Single-walled Carbon Nanotube Buckypaper Research Articles

Carbon Nanotube-Polyurethane Composite Sheets for Flexible Thermoelectric Materials.

Integration of single-wall carbon nanotubes (SWCNTs) in the form of fabriclike sheets or other preformed assemblies (films, fibers, etc.) simplifies their handling and allows for composites with higher nanotube contents, which is needed to better exploit their outstanding properties and achieve multifunctional materials with improved performance. Here, we show the development of p-type SWCNT-thermoplastic polyurethane (TPU) fabric materials with a wide range of SWCNT contents (from 5 to 90 wt %) by employing a one-step filtration method using a suspension of SWCNTs in a TPU solvent/nonsolvent mixture. The mechanical and thermoelectric (TE) properties of these SWCNT-TPU nanocomposites were tailored by varying the SWCNT/TPU wt % ratio, achieving significant advantages relative to the pristine SWCNT buckypaper (BP) sheets in terms of strength and stretchability. In particular, the SWCNT-TPU nanocomposite with a 50/50 wt % ratio composition (equivalent to 15 vol % of SWCNTs) shows a power factor (PF) of 57 μW m-1 K-2, slightly higher compared to the PF of the SWCNT BP prepared under the same conditions (54 μW m-1 K-2), while its mechanical properties significantly increased (e.g., ∼7-, 25-, and 250-fold improvements in stiffness, strength, and tensile toughness, respectively). These results represent a significant step toward the development of easy-to-process self-supporting and stretchable materials with robust mechanical properties for flexible thermoelectric devices.

Double-Layered Pebax® 3533/ZIF-8 Membranes with Single-Walled Carbon Nanotube Buckypapers as Support for Gas Separation.

Single-walled carbon nanotube buckypapers (SWCNT-bps) coated with a metal-organic framework ZIF-8 layer were used as supports for the preparation of Pebax® 3533 TFC membranes by both phase inversion and spin coating techniques. Upon proper characterization of the materials by X-ray diffraction, IR spectroscopy, thermogravimetry and electron microscopy, the obtained membranes were tested in gas separation experiments with a 15:85 CO2/N2 mixture. These experiments proved that the ZIF-8 layer prevented from the penetration of the polymer selective film into the SWCNT-bp support, giving rise to a highly permeable selective membrane. The optimum membrane was achieved by the spin-coating method, with better permeation results than that prepared by the phase inversion method, obtaining a CO2 permeance of 566 GPU together with a CO2/N2 selectivity of 20.9.

GO-SWCNT Buckypapers as an Enhanced Technology for Water Decontamination from Lead

Water decontamination is an important challenge resulting from the incorrect disposal of heavy metal waste into the environment. Among the different available techniques (e.g., filtration, coagulation, precipitation, and ion-exchange), adsorption is considered the cheapest and most effective procedure for the removal of water pollutants. In the last years, several materials have been tested for the removal of heavy metals from water, including metal-organic frameworks (MOFs), single-walled carbon nanotubes (SWCNTs), and graphene oxide (GO). Nevertheless, their powder consistency, which makes the recovery and reuse after adsorption difficult, is the main drawback for these materials. More recently, SWCNT buckypapers (SWCNT BPs) have been proposed as self-standing porous membranes for filtration and adsorption processes. In this paper, the adsorption capacity and selectivity of Pb2+ (both from neat solutions and in the presence of other interferents) by SWCNT BPs were evaluated as a function of the increasing amount of GO used in their preparation (GO-SWCNT buckypapers). The highest adsorption capacity, 479 ± 25 mg g−1, achieved for GO-SWCNT buckypapers with 75 wt.% of graphene oxide confirmed the effective application of such materials for cheap and fast water decontamination from lead.

Multivariate Metal-Organic Framework/Single-Walled Carbon Nanotube Buckypaper for Selective Lead Decontamination.

The search for efficient technologies empowering the selective capture of environmentally harmful heavy metals from wastewater treatment plants, at affordable prices, attracts wide interest but constitutes an important technological challenge. We report here an eco-friendly single-walled carbon nanotube buckypaper (SWCNT-BP) enriched with a multivariate amino acid-based metal–organic framework (MTV-MOF) for the efficient and selective removal of Pb2+ in multicomponent water systems. Pristine MTV-MOF was easily immobilized within the porous network of entangled SWCNTs, thus obtaining a stable self-standing adsorbing membrane filter (MTV-MOF/SWCNT-BP). SWCNT-BP alone shows a moderately good removal performance with a maximum adsorption capacity of 180 mg·g–1 and a considerable selectivity for Pb(II) ions in highly concentrated multi-ion solutions over a wide range of lead concentration (from 200 to 10000 ppb). Remarkably, these features were outperformed with the hybrid membrane filter MTV-MOF/SWCNT-BP, exhibiting enhanced selectivity and adsorption capacity (310 mg·g–1, which is up to 42% higher than that of the neat SWCNT-BP) and consequently enabling a more efficient and selective removal of Pb2+ from aqueous media. MTV-MOF/SWCNT-BP was able to reduce [Pb2+] from the dangerous 1000 ppb level to acceptable limits for drinking water, below 10 ppb, as established by the current EPA and WHO limits. Thus, the eco-friendly composite MTV-MOF/SWCNT-BP shows the potential to be effectively used several times as a reliable adsorbent for Pb2+ removal for household drinking water or in industrial treatment plants for water and wastewater lead decontamination.

Single-walled carbon nanotube buckypaper as support for highly permeable double layer polyamide/zeolitic imidazolate framework in nanofiltration processes

The development of membranes for nanofiltration applications requires not only selective layers but also suitable supports to control their synthesis as well as to enable efficient and competitive membrane performances. Single-walled carbon nanotube free-standing films (denoted as buckypaper) have been used as supports for the preparation of polyamide (PA) layers by interfacial polymerization (IP) and tested for dead-end nanofiltration for dyes removal (265–1017 Da) from water and organic solvents. The arrangement of the phases during the IP is essential, thus impregnation on the buckypaper support, first with the organic phase and then with the aqueous phase (denoted as inverse IP, iIP) leads to permeances (of up to 28.0 and 31.4 L m−2 h−1 bar−1 for water and methanol, respectively) and rejection values (>96%) that exceed those of the membranes prepared by reversing the impregnation order. Secondly, a double layer PA/zeolitic imidazolate framework (ZIF-8 or ZIF-93) was prepared on the buckypaper (bp). The design of this double layer led to superior membrane performance, in particular for the hydrophilic ZIF-93, as it changes the PA layer properties (increasing both hydrophilicity and surface roughness) providing higher permeances (up to 59.3 and 76.0 L m−2 h−1 bar−1 for water and methanol, respectively) and dye rejections (>98.5%) than the bare PA layer prepared by iIP. This attractive performance of the PA/ZIF-93/bp membrane has been corroborated with experiments in cross-flow nanofiltration and dead-end nanofiltration of aqueous salt solutions, long-term stability nanofiltration and the study the membrane separation performance after a chlorine treatment. The results reported here therefore show the enormous potential of these membrane architectures for a variety of selective separation processes.

Application of Nanoparticles of Metal Organic Framework Zif-8 as Solute for Water Ultrafiltration Through Self-Supported Single-Walled Carbon Nanotube Buckypaper Membranes

Application of Nanoparticles of Metal Organic Framework Zif-8 as Solute for Water Ultrafiltration Through Self-Supported Single-Walled Carbon Nanotube Buckypaper Membranes

Synthesis and Enhanced Capture Properties of a New BioMOF@SWCNT‐BP: Recovery of the Endangered Rare‐Earth Elements from Aqueous Systems (Adv. Mater. Interfaces 16/2021)

Composite Material for Lanthanides Recovery from Water In article number 2100730, Fiore Nicoletta, Giovanni De Filpo, Emilio Pardo, Donatella Armentano, and co-workers report the preparation of a novel bioMOF-based single-walled carbon nanotube buckypaper (MOF = metal–organic–framework) as a new and performant composite material for lanthanides recovery from water. This MOF-carbon-based membrane exhibits high efficiency in both static and dynamic regimes outperforming the state-of-the-art similar materials.

Synthesis and Enhanced Capture Properties of a New BioMOF@SWCNT‐BP: Recovery of the Endangered Rare‐Earth Elements from Aqueous Systems

AbstractHuman society is facing—among other environmental threats—an enormous challenge due to human activities. The extensive use of high‐tech devices and electronics equipment in the daily life makes, among others, rare‐earth elements (REEs) recovery from secondary sources highly required. Here, a novel bioMOF‐based single‐walled carbon nanotube buckypaper (SWCNTBP) is presented as a new and efficient composite material (BioMOF@SWCNT‐BP). The flexible and highly crystalline metal–organic framework (MOF), prepared from the natural amino acid L‐threonine, has been homogeneously dispersed within the tangled net of a self‐standing SWCNT‐BP for lanthanides recovery from water. This MOF‐carbon‐based membrane exhibits high efficiency, either in static or dynamic regimes, in the recovery of lanthanides from aqueous streams outperforming the state‐of‐the‐art. The capture performances of BPs are successfully improved after incorporation of such MOF featuring hexagonal functional channels decorated with the threonine amino acid residues, pointing toward the accessible void spaces, which boosts the capture properties of the final membrane, providing the adaptable functional environment to interact with lanthanides. This material's preparation presents also a potential for large‐scale applications with a potential benefit on natural aquatic ecosystems as well. It is highly demanded because REEs from non‐recycled waste materials are potential pollutants for surface waters.

Determining the Thermal Properties of Buckypapers Used in Photothermal Desorption.

Volatile organic compounds (VOCs) pose an occupational exposure risk due to their commonplace usage across industrial and vocational sectors. With millions of workers annually exposed, monitoring personal VOC exposures becomes an important task. As such, there is a need to improve current monitoring techniques by increasing sensitivity and reducing analysis costs. Recently, our lab developed a novel, preanalytical technique known as photothermal desorption (PTD). PTD uses pulses of high-energy, visible light to thermally desorb analytes from carbonaceous sorbents, with single-walled carbon nanotube buckypapers (BPs) having the best overall performance. To apply this new technology most effectively for chemical analysis, a better understanding of the theoretical framework of the thermal phenomena behind PTD must be gained. The objectives of the present work were 3-fold: measure the thermal response of BPs during irradiation with light; determine the best method for conducting such measurements; and determine the thermal conductivity of BPs. BPs were exposed to four energy densities, produced by light pulses, ranging from 0.28 to 1.33 J/cm2, produced by a xenon flash lamp. The resulting temperature measurements were obtained via fast response thermocouple (T/C) mounted to BPs by three techniques (pressing, adhering, and embedding). Temperature increase measured by T/C using the adhering and pressing techniques resulted in similar values, 29.2 ± 0.8 to 56 ± 3 °C and 29.1 ± 0.9 to 50 ± 5 °C, respectively, while temperature increase measured by embedding the T/C into the BP showed statistically larger increases ranging from 35.2 ± 0.9 to 76 ± 4 °C. Peak BP temperatures for each mounting technique were also compared with the temperatures generated by the light source, which resulted in embedded BPs demonstrating the most temperature conversion among the techniques (74–86%). Based on these results, embedding T/Cs into the BP was concluded to be the best way to measure BP thermal response during PTD. Additionally, the present work modeled BP thermal conductivity using a steady-state comparative technique and found the material’s conductivity to be 10.6 ± 0.6 W/m2. The present work’s findings will help pave the way for future developments of the PTD method by allowing calculation of the energy density necessary to attain a desired sorbent temperature and providing a means for comparing BP fabrication techniques and evaluating BP suitability for PTD before conducting PTD trials with analytes of interest. Sorbents with greater thermal conductivity are expected to desorb more evenly and withstand higher energy density exposures.

Green fabrication of Cu/rGO decorated SWCNT buckypaper as a flexible electrode for glucose detection

As a paper-like membrane composed of single-walled carbon nanotube (SWCNT), buckypaper possesses high conductivity, ideal flexibility, large surface area, great thermal/chemical stability and biocompatibility, which has manifested its potential as an alternative support material. However, due to the lack of defects, high quality SWCNT synthesized by arc-discharge method is difficult to be modified with metal nanoparticles for electro-catalysis. In this paper, a novel green strategy has been developed to fabricate SWCNT buckypaper decorated with Cu/reduced graphene oxide (Cu/rGO-BP) for the first time, in which graphene oxide functions as the intermediate between SWCNT and Cu nanoparticles. The fabricated Cu/rGO-BP was applied as a flexible electrode for electrochemical glucose detection. The electrode exhibited excellent electro-catalytic activity for glucose oxidation. The sensor based on Cu/rGO-BP performed a high upper limit of linear range (25 mM), which is close to commercial glucose sensors. The proposed strategy for Cu/rGO-BP fabrication can be extended to modify buckypaper with other metal or metal oxide nanoparticles, and thus opens an innovative route to potential practical applications of flexible buckypaper in wearable bioelectronics.

Real-time Data-driven Quality Assessment for Continuous Manufacturing of Carbon Nanotube Buckypaper

Carbon nanotube (CNT) thin sheet, or buckypaper, has shown great potential as a multifunctional platform material due to its desirable properties, including its lightweight nature, high mechanical properties, and good conductivity. However, their mass adoption and applications by industry have run into significant bottlenecks because of large variability and uncertainty in quality during fabrication. There is an urgent demand to produce high-quality, high-performance buckypaper at an industrial scale. Raman spectroscopy provides detailed nanostructure information within seconds, and the obtained spectra can be decomposed into multiple effects associated with diverse quality characteristics of buckypaper. However, the decomposed effects are high-dimensional, and a systematic quantification method for buckypaper quality assessment has been lacking. In this paper, we propose a real-time data-driven quality assessment method, which fills in the blank of quantifying the quality for continuous manufacturing processes of CNT buckypaper. The composite indices derived from the proposed method are developed by analyzing in-line Raman spectroscopy sensing data. Weighted cross-correlation and maximum margin clustering are used to fuse the fixed effects into an inconsistency index to monitor the long-term mean shift of the process and to fuse the normal effects into a uniformity index to monitor the within-sample normality. Those individual quality indices are then combined into a composite index to reflect the overall quality of buckypaper. A case study indicates that our proposed approach can determine the quality rank for ten samples, and can provide quantitative quality indices for single-walled carbon nanotube buckypaper after acid processing or functionalization. The quality assessment results are consistent with evaluations from the experienced engineers.

Preparation and transport properties of oriented buckypapers with single walled carbon nanotubes

Buckypapers (BP) with carbon nanotubes (CNT) are very promising for a lot of applications, in which their high conductance, strength and small weight are required. In this work, isotropic BP were prepared using the solution-based deposition that includes the single walled carbon nanotubes (SWCNT) dispersion and the dispersion filtration from a solvent. To increase the BP conductivity, the orientation of the SWCNT bundles composing BP and a following iodine doping were applied. The method of extrusion through the narrow (300 µm) gap was used for the SWCNT orientation. The temperature dependences of conductance for isotropic, oriented and doped BP were studied to understand the effect of CNT alignment and the mechanism of transport through SWCNT BP. It was shown that bundle orientation increases the BP conductivity from ~10 3 S × cm -1 to ~10 4 S × cm -1 , and iodine doping of oriented samples additionally increase the conductivity by an order. The fluctuation – assisted tunneling between CNT bundles was used to describe the mechanism of low temperature conductivity.

MnO2/SWCNT buckypaper for high performance supercapacitors

Abstract We report the supercapacitive performance of manganese oxide (MnO2)/single-walled carbon nanotube (SWCNT) buckypaper electrodes enabled via electrochemical deposition of MnO2 onto SWCNT buckypaper for the first time. The entangled SWCNT network provides electro-conductive pathways for the charge transfer. We demonstrate that the MnO2/SWCNT buckypaper supercapacitor exhibits a specific capacitance of 605 Fg−1 and gravimetric energy density of ∼120 Whkg−1. Furthermore, our MnO2/SWCNT buckypaper electrode shows excellent rate capability (85% capacity retention at 20 Ag−1) and long cycle life (1% capacity loss after 10,000 charge/discharge cycles). The excellent performance of MnO2/SWCNT buckypaper supercapacitor is attributed to the flower-like unique hierarchical porous architecture of MnO2 around SWCNTs arranged in “pearl necklace” formation, enabling large electrode/electrolyte interface and charge storage surface, better electrolyte penetration, and rapid charge transfer. The results suggest that the MnO2/SWCNT buckypaper electrode can provide excellent supercapacitive performance suitable for future generation electric vehicles.

Solution-Processed Carbon Nanotube Buckypapers for Foldable Thermoelectric Generators.

Freestanding single-walled carbon nanotube (SWCNT) buckypapers with thicknesses of ∼30 μm are fabricated using a simple bar-coating process. The Seebeck coefficient and electrical conductivity of the SWCNT buckypapers are affected by the composition of the dispersion solvent mixture. The maximum p-type power factor of a SWCNT buckypaper is 411 ± 13 μW m-1 K-2. The inverse relationship between the Seebeck coefficient and electrical conductivity of the SWCNT buckypapers may be explained by the number density of junctions between the SWCNT bundles. Using the SWCNT buckypapers, which can be cut, folded, and pasted, a foldable thermoelectric generator is fabricated. The thermoelectric generator folded to an area of 2.25 cm2 exhibits a maximum power of 10.3 μW at a vertical temperature difference of 30 K.

Preparation and transport properties of oriented buckypapers with single walled carbon nanotubes

Buckypapers (BPs) with carbon nanotubes (CNTs) are very promising for a lot of applications, in which their high conductance, strength and small weight are required. In this work, isotropic BPs were prepared using the solution-based deposition that includes the single walled carbon nanotubes (SWCNTs) dispersion and the dispersion filtration from a solvent. To increase the BP conductivity, the orientation of the SWCNT bundles composing BPs and a following iodine doping were applied. The method of extrusion through the narrow (300 µm) gap was used for the SWCNT orientation. The temperature dependences of conductance for isotropic, oriented and doped BPs were studied to understand the effect of CNT alignment and the mechanism of transport through SWCNT BPs. It was shown that bundle orientation increases the BP conductivity from ~103 S × cm-1 to ~104 S × cm-1, and iodine doping of oriented samples additionally increase the conductivity by an order. The fluctuation – assisted tunneling between CNT bundles was used to describe the mechanism of low temperature conductivity.

Facile Fabrication of NiO-Decorated Double-Layer Single-Walled Carbon Nanotube Buckypaper for Glucose Detection.

A novel NiO-decorated flexible buckypaper (NiO-BP) was fabricated by a simple and scalable vacuum filtration method for electrochemical detection of glucose. The NiO-BP consists of two layers: one side is composed of purified single-walled carbon nanotubes, serving as the supporting layer, whereas the other side comprises NiO-loaded single-walled carbon nanotubes, serving as the catalyst layer. The morphology and structure of NiO-BP were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The fabricated NiO-BP was applied to the electrochemical detection of glucose. Under optimized conditions, the sensor exhibited a wide linear range of 0.1-9 mM for the determination of glucose with high sensitivity (2701 μA mM-1 cm-2) and a short response time (<2.5 s). The present work reveals that the buckypaper with a unique double-layer structure is promising for wearable biosensors.

Stress transfer in nanocomposites enabled by poly(methyl methacrylate) wrapping of carbon nanotubes

Good dispersion and interfacial interaction of carbon nanotubes in polymer matrices are important to effectively achieve mechanical reinforcement in nanocomposites. Previously, it was shown that poly(methyl methacrylate) (PMMA) helically wraps around single wall carbon nanotubes (SWNTs), and thus prevents SWNT bundling. In this work, influence of PMMA-wrapped SWNTs on tensile properties of PMMA/SWNT composites and stress transfer from the matrix to the nanotubes were studied. The tensile modulus and tensile strength of the PMMA-wrapped SWNT nanocomposite buckypapers made by vacuum filtration are 5.9 and 3.7 times that of the SWNT buckypaper without PMMA wrapping, respectively. Stress transfer in SWNTs was determined by monitoring G′ Raman band shift during nanocomposite film tensile deformation. Results showed that during tensile deformation, PMMA-wrapped SWNTs in the nanocomposite buckypapers experienced up to 1 GPa stress, while negligible stress was observed in the SWNT buckypaper without PMMA wrapping. Solvent-cast nanocomposite films under tensile deformation, and with SWNT loading between 0.1 and 10 wt%, PMMA-wrapped SWNTs experience stress as high as 3.1 GPa, while nanocomposites made without PMMA wrapping experience only about half of this stress value. The improved tensile properties are a result of improved CNT dispersion and enhanced interfacial stress transfer achieved via PMMA wrapping of SWNTs. A new Raman band peak was observed at 2276 cm−1 in PMMA-wrapped nanocomposites. Dynamic mechanical properties of various nanocomposites were also studied and reported.

Lower limits of detection in using carbon nanotubes as thermoluminescent dosimeters of beta radiation

World-wide, on-going intensive research is being seen in adaptation of carbon nanotubes (CNTs) for a wide variety of applications, particular interest herein being in the thermoluminescent (TL) properties of CNTs and their sensitivity towards energetic radiations. Using beta radiation delivering dose levels of a few Gy it has been observed in previous study that strain and impurity defects in CNTs give rise to significant TL yields, providing an initial measure of the extent to which electron trapping centres exist in various qualities of CNT, from super-pure to raw. This in turn points to the possibility that there may be considerable advantage in using such media for radiation dosimetry applications, including for in vivo dosimetry. CNTs also have an effective atomic number similar to that of adipose tissue, making them suitable for soft tissue dosimetry. In present investigations various single-wall carbon nanotubes (SWCNT) samples in the form of buckypaper have been irradiated to doses in the range 35–1.3Gy, use being made of a 90Sr beta source, the response of the CNTs buckypaper with dose showing a trend towards linearity. It is shown for present production methodology for buckypaper samples that the raw SWCNT buckypaper offer the greatest sensitivity, detecting doses down to some few tens of mGy.

Effect of CNT length and structural density on viscoelasticity of buckypaper: A coarse-grained molecular dynamics study

Carbon nanotube (CNT) buckypapers, having exceptional mechanical and electrical properties, have been reported to demonstrate frequency-invariant and temperature-invariant viscoelastic properties. In an attempt to provide an in-depth insight into the viscoelasticity of buckypapers with (5, 5) single-walled CNTs (SWCNTs), we perform coarse-grained non-equilibrium molecular dynamics simulations to investigate the effects of oscillatory shear strain amplitude, buckypaper's density, and length of individual SWCNTs on the viscoelastic properties. SWCNT buckypapers exhibit linear viscoelasticity over shear strain amplitude from 0.03 to 0.05. Higher density SWCNT buckypapers can result in larger dynamic stiffness and a higher loss factor of up to ∼0.29. In the frequency-independent regime (≤1 GHz), increasing the length of individual SWCNTs causes a very slight decrease of elastic properties and has minor influence on the viscous mode. Thus, this study provides deep insight into the viscoelasticity of (5, 5) SWCNT buckypapers and demonstrates controllability of the excellent energy dissipation potential of buckypapers, and can thus help us design new energy dissipation devices from carbon nanomaterials.

Multifunctional Electroactive Nanocomposites Based on Piezoelectric Boron Nitride Nanotubes.

Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 °C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buckypaper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions.