Synthesized Polyaniline Films Research Articles

Performance of chemically synthesized polyaniline film based asymmetric supercapacitor: Effect of reaction bath temperature

Performance of chemically synthesized polyaniline film based asymmetric supercapacitor: Effect of reaction bath temperature

A New Method to Prepare Stable Polyaniline Dispersions for Highly Loaded Cathodes of All-Polymer Li-Ion Batteries.

A new method for the preparation of polyaniline (PANI) films that have a 2D structure and can record high active mass loading (up to 30 mg cm-2) via acid-assisted polymerization in the presence of concentrated formic acid was developed. This new approach represents a simple reaction pathway that proceeds quickly at room temperature in quantitative isolated yield with the absence of any byproducts and leads to the formation of a stable suspension that can be stored for a prolonged time without sedimentation. The observed stability was explained by two factors: (a) the small size of the obtained rod-like particles (50 nm) and (b) the change of the surface of colloidal PANI particles to a positively charged form by protonation with concentrated formic acid. The films cast from the concentrated suspension were composed of amorphous PANI chains assembled into 2D structures with nanofibrillar morphology. Such PANI films demonstrated fast and efficient diffusion of the ions in liquid electrolyte and showed a pair of revisable oxidation and reduction peaks in cyclic voltammetry. Furthermore, owing to the high mass loading, specific morphology, and porosity, the synthesized polyaniline film was impregnated by a single-ion conducting polyelectrolyte-poly(LiMn-r-PEGMm) and characterized as a novel lightweight all-polymeric cathode material for solid-state Li batteries by cyclic voltammetry and electrochemical impedance spectroscopy techniques.

Structural characteristics and opto-electrical properties of in-situ synthesized polyaniline films

In the present study, polyaniline (PAni) thin films have been deposited on glass substrates by in-situ chemical polymerization method using simple dip-coating technique and their opto-electrical properties have been studied. The structure of deposited films have been analysed with Fourier transform infrared (FTIR) and Raman spectroscopic techniques to investigate the effect of deposition times on the conjugation length, polaron/bipolaron concentrations and other molecular structure conformations. FTIR and Raman spectroscopy studies reveal increase in both the conjugation length and the polaron/bipolaron carrier concentration with increasing deposition time of the prepared PAni films. The optical properties and optical band-gap of the deposited films have been estimated through UV–visible spectroscopy. The optical band-gap of the deposited films has been found to decrease from 3.31 eV to 3.13 eV with increase in deposition time from 1.5 h to 2.5 h, and further it has been increased slightly to 3.19 eV for the PAni film deposited for 3 h. The electrical conductivity of the deposited films has been found to increase with decrease in optical band gap. The parameters estimated from FTIR, Raman, UV–visible spectroscopy and electrical measurements are in good agreement with each other. It has been observed that the optical and electrical properties of the deposited films depend on the conjugation length of PAni. The polymerization time of 2.5 h has been found to be optimum for obtaining PAni thin films with good electrical conductivity and low optical band gap.

Effect of sodium dodecyl sulfate and carbon particles/nanotubes on electrodeposition of polyaniline from oxalic acid solution

The effect of sodium dodecyl sulfate and carbon particles/nanotubes on the electropolymerization of aniline from oxalic acid solution onto a graphite electrode was investigated. The morphology and chemical structure of the as-synthesized polyaniline films were studied by means of SEM, XPS, NEXAFS, FTIR, and Raman spectroscopy. The electrochemical characteristics of the films were also analyzed in sulfuric acid solution. It has been shown that in the presence of sodium dodecyl sulfate, the polymerization rate increases significantly. In the synthesized polyaniline films, all imine groups and most of amine groups are protonated, with dodecyl sulfate ions being intercalated in the polymer. In the presence of sodium dodecyl sulfate, plate-like polyaniline forms large agglomerates with an extended surface and high electrochemical activity. It has been shown that the electrodeposition carried out in the presence of sodium dodecyl sulfate and suspended activated graphite particles or carbon nanotubes favors the formation of composite coatings with high specific capacitance.

Synthesis and Characterization of Polyaniline Doped with HCl, H2SO4 and PVA as Secondary Dopant for Toxic Gas (Ammonia) Sensor

In the present work, by simple chemical polymerization technique, H2SO4 (Sulphuric acid), HCl (Hydorochloric acid), poly (vinyl sulphonic acid) and PVA on PMMA substrate have been successfully synthesized PANI films for ammonia gas sensing. The polyaniline (PANI) thin films were synthesized by simple chemical polymerization technique, H2SO4 (Sulphuric acid), HCl (Hydorochloric acid), poly (vinyl sulphonic acid) and PVA on PMMA substrate as dopant. The ratio of monomer, dopant, and oxidant and reaction temperature has been optimized for better surface morphology of the synthesized PANI film. Scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), and Fourier transforms infrared spectroscopy (FTIR) is used for characterization of synthesized thin films of PANI. Also the response of the films towards ammonia gas (in the range from 20 to 250 ppm) is carried out. It was observed that these process parameters i.e. ratio of monomer, oxidants, doping acids, and deposition time and reaction temperature has major effect on the surface morphology of PANI film. The synthesized thin film structures of polyaniline doped with HCl, H2SO4 and PVA on polymethylmethacrylate (PMMA) shows the response to ammonia gas sensing in the range 20ppm-250ppm and can be used for ammonia sensing application.

Polyaniline films for efficient removal of aromatic acids from water

Adsorbents in the form of powders are commonly used to filtrate organic compounds in waters. However, this technique requires the separation of the solid phase from the solution after adsorption experiments. Here we propose the use of films as adsorbents. We synthesized polyaniline films by chemical oxidative polymerization of aniline on red ceramic brick. This film was tested to remove trimellitic, hemimellitic and pyromellitic acids as model molecules of the biodegradation of aquatic humic substances. We evaluated the effect of pH, contact time and initial concentration. Our results show that optimal adsorption conditions required 45 min of solid/liquid contact at pH 7 and an initial concentration of 20 mg/l. The maximum adsorption capacities for hemimellitic, trimellitic and pyromellitic acids are 154.83 for hemimellitic acid, 161.88 for trimellitic acid and 175.26 mg/g for pyromellitic acid. The adsorption efficiency of the polyaniline film decreased only by 13 % after four cycles. Overall, we conclude that polyaniline films are promising separable adsorbents compared to conventional adsorbents for removal of aromatic polycarboxylic acids from water.

Studies on morphology of polyaniline films formed at liquid–liquid and solid–liquid interfaces at 25 and 5 °C, respectively, and effect of doping

It is well accepted that the morphology of the nanomaterials has great effect on the properties and hence their applications. Therefore, morphology of materials has become a focus of research in the scientific world. The present study shows that interfacial polymerization and subsequent self-assembly provides a control over the morphology, nanorod/nanosheet, of polyaniline (PANI) films synthesized by liquid–liquid interface reaction technique and solid–liquid interface reaction technique. The synthesized PANI films and its particulate structure are characterized by using various spectroscopic techniques such as UV–visible, ATR-IR, Raman and XPS. The study confirmed the formation, the structure, the size and shape of particles and morphology of PANI by using analytical techniques namely, SAED, SEM and TEM. An important observation is that doping with HCl significantly improves the nanorod formation at the interface. The doped PANI electrode exhibits a higher area with rectangular shape in CV cycle and better cycle stability when compared with the performance of undoped PANI films. We believe that the results of these studies can give valuable leads to manoeuvre formation of PANI films with desired morphology for various applications.

Electrochemical oxidation of aniline on the surface of an amorphous metal alloy Al87Ni8Y5

The oxidation of aniline is studied by the potentiodynamic method on an electrode of an amorphous metallic alloy Al87Ni8Y5 and the results are compared with the analogous data on a polycrystalline aluminum electrode. The aniline oxidation and, correspondingly, the polyaniline deposition are shown to proceed more actively on the contact side of the amorphous metal alloy Al87Ni8Y5 electrode. The morphology of synthesized polyaniline films is studied on both sides of the working electrode. It is found that the polyaniline layer structure is to the large extent granulated on the contact side and smooth on the external side.

Enzymatically synthesized polyaniline film deposition studied by simultaneous open circuit potential and electrochemical quartz crystal microbalance measurements

The chemical and enzymatic deposition of polyaniline (PANI) films by in situ polymerization was studied and the resulting films were characterized. The film formation and polymerization processes were simultaneously monitored by the evolution of the open circuit potential and quartz-crystal microbalance measurements. Different substrates, such as Indium-Tin oxide electrodes and gold-coated quartz-crystal electrodes were used as substrates for PANI deposition. Electroactive PANI films were successfully deposited by in situ enzymatic polymerization at low oxidation potential. The electrogravimetric response of the enzymatically deposited PANI film was studied by cyclic voltammetry in monomer-free acidic medium. The morphology of the films was observed by scanning electron microscopy, revealing a granular structure in enzymatically deposited PANI. The PANI films were also characterized by thermogravimetric analysis, electrochemical impedance spectroscopy, and X-ray photoelectron and Fourier-transformed infrared spectroscopy. The simultaneous use of quartz crystal microbalance and open circuit potential is presented as a very useful technique to monitor enzymatic reactions involving oxidoreductases.

Enhanced field emission from polyaniline nano-porous thin films on PET substrate

Conducting polyaniline (PANI) nano-porous film synthesized on PET substrate by vapor deposition technique has shown excellent field emission behaviour and the emission was further enhanced by conditioning with vacuum electric discharge. Detailed study on the field emission for PANI films synthesized with different oxidant concentration was performed. Measurement was also carried out for different anode-sample separation. Turn-on field as low as 0.5 V/μm and emission current density as high as 20.96 mA/cm 2 was observed. The field enhancement factors were found to be in the range of 1192–3782. The films were characterized with X-ray diffraction, UV–vis spectroscopy, Fourier transformed infrared spectroscopy, scanning electron microscopy and also atomic force microscopy. The synthesized PANI films may be a promising material for field emission devices and also for plastic display industry.

Characterization of Nanostructure and Cell Compatibility of Polyaniline Films with Different Dopant Acids

Polyaniline (PANi) films were prepared by direct polymerizing deposition with four different kinds of acids as dopants or were prepared by a casting method on the surface of a polytetrafluoroethylene substrate. The properties of PANi films were characterized using atomic force microscopy, electrical conductivity measurements, and water contact angle measurements. Unlike the casting PANi film, experimental results indicated that the synthesized PANi films had a similar nanostructure as that of average nanoparticles (approximate diameter of 30-50 nm). To investigate the potential usefulness of PANi films in biomedical applications, we also studied their biocompatibility through the adhesion and proliferation properties of PC-12 pheochromocytoma cells. All the films were found to be biocompatible and allowed cell attachment and proliferation. However, the synthesized films have a much higher ability for cell adhesion than the casting film. After 4 days of culture on different PANi films, the cells formed more confluent monolayers on the synthesized PANi films than on the casting films. These results demonstrate that the PANi films could be used to culture neurotic cells and that their surface architecture on the nanoscale may affect cell function such as attachment and proliferation.

Application of polyaniline for the reduction of toxic Cr(VI) in water

Various oxidation states of polyaniline, as film and powder, were used for reduction of highly toxic Cr(VI) to less toxic Cr(III) ion. The effects of various parameters such as synthesis method, physical and oxidation state of polyaniline, film thickness, solution pH and initial Cr(VI) concentration on the kinetics and efficiency of reduction process were investigated. Results showed that a very broad concentration range of Cr(VI) solutions (10–10 5 ppb by emeraldine base and 10–10 6.5 ppb by leucoemeraldine) can be efficiently (>98%) reduced by polyaniline as film or powder. Cr(VI) solutions with concentrations higher than these ranges were caused to the overoxidation and degradation of polymer. Decreasing of solution pH, increased the kinetics and performance of reduction process, but lowered the Cr(VI) concentration ranges caused the overoxidation and degradation of the polymer. Higher reduction efficiencies were obtained for thicker electrochemically synthesized polyaniline films and for thinner chemically prepared polyaniline free standing films. The ability or capacity of various forms of polyaniline in Cr(VI) reduction was evaluated as the milligrams of Cr(VI) reduced by one gram of various forms of polyaniline.

Potentiometric study of polyaniline film synthesized with various dopants and composite-dopant: A comparative study

The potentiometric study of polyaniline (PANI) film synthesized with dopants viz. polyvinyl sulfonic acid (PVS),p-toluene sulfonic acid (p TS), dodecyl benzene sulfonic acid (DBS) and composite-dopants viz. PVS-p TS and PVS-DBS, has been carried out. The synthesized PANI films were characterized by electrochemical technique, UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and conductivity measurement. It was found that the PANI doped with PVS gives good electrochemical properties, conductivity as well as surface morphology as compared to p TS and DBS, whereas in composite dopants the PANI doped with PVS-pTS gives good polymer matrix as compared to PVS-DBS.

Effects of Polymerization Media on the Nanoscale Conductivity and Current−Voltage Characteristics of Chemically Synthesized Polyaniline Films

A current sensing atomic force microscope (CS-AFM) was used to probe the conducting homogeneity and band structures of fully doped polyaniline (PANI) films prepared from in situ chemical polymerization/deposition of aniline on indium tin oxide in various inorganic acids. The charge transport properties of PANI films depend on the film thickness as well as polymerization medium. Fluctuations in conductivity are observed on all acid-doped PANI films and the conducting homogeneity was dependent on the film thickness: the conductivity of thick film is more uniform. The current-voltage (I-V) characteristics of all thick (>200 nm) films displayed a metal-like behavior and conductivity as high as 40 S/cm was detected in high conducting regions of film thicker than 400 nm. Whereas thin (<120 nm) films revealed insulating, semiconducting, and semimetal conducting, wide distribution in conductivity and interband distances (estimated from the I-V ordI/dV-V curves) was found. The interband distances is 0-1.35, 0-1.0, and 0-0.78 eV for thin PANI film prepared from HCl(aq), HClO(4)(aq), and H2SO4(aq), respectively. PANI film (260 nm) prepared from H2SO4(aq) revealed fiberlike morphology, and compared to PANI films prepared from HCl(aq) and HClO4(aq) with similar thickness, it has higher average nanoscale conductivity but lower bulk conductivity. This result could be direct evidence which supports that the bulk conductivity of PANI depended on the carriers hopping between the conducting domains.

Monodispersed redox submicrometer particles created by polyaniline-coated polystyrene latex

A spherical electroactive particle, 65 nm in diameter, was synthesized by coating a sulfonated polystyrene latex particle with the electric conducting polymer (polyaniline). It was suspended in acidic solution, and hence its electrochemical properties were obtained by the usual electrochemical techniques. The following behavior is predicted: when the particle comes into contact with the electrode by diffusion, the polyaniline layer takes the same potential as the electrode owing to the electric conduction; consequently, the whole polyaniline layer reacts at the electrode simultaneously as if the number of electrons transferred was very large. The anodic voltammetric peak, due to the oxidation of the radical cation to the dication, was controlled by diffusion of the particle. The diffusion coefficient obtained by the limiting current was half the value evaluated from the Stokes–Einstein relation. The steady-state voltammogram at a microelectrode and a rotating disk electrode showed a −0.2 V potential shift from the surface waves of the electrochemically synthesized polyaniline film, probably due to stabilization of the radical cation in the colloidal form. The number of the charge relevant to the electrode reaction was n=4.2×105, determined not only by the bulk electrolysis, but also by the analysis of chronoamperometric curves. The overall process is diffusion of the particle composed of n redox sites, followed by n parallel sluggish charge-transfer reactions.

Comparison of Chemically and Electrochemically Synthesized Polyaniline Films

The electrochemical growth of thick (∼2 mm) emeraldine, polyaniline films from solutions containing 2 M and 0.25 M aniline is demonstrated. Electrochemically and chemically prepared films, cast from formic acid solutions, are compared. The combination of electrochemical results with Fourier transform infrared spectroscopic data indicates that pure and homogeneous standard material can be reproducibly prepared electrochemically. © 1999 The Electrochemical Society. All rights reserved.

The influence of counter-ions on nucleation and growth of electrochemically synthesized polyaniline film

The initial stages of polyaniline (PANI) film growth are investigated by a potentiostatic technique. The obtained I-t transients exhibit current maxima which are analyzed for the nucleation type. The evidence is given on two different stages of the nucleation process. It is established that the first stage of growth is a formation of a compact PANI layer which is followed by an additional nucleation process. For that nucleation process it is found that at lower concentrations of aniline monomer 3D progressive nucleation takes place, and with the increasing monomer concentration in perchloric acid solutions 3D instantaneous nucleation prevails. At later stages 1D growth takes place resulting in chain branching. The possibility to observe current maxima, indicating the particular nucleation process, depends on monomer concentration, on the potential of synthesis, and on the counter-ion present, ie on the rate of PANI polymerization. It is shown that clusters resulting from the nucleation process form different shapes depending on the counter-ion present.

Characteristics of an organic semiconductor polyaniline film as a sensor for NH 3 gas

A polyaniline film formed by chemical oxidative polymerization is found to possess detectable sensitivity in the form of an increasing change in resistivity for NH 3 gas (49.80Ω/ppm). For inorganic gases such as Cl 2 and HCl, the opposite response is obtained with similar sensitivity. The above sensitivity remains the same even in the presence of 1000 ppm of H 2, CO and O 2 gases. In other words, the synthesized polyaniline film has a selective detectability for NH 3 gas and can be used as a sensor for NH 3 gas in the temperature range 15–40 °C.

Polyaniline Surface Morphology During The Doping Process Using Atomic Force Microscopy

ABSTRACTChemically synthesized polyaniline films were studied during the doping and dedoping process by imaging the polymer surface using in-situ Atomic Force Microscopy (AFM). The polymer, which was initially in the base non-conducting form was doped using aqueous acidic solutions of both tosylic (pH=0.2) and HCl (pH of 0.2 and 1.0). Dedoping was accomplished by exposing the same doped polymer surface to NH4OH (pH=12) base solution. AFM images showed that it was necessary to cycle the polymer surface 3 times between acid and base before a reproducible surface morphology was established between the doped and dedoped states. For the case of doping with tosylic acid AFM images showed that the polyaniline surface was immediately roughened. In addition there appeared to be an increase in the size of surface channels and cracks. When doping with HC1 (pH=1.0), no change in surface morphology was observed; however, noticeable surface roughening occurred over 10 Minutes for the case of the lower pH=0.2 solution. The complex permittivity and DC conductivity was measured to estimate the level of protonation in the AFM samples.

Electronic and structural characterization of electrochemically synthesized conducting polyaniline from XPS studies

AbstractWe report high‐resolution XPS data on three forms of the electrochemically synthesized polyaniline films: the highly conducting emeraldine salt form and the films obtained after KOH treatment and electrochemical reduction in HCI. The deconvoluted N 1s peaks in these films show clear evidence of the existence of the existence of four states of nitrogen, which are attributed to the amine, polaron and localized bipolaron defect configurations. The trends observed after the KOH treatment and electrochemical reduction in HCI in the N 1s spectra, plus the C 1s and O 1s peak shapes, support this assignment scheme.