Carbon Nanotube Composite Films Research Articles

Effect of purification methods on the cross-sectional field emission properties of carbon nanotube and graphene composite films

Abstrace Carbon nanotubes (CNTs) are excellent materials for field emission because of their large aspect ratio, low-threshold field and stable chemical structure. However, the low adhesive bonding strength between CNTs and the supports presents a practical challenge in environments with a high field emission current density. We used a vacuum filtration method to prepare multiwalled CNT (MWCNT)/reduced grapheme oxide (r-GO) composite films in which CNTs were uniformly dispersed in the r-GO layers. Compared with unmodified films, films in which CNTs are dispersed show better field emission performance, and the adhesive bonding strength between the CNTs and the supports is enhanced. At the same time, because MWCNTs grown by chemical vapor deposition (CVD) contain impurities such as carbonaceous materials and catalyst particles, we use different purification methods to treat the MWCNTS, and the effects of these purification methods on the field emission properties of the composite films are analyzed. A comparison of the field emission properties of the unpurified, calcined, calcined/centrifuged and acid-purified composite films shows that the calcined/centrifuged composite films have the best field emission performance.

An optical fiber sensor based on carboxymethyl cellulose/carbon nanotubes composite film for simultaneous measurement of relative humidity and temperature

In this paper, a carboxymethyl cellulose (CMC)/carbon nanotubes (CNTs) composite film was manufactured and used as a good humidity sensitive material to design a humidity and temperature simultaneous measurement sensor with simple structure, high sensitivity and fast response time. The sensor is constructed by a fiber Bragg grating (FBG) and then connected a hollow-core fiber (HCF) on the end face of which coated a CMC/CNTs hydrogel composite film. Through contrast experimental tests, the results show that the humidity sensitivity of the sensor with CMC film is 170.55 pm/%RH, while the sensitivity of the sensor with CMC/CNTs composite film is 230.95 pm/%RH. The humidity-insensitive FBG can be used to obtain accurate temperature information, and the temperature sensitivity is 26.35 pm/°C. This paper not only proves that CMC is an excellent humidity sensitive material for optical fiber sensors but also proves that carbon nanotubes can increase the humidity sensitivity of the hydrogel film effectively. This temperature and humidity simultaneous measurement sensor has a good application prospect.

Enhancement of image contrast for carbon nanotube and polymer composite film in scanning electron microscope.

Image contrast between carbon nanotubes (CNTs) and polytetrafluoroethylene (PTFE) in a CNT/PTFE composite film, which is difficult to obtain by conventional backscattered electron (BSE) imaging, was optimized to better elucidate the distribution of CNT in the film. Ultra-low landing energy condition (0.3keV in this study) was used to prevent specimen damage due to electron beam irradiation. Signal acceptance maps, which represent the distributions of energy and take-off angle, were calculated to evaluate the features of the signal detection system used in this study. SEM images of this composite film were taken under several sets of conditions and analyzed using these acceptance maps. CNT and PTFE in the composite film can be clearly distinguished with material and topographic contrasts using the BSE signal under optimized energy and take-off angle ranges, even at ultra-low landing energy conditions.

Rewritable bistable memory device in polymethyl methacrylate carbon nanotube composite films

The rewritable bistable memory characteristics have been studied in polymethyl methacrylate (PMMA) and carboxylated multi-walled carbon nanotubes (CNT) composite films. The sandwich structure FTO/PMMA + CNTs/Ag devices were prepared by spin coating and vacuum evaporation process. The device exhibited rewritable bistable resistive switching with switch-on voltage of ~ − 1.5 V, switch-off voltage of ~ 3.4 V, and a high ON/OFF ratio almost of 105. The rewritable behavior of the FTO/PMMA + CNTs/Ag device has been investigated by the endurance test, retention test, and the write-read-erase-reread multiple-cycle tests. The FTO/PMMA + CNTs/Ag device exhibited good retention performance for 2 × 105 s and underwent 104 read pulses. The conduction mechanism in ON state obeys Ohmic conduction; simultaneously, for OFF state, trap-limited space-charge limited conduction was discovered to be the dominant conduction mechanism.

Electrical, mechanical, and optical changes in MWCNT-doped PMMA composite films

In this study, we report the preparation of poly (methyl methacrylate)/multi-walled carbon nanotube (MWCNT) composite thin films by simple and efficient solution mixing and ultrasonic method and the electrical, optical, and mechanical characterizations. Scattered light intensity ( I sc), tensile modulus ( E), and surface conductivity ( σ) of these composites have increased with the addition of MWCNT into the composite. The observed behavior in electrical, optical, and mechanical properties of the poly (methyl methacrylate)/MWCNT composites was interpreted by site and classical percolation theory. The optical mechanical and electrical percolation thresholds of poly (methyl methacrylate)/MWCNT composites were determined as φ op = 3 wt%, φ m = 0 wt%, and φσ = 5 wt%, respectively. The optical ( t op), mechanical ( t m), and electrical ( t σ) critical exponents were calculated as 2.23, 0.43, and 0.11, respectively. Both the tensile modulus and tensile strength of poly (methyl methacrylate)/MWCNT composites were increased with increasing MWCNT content until it reaches to 10 wt%. However, above φ = 10 wt%, the mechanical properties of the composites were decreased due to the aggregation of MWCNTs, while the toughness does not show a significant change until φ = 10 wt% MWCNT content, whereas it was decreased above this value.

Highly Selective Simultaneous Detection of 1,4-Dihydroxybenzene and 1,2-Dihydroxybenzene Based on CdSe Quantum Dots-Multiwalled Carbon Nanotube Composite

A new electrochemical sensor based on CdSe quantum dots-multiwalled carbon nanotube composite film (CdSeQDs-cMWCNTs) was developed for highly selective simultaneous determination of 1,4-dihydroxybenzene (hydroquinone, HQ) and 1,2-dihydroxybenzene (catechol, CC) in 0.1 M phosphate buffer solution (pH 7.4). CdSeQDs-cMWCNTs/GCE exhibited two well-distinguished anodic peaks with large currents for simultaneous detection of HQ and CC in comparison with bare GCE and cMWCNTs/GCE. Furthermore, CdSeQDs-cMWCNTs/GCE has an excellent anti-interference ability for the detection of HQ and CC in the presence of some inorganic compounds and phenol derivatives. Under the optimized condition, CdSeQDs-cMWCNTs/GCE showed wide linear responses from $0.5~\mu \text{M}$ to $110~\mu \text{M}$ for HQ, and from $0.5~\mu \text{M}$ to $110~\mu \text{M}$ for CC, with the detection limits of $0.35~\mu \text{M}$ and $0.25~\mu \text{M}$ , respectively. CdSeQDs-cMWCNTs/GCE was successfully applied to the simultaneous determination of HQ and CC in tap water with satisfactory recovery.

Facile production of natural silk nanofibers for electronic device applications

Natural silk nanofibers (SNFs) have been attracted more attentions in flexible functional devices and biomaterials. However, its mass production and complex fabrication process remains challenging. In this study, we successfully developed a new physical-chemical strategy to fabricate natural SNFs with high yield (~87%). The natural SNFs performed an excellent dispersion in aqueous solution with uniform diameter (approximately 280 nm) and 10–30 μm length. The high-flexible natural SNFs/single-wall carbon nanotube (CNTs) composite films were prepared to evaluate their potential in electronic devices. The composite films exhibited remarkable dimensional stability, chemical durability, and Young's modulus (498.7 ± 64.4 MPa). Furtherly, the composite films also presented excellent electrical heating properties and potential utilities in electronics. These natural SNFs/CNTs composite films with high-mechanical and electrical features offer new starting materials for bioelectronics devices applications, such as conductive wire, electronical heater, and capacitor.

Functionalized Multi-Walled Carbon Nanotubes and Micro Cellulose Reinforced Poly (Vinyl Alcohol) Hybrid Composite Films: Characterization and Reprocessing Performance

The aim of this research paper was to investigate the synergetic effect of micro cellulose and multi-walled carbon nanotubes (MWCNTs) combination on physicochemical, mechanical and reprocessing performance of Poly (Vinyl Alcohol) hybrid composite films. The hybrid composite films production was carried out by the solution casting method, and the reprocessed films were produced using defective (torn, faulty) films from primary production by the same method. The combined use of MWCNTs and micro cellulose improved the hydrophobicity approximately 85% in ratio. After the reprocessing, decreased intensities of the peaks in the FTIR and Raman results confirmed the reduced molecular interaction between all components of the hybrid composite film, moreover, SEM and TEM revealed the negative defects such as agglomeration which caused mechanical strength decrease. The tensile strength of PVA hybrid composite films loaded cellulose/MWCNTs, reached 97 MPa strength value and elongation at break decreased to 33% according to the neat PVA film. The study results revealed that hybridization had a remarkable impact on improving characteristic properties of composite films and reprocessing process might have been compatible with solution casting method.

Development of voltammetric sensor based on polyimide-MWCNT composite membrane for rapid and highly sensitive detection of paracetamol

In this work, for low level detection of paracetamol (PA) a voltammetric sensor was obtained. Polyimide-multiwall carbon nanotube (PI-MWCNT) composite film was used for modification of platinum (Pt) electrode as selective membrane. Firstly, this PI-MWCNT film was synthesized with 2,5-diaminopyridine (DAP), 4,4′-oxydiphthalic anhydride (ODPA) and MWCNT as a reinforcement by thermal imidization technique. The morphology, micro and chemical structures of the obtained composite film were studied by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and thermal analysis techniques. Then, the paracetamol sensor was prepared via the modification of Pt electrode with prepared PI-MWCNT composite film. Pt electrode was modified by coating with prepared PI-MWCNT composite film. Modified Pt electrode was used as PA sensor due to its selective membrane property in the presence of interfering substances for the electrochemical detection of PA. Electrochemical behaviour of paracetamol at the polyimide film modified Pt electrode was obtained by differential pulse voltammetry (DPV) and cyclic voltammetry (CV) method. It has shown that the modified electrode exhibits remarkable repeatability and precision in analytical paracetamol response as compared with other modified paracetamol electrodes. Comparing the responses of modified electrode with the unmodified Pt electrode, selectivity, sensitivity and stable responses significantly enhanced. A linear calibration plot having a correlation coefficient of 0.997 was obtained in the concentration range from 0.3 to 1.8 mM paracetamol. A linear calibration plot for low concentration area having a correlation coefficient of 0.999 was obtained in the concentration range from 0.002 to 0.05 mM paracetamol. Detection limit (LOD) and quantitative limit (LOQ) for paracetamol detection of PI-MWCNT modified electrode were calculated as 0.002 mM and 0.006 mM respectively. In addition, the presented method was applied for determination of PA in commercial tablets. The recovery efficiency of the PI modified electrode was obtained range of 96% and 102% for three different tablets. As a result; a simple, rapid, low cost, repeatable method showing good accuracy and precision (99.4%) has been developed for the selective and sensitive determination of paracetamol by prepared PI-MWCNT composite film modified electrode.

Preparation of electrospun poly(acrylic acid)/multiwalled carbon nanotubes composite nanofiber for glucose detection

In this study, poly(acrylic acid) and multiwalled carbon nanotubes (PAA/MWNTs) composite nanofiber thin film was prepared on fluorine doped indium tin oxide–coated glass substrate through electrospinning method. The electrospun PAA/MWNTs nanofiber thin film was modified with layer–by–layer (LbL) self–assembled multilayers of glucose oxidase (GOD) and poly(dialyldimethylammoniumchloride) (PDADMAC) prior to employ for glucose detection. The obtained nanofiber thin film was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The prepared nanofibers thin film shows a good potential for detection of glucose at constant applied potential through an electrochemical method.

A novel flexible UV-cured carbon nanotube composite film for humidity sensing

A new flexible resistor-type humidity sensor was developed based on UV-cured carbon nanotube composite film as humidity-sensing material. Carbon nanotubes (CNTs) were firstly mixed with UV-curable resin via ball-milling. Simply by spin-coating of this mixture on flexible interdigitated electrode and subsequent UV-curing, a flexible humidity sensor based on UV-cured CNTs composite film was thus fabricated. With the utilization of UV-curing technology, this fabricating strategy is rather simple, highly efficient (accomplished in several minutes), cost-effective, and environmental-friendly (no organic solvent). The effect of the CNTs content, the nature of the UV-curable resin as well as their ratios on the humidity-sensing performance was systematically investigated. Under optimized conditions, the UV-cured CNTs composite film showed remarkable sensing performance over a wide humidity span from 6% to 84%. In addition, the as-prepared CNTs composite film exhibited small hysteresis and fast response. Moreover, good repeatability and long-term stability was demonstrated. This work offers a novel, economical and promising way to fabricate humidity sensors considering the facile, efficient and green preparation strategy and outstanding sensing properties.

A flexible NO2 gas sensor based on polypyrrole/nitrogen-doped multiwall carbon nanotube operating at room temperature

A flexible NO2 gas sensor based on a polypyrrole/nitrogen-doped multi-walled carbon nanotube (PPy/N-MWCNT) composite film was successfully prepared on PI substrates using a combined in situ self-assembly and annealing treatment method. After annealing at 350 °C, the gas sensor exhibited a high response of 24.82% ((Rg−Ra)/Ra×100%) under 5 ppm of NO2, which is 44.12 times greater than that of the unannealed sensor. The PPy/N-MWCNT gas sensor exhibited excellent repeatability, remarkable selectivity, good long-term stability, and acceptable flexibility. Furthermore, the effect of the relative humidity on the gas sensing properties was examined. The excellent gas sensing performances of the sensor were attributed to the enriched adsorption sites due to degradation of the amount of stacked PPy structures on the surface of the N-MWCNTs after the annealing treatment. The results demonstrated that PPy/N-MWCNT composite films are highly promising for potential applications in the field of NO2 gas sensing.

A flexible tactile sensor integrated with carbon black/carbon nanotube composite film and flexible printed circuit

In this study, two kinds of composite films, carbon black (CB) and carbon nanotube (CNT) composite films, were fabricated and integrated with flexible printed circuit (FPC) for the flexible tactile sensor. CB and CNT with high compressive strength and low resistivity were immersed into the tissue paper as the sensing materials. The flexible tactile sensors were fabricated by sandwiching the CB/CNT composite film with FPC between two thin polydimethylsiloxane sheets. The tactile sensor is operated by the contact resistance change between CB/CNT composite film and FPC electrode by the different applied force. The measurements of the sensitivity, response time and stability of the fabricated tactile sensors were carried out. The fabricated CB composite film tactile sensor exhibits the sensitivity of 5.05 × 10−2 kPa−1 in the range below 20 kN m−2, the response time of 10 ms, and with the high stability of the loading and unloading pressure.

Nanowire Array-Coated Flexible Substrate to Accommodate Lithium Plating for Stable Lithium-Metal Anodes and Flexible Lithium-Organic Batteries.

Although lithium metal is an ideal anode with high theoretical capacity, Li dendrite formation and volume change have limited its application. We report a vertical polyaniline nanowire-coated carbon nanotube (CNT/PANI) composite flexible electrode on which Li could be homogeneously deposited to obtain a CNT/PANI@Li anode. In the composite, CNT/PANI acted as a host matrix with well-distributed Li ion flux attributed to high electroactive surface area, thereby effectively suppressing the Li dendrite. Compared with the pure CNT electrode, the CNT/PANI electrode presented low overpotential and stable long-term cycling with much less fluctuant stripping/plating profiles. The potential application of CNT/PANI@Li in all-flexible full cells was demonstrated by combining flexible organic poly(2,5-dihydroxyl-1,4-benzoquinonyl sulfide)/carbon nanotube (PDHBQS/CNT) composite films, in which the cathode achieves an eminent performance of 120 mA h g-1 at 50 mA g-1. Furthermore, pouch batteries with good flexibility were tested successfully, which demonstrated a promising future for all-flexible and high-performance Li-metal batteries.

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.