the proposed sensor, MWCNTs are considered to be grown in the AAO (Al2O3) template. By removing one or two rows of the MWCNTs and creating a linear defect within the sensor structure, whereas oil derivatives are injected into the defect area. We have achieved a sensitivity up to 870 nm/RIU. This proposed sensor with un-reactive structure of MWCNTs can be used in environments with high temperature and pressure such as oil refinery industry and other chemical processes industries under wide range of different reaction conditions.

Electrically activated chemical bath deposition of CdS on carbon nanotube arrays

Electrically stimulated depositions of CdS nanoparticles on the surface of aligned multi-walled carbon nanotube (CNT) arrays were investigated by applying a voltage of 3 V to the electrodes placed into a chemical bath with an aqueous ammonium solution of CdCl2 and thiourea. The CNT arrays were fixed on positive, negative, and neutral electrodes. Morphology, composition and structure of CdS-CNT hybrids were studied using scanning electron microscopy, Raman scattering and X-ray photoelectron spectroscopy. CdS nanocrystallites in the hybrids were found to exhibit synthesis-dependent luminescence properties. S-vacancy enriched CdS grown on the positively charged CNT array possessed red photoluminescence (PL). Purple emission was attributed to small-size CdS nanocrystals synthesized on the negatively charged CNTs. The CNT array located on a neutral electrode was uniformly covered by CdS nanoparticles with a highly intense blue PL. Our results indicate a promising effect of the electrical field for enhancement of the growth rate of CdS nanocrystals.