Showing papers on "Carbon nanotube published in 2019"

Carbon Nanotube Chemical Sensors

Abstract: Carbon nanotubes (CNTs) promise to advance a number of real-world technologies. Of these applications, they are particularly attractive for uses in chemical sensors for environmental and health monitoring. However, chemical sensors based on CNTs are often lacking in selectivity, and the elucidation of their sensing mechanisms remains challenging. This review is a comprehensive description of the parameters that give rise to the sensing capabilities of CNT-based sensors and the application of CNT-based devices in chemical sensing. This review begins with the discussion of the sensing mechanisms in CNT-based devices, the chemical methods of CNT functionalization, architectures of sensors, performance parameters, and theoretical models used to describe CNT sensors. It then discusses the expansive applications of CNT-based sensors to multiple areas including environmental monitoring, food and agriculture applications, biological sensors, and national security. The discussion of each analyte focuses on the strategies used to impart selectivity and the molecular interactions between the selector and the analyte. Finally, the review concludes with a brief outlook over future developments in the field of chemical sensors and their prospects for commercialization.

Large-area graphene-nanomesh/carbon-nanotube hybrid membranes for ionic and molecular nanofiltration.

Abstract: Nanoporous two-dimensional materials are attractive for ionic and molecular nanofiltration but limited by insufficient mechanical strength over large areas. We report a large-area graphene-nanomesh/single-walled carbon nanotube (GNM/SWNT) hybrid membrane with excellent mechanical strength while fully capturing the merit of atomically thin membranes. The monolayer GNM features high-density, subnanometer pores for efficient transport of water molecules while blocking solute ions or molecules to enable size-selective separation. The SWNT network physically separates the GNM into microsized islands and acts as the microscopic framework to support the GNM, thus ensuring the structural integrity of the atomically thin GNM. The resulting GNM/SWNT membranes show high water permeance and a high rejection ratio for salt ions or organic molecules, and they retain stable separation performance in tubular modules.

Active Sites and Mechanism of Oxygen Reduction Reaction Electrocatalysis on Nitrogen-Doped Carbon Materials.

Abstract: The oxygen reduction reaction (ORR) is a core reaction for electrochemical energy technologies such as fuel cells and metal-air batteries. ORR catalysts have been limited to platinum, which meets the requirements of high activity and durability. Over the last few decades, a variety of materials have been tested as non-Pt catalysts, from metal-organic complex molecules to metal-free catalysts. In particular, nitrogen-doped graphitic carbon materials, including N-doped graphene and N-doped carbon nanotubes, have been extensively studied. However, due to the lack of understanding of the reaction mechanism and conflicting knowledge of the catalytic active sites, carbon-based catalysts are still under the development stage of achieving a performance similar to Pt-based catalysts. In addition to the catalytic viewpoint, designing mass transport pathways is required for O2 . Recently, the importance of pyridinic N for the creation of active sites for ORR and the requirement of hydrophobicity near the active sites have been reported. Based on the increased knowledge in controlling ORR performances, bottom-up preparation of N-doped carbon catalysts, using N-containing conjugative molecules as the assemblies of the catalysts, is promising. Here, the recent understanding of the active sites and the mechanism of ORRs on N-doped carbon catalysts are reviewed.

The Regulating Role of Carbon Nanotubes and Graphene in Lithium‐Ion and Lithium–Sulfur Batteries

Abstract: The ever-increasing demands for batteries with high energy densities to power the portable electronics with increased power consumption and to advance vehicle electrification and grid energy storage have propelled lithium battery technology to a position of tremendous importance. Carbon nanotubes (CNTs) and graphene, known with many appealing properties, are investigated intensely for improving the performance of lithium-ion (Li-ion) and lithium-sulfur (Li-S) batteries. However, a general and objective understanding of their actual role in Li-ion and Li-S batteries is lacking. It is recognized that CNTs and graphene are not appropriate active lithium storage materials, but are more like a regulator: they do not electrochemically react with lithium ions and electrons, but serve to regulate the lithium storage behavior of a specific electroactive material and increase the range of applications of a lithium battery. First, metrics for the evaluation of lithium batteries are discussed, based on which the regulating role of CNTs and graphene in Li-ion and Li-S batteries is comprehensively considered from fundamental electrochemical reactions to electrode structure and integral cell design. Finally, perspectives on how CNTs and graphene can further contribute to the development of lithium batteries are presented.

Carbon-Based Nanomaterials for Biomedical Applications: A Recent Study.

Abstract: The study of carbon-based nanomaterials (CBNs) for biomedical applications has attracted great attention due to their unique chemical and physical properties including thermal, mechanical, electrical, optical and structural diversity. With the help of these intrinsic properties, CBNs, including carbon nanotubes (CNT), graphene oxide (GO), and graphene quantum dots (GQDs), have been extensively investigated in biomedical applications. This review summarizes the most recent studies in developing of CBNs for various biomedical applications including bio-sensing, drug delivery and cancer therapy.

Toward the Application of High Frequency Electromagnetic Wave Absorption by Carbon Nanostructures

Abstract: With the booming development of electronic information technology, the problems caused by electromagnetic (EMs) waves have gradually become serious, and EM wave absorption materials are playing an essential role in daily life. Carbon nanostructures stand out for their unique structures and properties compared with the other absorption materials. Graphene, carbon nanotubes, and other special carbon nanostructures have become especially significant as EM wave absorption materials in the high-frequency range. Moreover, various nanocomposites based on carbon nanostructures and other lossy materials can be modified as high-performance absorption materials. Here, the EM wave absorption theories of carbon nanostructures are introduced and recent advances of carbon nanostructures for high-frequency EM wave absorption are summarized. Meanwhile, the shortcomings, challenges, and prospects of carbon nanostructures for high-frequency EM wave absorption are presented. Carbon nanostructures are typical EM wave absorption materials being lightweight and having broadband properties. Carbon nanostructures and related nanocomposites represent the developing orientation of high-performance EM wave absorption materials.

Printing Conductive Nanomaterials for Flexible and Stretchable Electronics: A Review of Materials, Processes, and Applications

Abstract: DOI: 10.1002/admt.201800546 manufacturing processes and relatively high production cost.[12,13] PE has been explored for the manufacturing of flexible and stretchable electronic devices by printing functional inks containing soluble or dispersed materials,[14–16] which has enabled a wide variety of applications, such as transparent conductive films (TCFs), flexible energy harvesting and storage, thin film transistors (TFTs), electroluminescent devices, and wearable sensors.[17–24] The global PE market should reach $26.6 billion by 2022 from $14.0 billion in 2017 at a compound annual growth rate of 13.6%.[25] PE devices are manufactured by a variety of printing technologies. Typical printing technologies can be divided into two broad categories: noncontact patterning (or nozzle-based patterning) and contact-based patterning. The noncontact techniques include inkjet printing, electrohydrodynamic (EHD) printing, aerosol jet printing, and slot die coating, while screen printing, gravure printing, and flexographic printing are examples of the contact techniques. Each of these techniques has its own advantages and disadvantages, but they all rely on the principle of transferring inks to a substrate. Understanding the characteristics and recent advances of each printing technique is important to further the progress in PE. Moreover, to promote the lab-scale printing technologies to large-scale production process, roll-toroll (R2R) printing, which is one of the manufacturing methods to obtain large-area films with low cost and excellent durability, has drawn much attention from both industry and the research community. Nearly all of devices based on PE require conductive structures, interconnects, and contacts; therefore, highly conductive patterns, usually with high transparency and/or high resolution, fabricated by means of printing conductive materials are one of the most critical components in PE devices. Various printable conductive nanomaterials, such as metal nanomaterials (e.g., metal nanoparticles and metal nanowires) and carbon nanomaterials (e.g., graphene and carbon nanotubes (CNTs)), have been explored and used as major materials for PE. Applying printing technology to deposition of the conductive nanomaterials requires formulation of suitable inks. After depositing inks on different substrates, post-printing treatment, Printed electronics is attracting a great deal of attention in both research and commercialization as it enables fabrication of large-scale, low-cost electronic devices on a variety of substrates. Printed electronics plays a critical role in facilitating widespread flexible electronics and more recently stretchable electronics. Conductive nanomaterials, such as metal nanoparticles and nanowires, carbon nanotubes, and graphene, are promising building blocks for printed electronics. Nanomaterial-based printing technologies, formulation of printable inks, post-printing treatment, and integration of functional devices have progressed substantially in the recent years. This review summarizes basic principles and recent development of common printing technologies, formulations of printable inks based on conductive nanomaterials, deposition of conductive inks via different printing techniques, and performance enhancement by using various sintering methods. While this review places emphasis on conductive nanomaterials, the printing techniques and ink formulations can be applied to other materials such as semiconducting and insulating nanomaterials. Moreover, some applications of printed flexible and stretchable electronic devices are reviewed to illustrate their potential. Finally, the future challenges and prospects for printing conductive nanomaterials are discussed.

Conductive nanomaterials for 2D and 3D printed flexible electronics

Abstract: This review describes recent developments in the field of conductive nanomaterials and their application in 2D and 3D printed flexible electronics, with particular emphasis on inks based on metal nanoparticles and nanowires, carbon nanotubes, and graphene sheets. We present the basic properties of these nanomaterials, their stabilization in dispersions, formulation of conductive inks and formation of conductive patterns on flexible substrates (polymers, paper, textile) by using various printing technologies and post-printing processes. Applications of conductive nanomaterials for fabrication of various 2D and 3D electronic devices are also briefly discussed.

Ultrathin and Flexible CNTs/MXene/Cellulose Nanofibrils Composite Paper for Electromagnetic Interference Shielding.

Abstract: As the rapid development of portable and wearable devices, different electromagnetic interference (EMI) shielding materials with high efficiency have been desired to eliminate the resulting radiation pollution. However, limited EMI shielding materials are successfully used in practical applications, due to the heavy thickness and absence of sufficient strength or flexibility. Herein, an ultrathin and flexible carbon nanotubes/MXene/cellulose nanofibrils composite paper with gradient and sandwich structure is constructed for EMI shielding application via a facile alternating vacuum-assisted filtration process. The composite paper exhibits outstanding mechanical properties with a tensile strength of 97.9 ± 5.0 MPa and a fracture strain of 4.6 ± 0.2%. Particularly, the paper shows a high electrical conductivity of 2506.6 S m−1 and EMI shielding effectiveness (EMI SE) of 38.4 dB due to the sandwich structure in improving EMI SE, and the gradient structure on regulating the contributions from reflection and absorption. This strategy is of great significance in fabricating ultrathin and flexible composite paper for highly efficient EMI shielding performance and in broadening the practical applications of MXene-based composite materials.

Nanomaterial Applications in Photothermal Therapy for Cancer

Abstract: As a result of their unique compositions and properties, nanomaterials have recently seen a tremendous increase in use for novel cancer therapies. By taking advantage of the optical absorption of near-infrared light, researchers have utilized nanostructures such as carbon nanotubes, gold nanorods, and graphene oxide sheets to enhance photothermal therapies and target the effect on the tumor tissue. However, new uses for nanomaterials in targeted cancer therapy are coming to light, and the efficacy of photothermal therapy has increased dramatically. In this work, we review some of the current applications of nanomaterials to enhance photothermal therapy, specifically as photothermal absorbers, drug delivery vehicles, photoimmunological agents, and theranostic tools.

Flexible layer-structured Bi2Te3 thermoelectric on a carbon nanotube scaffold

Abstract: Inorganic chalcogenides are traditional high-performance thermoelectric materials. However, they suffer from intrinsic brittleness and it is very difficult to obtain materials with both high thermoelectric ability and good flexibility. Here, we report a flexible thermoelectric material comprising highly ordered Bi2Te3 nanocrystals anchored on a single-walled carbon nanotube (SWCNT) network, where a crystallographic relationship exists between the Bi2Te3 < $$\bar{1}2\bar{1}0$$ > orientation and SWCNT bundle axis. This material has a power factor of ~1,600 μW m−1 K−2 at room temperature, decreasing to 1,100 μW m−1 K−2 at 473 K. With a low in-plane lattice thermal conductivity of 0.26 ± 0.03 W m−1 K−1, a maximum thermoelectric figure of merit (ZT) of 0.89 at room temperature is achieved, originating from a strong phonon scattering effect. The origin of the excellent flexibility and thermoelectric performance of the Bi2Te3–SWCNT material is attributed, by experimental and computational evidence, to its crystal orientation, interface and nanopore structure. Our results provide insight into the design and fabrication of high-performance flexible thermoelectric materials. Bi2Te3 materials suffer from brittleness, limiting their application for thermoelectric harvesting. By depositing ordered nanocrystals onto single-wall carbon nanotubes, a flexible material is formed that achieves ZT of 0.89 at room temperature.

Carbon-based nanomaterials as an emerging platform for theranostics

Abstract: Carbon-based nanomaterials include fullerenes, carbon nanotubes, graphene and its derivatives, graphene oxide, nanodiamonds, and carbon-based quantum dots. Due to their unique structural dimensions and excellent mechanical, electrical, thermal, optical and chemical properties, these materials have attracted significant interest in diverse areas, including biomedical applications. Among them, there has been recent focus on the imaging of cells and tissues and the delivery of therapeutic molecules for disease treatment and tissue repair. The broad-range one-photon property of carbon based-nanomaterials together with their biocompatibility and ease of functionalization has made them candidate imaging agents for tumor diagnosis. In particular, the intrinsic two-photon fluorescence property of carbon based-nanomaterials in the long wavelength region (near-infrared II) allows deep-tissue optical imaging. This review highlights the recent development on carbon based-nanomaterials in the field of one-photon and two-photon imaging and discusses their possible and promising diagnostic and therapeutic applications for the treatment of various diseases including cancer.

Ultralight and Mechanically Robust Ti3C2Tx Hybrid Aerogel Reinforced by Carbon Nanotubes for Electromagnetic Interference Shielding.

Abstract: Lightweight materials with high electrical conductivity and robust mechanical properties are highly desirable for electromagnetic interference (EMI) shielding in modern portable and highly integrated electronics. Herein, a three-dimensional (3D) porous Ti3C2Tx/carbon nanotube (CNT) hybrid aerogel was fabricated via a bidirectional freezing method for lightweight EMI shielding application. The synergism of the lamellar and porous structure of the MXene/CNT hybrid aerogels contributed extensively to their excellent electrical conductivity (9.43 S cm-1) and superior electromagnetic shielding effectiveness (EMI SE) value of 103.9 dB at 3 mm thickness at the X-band frequency, the latter of which is the best value reported for synthetic porous nanomaterials. The CNT reinforcement in the MXene/CNT hybrid aerogels enhanced the mechanical robustness and increased the compressional modulus by 9661% relative to that of the pristine MXene aerogel. The hybrid aerogel with high electrical conductivity, good mechanical strength, and superior EMI shielding performance is a promising material for inhibiting EMI pollution.

Pea-like Fe/Fe3C Nanoparticles Embedded in Nitrogen-Doped Carbon Nanotubes with Tunable Dielectric/Magnetic Loss and Efficient Electromagnetic Absorption

Abstract: One-dimensional microstructure has been regarded as one of the most desirable configurations for magnetic carbon-based microwave absorbing materials (MAMs). Herein, pea-like Fe/Fe3C nanoparticles embedded in nitrogen-doped carbon nanotubes (Fe/Fe3C@NCNTs) are successfully prepared through a direct pyrolysis of the mixture of FeCl3·6H2O and melamine under inert atmosphere. The chemical composition and microstructural feature of these Fe/Fe3C@NCNTs composites are highly dependent on the pyrolysis temperature. As a result, their electromagnetic properties can be also manipulated, where dielectric loss gradually decreases with the increasing pyrolysis temperature and magnetic loss presents a reverse variation trend. When the pyrolysis temperature reaches 600 °C, the as-obtained composite, Fe/Fe3C@NCNTs-600 can perform a maximum reflection loss of −46.0 dB at 3.6 GHz with a thickness of 4.97 mm and a qualified bandwidth of 14.8 GHz with the integrated thickness from 1.00 to 5.00 mm. It is very interesting that...

High areal capacity battery electrodes enabled by segregated nanotube networks

Abstract: Increasing the energy storage capability of lithium-ion batteries necessitates maximization of their areal capacity. This requires thick electrodes performing at near-theoretical specific capacity. However, achievable electrode thicknesses are restricted by mechanical instabilities, with high-thickness performance limited by the attainable electrode conductivity. Here we show that forming a segregated network composite of carbon nanotubes with a range of lithium storage materials (for example, silicon, graphite and metal oxide particles) suppresses mechanical instabilities by toughening the composite, allowing the fabrication of high-performance electrodes with thicknesses of up to 800 μm. Such composite electrodes display conductivities up to 1 × 104 S m−1 and low charge-transfer resistances, allowing fast charge-delivery and enabling near-theoretical specific capacities, even for thick electrodes. The combination of high thickness and specific capacity leads to areal capacities of up to 45 and 30 mAh cm−2 for anodes and cathodes, respectively. Combining optimized composite anodes and cathodes yields full cells with state-of-the-art areal capacities (29 mAh cm−2) and specific/volumetric energies (480 Wh kg−1 and 1,600 Wh l−1). While thicker battery electrodes are in high demand to maximize energy density, mechanical instability is a major hurdle in their fabrication. Here the authors report that segregated carbon nanotube networks enable thick, high-capacity electrodes for a range of materials including Si and NMC.

Electronic and Structural Engineering of Carbon-Based Metal-Free Electrocatalysts for Water Splitting.

Abstract: Since first being reported as possible electrocatalysts to substitute platinum for the oxygen reduction reaction (ORR), carbon-based metal-free nanomaterials have been considered a class of promising low-cost materials for clean and sustainable energy-conversion reactions. However, beyond the ORR, the development of carbon-based catalysts for other electrocatalytic reactions is still limited. More importantly, the intrinsic activity of most carbon-based metal-free catalysts is inadequate compared to their metal-based counterparts. To address this challenge, more design strategies are needed in order to improve the overall performance of carbon-based materials. Herein, using water splitting as an example, some state-of-the-art strategies in promoting carbon-based nanomaterials are summarized, including graphene, carbon nanotubes, and graphitic-carbon nitride, as highly active electrocatalysts for hydrogen evolution and oxygen evolution reactions. It is shown that by rationally tuning the electronic and/or physical structure of the carbon nanomaterials, adsorption of reaction intermediates is optimized, consequently improving the apparent electrocatalytic performance. These strategies may facilitate the development in this area and lead to the discovery of advanced carbon-based nanomaterials for various applications in energy-conversion processes.

Thermal conductivity of carbon nanotube networks: a review

Abstract: Depending on their structure and order (individual, films, bundled, buckypapers, etc.), carbon nanotubes (CNTs) demonstrate different values of thermal conductivity, from the level of thermal insulation with the thermal conductivity of 0.1 W/mK to such high values as 6600 W/mK. This review article concentrates on analyzing the articles on thermal conductivity of CNT networks. It describes various measurement methods, such as the 3-ω method, bolometric, steady-state method and their variations, hot-disk method, laser flash analysis, thermoreflectance method and Raman spectroscopy, and summarizes the results obtained using those techniques. The article provides the main factors affecting the value of thermal conductivity, such as CNT density, number of defects in their structure, CNT ordering within arrays, direction of measurement in relation to their length, temperature of measurement and type of CNTs. The practical methods of using CNT networks and the potential directions of future research in that scope were also described.

Active Edge‐Site‐Rich Carbon Nanocatalysts with Enhanced Electron Transfer for Efficient Electrochemical Hydrogen Peroxide Production

Abstract: A highly efficient, metal-free carbon nanocatalyst is presented that possesses abundant active, oxygenated graphitic edge sites. The edge site-rich nanocarbon catalyst exhibits about 28 times higher activity for H2 O2 production than a basal plane-rich carbon nanotube with a H2 O2 selectivity over 90 %. The oxidative treatment further promotes the H2 O2 generation activity to reach close to the thermodynamic limit. The optimized nanocarbon catalyst shows a very high H2 O2 production activity, surpassing previously reported catalysts in alkaline media. Moreover, it can stably produce H2 O2 for 16 h with Faradaic efficiency reaching 99 % and accumulated H2 O2 concentration of 24±2 mm. Importantly, we find that the heterogeneous electron transfer kinetics of the carbon-based catalyst is closely related to the electrocatalytic activity, suggesting that first outer-sphere electron transfer to O2 is an important step governing the H2 O2 production rate.