Single-walled Carbon Nanotubes Research Articles

Diameter-Controlled Synthesis of Carbon Nanotubes Using [2n]Collarenes as Rigid Organic Templates.

An effective route to diameter-controlled single-walled carbon nanotubes (SWCNTs) remains elusive. The use of organic templates to precisely control the diameter of the resulting nanotubes holds great promise in this regard but has hitherto had very limited practical success. A main obstacle is the limited availability of suitable organic templates. Here, we report the diameter-controlled bottom-up synthesis of SWCNTs with elaborately designed [2n]collarenes, hydrocarbon belts consisting of alternating phenylene and 1,4-cyclohexadiene rings, as rigid organic templates. A new approach has been developed to construct these collarenes, which are then used as templates in the bottom-up growth of SWCNTs. The resulting SWCNTs exhibit narrow diameter distributions, matching the diameters of the employed collarene templates. This work greatly propels the synthesis of diameter-controlled SWCNTs.

A novel miniaturized potentiometric electrode based on carbon nanotubes and molecularly imprinted polymer for the determination of lidocaine.

A novel miniaturized, solid-contact potentiometric screen-printed electrode was developed for highly sensitive and selective determination of lidocaine anesthetic. The electrode integrated single-walled carbon nanotubes as a solid-contact material and a molecularly imprinted polymer as a recognition sensory material. The performance characteristics of the electrode were evaluated and optimized to display a Nernstian slope of 58.92 ± 0.98mV/decade over a linear concentration range of 4.53 × 10-7 to 6.18 × 10-3mol/l within < 6s. Thedetection limit was 7.75 × 10-8mol/l (18.16ng/ml) of lidocaine. The use of the molecularly imprinted polymer significantly enhanced the selectivity of the electrode, and carbon nanotubes increased the sensitivity, accuracy, and potential stability. The electrode was successfully used for determining lidocaine in pharmaceutical preparations and human urine. The results favorably compared with data obtained by liquid chromatography-tandem mass spectrometry.

Modulation for Redox States of Single-Walled Carbon Nanotubes: Effect of Wrapping Conjugated Polymers.

Controlling the redox states of single-walled carbon nanotubes (SWNTs) is important for the optimization of their real performances in various fields. By means of in situ photoluminescence (PL) spectroelectrochemical measurements, we report a successful modulation for the redox parameters (redox potentials and electrochemical band gap) of (6,5) and (7,5)SWNTs with a simple change in conjugated polymers (CPs) non-covalently wrapped on the nanotubes. The large shift in the band gap (187 meV for (6,5)SWNTs and 101 meV for (7,5)SWNTs) was connected to the prominent difference in the interactions between the CPs and SWNTs as suggested by molecular dynamics (MD) simulations, while a striking difference in the 𝜋-electrons states of CP/SWNTs enabled the tuning of SWNTs' electronic states. Asymmetrical modulation for the reduction potential (LUMO) and oxidation potential (HOMO) of the SWNTs was observed as well. Our results can be promising for a simple but precise control of the electric states of SWNTs.

The effect of single walled carbon nanotubes on conductivity and thermal properties of glass fiber reinforced composites

Abstract This paper reports on a comprehensive study of the effect of single-walled carbon nanotube (SWCNT) on the alternating current (AC) conductivity, thermal and morphological properties of the unsaturated polyester based glass fiber reinforced polymer composite (GFRPC). AC conductivity measurements were carried out using the impedance spectrum and thermal measurements were carried out using differential scanning calorimetry (DSC) at a temperature range of 24-900 °C and heating rates of 20 °C/min. Impedance results showed that the conductivity behavior in the nanotube-loaded composite laminate obeys a Jonscher-type mechanism. At low frequencies, the conductivity value remains almost constant for the doped material and takes the value of 10-5 S/cm. It is observed that the AC conductivity starts to increase after the critical frequency value of approximately 103 Hz and increases up to 10-2 S/cm due to hopping and tunneling mechanisms caused by space charge polarization accumulated in the local regions at high frequencies. The pure material with an insulating nature also exhibited a typical insulating behavior. Thermal testing showed that nanotube reinforcement increases thermal conductivity in three different directions. DSC thermocurves analysis also revealed that the addition of carbon nanotubes increased the glass transition temperature of the material from 180°C to 190°C. The scaling and fractal analysis methods were also applied to obtain hetero morphological structure of materials. The fractal analysis results indicated that carbon nanotube doping to the standard sample increases the coating rates, scalability and heterogeneity of the solid phase surface of the sample. The coating rates of composite surfaces were calculated as 45% and 36%, respectively. Morphology analysis revealed that the probability of finding surface particles for the nanotube-doped sample decreased compared to the undoped sample, but the fractal dimension value increased. While this value was 1.83 in the pure sample, it increased to 1.92 in the nanotube material.

Evaluation of Electrical Properties and Uniformity of Single Wall Carbon Nanotube Dip-Coated Conductive Fabrics Using Convolutional Neural Network-Based Image Analysis

This study proposes a convolutional neural network (CNN)-based image analysis method to evaluate the electrical properties and uniformity of conductive fabrics treated with single-walled carbon nanotube (SWCNT) dip-coating. The conductive fabric was produced by dip-coating cotton-blended spandex with SWCNT, and the surface images were scanned and preprocessed to obtain image data, while resistance measurements were conducted to obtain labels and build the dataset. SEM analysis revealed that as the number of dip-coating cycles increased, particle density and path formation improved. The CNN model learned the relationship between surface images and resistance values, achieving a high predictive performance, with an R-squared (R²) value of 0.9422. The model demonstrated prediction accuracies of 99.1792% for the coefficient of variation (CV) of uniformly coated fabrics and 96.8877% for non-uniformly coated fabrics. Additionally, p-value analysis of all fabric samples yielded a result of 0.96044, indicating no statistically significant difference between the predicted and actual values. The proposed CNN-based model can accurately evaluate the electrical uniformity of conductive fabrics, showing potential for contributing to quality control and process optimization in production.

Interfacial Charge Transfer in One-Dimensional AgBr Encapsulated inside Single-Walled Carbon Nanotube Heterostructures.

The advent of one-dimensional van der Waals heterostructure (1D vdWH) nanomaterials has provided valuable opportunities for the advancement of electronic or optical devices, as well as for exploring various condensed matter phenomena. Electron transfer is a fundamental process in host-guest interactions, significantly influencing nanoscale physicochemical processes. Elucidating the mechanism by which the host influences the electronic structure of the guest is essential for elucidating these interactions. This study reports the successful synthesis of a material system consisting of precisely resolved AgBr nanowires encapsulated within single-walled carbon nanotubes (SWCNTs) that has been successfully synthesized and utilized to investigate the intrinsic electron transfer across 1D vdWHs. Cyclic voltammetry (CV) was employed to investigate the 1D vdWH interaction between AgBr and SWCNTs, which provided a more intuitive and accurate characterization of the charge transfer from SWCNTs to AgBr. Furthermore, Kelvin probe force microscopy showed a 149 mV reduction in the average surface potential of carbon nanotubes after AgBr filling, supporting the efficacy of CV in probing electron dynamics in 1D vdWHs. Finally, theoretical calculations indicated a charge transfer of 0.11 e- per simulation cell, reinforcing the effectiveness of CV in assessing the interactions within 1D vdWHs.

Chitosan-Based Electronics: The Importance of Acid Strength and Plasticizing Additives on Device Performance.

A rise in demand for disposable consumer electronics such as smart packaging, wearable electronics, and single-use point-of-source sensors requires the development of eco-friendly and compostable electronic materials. Chitosan is derived from crustacean waste and offers high dielectric constant values without requiring rigorous purification, making it sustainable for large-scale electronic device manufacturing. When processed in acidic media, the protonated backbone of chitosan pairs with counterions from the acid dissociation to form chitosan thin films with electrical double layers (EDLs) and tunable capacitive properties. We report the importance of the choice of acid when processing chitosan by surveying a series of halogenated and biosourced acids with varying pKa values and solutions with different pH values. Oxalic acid outperforms other acids, with a maximum areal capacitance of 161 nF·mm-2. Tartaric acid and citric acid, despite lower capacitance values, showed promising results with a stable EDL capacitance and high reproducibility, making them optimal for large-area manufacturing. The incorporation of sorbitol as a plasticizer boosts the EDL formation onset of all chitosan-acid combinations to 1 × 103-105 Hz and improves reproducibility. High-performing single-walled carbon nanotube thin film transistors were made using chitosan-based dielectrics treated with different acids with and without sorbitol, leading to transconductance as high as ≈5.2 μS and Ion/Ioff of 105. The capacitors and transistors remain functional after one year of storage in ambient conditions. Overall, this study demonstrates durable high-performance electronics based on chitosan and stresses the importance of processing acid and the use of plasticizing additives, such as sorbitol.

THIN FILM METHANE SENSOR BASED ON CARBON COMPOSITE

Today, with the oil and gas industry playing a key role in the global energy sector, issues related to the effective control and detection of methane leaks are becoming an integral part of the strategic tasks of the industry. The article is devoted to the research and development of a thin-film sensor for detecting methane in the air using a carbon composite. The technical result of this study is the creation of a highly sensitive and energy efficient sensor for measuring methane concentration. The basis for the sensitive element is a thin film of a carbon composite, consisting of a polymer, single-wall carbon nanotubes and graphene oxide, with aluminum electrodes. The sensor has a number of advantages, including responding to the presence of methane without the need for heating, the simplicity of the sensitive material preparation process, and low cost. The ability to quickly start small-scale production, simplified manufacturing due to the use of only one pair of electrodes, as well as increased energy efficiency due to the absence of the need for heating are also positive characteristics of this device. The study presents the results of manufacturing the sensor, including the steps of cleaning the surface of the substrate, creating a shadow mask, spraying electrodes, forming a thin film of the composite by centrifugation, as well as analyzing the microstructure of the sensor using an atomic force microscope. Also presented are data on obtaining multilayer structures of thin-film resistive sensors based on a polymer matrix nanocomposite, single-wall carbon nanotubes and graphene oxide, including the process of creating electrodes. This study is important for the development of methane monitoring methods in the oil and gas industry and other industrial areas, offering promising technical solutions to ensure environmental and economic sustainability of production.

High-speed optical-waveguide integrated single-walled carbon nanotube bolometer

The rapid development of photonic integrated circuits (PICs) and their applications in various fields of science and technology requires the creation of easy-to-manufacture high-speed integrated detectors. In this work, we fabricated and studied planar waveguide-integrated bolometers based on a thin film of single-walled carbon nanotubes (SWCNTs) on the silicon nitride platform. This bolometer showed good internal responsivity and a high bandwidth &amp;gt;1 GHz. In-depth analysis allowed us to retrieve the main parameters of the SWCNT film that govern the bolometric response that can be difficult to measure directly. The results obtained show a promising prospect of using SWCNT bolometers for PIC applications.

Structural, Mechanical, and Optical Properties of Laminate-Type Thin Film SWCNT/SiOxNy Composites

The development of new encapsulating coatings for flexible solar cells (SCs) can help address the complex problem of the short lifespan of these devices, as well as optimize the technological process of their production. In this study, new laminate-type protective composite coatings were prepared using a silicon oxynitride thin-film matrix obtained by curing the pre-ceramic polymer perhydropolysilazane (PHPS) through two low-temperature methods: (i) thermal annealing at 180 °C and (ii) exposure to UV radiation at wavelengths of 185 and 254 nm. Single-walled carbon nanotubes (SWCNTs) were used as fillers via dry transfer, facilitating their horizontal orientation within the matrix. The optical, adhesive, and structural properties of the matrix films and SiOxNy/SWCNT composite coatings, along with their long-term stability, were studied using Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, HR-SEM, spectral ellipsometry, and a progressive-load scratch test. In this work, the optical constants of PHPS-derived films were systematically studied for the first time. An antireflection effect was observed in the composites revealing their two-component nature associated with (i) the refractive index of the SiOxNy matrix film and (ii) the embedding of a SWCNT filler into the SiOxNy matrix. The curing method of PHPS was shown to significantly affect the resulting properties of the films. In addition to being used as protective multifunctional coatings for SCs, both SiOxNy/SWCNT composites and SiOxNy matrix films also function as broadband optical antireflective coatings. Furthermore, due to the very low friction coefficients observed in the mechanical tests, they show potential as scratch resistant coatings for mechanical applications.

Change in the Chemical State of Phosphorus Sulfide Molecules Inside Single‐Walled Carbon Nanotubes

This article presents the first experiments on filling single‐walled carbon nanotubes (SWCNTs) with the phosphorus sulfides P4S3 and P4S10 using the ampoule method. Transmission electron microscopy examination reveals the encapsulation of phosphorus and sulfur species inside the cavities of SWCNTs without the formation of any regular structures. X‐ray photoelectron spectroscopy observes different oxidation states of P and S atoms, depending on the P/S ratio in the initial mixture used to fill the nanotubes. The Raman signals associated with the encapsulated species are low in intensity, and the vibrational modes are shifted and broadened as compared to those in crystalline P4S3 and P4S10. The proposed models for the arrangement of sulfur and phosphorus inside SWCNTs suggest the formation of 1D amorphous glassy phosphorus sulfides with stoichiometric ratios close to those of elemental phosphorus and sulfur in the initial mixtures.

The probing of local charge with sulfur encapsulated in single-walled carbon nanotubes

In this study, we demonstrated the remarkable sensitivity to electrochemical local charge of sulfur chains encapsulated in small-diameter single-walled carbon nanotubes (S@SWCNTs). To perform micro- and macro-spectroscopic probing, a transparent electrochemical cell was designed in which the charging electrode is formed based on S@SWCNTs. During a short-term electrochemical charging, significant reversible changes were observed in-situ in both Raman and UV–vis-Nir spectra of S@SWCNTs. The optical response was found to depend on the magnitude and sign of the charge, as well as on the duration of the electrochemical charging process at a given potential. The enhanced Raman modes of sulfur chains exhibited a notable linear shift (up to 10 cm-1) accompanied by a redistribution of their intensities. A correlation is identified of the chronoamperometry curve (charging current versus time) and transformations of the Raman spectrum of single-atom sulfur chains. Atomistic simulations allowed to attribute these changes in the Raman spectrum to the softening of the sulfur bonds upon charging. Our findings revealed that the nanotube inhibits the chemical interactions between encapsulated sulfur and local charge sources, thus rendering S@SWCNTs suitable for repeated utilization in local charge analysis.

Chemi-Impeditive Sensing Platform Based on Single-Walled Carbon Nanotubes.

Chemical sensing methodology based on electrochemical impedance spectroscopy (EIS) targeting analytes in aqueous samples on functionalized single-walled carbon nanotube (SWCNT) is reported. The SWCNT in contact with electrolyte shows unique impedance spectra that cannot be analyzed with classical equivalent circuit models. Inspired by the charge transport property of mixed ionic-electronic conductors, we propose an equivalent circuit based on transmission line model (TLM), by which the impedance of the CNT-electrolyte system can be analyzed to track down all the equivalent circuit parameters. By combining multiple pieces of information, which are technically immeasurable with conventional chemiresistive or chemicapacitive techniques, several analyte species responding to the sensor can be differentiated from each other. We demonstrate the "chemi-impeditive" concept on chemically modified SWCNTs for detecting perfluoroalkyl substances (PFAS) in aqueous solutions. The EIS coupled with a fluorination chemistry on SWCNT surface provides unique changes in equivalent circuit components for each PFAS, i.e., changes in CNT and solution resistances, as well as interfacial CNT-solution capacitance, through which perfluorooctanesulfonic acid, perfluorooctanoic acid, hexafluoropropylene oxide dimer acid, and perfluorobutanesulfonic acid are detected in a discriminative manner. The new impedimetric method opens up new vistas in chemical sensing in that the EIS analysis provides an additional dimension of information beyond the single resistance or capacitance typically measured by many conventional types of sensors.

Analysis of Delay and Dynamic Crosstalk in Spatially Arranged Mixed CNT Bundle Interconnects at Different Technology Nodes

In the present nanoscale regime, mixed carbon nanotube bundles (MCBs) are considered to be highly promising interconnect options. This research paper introduces a spatially arranged mixed carbon nanotubes (CNTs) bundle (MCB), wherein single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) occupy equal halves in the MCB. An equivalent single conductor (ESC) model for MCB is employed to analyze the interconnect performances in terms of signal transmission delay and dynamic crosstalk delay at different technology nodes (i.e., 32nm, 22nm, and 16 nm). Encouragingly, a significant reduction in signal transmission delay and dynamic crosstalk induced delay are observed at 32 nm technology node. It is observed that at 32 nm technology node, the propagation delay and crosstalk induced delay significantly improves by 29.40% and 55.53%, respectively, compared to 22 nm technology node and 187.88% and 185.94%, respectively, compared to 16 nm technology node. The improvement in interconnect performances can primarily be attributed to the improvement in the number of conducting channels inside the MCB at 32 nm, which greatly impacted the interconnect parasitics such as quantum resistance, quantum capacitance, kinetic inductance etc.

Buckling analysis of single‐walled carbon nanotubes using the initial value method and approximate transfer matrix based on nonlocal elasticity theory

AbstractIn this study, a novel method is presented to analyze the buckling behavior of single‐walled carbon nanotubes (SWCNTs) using the initial value method (IVM) in conjunction with the approximate transfer matrix, within the framework of nonlocal elasticity theory. The study aims to accurately approximate critical buckling load parameters under various boundary conditions, without encountering high computational requirements. IVM enables the computation of displacements and stress resultants along the entire beam from given initial conditions. The approximate transfer matrix is employed to analyze system states at different points through successive integration of solutions, generating the principal matrix needed for IVM and ensuring systematic and precise results that optimize the accuracy of the analysis. A convergence study confirms the effectiveness and precision of the proposed method, revealing a decrease in the critical buckling load parameters as the nonlocal parameter increases, applicable across all boundary conditions studied (simply supported, clamped–clamped, clamped–simply supported, and clamped‐free). These results underscore the need to incorporate nonlocal effects for more accurate nanostructure mechanics predictions. The integration of IVM and the approximate transfer matrix provides a computationally efficient alternative to traditional numerical and semi‐analytical methods, aiding researchers and engineers working with SWCNTs and other nanomaterials.

Conductive Biocomposite Made by Two-Photon Polymerization of Hydrogels Based on BSA and Carbon Nanotubes with Eosin-Y

Currently, tissue engineering technologies are promising for the restoration of damaged organs and tissues. For regeneration of electrically conductive tissues or neural interfaces, it is necessary to provide electrical conductivity for the transmission of electrophysiological signals. The developed biocomposite structures presented in this article possess such properties. Their composition includes bovine serum albumin (BSA), gelatin, eosin-Y and single-walled carbon nanotubes (SWCNTs). For the first time, a biocomposite structure was formed from the proposed hydrogel using a nanosecond laser, and a two-photon absorption cross section value of 580 GM was achieved. Increased viscosity over 3 mPa∙s and self-focusing with a nonlinear refractive index of 42 × 10−12 cm2/W make it possible to create a biocomposite structure over the entire specified area. The obtained electrical conductivity value was 19 mS∙cm−1, due to the formation of effective electrically conductive networks. For a biocomposite with a concentration of gelatin 3 wt. %, formed by low-energy near-IR pulses, the survival of Neuro 2A nerve tissue cells was confirmed. The obtained results are important for the creation of new tissue engineering structures and neural interfaces from a biopolymer hydrogel based on the organic dye eosin-Y and carbon nanotubes by two-photon polymerization.

Precursor-Driven Confined Synthesis of Highly Pure 5-Armchair Graphene Nanoribbons.

Armchair graphene nanoribbons (AGNRs) known as semiconductors are holding promise for nanoelectronics applications and sparking increased research interest. Currently, synthesis of 5-AGNRs with a quasi-metallic gap has been achieved using perylene and its halogen-containing derivatives as precursors via on-surface synthesis on a metal substrate. However, challenges in controlling the polymerization and orientation between precursor molecules have led to side reactions and the formation of by-products, posing a significant issue in purity. Here a precision synthesis of confined 5-AGNRs using molecular-designed precursors without halogens is proposed to address these challenges. Perylene and its dimer quaterrylene are utilized for filling into single-walled carbon nanotubes (SWCNTs), following a precursor-driven transition into 5-AGNRs by heat-induced polymerization and cyclodehydrogenation. SWCNTs restrict the alignment of confined quaterrylene enabling their polymerization with a head-to-tail arrangement, which results in the formation of pure 5-AGNRs with three times higher yield than that of perylene, as the free rotation capability of perylene molecules inside SWCNTs lead to the formation of 5-AGNRs concomitant with by-products. This work provides a templated route for synthesizing desired GNRs based on molecular-designed precursors and confined polymerization, bringing advantages for their applications in electronics and optoelectronics.

Fermi level regulation of single-walled carbon nanotubes by metal chloride doping for enhanced NO2 sensing performance

Pristine single-walled carbon nanotubes (SWCNTs) typically exhibit limited sensitivity due to the low charge transfer dynamics between nanotubes and gas molecules. Among various enhancement methods, the Fermi level regulation proves to be effective in promoting the charge transfer between SWCNTs and gas molecules, consequently improving the sensing performance. Herein, we firstly report a non-destructive method to regulate the Fermi level of SWCNTs through doping metal chlorides, and the interfacial charge transfer between SWCNTs and different metal chlorides has been well investigated by combining Raman shift with X-ray photoelectron spectroscopy. Experimental results reveal that the interfacial charge transfer dynamics determine the sensing properties of SWCNTs doped with chlorides. The as-fabricated FeCl3-doped SWCNT sensors exhibit a high response of 196.9 % in response to 100 ppb NO2 gas with excellent selectivity. The Kelvin probe force microscope (KPFM) results directly prove the doping effect of metal chlorides due to the shift down of Fermi level of SWCNTs after doping FeCl3. Our work not only proposes a novel method to controllably regulate the Fermi level of SWCNTs but also provides a guidance for high-performance SWCNT-based sensing devices.

Data-driven prediction of higher-order structure in carbon nanotube films for high thermoelectric power factor

We optimized the higher-order structures and semiconducting purity of single-walled carbon nanotubes (SWCNTs) to enhance the thermoelectric power factor PF by combining the thermoelectric random stick network (TE-RSN) method and a genetic algorithm. The PF of the optimized films was increased approximately fivefold for initial random structures. In addition, while the random structures showed the maximum PF when the ratio of semiconducting to metallic SWCNTs R s exceeded 0.98, the optimized structures converged to an R s of approximately 0.9. The optimized structures exhibited an increased local density and the peak of alignment angle distribution, leading to an increase in both the electrical conductivity and the Seebeck coefficient. We interpreted the increase in the Seebeck coefficient using a serial model. The results indicated that the reduction in the number of contacts within the paths and the subsequent increase in temperature difference on semiconducting SWCNTs led to the increase in the Seebeck coefficient.

N-Type Nanocomposite Films Combining SWCNTs, Bi2Te3 Nanoplates, and Cationic Surfactant for Pn-Junction Thermoelectric Generators with Self-Generated Temperature Gradient Under Uniform Sunlight Irradiation.

Flexible thermoelectric generators (TEGs) with pn-junction single-walled carbon nanotube (SWCNT) films on a polyimide substrate have attracted considerable attention for energy harvesting. This is because they generate electricity through the photo-thermoelectric effect by self-generated temperature gradient under uniform sunlight irradiation. To increase the performance and durability of the pn-junction TEGs, n-type films need to be improved as a priority. In this study, bismuth telluride (Bi2Te3) nanoplates synthesized by the solvothermal method were added to the n-type SWCNT films, including a cationic surfactant to form the nanocomposite films because Bi2Te3 has high n-type thermoelectric properties and high durability. The performances of the pn-junction TEGs were investigated by varying the heat treatment times. When the artificial sunlight was uniformly irradiated to the pn-junction TEGs, a stable output voltage of 0.47 mV was observed in the TEG with nanocomposite films heat-treated at 1 h. The output voltage decreased with increasing heat treatment time due to the decrease in the p-type region. The output voltage of TEG at 1 h is higher than that of the TEGs without Bi2Te3 nanoplates under the same conditions. Therefore, the addition of Bi2Te3 nanoplates was found to improve the performance of the pn-junction TEGs. These findings may aid in the development of facile and flexible optical devices, including photodetectors and hybrid devices integrating solar cells.