Carbon Nanotube Composite Films Research Articles

Flexible and free-standing thermoelectric devices prepared from poly(vinylidene fluoride-co-hexafluoropropylene)/graphite nanoplatelet/single-walled carbon nanotube composite films

In this study, poly(vinylidene fluoride-co-hexafluoropropylene)/carbon composite films with enhanced thermoelectric performance are prepared. A hybrid filler of graphite nanoplatelets (GNPs) and single-walled carbon nanotubes (SWNTs) increase the electrical conductivity as a bridge between neighboring GNPs in the carbon hybrid films. The improved electrical conductivity is due to the purification process performed in an acid solution, which effectively removes the amorphous carbon, additives, and impurities in the carbon fillers. The Seebeck coefficient of the composite films is similarly maintained at approximately 40 μV/K owing to the intrinsic properties of the material. The calculated power factor is considerably increased to approximately 14 μW/mK2 owing to purification of the SWNTs, which is twice the value of the highest value reported value for freestanding-type thermoelectric materials based on polymer/carbon composites.

High Performance Polymer Thermoelectric Composite Achieved by Carbon-Coated Carbon Nanotubes Network

Poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate)/carbon nanotube (PEDOT:PSS/CNTs) composite films have been demonstrated to offer an excellent thermoelectric performance. In this work, p-type thermoelectric films prepared by a simple dipping coating process based on the carbon-coated carbon nanotubes (C-CNTs) continuous network are investigated. The highest power factor obtained in this work is 504.8 μW/mK2 (at 300 K) due to the relatively high electrical conductivity and Seebeck coefficient. The excellent TE properties of the C-CNTs/PEDOT:PSS composite film are attributed to the interfacial carrier scattering introduced by the unique structure. Composite materials based on a continuous network would open up new opportunities to develop high performance organic thermoelectric materials.

Characterization of Polyaniline/Single-Walled Carbon Nanotube Composite Films Prepared by Plasma Polymerization

Characterization of Polyaniline/Single-Walled Carbon Nanotube Composite Films Prepared by Plasma Polymerization

High performance p-type organic thermoelectric materials based on metalloporphyrin/single-walled carbon nanotube composite films

Single-walled carbon nanotube/organic small molecule based thermoelectric materials have attracted significant scientific attention in recent years. However, up to now, no detailed thermoelectric study reported is focused on the single-walled carbon nanotube/organometallic complex composite films. By considering the excellent properties of tetraphenylporphyrin (such as its π-conjugated system, versatile structure and stability) and the important roles of metal ions in improving thermoelectric properties, metalloporphyrins manifest great potential as composites for single-walled carbon nanotubes. Hence, in this work, we first propose a convenient strategy to obtain high-performance thermoelectric composites containing metalloporphyrin molecules and single-walled carbon nanotubes. It is found that the single-walled carbon nanotube/ZnTPP composite film demonstrates the best thermoelectric performance with a maximum power factor of 247.2 μWm−1K−2 at 340 K, which is perhaps one of the highest thermoelectric power factors reported for single-walled carbon nanotube/organic small molecule-based p-type materials. Three p-type materials exhibit outstanding electric conductivities with a maximum of 1028.7 S cm−1 (single-walled carbon nanotube/CuTPP at 340 K). Furthermore, the produced thermoelectric materials manifest outstanding air stability and thermostability. Therefore, our proposed method can be a promising reference for fabricating novel p-type high-performance thermoelectric materials using metalloporphyrin-based building blocks.

Percolation-amplified infrared sensitivity in titanium oxide-multi-walled carbon nanotube composite films

Titanium dioxide (TiO2)-multi-walled carbon nanotube (MWCNT) thin films were prepared and studied systematically for the effects of the concentration of MWCNTs on the electro-optical properties. Result shows that the addition of MWCNTs not only improves the optical absorption and electrical conductivity, but also reduces the 1/f noise of the films. Percolation phenomenon is observed at MWCNT concentrations of 0.20–0.25 wt%. In this concentration range, the composite films exhibit an abrupt rise of the temperature coefficient of resistance value (−2.93% K−1) and large general thermal parameter, both of which are desirable for applications in uncooled infrared detectors.

Flexible and Highly Sensitive Humidity Sensor Based on Cellulose Nanofibers and Carbon Nanotube Composite Film.

Flexible and highly sensitive humidity sensors are crucial for humidity detection. In this study, a flexible cellulose nanofiber/carbon nanotube (NFC/CNT) humidity sensor with high sensitivity performance was developed via fast vacuum filtration. CNTs were well dispersed in water by using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized NFC as a dispersant. More importantly, NFC also acted as a humidity sensitive material, achieving superior performance of NFC/CNT humidity sensors. The obtained NFC/CNT humidity sensor with 5 wt % CNT loading exhibits outstanding sensitive performance, and its response value reaches a maximum of 69.9% (Δ I/ I0) at 95% relative humidity (RH). It also displays good bending resistance and long-term stability. In addition, the NFC/CNT humidity sensor was employed to monitor human breath. Therefore, we believe that the flexible, highly sensitive, and simply designed NFC/CNT humidity sensor is a promising candidate for various applications in the field of humidity measurement.

Sensitivity Enhancement of Acetone Gas Sensor using Polyethylene Glycol/Multi-Walled Carbon Nanotubes Composite Sensing Film with Thermal Treatment.

There is a need to develop a chemiresistive gas sensor equipped with a thermostat over a wide area for the sensor, which can protect the sensor from the influence of ambient temperature due to the uniform temperature of the thermostat. In this paper, we demonstrated an acetone gas sensor based on a polyethylene glycol (PEG)/Multi-walled Carbon Nanotubes (MWCNTs) composite film, which was equipped with a thermostat. The sensor was operated at modest working temperatures for sensor sensitivity enhancement. The optimum design of the polyimide-based thermostat with widely uniform thermal distribution was investigated in detail. It was found that the temperature uniformity of the thermostat was achieved using double spiral geometry. The experimental results of the sensor response showed that the PEG/MWCNTs composite film with a moderate working temperature revealed a higher sensitivity than that without thermal treatment. Moreover, the sensing mechanisms of the PEG/MWCNTs composite gas sensor to acetone vapor were studied as well.

Improved thermoelectric performance of P3HT/SWCNTs composite films by HClO4 post-treatment

Abstract In this work, the thermoelectric performance of poly(3-hexylthiophene)/single walled carbon nanotubes (P3HT/SWCNTs) composite films has been effectively improved by HClO 4 post-treatment. The P3HT/SWCNTs composite films with 20 wt% of fillers achieved an optimal power factor of 27.99 μW m−1 K−2 after HClO4 post-treatment for 2 h. The increased thermoelectric performance of P3HT/SWCNTs composite films can be attributed to the HClO4 treatment that can promote the transitions of the P3HT spacers between the adjacent SWCNTs from their neutral state to the bipolaron state, which significantly increased the electrical conductivity of the composite films. P3HT/SWCNTs composite films filled with low-content SWCNTs possessed excellent flexibility. This excellent performance of P3HT/SWCNTs composite films should be attributed to the combination of advantages of organic/inorganic hybridization and acid post-treatment. This is an important strategy to improve the performance of thermoelectric materials in recent years.

Mechanical and Electroconductive Properties of Mono- and Bilayer Graphene–Carbon Nanotube Films

This article presents the results of a computer study of electrical conductivity and deformation behavior of new graphene–carbon nanotube (CNT) composite films under bending and stretching. Mono- and bilayer hybrid structures with CNTs (10,0) and (12,0) and an inter-tube distance of 10 and 12 hexagons were considered. It is revealed that elastic deformation is characteristic for mono- and bilayer composite films both in bending and stretching. It is found that, in the case of bending in a direction perpendicular to CNTs, the composite film takes the form of an arc, and, in the case of bending in a direction along CNTs, the composite film exhibits behavior that is characteristic of a beam subjected to bending deformation as a result of exposure to vertical force at its free end. It is shown that mono- and bilayer composite films are more resistant to axial stretching in the direction perpendicular to CNTs. The bilayer composite films with an inter-tube distance of 12 hexagons demonstrate the greatest resistance to stretching in a direction perpendicular to CNTs. It is established that the CNT diameter and the inter-tube distance significantly affect the strength limits of composite films under axial stretching in a direction along CNTs. The composite films with CNT (10,0) and an inter-tube distance of 12 hexagons exhibit the highest resistance to stretching in a direction along CNTs. The calculated distribution of local stresses of the atomic network of deformed mono- and bilayer composite films showed that the maximum stresses fall on atoms forming covalent bonds between graphene and CNT, regardless of the CNT diameter and inter-tube distance. The destruction of covalent bonds occurs at the stress of ~1.8 GPa. It is revealed that the electrical resistance of mono- and bilayer composite films decreases with increasing bending. At the same time, the electrical resistance of a bilayer film is 1.5–2 times less than that of a monolayer film. The lowest electrical resistance is observed for composite films with a CNT (12,0) of metallic conductivity.

Fabrication and Radioactive Heating Simulation of the flying Balloon Based on Carbon Nanotube Freestanding Films

A light-driven flying balloon has been fabricated using multi-walled carbon nanotube (MWNT) composite films, of which thickness and density are approximately 6 µm and 0.5 mg/cm2, respectively. The shape of balloon is a regular tetrahedron with approximately 11 cm length on a side. By irradiating light using a tungsten lamp to the balloon, the balloon can be levitated like a hot-air balloon because the temperature of MWNT film is rapidly increased and the temperature of air inside the balloon is gradually increased. We confirmed that the maximum levitation height is ap-proximately 14 cm during light irradiation. The balloon developed in this study could be utilized for a flying platform of autonomous flying monitoring system.

High absorption shielding material of poly(phthalazinone etherketone)/multiwall carbon nanotube composite films with sandwich configurations.

Sandwich structure can be induced to achieve excellent electromagnetic interference shielding effectiveness (EMI SE) as is well known. However, how to optimize the structure to achieve performance optimization is still a problem. Herein, a poly(phthalazinone etherketone)/multiwall carbon nanotube (PPEK/MWCNT) composite with homodisperse and high content (15 wt%) of MWCNT was prepared by a water induced phase separation process. A sandwich structure was designed by introducing a wave-transmitting layer between the PPEK/MWCNT composite films. The MWCNT loading of the shielding layer and the wave-transmitting layer thickness (d) were varied to systematically investigate their influence on shielding performance in the X-band (8.2–12.4 GHz). EMI SE shows strong d value dependence. When the shielding layer was fixed, EMI SE showed a trend of decreasing, rising, leveling off and then decreasing again with d value increasing. The d value in the leveling off stage is the best value for performance optimization. The best d value decreased with increasing MWCNT content of the shielding layer. An absorption dominated SE up to 65 dB and a high increment rate of 140% of SE were achieved by optimization of the d value and shielding layer.

Effects of low-temperature sintering on surface morphology and electrical performance of silver nanoparticle/carbon nanotube composite films

Silver nanoparticle (AgNP)/carbon nanotube (CNT) composites are drawing increasing attention for several applications, especially where transparency is required. However, interfacial interaction and stability of the AgNP/CNT composites have been scarcely investigated. In the present study, transparent coatings were prepared from dispersed AgNP-coated multiwalled CNTs and exposed to different sintering conditions. The changes in surface morphology and evolution of interfacial configuration of AgNP-decorated CNT transparent composite films were investigated. Under certain conditions, CNT ropes were glued to one another by the melted AgNP aggregates, resulting in the improvement of the measured electrical properties. The in situ measurements of the electrical properties allowed correlating the AgNPs sintering mechanism with the morphological observations. Notably, at a given temperature, increasing the initial film density increased the time necessary to complete the AgNPs sintering. The obtained results show that the electrical resistance can be used as a tool to indirectly monitor the network state of transparent AgNP-decorated CNT composite films, hence paving the way to tuning the composite film properties with a high precision for the desired application. These findings also explain the mechanism of reinforcement of polymer nanocomposites by the current nanofillers.

Characterization of NH\(_3\) Sensing Properties of P3HT+rGO+CNT Composite Films Made by Spin-coating

Thin films of poly(3-hexylthiophene) (P3HT) incorporated with reduced graphene oxide (rGO) and multi-walled carbon nanotubes (CNTs) were prepared by spin-coating technique. Atomic force microscope (AFM) surface morphology, UV-Vis spectra and NH3 gas sensing of the films were studied. Results showed that the P3HT embedded with a content of 20 wt.% of rGO and 10 % of CNTs (abbreviated to P3GC) resulted in the formation of nanostructured composites, exhibiting 1.50 nm-roughness surface and a semiconducting material with a bandgap of 1.92eV. These structure and composition of the P3GC film are appropriate for making film sensors whose resistance changes as a function of gas concentration. Monitoring ammonia gas by the sensors showed that the responding time of the sensing reached a value as fast as 30 s, the response at ammonia gas content of 10 ppm attained a value as large as 0.8% and the relative sensitivity was of 0.05 %/ppm.

Chemiresistive humidity sensor based on chitosan/zinc oxide/single-walled carbon nanotube composite film

A chemiresistive humidity sensor based on chitosan (CS)/zinc oxide/single-walled carbon nanotube (SWCNT) composite was developed. The sensor film was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The humidity sensing properties were investigated in a wide range of relative humidity (RH) (11%–97%) at room temperature. The SWCNT response to humidity was significantly improved with the aid of conjugate material in the composite, especially the CS. The composite also exhibited good reproducibility. The RH-dependent relationship revealed that the sensing response corresponded to the water sorption characteristic of CS. The sensing mechanism was attributed to the swelling effect of CS surrounding the nanotubes through which the hopping conduction path between nanotubes changed.

Effect of microstructure on the piezoresistive behavior of carbon nanotube composite film

This paper focuses on the piezoresistivity of a nanocomposite film under tensile strain, which consists of continuous carbon nanotube (CNT) network and is synthesized by floating catalyst chemical vapor deposition. The effects of matrix content, film thickness, CNT alignment and purification on the piezoresistive sensitivity of CNT composite film were investigated. The results show that the resistance changes of all these CNT composite films are consistent with the pattern of applied strain, which monotonically increase with increasing tensile strain during loading process. As matrix content increases, the piezoresistive response of CNT composite film becomes less obvious. The thicker composite film shows a bigger gauge factor than the thinner one. For aligned composite film, CNT’s intrinsic resistance becomes the controlling factor on the overall resistance change, and its piezoresistivity along aligned direction becomes more sensitive than random composite film. Aligned CNT composite film has an anisotropic piezoresistive behavior. The gauge factor along perpendicular direction to alignment is smaller than that in aligned direction. After purification with hydrochloric acid the piezoresistive behavior becomes more obvious for both random and aligned composite films. The baseline of resistance change shifts towards higher resistance for R-CNT/epoxy, while purified CNT composite film exhibits stable resistance change after 100 cycles. The gauge factors of aligned and random CNT/epoxy composite film after purification are 11.3 and 15.7, respectively. These results reveal the key factors for tailoring piezoresistive response of CNT composite film.

Simultaneous Electrochemical Detection of Glucose and Non-Esterified Fatty Acids (NEFAs) for Diabetes Management

In this paper, the feasibility of simultaneous electrochemical detection of glucose and non-esterified fatty acids (NEFA) is investigated using enzyme-based biosensors. The detection of glucose is based on ferrocene-Nafion-glucose oxidase (Fc-Nafion-GOx) modified screen-printed electrodes (SPEs). Solutions of Fc-Nafion-GOx were drop casted on SPEs and dried at room temperature allowing immobilisation of GOx entrapped in Nafion polymer with Fc. The detection of NEFA is based on bi-enzyme electrodes fabricated by the layer-by-layer technique applied onto SPEs using multilayers of poly(dimethyldiallyammonium chloride) polymer, multi-walled carbon nanotube composite films, and two enzymes: acyl-CoA synthetase and acyl-CoA oxidase. Oleoyl coenzyme A lithium salt (OACoA) and oleic acid (OA) were used as NEFA of interests because they are two of the most employed markers in clinical tests. Preliminary results demonstrated that enzyme electrodes showed linear response within the physiological concentration range of glucose and OA in human blood plasma as 5 and 1.2 mM, respectively. These results indicate a promising multi-biosensor platform for rapid one-step determination of glucose and NEFA simultaneously. This could lead the way toward the fabrication of glucose-NEFA biosensors, which can be important in diabetes management and early diagnosis.

Quick Heat Dissipation in Absorption-Dominated Microwave Shielding Properties of Flexible Poly(vinylidene fluoride)/Carbon Nanotube/Co Composite Films with Anisotropy-Shaped Co (Flowers or Chains).

The facile fabrication of thin flexible electromagnetic interference (EMI) shielding materials with fast heat dissipation for adaptable tuning in both civil and military applications is in urgent demand. In our work, the flexible poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT) composite films decorated with anisotropy-shaped Co in flowers or chains were prepared and studied. The results showed that by increasing the Co filler contents, the EC (electrical conductivity), TC (thermal conductivity), and EMI shielding properties of such PVDF/CNT/Co (flowers or chains) flexible films were significantly improved. In contrast, the PVDF/CNT/Co-chain flexible films exhibit higher performance with respect to the EC, TC, and EMI shielding properties. Total shielding of 35.3 and 32.2 dB were, respectively, obtained by the PVDF/CNT/6 wt % Co-chain with an EC of 2.28 S/cm and the PVDF/CNT/6 wt % Co-flower with an EC of 1.94 S/cm at a film thickness of 0.3 mm. Possibly owing to the conductive dissipation, interfacial polarization, magnetic loss, multiple reflections, and scattering of EM waves, such flexible composite films possessed a remarkable absorption-dominated EMI shielding behavior. These new composite films with enhanced TC are easily able to transform microwave energy into Joule heating systems, making themselves greatly potential for effective EMI shielding as well as rapid heat dissipation.

Computational design as a green approach for facile preparation of molecularly imprinted polyarginine-sodium alginate-multiwalled carbon nanotubes composite film on glassy carbon electrode for theophylline sensing

This paper reports on the synthesis of a novel molecularly imprinted composite film using the mathematical modeling. This composite was then used in the electrode modification for the determination of theophylline. The ratio of monomer to template in optimum condition was obtained to be 4. The modification of electrode was performed in the presence of theophylline through the electropolymerization of arginine on the composite of sodium alginate/multiwalled carbon nanotubes (SA-MWCNTs), which had been coated on glassy carbon electrode (GCE). The SA-MWCNTs composite with netlike morphology demonstrated high conductivity and electrocatalytic activity. Cyclic voltammogram of modified electrode (MIP/SA-MWCNTs/GCE) in the presence of theophylline showed a sensitive anodic peak in 1170 mV in buffer solution of phosphate (pH 7.0). The investigation and optimization of the effective factors on the response and electrochemical behavior of target theophylline were accurately done on the surface of the modified electrode. Theophylline response was linearly within the range of 0.01–60.0 μM with detection limit of 3.2 nM. Regarding the added standards, the recoveries were values between 93.4–105%. The function of this electrode was satisfactory in the determination of theophylline in real samples like theophylline tablet, theophylline oral solution and human plasma samples.

Electrodeposition and Properties of Composites Consisting of Carbon Nanotubes and Copper

Copper–matrix–carbon nanotubes (Cu–CNTs) composite films were prepared in a Cu plating solution with multiwall carbon nanotubes (MWCNTs) using electrodeposition. The MWCNTs surface treatment method, electroplating solution system, electroplating conditions, heat treatment process and other parameters of this process are discussed. The results showed that MWCNTs purified by HCl treatment and dispersed by stearyltrimethylammonium bromide are more suitable as add-on materials for the preparation of the copper matrix composite films by electrodeposition. An appropriate heat treatment process was able to improve the structures and properties of the composite films. The final products showed that the MWCNTs were evenly distributed in the composite films and joined with the copper grains to form a mutually entangled mesh structure with excellent corrosion resistance (3.19 × 10−8 Ω M) and a hardness of 53.5 HV. All this was possible through extensive optimization of the electrodeposition and post-treatment parameters.

Ionic liquid/single‐walled carbon nanotubes composite film modified carbon‐ceramic electrode as an electrochemical sensor for the simultaneous determination of epinephrine and uric acid

In the present work, a carbon–ceramic electrode (CCE) modified by a composite of an ionic liquid and single-walled carbon nanotubes (IL-SWCNT/CCE) was prepared for the electrochemical determination of epinephrine (EP) in the presence of uric acid (UA). The morphology and surface characteristics of the prepared modified CCE were studied using scanning electron microscopy (SEM). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used for electrochemical studies and determinations. Their results showed that the IL-SWCNT/CCE has high electrocatalytic activity toward the oxidation of EP. The electrochemical behavior of EP is closely dependent on the pH; in basic media, its oxidation process is irreversible and there is no cathodic peak in reverse scan, while in acidic media the electrochemical behavior of EP becomes reversible. DPV measurements showed that the oxidation peak current was linear in the concentration range 1.0 × 10−7 to 2.0 × 10−4 M, and the detection limit was 2.8 × 10−8 M. Also, it was confirmed that the IL-SWCNT/CCE can be used for the simultaneous measurement of EP and UA. The obtained results indicate that the IL-SWCNT/CCE has high stability, reproducibility, and repeatability. Finally, the developed electro-analytical method was successfully applied for the determination of EP in human serum and urine samples without any interference.