Electronic Properties Of Carbon Nanotubes Research Articles

Density functional theory study of adsorption and dissociation of CH2Cl2 on the surfaces of transition metal (Fe, Co, Ni, and Cu)-doped carbon nanotubes

A DFT study was carried out on the adsorption capacity and dissociation mechanism of dichloromethane by intrinsic carbon nanotubes and Fe, Co, Ni and Cu adsorption-modified carbon nanotube systems. The calculated results indicated the dopant of transition metal can effectively enhance the electronic properties of carbon nanotubes. The adsorption of carbon nanotubes for CH2Cl2 is also enhanced, and the dissociations of CH2Cl2 on the four metal-decorated carbon nanotubes are exothermic. Especially in the case of Fe adsorption modification (adsorption energy reaches -1.91 eV), which is much higher than the intrinsic carbon nanotube adsorption energy of CH2Cl2 (-0.38 eV), and the reactive energy barrier of the dissociation process of the CH2Cl2 is as low as 0.493 eV. Meanwhile, the dissociation process can occur spontaneously at room temperature, which contributes to the dissociation of CH2Cl2 on Fe adsorption-modified carbon nanotube systems, providing theoretical support for the subsequent governance process of CH2Cl2.

Сенсорные свойства углеродных нанотрубок, содержащих примесные атомы бора

Nanotubes, being one of the most sought-after materials in nanotechnology, are finding new applications. One such area is their use as highly sensitive sensors. However, in the practical application of nanotubes, it often turns out that, despite their positive sorption properties, the change in their electronic state does not occur after the capture of the analyzed substance. This fact significantly complicates the possibility of their use as sensor nanosensors. One of the ways to improve the electronic properties of carbon nanotubes by creating heterostructures on their surface is by modifying them with different atoms. In this case, one of the most effective for the substitution reaction is boron. It enables the creation of redistribution of electron density on the surface of nanotubes while making no significant changes to the topology of the nanotube surface. This paper analyzes a model experiment to study the possibility of using the nanotubes themselves as highly sensitive nanosensors with respect to carbon dioxide molecules. It is concluded that in order to control the sorption properties of carbon nanotubes for their use in fire-fighting devices, it is sufficient to modify them with impurity boron atoms without the introduction of additional functional groups.

Carbon nanotubes: revolutionizing construction materials for a sustainable future: A review

This review article explores the use of carbon nanotubes (CNTs) as material enhancers in construction and their advantages. It emphasizes ongoing research to gather accurate data on CNT-enhanced material properties and their role in creating more efficient and stronger building materials. The various methods of obtaining and incorporating CNTs into building materials, including chemical vapor deposition and electric arc synthesis, are discussed. A comparative analysis of building materials with and without CNTs is presented to examine their characteristics. The article also discusses future prospects for CNTs in various industries. The study aims to investigate experimental methods for obtaining CNTs, their properties, and their introduction into building materials. The research methodology involves studying literature sources, analyzing experimental results, and examining the structural, mechanical, and electronic properties of CNTs. Analytical methods based on scientific articles and publications related to CNTs in construction were used to ensure the article's reliability, validity, completeness, and objectivity. The research highlights CNTs' potential as material enhancers in construction, owing to their unique mechanical properties, such as high strength, stiffness, and corrosion resistance. Specific studies demonstrating the use of CNTs to increase the strength of concrete and other construction materials are provided, indicating the promising application of CNTs in future construction projects. However, technical challenges must be addressed, and appropriate standards and regulations should be developed before practical implementation.

Sensory properties of carbon nanotubes containing impurity boron atoms

Nanotubes, being one of the most demanded nanotechnology materials, are finding new areas of application. One of these areas is their use as highly sensitive sensors. However, in the practical application of nanotubes, it often turns out that, despite the positive sorption properties, a change in their electronic state does not occur after the capture of the analyte. This fact significantly complicates the possibility of their use as sensory nanosensors. One of the ways to improve the electronic properties of carbon nanotubes by creating heterostructures on their surface is modification with various atoms. At the same time, one of the most effective substances for carrying out the substitution reaction is boron. It makes it possible to create a redistribution of electron density on the surface of nanotubes without introducing significant changes in the topology of the nanotube surface. This article analyzes a model experiment to study the possibility of using the nanotubes themselves as highly sensitive nanosensors in relation to carbon dioxide molecules.

(Invited) Comprehensive Analysis of Electronic Properties of Carbon Nanotube Fibers

The electronic properties of various carbon nanotube (CNT) fibers that were produced by dry spinning from multi-walled CNT (MWCNT) forests, direct spinning from a CVD furnace and wet spinning of CNTs, are systematically investigated. The electrical conductivity of the fibers is significantly correlated with the effective CNT length [1], yarn density, and CNT alignment in the yarns. In contrast, the tensile strength depends more on the yarn density and the CNT alignment. The temperature dependence of the electronical properties of the CNT fibers are also investigated. Even though the constituent CNTs are very similar, the CNT fibers produced by the wet spinning of the acid treated CNT dispersion and the micelle CNT solution show different temperature dependences in the lower temperature region. The difference can be explained by the different conduction paths in the two wet-spinning fibers. Further, the iodide doping effect on the electronic property of the wet-spinning fiber produced by the acid treated dispersion is also discussed. This work was supported by a project (JPNP16010) commissioned by the New Energy and Industrial Technology Development Organization (NEDO).[1] T. Morimoto et al., ACS Nano, 8, 9897–9904 (2014).

Development of Organic Color Center Based Nanosensors for Proinflammatory Cytokine Detection

Organic color centers, also known as fluorescent sp3 quantum defects, on single walled carbon nanotubes, have opened exciting opportunities to re-engineer the optical and electronic properties of carbon nanotubes via covalent surface chemistry. Organic color centers produce molecularly tunable fluorescence in the near-infrared, conferring new chemical and optical functionalities that are suitable for biosensing applications. In this talk, we discuss the strategies that enhance the physical stability and optical response of the nanosensors for robust, transient detection of proinflammatory cytokines in biofluids. The sensor technology incorporates functional organic color centers augmented by biodesigned supercharged molecular recognition proteins.

4f-metal chlorides effect on electronic properties of carbon nanotubes

In the present work, the channels of single-walled carbon nanotubes were filled with melts of ZnCl2, CdCl2, and TbCl3 by a capillary method with subsequent slow cooling. The detailed study of electronic structure of filled nanotubes was performed using Raman, optical absorption, and X-ray photoelectron spectroscopy. The obtained data are in mutual agreement and it proves that the filling of carbon nanotube channels with all these salts leads to the charge transfer from nanotube walls to the incorporated compounds, thus acceptor doping of nanotubes takes place. It was found out that encapsulated terbium chloride has the largest influence on the electronic properties of carbon nanotubes.

Electrochemical Features of Low Pt Electrocatalysts Deposited Over Doped Carbon Nanotubes

Carbon nanotubes (CNT) are being utilized in PEM fuel cells electrocatalysts, due to their physical and chemical characteristics. Diverse studies have been reported on their use as support of Pt to improve the metal particles dispersion, as well as to provide a higher mechanical and electrochemical stability. As it is known, the development of highly efficient electrocatalysts with low platinum loading is crucial in order to achieve the massive application of PEM fuel cells. The electronic properties of CNT can still be improved, since they play an important role in the electrochemical performance. Recently, it has been reported that the incorporation of heteroatoms to the CNT structure (i.e. N, B, F, S, Si, etc.) can change positively their properties such as stability. Also, it is expected the dopant to have an effect on the Pt nanoparticles dispersion, affecting the electrochemical activity. The bonds form with the heteroatoms, as well as their concentration within the volumetric structure of the carbon, generally influence the properties of the material and change its structural geometry. The morphology and characteristics of the materials differ for each type of doping. For example, N-doping creates hollow sections separated by one or a few graphitic layers, while S-doping produces branched morphologies. Hence, it is of great interest to take advantage of the defects created by addition of heteroatoms to the CNT structure. In this research work low-Pt over doped CNT systems were obtained and evaluated. The doped carbon nanotubes were synthesized using a modified chemical vapor deposition (M-CVD) system in a high-temperature argon flow furnace. Toluene was used as a carbon source, ferrocene as a catalytic agent, adding different precursors of the heteroatoms. Low Pt loadings were deposited over pristine and doped CNT using a colloidal methodology. The structure of the obtained materials was analyzed by X-ray diffraction and Raman spectroscopy. Also, energy dispersive X-ray spectroscopy and scanning electron microscopy studies were done in order to obtain the chemical properties and the morphology. Electrochemical impedance spectroscopy (EIS) studies were done in the presence of 0.5 M H2SO4 and at an amplitude of 10 mV at different potentials vs AgAgCl (KCl sat), within a frequency range of 100 mHz to 100 KHz, in order to analyze the conductivity of the doped CNT used as support. In addition, electrochemical evaluation was performed by cyclic and lineal voltammetry in a conventional three electrode cell, in acidic electrolyte and using Ag/AgCl (KCl sat) as reference electrode, and Pt wire as a counter. In addition, in order to compare the same analyzes were carried out on reference materials such as vulcan carbon and nanotubes without dopant (pristine). The results of an extensive physical and chemical characterization confirmed the growth of doped CNT with different heteroatoms. It was possible to establish that the morphological characteristics of the obtained doped carbon nanotubes varied, depending on the dopant. Differences on the diameter, length, as well as the graphitization degree of the structure were found. Also, it was possible to confirm the low Pt loading over the supports. The evaluation of the electrochemical properties yielded interesting differences. Hence, results obtained of low-Pt loading over doped CNT electrochemical systems, will be presented and discussed at the conference.Acknowledgments: We thank the Fund "CONACyT-SENER-Sustainability Energy" (No. 254667) for the support provided for the development of this project.

Electronic structure of nitrogen-doped carbon nanotubes under stress

Due to the demand for miniaturization and low energy consumption of electronic device, field-effect transistors based on carbon nanotubes have received extensive attention. However, the electronic properties of carbon nanotubes, especially when subjected to stress and doping, are not very clear. In this study, first-principles calculations are used to investigate the deformation of carbon nanotubes under the action of nitrogen doping and tensile stress, as well as the changes in electronic energy bands. The results show that nitrogen atom doping will reduce the tensile strength of carbon nanotubes and increase the conductivity of carbon nanotubes, while stress helps to open the band gap. Our research has guiding significance for the prediction of electronic properties of carbon nanotubes under doping and stress.

First-principles calculation of volatile organic compound adsorption on carbon nanotubes: Furan as case of study

Sensing of volatile organic compounds (VOCs) is a growing research topic because of the concern about their hazard for the environment and health. Furan is a VOC produced during food processing, and it has been classified as a risk molecule for human health and a possible biomarker of prostate cancer. The use of carbon nanotubes for VOCs sensing systems design could be a good alternative. In this work, a theoretical evaluation of the interactions between furan and zigzag single-wall carbon nanotubes takes into account different positions and orientations of the furan molecule, within a density-functional theory first-principles approach. The van der Waals interactions are considered using different exchange-correlation functionals (BH,C09, DRSLL and KBM). The results indicate that vdW-functionals do not significantly affect geometry; however, the binding energy and the distance between furan and nanotube are strongly dependent on the selected exchange-correlation functional. On the other hand, the effects of single and double vacancies on carbon nanotube are considered. It was found that the redistribution of charge around the single-vacancy affects the bandgap, magnetic moment, and binding energy of the complex, while furan interaction with a double-vacancy does not considerably change the electronic structure of the system. Our results suggest that to induce changes in the electronic properties of carbon nanotubes by furan, it is necessary to change the nanotube surface, for example, by means of structural defects.

Double-walled carbon nanotube film as the active electrode in an electro-optical modulator for the mid-infrared and terahertz regions

The lack of efficient optical components operating with terahertz (THz) radiation is a limiting step in the ongoing large-scale development of this technology in fields such as telecommunication and imaging. In this work, we propose the use of double-walled carbon nanotube (DWCNT) films as the active electrode in THz modulation devices. Using six bounces in an internal total reflection configuration in a silicon waveguide prism, we achieved high attenuation from a 5 nm thin film, reaching up to −ΔT/T=6% at 50 THz, albeit with a slow speed of modulation on the order of minutes. Moreover, this attenuation −ΔT/T attains a value of 20% at 30 THz using a thicker 20 nm DWCNT film. As a consequence of doping, the modulation of a phonon-related Fano resonance is also observed in the mid-infrared, which could be used as a modulable narrow-band optoelectronic filter. Our study provides a sense of the capabilities unlocked by exploiting the optical and electronic properties of carbon nanotubes in the terahertz and infrared regimes.

Electronic properties of carbon nanotubes as detected by photoemission and inverse photoemission

The relation between morphology and energy level alignment in carbon nanotubes (CNT) is a crucial information for the optimization of applications in nanoelectronics, optics, mechanics and (bio)chemistry. Here we present a study of the relation between the electronic properties and the morphology of single wall CNT (SWCNT), aligned multi wall CNT (MWCNT) and unaligned MWCNT. The CNT were synthesized via catalytic chemical vapor deposition in ultra-high vacuum conditions. Combined ultraviolet photoemission and inverse photoemission (IPES) spectra reveal a high sensitivity to the nanotube morphology. In the case of unaligned SWCNT the distinctive unoccupied Van Hove singularities (vHs) features are observed in the high resolution IPES spectra. Those features are assigned to semiconducting and metallic SWCNT states, according to calculated vHs DOS. The two MWCNT samples are similar in the diameter of the tube (about 15 nm) and present similar filled and empty electronic states, although the measured features in the aligned MWCNT are more defined. Noteworthy, interlayer states are also revealed. Their intensities are directly related to the MWCNT alignment. Focussing and geometrical effects associated to the MWCNT alignment are discussed to account the spectral differences.

Manipulating the electronic properties of CNT by doping metal

Carbon nanotube (CNT) has received tremendous attention for potential use in many field due to its excellent physicochemical properties. However, the application performance derived from the electronic properties has remained a great challenge. Motivated by the electronic property of CNT, metal (M) such as silver (Ag), gold (Au) or platinum (Pt) doping effect on the electronic properties of CNT was investigated here. The hydroxyl-functionalized-CNT (OH-CNT) was taken as the model and the electronic of OH-CNT-Mn (Mn means metal clusters, n = 1~4) were studied based on first-principles. The formation of Ag-O bond makes the energy gap always present in OH-CNT-Agn and the energy gap of OH-CNT-Aun cases with even atomic Au cluster disappears. However, only Pt-C bonds are formed and the energy gap is gradually reduced to no gap in OH-CNT-Ptn. This theoretical study at the electronic level can give an idea for the research on the properties of metal-based CNT materials.

Multifunctional inkjet printed sensors for MMOD impact detection

The sensitivity of the electronic properties of carbon nanotubes to gases, chemicals, temperature, and mechanical strain enables their use as fillers in nanocomposites for sensing applications. In this paper, the authors develop a low-cost and scalable process based on inkjet printing technology to fabricate printed flexible sensors used for strain and damage detection. A well-dispersed conductive water-based ink is fabricated with functionalized multiwall carbon nanotubes (MWCNT) and deposited onto paper and Kapton substrates to obtain a sheet resistance as low as 500 Ω sq−1 with about 30 printed layers. The number of printed layers, the direction of the electrical resistance measurement, and the type of substrate have clear effects on the sensor’s electrical performances related to the detection of mechanical strain and impact damage. This work demonstrates the effectiveness of the printed sensors for micrometeoroid and orbital debris (MMOD) impact damage detection through hypervelocity testing.

Influence of substitutional doping on the electronic properties of carbon nanotubes with Stone Wales defects: density functional calculations

In this work, we implemented density function theory to investigate the structural and the electronic properties of nitrogen doped single walled carbon nanotube under different orientations of Stone Wales defect. We have found that, the doped defected structures are more stable than the non-doped defected structures. Furthermore, doping defected carbon nanotubes with a nitrogen atom has significantly narrowed the band gap and slightly shifted the Fermi level toward the conduction band. Moreover, nitrogen substitution creates new band levels just above the Fermi level which exemplifies an n-type doping. However, the induced band gap is indirect band gap compared to direct band gap as in pristine carbon nanotubes. Furthermore, the electronic and structural properties of nitrogen doped carbon nanotube with Stone Wales defects is crucially affected by the dopant site as well as the orientations of Stone Wales defects.

Structural effects on carrier doping in carbon nanotube thin-film transistors

Based on density functional theory, we studied the electronic properties of carbon nanotube (CNT) thin films under an external electric field. The carrier accumulation resulting from an electric field depends slightly on the CNT species that form the thin films and their arrangement with respect to the electrode. Although most of the carriers are accumulated in the CNTs located at the electrode side, wave function hybridization between semiconducting CNTs slightly enhances the carrier penetration into the opposite CNT layer. Metallic CNTs strongly depress or enhance the carrier penetration for the thin films when they are located at the electrode side or not, respectively.

Electrochemical Reaction Assisted 2D π-Stacking of Benzene on a MWCNT Surface and its Unique Redox and Electrocatalytic Properties.

Turning the π-structure and electronic properties of carbon nanotubes (CNTs) is a cutting-edge research topic in interdisciplinary areas of material chemistry. In general, chemical functionalization of CNT has been adopted for this purpose, which has resulted in a few monolayer thickness increment of CNT diameter size. Herein, we report an interesting observation of >10-fold increment in the apparent diameter of multiwalled carbon nanotubes (MWCNTs) brought about by a process of self-assembly of the BZ moiety on MWCNT, which is formed by electrochemical oxidation of a surface-adsorbed benzene-water cluster, {BZ-nH2O}. From physicochemical characterizations by transmission electron microscopy (TEM) and Raman and IR spectroscopic techniques and electrochemical characterizations by several radical scavenger species, it has been revealed that benzene radical moieties as a series of π-stacked layers ([BZ]-π-stack) were self-assembled on the MWCNT surface. A possible mechanism for their formation was proposed to be electrochemical oxidation of H2O from the MWCNT@{BZ-nH2O}ads layer to oxygen gas via hydroxyl radical formation and benzene cationic radical species at 1.2 V vs Ag/AgCl followed by its self-assembly into a unique MWCNT@[BZ]-π-stack network. The scanning electrochemical microscopic (SECM) technique was used to identify the in situ •OH radical formation. The electrochemical studies of a glassy-carbon-modified MWCNT@[BZ]-π-stack system showed a well-defined and highly symmetrical redox peak at an equilibrium potential E1/2 = 0.2 V vs Ag/AgCl (pH 2 HCl/KCl), with a peak-to-peak potential separation of 0 V, highlighting the ideal-surface-confined electron-transfer nature of the redox couple. Furthermore, enhanced electrical conductivity over the unmodified MWCNT was observed when testing the surface-sensitive redox couple Fe3+/Fe2+ with the modified electrode. This new redox material showed a specific electrocatalytic reduction of hydrogen peroxide at neutral pH (pH 7 phosphate buffer solution) unlike the quinone and other organic redox mediators, which show the reduction signal only in the presence of horseradish peroxidase enzyme.

Role of electronic properties in partition of radical and nonradical processes of carbocatalysis toward peroxymonosulfate activation

Nanocarbon-catalyzed advanced oxidation processes for wastewater remediation are green and state-of-the-art methods, nevertheless, the origins of carbocatalysis remain unresolved. In this study, carbon nanotubes (CNTs) are employed as typical metal-free catalysts for catalytic peroxymonosulfate (PMS) activation and phenol oxidation. The surface chemistry and electronic properties of CNTs are deliberately tailored by liquid acid oxidation and subsequent thermal treatment. It is unveiled that the electron-rich carbon surface and carbonyl groups can affect organic adsorption capacity of the carbocatalysts and modulate persulfate activation in different catalytic manners. Furthermore, the relationship between the surface chemistry (oxygen functionality and electron density) and carbocatalysis is established, which is decisive to regulate the radical/nonradical pathways in the catalytic oxidation for water purification. This study provides new insights to carbon-catalyzed persulfate activation with manipulated reaction pathways and redox potentials.

Defect Evolution of Ion-Exposed Single-Wall Carbon Nanotubes

The electronic properties of carbon nanotubes depend on several factors such as diameter, chirality, and defects. Defects such as vacancies can drastically modify the electronic properties of these nanostructures. The introduction of defects by irradiation processes can not only lead to interesting defective nanomaterials but also tailor its intrinsic properties for specific electronic applications. The ability to accurately identify and quantify defects in carbon nanotubes is of major importance for their incorporation into electronic devices. We report on a newly developed quantitative method which combines a known fluence or pulse of ions from a focused beam source with Raman spectroscopy for characterization of defects enabling the detection of systematic variations in defect concentration emerging at 0.5% from different single-wall carbon nanotube (SWCNT) types, semiconducting and metallic. It was also demonstrated that this result is independent from the selected ion species and its energy for thin ...

Nanostructured aptamer-based sensing platform for highly sensitive recognition of myoglobin.

A composite was prepared from PtSn nanoparticles and carbon nanotubes (PtSnNP/CNTs) and applied to the electrochemical determination of myoglobin (Mb). An Mb-aptamer was immobilized on a glassy carbon electrode (GCE), and hexcyanoferrate was used as an electrochemical probe. The PtSnNP/CNTs were synthesized by a microwave-aided ethylene glycol reduction method. Detection is based on electron transfer inhibition that is caused by the folding and conformational change of the Mb-aptamer in the presence of Mb. The amperometric signal for hexacyanoferrate, best measured at 0.2V vs. Ag/AgCl depends on the concentration of Mb that interacts with the aptamer on the GCE. This approach is selective and sensitive for Mb due to (a) the highly specific recognition ability of the aptamer for Mb, (b) the powerful electronic properties of carbon nanotubes, (c) the arranged decoration of CNTs with PtSnNPs, and (d), the superior electron transfer to hexacyanoferrate. The assay is highly selective, with linear relationships from 0.01-1nM and 10nM-200nM, and a limit of detection as low as 2.2 ± 0.1 pM. The modified GCE was applied to the quantitation of Mb in spiked human serum samples. Graphical abstract Schematic illustration of the method for Mb detection.