Polyaniline Carbon Nanotubes Research Articles

Polypyrrole/Carbon Nanotube and Polyaniline/Carbon Nanotube Nanocomposites: Synthesis and Characterization

The aim of this research work is to investigate the preparation of polypyrrole/carbon nanotube (PPy/CNT) and polyaniline/carbon nanotube (PAn/CNT) nanocomposites in aqueous media by chemical polymerization of pyrrole and aniline in presence of ferric chloride and potassium iodate as an oxidants, respectively. The products were investigated in terms of morphology, chemical structure and thermal stability with scanning electron microscope (SEM), Fourier transform infrared (FTIR) and thermal gravimetric analysis (TGA) methods, respectively. The results indicate that properties of products are dependent on nanocomposite structure. Also, it was found that PAn/CNT and PPy/CNT nanocomposites show remarkable improved thermogravimetric stability by comparison with the PAn and PPy homopolymers.

Study on the Infrared Property of Polyaniline/Multi-Wall Carbon Nanotube Composite

Composites of polyaniline (PANI) and multi-wall carbon nanotube (MWNT) were synthesized by in situ polymerization with different MWNT content. The composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The SEM photos indicated that a mass of MWNT was enchased into PANI matrix when the content of MWNT was low. With the MWNT content increases, the surface of MWNT was covered with PANI and formed the core-shell structure. From the FT-IR spectroscopy of the composites, it can be confirmed that there was interaction between PANI and multi-wall carbon nanotube. The composites had better thermal stability than pure PANI. Infrared emission property of the composites was analyzed by an IR-II infrared emissivity instrument and an infrared camera. It was found that infrared emission of the composites was lower than pure PANI in all wavelength range and infrared emissivity value was related to the content of MWNT in the composites.

Carbon nanotube-polyaniline nanohybrids: Influence of the carbon nanotube characteristics on the morphological, spectroscopic, electrical and thermoelectric properties

We report on the fabrication of polyaniline (PANI)/carbon nanotube (CNT) nanohybrids using a novel approach of CNT-templated polymerization process. The physical properties of the nanohybrids can be tuned by keeping a constant amount of CNTs and changing their nature, i.e., using single-walled, multiple-walled, oxidized or unoxidized. SEM investigations evidenced fibrous morphology in all PANI/CNT hybrids with nanometer-sized diameters. Spectroscopic (UV–vis, IR and Raman) analyses of the nanocomposites evidenced good π–π interactions between PANI rings and CNTs. X-ray crystallography supports the presence of nanocrystalline domains at 2θ ∼6.5°. Electrical and thermoelectric properties of nanohybrids containing: (a) unoxidized MWNTs or (b) oxidized SWNTs or oxidized MWNTs are reported for the first time. In the series of samples studied, the PANI/unoxidized SWNTs provided the most promising electrical (conductivity: σ=530Scm−1) and thermoelectric characteristics (seebeck coefficient: S=33μVK−1 and power factor: PF=0.6μWm−1K−2).

Influence of Ammonium Hydroxide Treatment on Structural Stability of Polyaniline/Multi–Walled Carbon Nanotube Nanocomposites

The composites consisting of multi–walled carbon nanotubes (MWCNTs) core and polyaniline (PANI) shell were prepared in aqueous solution of hydrochloric acid, and then a de–doping process was achieved through a simple ammonium hydroxide (NH4OH) treatment. The influences of NH4OH treatment on the morphology, microstructure and thermal stability of the as–prepared composites were studied. It is found that after the removal of hydrochloric acid (HCl) as a volatile dopant and the low molecular weight components, structural stability of the treated composite could be achieved, leading to a significant enhancement on thermal properties.

Electrochemical detection of carbamate pesticides in fruit and vegetables with a biosensor based on acetylcholinesterase immobilised on a composite of polyaniline–carbon nanotubes

A sensitive electrochemical acetylcholinesterase (AChE) biosensor was successfully developed on polyaniline (PANI) and multi-walled carbon nanotubes (MWCNTs) core–shell modified glassy carbon electrode (GC), and used to detect carbamate pesticides in fruit and vegetables (apple, broccoli and cabbage). The pesticide biosensors were applied in the detection of carbaryl and methomyl pesticides in food samples using chronoamperometry (CA). The GC/MWCNT/PANI/AChE biosensor exhibited detection limits of 1.4 and 0.95μmolL−1, respectively, for carbaryl and methomyl. These detection limits were below the allowable concentrations set by Brazilian regulation standards for the samples in which these pesticides were analysed. Reproducibility and repeatability values of 2.6% and 3.2%, respectively, were obtained in the conventional procedure. The proposed biosensor was successfully applied in the determination of carbamate pesticides in cabbage, broccoli and apple samples without any spiking procedure. The obtained results were in full agreement with those from the HPLC procedure.

Portable cholesterol detection with polyaniline-carbon nanotube film based interdigitated electrodes

Polyaniline-carboxylic multiwalled carbon nanotubes composite film (PANi-MWCNT) has been polymerized on the surface of interdigitated platinum electrode (fabricated by MEMS technology) which was compatibly connected to Autolab interface via universal serial bus (USB). An amperometric biosensor based on covalent immobilization of cholesterol oxidase (ChOx) on PANi–MWCNT film with potassium ferricyanide (FeCN) as the redox mediator was developed. The mediator helps to shuttle the electrons between the immobilized ChOx and the PANi-MWCNT electrode, therefore operating at a low potential of −0.3 V compared to the saturated calomel electrode (SCE). This potential precludes the interfering compounds from oxidization. The bio-electrode exhibits good linearity from 0.02 to 1.2 mM cholesterol concentration with a correlation coefficient of 0.9985.

Multi-wall carbon nanotube-polyaniline biosensor based on lectin–carbohydrate affinity for ultrasensitive detection of Con A

In this paper, a novel method for detecting concanavalin A (Con A) was developed based on lectin–carbohydrate biospecific interactions. Multi-wall carbon nanotube-polyaniline (MWNT–PANI) nanocomposites, synthesized by in situ polymerization, were chosen to immobilize d-glucose through the Schiff-base reaction. The immobilized d-glucose showed high binding sensitivity and excellent selectivity to its target lectin, Con A. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM) and atomic force microscopy (AFM) were applied to characterize the assembly process of the modified electrode. Due to the high affinity of Con A for d-glucose and high stability of the propounded sensing platform, the fabricated biosensor achieved ultrasensitive detection of Con A with good sensitivity, acceptable reproducibility and stability. The changes of response current were proportional to the Con A concentrations from 3.3pM to 9.3nM, with a detection limit of 1.0pM. Therefore, the combination of MWNT–PANI nanocomposites and the special binding force between lectin and carbohydrate provides an efficient and promising platform for the fabrication of bioelectrochemical devices.

Synthesis of carbon nanotube–Poly aniline nano composite and evaluation of electrochemical properties

In this paper, carbon nanotube (CNT)- polyaniline (PANI) nanocomposites were developed from in situ polymerization of aniline. The CNT can be prepared by either acid treatment of CNTs suspension by grafting functional groups to CNTs surface. In this study, CNT and acid treatment CNT was used for preparation of nanocomposite. The PANI-CNT nanocomposite was characterized by FTIR, SEM. CNT can be prepared by either acid treatment of CNTs suspension to make them ionized or by grafting functional groups to CNTs surface. In addition, the electrochemical measurements such as cyclic voltametric (CV) curves showed that the conductivity of the obtained nanocomposite increased. Therefore, the supercapacitors behavior of polyaniline improves with adding CNT especially with acid treatment CNT.

Effectively enhanced sensitivity of a polyaniline–carbon nanotube composite thin film bolometric near-infrared sensor

The polyaniline–carbon nanotube composite thin film bolometric near-infrared sensor exhibited more than a two orders of magnitude sensitivity enhancement over both the polyaniline thin film and carbon nanotube network NIR sensor. We also investigated the mechanism of the effectively enhanced sensitivity of the composite material and demonstrated that it is a synergistic effect due to the higher heat generation of carbon nanotubes and higher temperature coefficient of resistance of polyaniline.

Increased response/recovery lifetimes and reinforcement of polyaniline nanofiber films using carbon nanotubes

We have prepared high surface area, conductive, mechanically robust, responsive polyaniline–carbon nanotube composite films. These were produced by filtration from dilute dispersions of polyaniline nanofibers and single-walled carbon nanotubes. Unlike polyaniline alone, these composites are mechanically stable, maintain large intractable surfaces and exhibit greatly enhanced response/recovery behavior to changes in their local environment. This is illustrated by exposing the films to ammonia.

Synthesis and electrochemical properties of composites based on carbon nanotubes and polyaniline

composites made of polyaniline and multiwalled carbon nanotubes have been electrochemically synthesized. The modification of multiwalled carbon nanotubes by a salt of phenyldiazonium significantly increases the redox currents of the polyaniline matrix in the composite. As a result of modification, the conformational state of polyaniline macrochains changes, leading to changes in the morphology, structure, and chemical composition of the composite.

Structural assembly effects of Pt nanoparticle–carbon nanotube–polyaniline nanocomposites on the enhancement of biohydrogen fuel cell performance

In this work, we designed various polyaniline (PANI) nanocomposites with platinum (Pt) nanoparticle-decorated multi-walled carbon nanotubes (MWCNTs), employed them as anodic catalysts, and studied their structural assembly effects with regard to enhancing biohydrogen fuel cell performance. Of two proposed structures, the PANI/Pt/MWCNTs multilayer nanocomposites showed superior electrocatalytic activities in the hydrogen oxidation reaction and in fuel cell power density relative to the Pt/MWCNTs@PANI core–shell design. These enhancements were attributed to the active interface formed between the Pt nanoparticles and polyaniline nanofibers, where the higher electronic and ionic conductivities of the thin PANI nanofiber layers in contact with Pt active sites were better than with the PANI bound Pt/MWCNTs. We also investigated the change in the electronic state of the composites and the charge-transfer rate caused by varying the structural assembly. Finally, the role of each catalyst component was examined to understand its individual effect on fuel cell performance and to understand its structural assembly effect on enhanced power density.

Electrodeposition of polyaniline–carbon nanotubes composite films and investigation on their role in corrosion protection of austenitic stainless steel by SNIFTIR analysis

Composite films of polyaniline (PANI) and carbon nanotubes (CNTs) were prepared by electrochemical co-deposition from solutions of the corresponding monomer containing two different kinds of CNTs. The first type was commercial (diameter = 110–170 nm, length = 5–9 μm) and the second one was home-made (diameter = 30 nm, length = 5–20 μm). The electrochemical behaviour of PANI–CNTs composite films was investigated with Cyclic Voltammetry and the surface morphology was analysed by Scanning Electron Microscopy (SEM). Subtractively Normalised Interfacial FT-IR procedure was used to investigate the presence of corrosion products when the films were deposited on stainless steel substrates and exposed to acid environment. The spectral investigations were utilised to understand the role of composite films in the corrosion protection and to discriminate the best performance CNTs.

Effect of Temperature on the Electrical and Gas Sensing Properties of Polyaniline and Multiwall Carbon Nanotube Doped Polyaniline Composite Thin Films

In the present work we have reported the effect of temperature on the gas sensing properties of pure Polyaniline (PANI) and Multiwall carbon nanotube (MWNT) doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and MWNT doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline using ammonium persulfate in an acidic medium. The thin sensing film of chemically synthesized PANI and MWNT doped PANI composite were deposited onto finger type Cu-interdigited electrodes using spin cast technique to prepared chemiresistor type gas sensor. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature, MWNT doped PANI composite sensor shows higher response value and sensitivity with good repeatability in comparison to pure PANI thin film sensor. It was also observed that both PANI and MWNT doped PANI composite thin film based sensors showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

Synthesis of Multishell Carbon Nanotube Composites via Template Method

Multishell nanotubes of polyaniline and carbon were synthesized via a template approach. A thin layer of MnO2 coated on carbon nanotubes acts as a reactive template for the consequent formation of the polyaniline coating. The polyaniline-carbon nanotubes show enhanced dispersibility in water and can be possibly used as a functional material of electrochemical capacitors with improved performance. The general method operates by coating carbon nanotubes on functional materials such as poly (3,4-ethylenedioxythiophene), polypyrrole, silica, and carbon.

Polyaniline/MWCNT Nanocomposite Based Hydrogen Sensor Operating at Room Temperature

A nanocornposite of polyaniline (PANI) and multiwall carbon nanotubes (MWCNT) has been synthesized and investigated as a sensing material for hydrogen gas at room temperature. The PANI/MWCNT nanocomposite was prepared by in situ chemical polymerization. The nanomaterial characterization was conducted through Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). From these data it was concluded that the PANI formed conformal layer with thickness of approximately 7 nm aligned to the outer layer of the MWCNT. A hydrogen sensor was developed by airbrushing the solution over the surface of heated conductometric transducer. The sensor was tested towards different concentrations of hydrogen gas at room temperature. At 1% of H(2) an increase in the sensing film resistance of 112 Omega was observed. The sensor maintained its stable baseline and repeatability during the testing period which makes it useful for commercialization purposes.

An amperometric oxalate biosensor based on sorghum oxalate oxidase bound carboxylated multiwalled carbon nanotubes–polyaniline composite film

A highly sensitive, specific and rapid electrochemical oxalate biosensor was constructed by covalently immobilizing sorghum leaf oxalate oxidase on carboxylated multiwalled carbon nanotubes and conducting polymer, polyaniline nanocomposite film electrodeposited over the surface of platinum (Pt) wire using N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry. The modified electrode was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrophotometry. The optimized oxalate biosensor showed linear response range of 8.4–272 μM with correlation coefficient of 0.93 and rapid response within 5 s at a potential of 0.4 V vs Ag/AgCl. The sensitivity was approximately 0.0113 μA/μM with a detection limit of 3.0 μM. Proposed oxalate biosensor was successfully applied to human urine sample.

The carbon nanotubes-polyaniline composites and their effect on catalytic properties of deposited catalysts

Composites of functionalized single-wall carbon nanotubes and polyaniline are deposited onto electrodes by in situ electrochemical polymerization. Their electrochemical behavior and differential capacitance are studied by cyclic voltammetry, electrochemical impedance spectroscopy, and chronovoltamperometry. The differential capacitance of the composite electrode exceeds that of pure polyaniline film deposited onto electrode, which can be explained by the nanotubes’ loosening effect on the polyaniline structure. The composite-electrode capacitance is as large as 1000 F g−1 or higher. Thus obtained composite films were used as a support for deposited platinum-ruthenium catalyst. The Pt-Ru structure and catalytic properties in the methanol oxidation reaction are studied. It is shown that the specific current of methanol oxidation at Pt-Ru is larger by a factor of 7–15 than those measured when pure polyaniline, pure carbon nanotubes, or standard Vulcan XC-72 carbon black are used as supports. It is found that the catalytic activity is the same for all studied supports, provided the current is reduced to the unit of Pt-Ru true surface area. Thus, the observed large catalytic effect is associated with the structure and high dispersivity of the electrodeposited metals incorporated to the single-wall carbon nanotubes-polyaniline composite.

Fabrication of a Self-Powered Glucose Sensor Using Carbon Nanotube-Based Nanomesh and Direct Electron Transfer: A Prospective Approach for Energy Harvesting in Sensor Networks

This study demonstrates a new design concept of a glucose/oxygen biofuel cell (BFC) involving direct electron transfer between the active sites of the enzyme, glucose oxidase (GOx), and the electrode surface modified with multiwall carbon nanotube―polyaniline nanomesh (MWNT@PANI(NM)). GOx and catalase were immobilized independently into MWNT@PANI(NM) to fabricate the bioanode and biocathode, respectively, for the glucose BFC. The MWNT@PANI(NM)/GOx bioanode exhibited excellent electrochemical sensor characteristics towards glucose in phosphate buffer (pH 7) over a wide concentration range (1―30 mM) with a high sensitivity (1.66 μA/mM). The fabricated glucose BFC, MWNT@PANI(NM)/GOx//MWNT@PANI(NM)/Cat, provides a maximum power density of 35.7 μW/cm ―2 at a potential that is close to the formal potential of GOx. Thus, MWNT@PANI(NM)/GOx functions as a mediator-less bioanode for the generation of electrical power. The present investigation conceptually provides a platform for resolving limitations that are related to the energy harvesting and power management issues in electronic healthcare devices such as wireless body area network (WBAN). We presume that the present work would be beneficial in resolving restrictions on the limited capacity of energy resources for the sensors in a WBAN.

Preparation and electrochemical performance of polyaniline-based carbon nanotubes as electrode material for supercapacitor

Nitrogen-containing carbon nanotubes (CNTs) with open end and low specific surface area were prepared via the carbonization of polyaniline (PANI) nanotubes synthesized by a rapidly mixed reaction. On the basis of analyzing the morphologies and structures of the original and carbonized PANI nanotubes, the electrochemical properties of PANI-based CNTs obtained at different temperatures as electrode materials for supercapacitors using 30 wt.% aqueous solution of KOH as electrolyte were investigated by galvanostatic charge/discharge and cyclic voltammetry. It was found that the carbonized PANI nanotubes at 700 °C exhibit high specific capacitance of 163 F g −1 at a current density of 0.1 A g −1 and excellent rate capability in KOH solution. Using X-ray photoelectron spectroscopy measurement the nitrogen state and content in PANI–CNTs were analysed, which could play important roles for the enhancement of electrochemical performance. When the appropriate content of nitrogen is present, the presence of pyrrole or pyridone and quaternary nitrogen is beneficial for the improvement of electron mobility and the wettability of electrode.