Properties Of Single-walled Carbon Nanotubes Research Articles

Theoretical Study of the Impact and Control of Topological Defects on the Electrical Properties of Single-Walled Carbon Nanotubes: Implications for Carbon-Based Transistor Regulation

Theoretical Study of the Impact and Control of Topological Defects on the Electrical Properties of Single-Walled Carbon Nanotubes: Implications for Carbon-Based Transistor Regulation

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.

Morphology Determination of Luminescent Carbon Nanotubes by Analytical Super-Resolution Microscopy Approaches.

The ability to determine the precise structure of nano-objects is essential for a multitude of applications. This is particularly true of single-walled carbon nanotubes (SWCNTs), which are produced as heterogeneous samples. Current techniques used for their characterization require sophisticated instrumentation, such as atomic force microscopy (AFM), or compromise on accuracy. In this paper, we propose to use super-resolution microscopy (SRM) to accurately determine the morphology (orientation, length, and shape) of individual luminescent SWCNTs. We generate super-resolved images using three recently published SRM analytical software packages (DPR, eSRRF, and MSSR) and metrologically compare their performances to determine the morphological properties of SWCNTs. For this, ground-truth information on nanotube morphologies was obtained using polarization measurements and AFM to directly correlate the results from SRM at the single particle level. We show a more than 4-fold improvement in resolution over standard photoluminescence imaging, revealing hidden morphologies as efficiently as AFM. We finally demonstrate that DPR, and eventually eSRRF, can effectively assess SWCNT length distribution in a much faster and more accessible way than AFM. We believe that this approach can be generalized to other types of luminescent nanostructures and thus become a standard for rapid and accurate characterization of samples.

Integrating Single-Walled Carbon Nanotubes into Supramolecular Assemblies: From Basic Interactions to Emerging Applications.

Integrating single-walled carbon nanotubes (SWCNTs) into supramolecular self-assemblies harnesses the distinctive mechanical, optical, and electronic properties of the nanoparticles alongside the structural and chemical properties of the assemblies. Organic molecules capable of forming supramolecular assemblies through hydrophobic, van der Waals, and π-π interactions have been demonstrated to be particularly effective in dispersing and functionalizing SWCNTs, as these same interactions facilitate the binding to the hydrophobic graphene-like surface of the SWCNTs. This review discusses a variety of self-assembling structures that were shown to integrate SWCNTs, ranging from simple micelles and ring structures to complex DNA origami and three-dimensional hydrogels formed by low-molecular-weight gelators. We explore the integration of SWCNTs into various supramolecular assemblies and highlight emerging applications of these composite materials, such as the mechanical enforcement of self-assembling hydrogels and leveraging the near-infrared (NIR) fluorescence properties of SWCNTs for monitoring the molecular self-assembly process. Notably, the distinctive NIR fluorescence of SWCNTs, which overlaps with the biological transparency window, offers significant opportunities for noninvasive sensing applications within the supramolecular platforms. Future research into a deeper understanding of the interactions between SWCNTs and different supramolecular frameworks will expand the potential applications of SWCNT-integrated supramolecular assemblies in fields like biomedical engineering, electronic devices, and environmental sensing.

The electronic transport characteristics subsequent to linear doping with nitrogen or boron in (8,0) single-walled carbon nanotubes

The electronic transport properties of single-walled carbon nanotubes (SWCNTs) have long been a focus of attention, with the potential for modulating their conductivity through doping. Commonly adopted doping methods, such as point doping and asymmetric doping, have been prevalent in research, are very common in research, while there is relatively little research on doping of impurity atoms in crystal columns along the tube axis direction, and there is also a lack of exploration related to their electron transport. This study delves into the influence of B/N linear doping on (8,0) carbon nanotube devices, systematically analyzing its effects on device band structure, density of states, current characteristics, and transmission eigenstates. The elucidation of the contributions of distinct doping atoms and the quantity of doping lines to conduction band transport near the Fermi level is approached through the lens of band theory. This analysis provides valuable insights into the nuanced impact of linear doping on the electron transport dynamics in carbon nanotubes. Additionally, a linear regression methodology is employed to discern the quantitative relationship between the number of linear dopants and resultant current values, revealing discernible patterns in the variation of current with the quantity of nitrogen atoms. Such insights contribute to a more profound understanding of the mechanisms underlying the enhancement of conductivity in carbon nanotubes facilitated by multi-line doping in semiconductor devices.

Dynamic Tracking of Biological Processes Using Near-Infrared Fluorescent Single-Walled Carbon Nanotubes.

Biological processes are characterized by dynamic and elaborate temporal patterns driven by the interplay of genes, proteins, and cellular components that are crucial for adaptation to changing environments. This complexity spans from molecular to organismal scales, necessitating their real-time monitoring and tracking to unravel the active processes that fuel living systems and enable early disease detection, personalized medicine, and drug development. Single-walled carbon nanotubes (SWCNTs), with their unique physicochemical and optical properties, have emerged as promising tools for real-time tracking of such processes. This perspective highlights the key properties of SWCNTs that make them ideal for such monitoring. Subsequently, it surveys studies utilizing SWCNTs to track dynamic biological phenomena across hierarchical levels─from molecules to cells, tissues, organs, and whole organisms─acknowledging their pivotal role in advancing this field. Finally, the review outlines challenges and future directions, aiming to expand the frontier of real-time biological monitoring using SWCNTs, contributing to deeper insights and novel applications in biomedicine.

Exfoliated MoS2 anchored on graphene oxide nanosheets for enhancing thermoelectric properties of single-walled carbon nanotubes

Carbon nanotubes-based thermoelectric materials with high electrical conductivity (σ) and excellent mechanical properties have promising applications in flexible wearable devices. Two-dimensional transition metal sulfide MoS2 has been used to enhance the thermoelectric properties of carbon nanotubes due to its high Seebeck coefficient (S). However, MoS2 nanosheets are prone to agglomeration due to their high specific surface area, which causes lower doping efficiency. In this work, MoS2@GO hybrids are successfully fabricated using a hydrothermal in-situ growth method to anchor exfoliated MoS2 on graphene oxide (GO) nanosheets, and MoS2@GO hybrids significantly enhance the interfacial interaction between MoS2 and single-walled carbon nanotubes (SWCNT), improve the carrier mobility, lead to a simultaneous enhancement of the S and the σ. The maximum S value of MoS2@GO/SWCNT is 42.3 ± 0.2 μV K−1, the σ is 1173.2 ± 45.6 S cm−1, and an optimum power factor (PF) of 208.8 ± 8.5 μW m−1 K−2 is obtained at room temperature, which reaches 261.3 ± 10.2 μW m−1 K−2 at 385 K. For application demonstration, a thermoelectric device is assembled by connecting six pairs of p-type MoS2@GO/SWCNT and n-type copper sheets in series, which demonstrates an open-circuit voltage of 17.4 mV and an output power of 2.1 μW under a temperature difference of 50 K. Therefore, this study enriches the design and synthesis strategy of exfoliated MoS2 and provides a new approach for the development of high-performance SWCNT-based thermoelectric materials, which has important potential applications in the field of wearable electronics.

(Invited) Non-Invasive Injectable Nanotube-Hydrogel Formulations for Local Analyte Detection

Rapid, minimally-invasive in situ detection of analytes in vivo remains a goal to study inflammatory signaling molecules, disease biomarkers, and pharmacology of therapeutics. To achieve this, we are using the near-infrared fluorescent properties of single-walled carbon nanotubes (SWCNT) to design sensors for use in live mice. SWCNT fluorescence is responsive to the local environment, in the tissue-transparent window, and does not photobleach, allowing for long-term signal monitoring. In this work, we are exploring several formulations of SWCNT embedded within hydrogels which gel in situ. We have investigated the kinetics of penetration of several classes of analytes—proteins, small molecules, and ions—through the hydrogel and their interaction with SWCNT sensors in vitro. Then, we explored the long-term stability of these nanotube-hydrogel formulations in live mice prior to detection of the chemotherapeutic doxorubicin. In ongoing work, we are exploring disease biomarker-specific sensing and monitoring of inflammatory cytokines in mouse models of disease using this nanotube-hydrogel system. We anticipate long-term applications of this work may include minimally-invasive and rapid clinical diagnostic development.

(Nanocarbons Division Richard E. Smalley Research Award) Fluorescence of Single-Walled Carbon Nanotubes: From Discovery to Real-World Applications

The unique physical and chemical properties of single-walled carbon nanotubes (SWCNTs) continue to inspire extensive research by many basic and applied researchers. One of the most remarkable features of SWCNTs is their variety of pi-electronic structures associated with specific diameters and roll-up angles. Approximately two-thirds of these structural species are semiconducting and display near-infrared photoluminescence (fluorescence) through direct band gap transitions. I will describe the discovery of this SWCNT fluorescence and the assignment of specific spectral features to physical nanotube structures. Several illustrations of using SWCNT emission spectroscopy in research will then be described, including characterizing sample compositions, capturing images and spectra of single nanotubes in physical and biological environments, and guiding covalent tailoring of nanotube excitonic properties. Finally, I will present an update on an emerging technology for industrial strain measurement that uses SWCNTs as strain sensors that report through spectral shifts in their emission spectra.

(Invited) Probing Charge Carrier-Induced Changes in the Complex Dielectric Function in Carbon Nanotube Dispersions

The injection of charge carriers into pi-conjugated semiconductors, whether by electrochemical injection or chemical charge transfer, is a powerful approach to tune their electrical conductivity. Recently, the concept of dielectric catastrophe, where the charge carrier density is sufficiently large to significantly alter the intrinsic dielectric properties, has been demonstrated at high doping levels in organic semiconductor thin films. The observed increase in the dielectric constant leads to reduced coulombic interactions between charge carriers and the associated counterions, promoting enhanced free carrier generation and transport.Here, we employ a combination of steady state optical spectroscopy, quantitative 19F NMR studies, and microwave dielectric loss spectroscopy to probe charge carrier density and transport in doped single-walled carbon nanotube dispersions. We demonstrate that a similar dielectric catastrophe phenomenon can be observed even in isolated single-walled carbon nanotubes dispersed in a low dielectric constant solvent AND, perhaps more surprisingly, at carrier densities less than one carrier per nanotube. The precise details of the observed changes in complex dielectric function are dependent on the chemical structure of the charge-transfer dopant, with a near-instantaneous increase in the dielectric constant and electrical conductivity observed for low carrier densities using bulky benzyloxy-substituted icosahedral dodecaborane cluster dopants, DDBs. We attribute the observations to weak coulombic interactions between the injected charge carrier and the dopant counterion, along with the large polarizability afforded by the unique physicochemical properties of single-walled carbon nanotubes. If time permits, we will show results from recent studies where we extend this approach to the doping of other nanocarbons.

Molecular Dynamics Simulations of Effects of Geometric Parameters and Temperature on Mechanical Properties of Single-Walled Carbon Nanotubes

Carbon nanotubes (CNTs) are considered an advanced form of carbon. They have superior characteristics in terms of mechanical and thermal properties compared to other available fibers and can be used in various applications, such as supercapacitors, sensors, and artificial muscles. The properties of single-walled carbon nanotubes (SWNTs) are significantly affected by geometric parameters such as chirality and aspect ratio, and testing conditions such as temperature and strain rate. In this study, the effects of geometric parameters and temperature on the mechanical properties of SWNTs were studied by molecular dynamics (MD) simulations using the Large-scaled Atomic/Molecular Massively Parallel Simulator (LAMMPS). Based on the second-generation reactive empirical bond order (REBO) potential, SWNTs of different diameters were tested in tension and compression under different strain rates and temperatures to understand their effects on the mechanical behavior of SWNTs. It was observed that the Young’s modulus and the tensile strength decreases with increasing SWNT tube diameter. As the chiral angle increases, the tensile strength increases, while the Young’s modulus decreases. The simulations were repeated at different temperatures of 300 K, 900 K, 1500 K, 2100 K and different strain rates of 1 × 10−3/ps, 0.75 × 10−3/ps, 0.5 × 10−3/ps, and 0.25 × 10−3/ps to investigate the effects of temperature and strain rate, respectively. The results show that the ultimate tensile strength of SWNTs increases with increasing strain rate. It is also seen that when SWNTs were stretched at higher temperatures, they failed at lower stresses and strains. The compressive behavior results indicate that SWNTs tend to buckle under lower stresses and strains than those under tensile stress. The simulation results were validated by and consistent with previous studies. The presented approach can be applied to investigate the properties of other advanced materials.

Novel synthesis of thermoresponsive single-walled carbon nanotubes/poly(N-isopropylacrylamide) hybrids

Poly(N-isopropylacrylamide) (PNIPAM) is one of the most well studied thermoresponsive polymers and its microgels undergo a reversible volume phase transition (VPT) at temperatures close to that of the human body. Coupling this property with the unique optical properties of single-walled carbon nanotubes (SWCNT) in the near infrared (NIR) leads to interesting nanohybrids that could be used as multi-responsive sensors/actuators for biological applications.We show the synthesis of thermoresponsive SWCNT/PNIPAM hybrids using two different non-covalent strategies, preserving the nanotube optical properties such as fluorescence. The first strategy involves the dispersion of the SWCNT in water with sodium dodecyl sulfate (SDS), and subsequent in situ synthesis of PNIPAM microgels inside the SDS coatings around the nanotubes. The second strategy starts with modifying the nanotubes with a pyrene derivative, which in turn is used as the starting point for the in situ polymerization of the PNIPAM microgels, thus ensuring that the polymer grows around the nanotubes. In both cases, we obtain hybrids showing a phase transition at temperatures close to that of the human body, with the absorption and fluorescence spectra of the hybrids in the NIR changing in response to the changing dielectric environment. These systems could be used as actuators/sensors in biological systems.

Structural, Electrical, and Optical Properties of Single-Walled Carbon Nanotubes Synthesized through Floating Catalyst Chemical Vapor Deposition.

Single-walled carbon nanotube (SWCNT) thin films were synthesized by using a floating catalyst chemical vapor deposition (FCCVD) method with a low flow rate (200 sccm) of mixed gases (Ar and H2). SWCNT thin films with different thicknesses can be prepared by controlling the collection time of the SWCNTs on membrane filters. Transmission electron microscopy (TEM) showed that the SWCNTs formed bundles and that they had an average diameter of 1.46 nm. The Raman spectra of the SWCNT films suggested that the synthesized SWCNTs were very well crystallized. Although the electrical properties of SWCNTs have been widely studied so far, the Hall effect of SWCNTs has not been fully studied to explore the electrical characteristics of SWCNT thin films. In this research, Hall effect measurements have been performed to investigate the important electrical characteristics of SWCNTs, such as their carrier mobility, carrier density, Hall coefficient, conductivity, and sheet resistance. The samples with transmittance between 95 and 43% showed a high carrier density of 1021-1023 cm-3. The SWCNTs were also treated using Brønsted acids (HCl, HNO3, H2SO4) to enhance their electrical properties. After the acid treatments, the samples maintained their p-type nature. The carrier mobility and conductivity increased, and the sheet resistance decreased for all treated samples. The highest mobility of 1.5 cm2/Vs was obtained with the sulfuric acid treatment at 80 °C, while the highest conductivity (30,720 S/m) and lowest sheet resistance (43 ohm/square) were achieved with the nitric acid treatment at room temperature. Different functional groups were identified in our synthesized SWCNTs before and after the acid treatments using Fourier-Transform Infrared Spectroscopy (FTIR).

Shielding Effects Provide a Dominant Mechanism in J-Aggregation-Induced Photoluminescence Enhancement of Carbon Nanotubes.

The unique photophysical properties of single-walled carbon nanotubes (SWCNTs) exhibit great potential for bioimaging applications. This led to extensive exploration of photosensitization methods to improve their faint shortwave infrared (SWIR) photoluminescence. Here, we report the mechanisms of SWCNT-assisted J-aggregation of cyanine dyes and the associated photoluminescence enhancement of SWCNTs in the SWIR spectral region. Surprisingly, we found that excitation energy transfer between the cyanine dyes and SWCNTs makes a negligible contribution to the overall photoluminescence enhancement. Instead, the shielding of SWCNTs from the surrounding water molecules through hydrogen bond-assisted macromolecular reorganization of ionic surfactants triggered by counterions and the physisorption of the dye molecules on the side walls of SWCNTs play a primary role in the photoluminescence enhancement of SWCNTs. We observed 2 orders of magnitude photoluminescence enhancement of SWCNTs by optimizing these factors. Our findings suggest that the proper shielding of SWCNTs is the critical factor for their photoluminescence enhancement, which has important implications for their application as imaging agents in biological settings.

Enhancing thermoelectric performance of single-walled carbon nanotube films by poly(styrene sulfonate acid) dispersing and sequential base treatment

Despite single-walled carbon nanotubes (SWCNTs) have attracted great interest for thermoelectric (TE) conversion, the strong van der Waals forces between SWCNTs cause them to aggregate into bundles with poor dispersibility, which dramatically deteriorates the charge carrier transport, and thereby induces low electrical conductivity and TE power factor. Herein, we report a facile and efficient approach to enhance TE performance of SWCNTs via the addition of poly(styrene sulfonic acid) (PSSH) and sequential base treatment. PSSH is served as a dispersant and dopant to improve the dispersibility of SWCNTs and facilitate charge carrier conduction, contributing to high electrical conductivity of 3749 ± 122 S cm−1 and power factor of 117.7 ± 3.4 μW m−1 K−2 for 20 wt% PSSH/SWCNT composite film. Further base treatment induces partial removal of insulative PSSH and de-doping effect of SWCNTs, which decreases the barriers between adjacent nanotubes junctions and modulates charge carrier transport to synergistically optimize the electrical conductivity and Seebeck coefficient. With fine-tuning base treatment temperature, the PSSH/SWCNT composite film reaches highest power factor of 160.6 ± 7.9 μW m−1 K−2, higher than pristine SWCNTs of 70.2 ± 4.4 μW m−1 K−2. This work demonstrates the feasibility of this approach to boost the TE properties of SWCNTs, exhibiting potential application for high performance renewable energy harvesting.

Functionalized single‐walled carbon nanotubes electrochemical aptasensor for human epidermal growth factor receptor 2 (HER2) breast cancer detection

AbstractIn this study, we present a novel functionalized single‐walled carbon nanotubes (SWCNTs) electrochemical aptasensor designed for the detection of HER2 breast cancer. The well‐organized SWCNTs were attained through a concentration‐based and single‐step ultrasonication‐directed assembly methodology, resulting in a well‐dispersed state and a thin, even coating on the transducer substrate. Well‐organized SWCNTs were systematically analyzed through X‐ray diffraction spectroscopy (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy and elemental mapping (TEM‐mapping) and X‐ray photoelectron spectroscopy (XPS) confirmed the superior quality and organization of the SWCNTs. Furthermore, the electrochemical sensor exhibited outstanding performance, showcasing the potential of the SWCNTs as an ideal material for such applications, including their anticancer activity against human breast cancer cells. The single‐step ultrasonication‐directed assembly approach not only enhances the electrochemical properties of SWCNT but holds promise as a potentially as versatile substrate for immobilizing enzymes, antibodies, and DNA. This versatility opens up opportunities for the creation of highly functional biosensors with broad medical applications. Overall, our findings highlight the scientific significance of SWCNTs in advancing electrochemical sensing technologies and their potential in combating breast cancer.

High figure-of-merit of single-walled carbon nanotubes films with metallic type conduction

Carbon nanotubes are promising candidates for thermoelectric power generation because of their one-dimensionality mediated high Seebeck coefficient, high electrical conductivity with added advantages of flexibility, light weight, and scalability. We report the temperature-dependent thermoelectric properties of single-walled carbon nanotube (SWCNTs) films. The SWCNTs films exhibit p-type metallic conduction with high Seebeck coefficient (∼69.5 μVK−1) and moderate electrical conductivity (∼76 Scm−1). The films exhibit low thermal conductivity (∼0.1 Wm−1 K−1) due to phonon scattering at the interjunction region. The synergetic combination of thermoelectric properties resulted in a high figure-of-merit of ∼0.11 at 305 K. A flexible thermoelectric generator based on SWCNTs films mounted on a curved hot surface exhibited an output of 17 mV and 54 μA under a small temperature gradient of 10 K. The present work provides possible avenues for developing wearable SWCNTs based thermoelectric power generation modules for harvesting body heat.

Influence of temperature and nonlinear damping on mechanical properties of single-walled carbon nanotubes

Existing experiments have demonstrated that the nonlinear terms caused by damping impact the dynamical behaviors of single-walled carbon nanotubes (SWCNTs) significantly. Although, it is still an open question to precisely describe the vibrations of SWCNTs with the combined effects, such as the scale effect, the thermal effect, and the nonlinear damping. In the present research, we proposed a new nonlocal nonlinear Euler-Bernoulli theory to model an SWCNT's mechanical properties with the combined effect of three factors. A (10,10)SWCNT was brought to demonstrate the influence of the three factors on the elastic buckling and the forced bending vibrations. The results indicate for slender SWCNTs that the combined effects have some more remarkable impacts on nonlinear mechanical behaviors than individual factors, and dramatic deviation may emerge in the vibrations once nonlinear damping terms are absent.

Modulation of Carbon Nanotube Electronic Structure by Grain Boundary Defects in RbI on Au(111).

The electronic properties of single-walled carbon nanotubes (SWCNTs) are known to be highly sensitive to environmental effects. Here, we use scanning tunneling microscopy and spectroscopy to investigate the electronic properties of SWCNTs deposited on RbI monolayer films grown on Au(111). We find that grain boundary defects in RbI monolayers cause the appearance of spatially confined localized states in the SWCNTs. Our density functional theory calculations show that grain boundary defects in RbI/Au(111) produce a stabilizing electrostatic potential caused by reduced coordination of iodine atoms at the RbI grain boundary. The presented results may offer insights into the performance of devices involving transport through SWCNTs subjected to external electrostatic disorder.

Narrow band absorption and sensing properties of single-walled carbon nanotubes at terahertz metasurface

Due to their excellent electrical and optical properties, carbon nanotubes have unique application prospects in the field of optoelectronics. In this work the vacuum self-assembly method is used to obtain an isotropic single-walled carbon nanotube film with a thickness of 2 μm by the dispersion of single-walled carbon nanotube powder through vacuum filtration; on the basis of extracting the dielectric parameters of the thin film in a range from 0.4 to 2.0 THz, a novel terahertz metasurface narrowband absorber based on single-walled carbon nanotube films is designed and prepared. This metasurface absorber is composed of square and I-shaped narrow slot resonators. The experimental and simulation results show that the proposed terahertz metasurface absorber exhibits four distinct resonance absorption peaks at 0.65, 0.85, 1.16, and 1.31 THz, respectively, achieving a perfect absorption of up to 90%. The absorption mechanism of this novel multi band terahertz metasurface is elucidated by using the theory of multiple reflection interference. By setting analytical layers with different refractive indices on the surface of metasurface device, the sensing performance of metasurface acting as refractive index sensor is studied in depth. The research results indicate that this new type of metasurface absorber has high sensitivity for refractive index sensing, providing new ideas and solutions for further developing carbon-based new terahertz metasurface absorbers.