Synthesis of sulfonated polyaniline by polymerization of the aniline heterodimer 4-aminodiphenylamine-2-sulfonic acid

The aniline heterodimer 4-aminodiphenylamine-2-sulfonic acid has been polymerized in aqueous ammonium persulfate solution to yield a new form of sulfonated polyaniline (SPAn). This polymer, obtained as a green powder, is soluble in aqueous base (violet solution) and polar solvents (green solution, turning blue on standing). Its FTIR, UV–VIS and EPR spectra are quite similar to those of SPAn obtained by direct ring-sulfonation of polyaniline. The room temperature dc conductivity of the polymer is about 1.3×10⁻⁵ S/cm, indicative of considerable disorder in the sample. Cyclic voltammetry in 1.0 M HCl shows two redox peaks at E_1/2,1=0.50 V and E_1/2,2=0.68 V against Ag/AgCl electrode, characteristic of SPAn.     

Electrochromic properties of sulfonic acid ring-substituted polyaniline in aqueous and non-aqueous media

It is a simple way to prepare the sulfonic acid ring-substituted polyaniline (SPAn) electrode via the directly chemical reaction of polyaniline (PAn) film polymerized on the indium-tin oxide (ITO) conducting glass with the concentrated sulfuric acid. The in situ visible spectra show that the color of the SPAn film in 0.3 M Na₂SO₄ solution with pH 7.0 still changes with the applied potential. The pH range for the change in the color of the SPAn film is larger than that of polyaniline film. In 0.25 M LiClO₄ propylene carbonate (PC) solution, the color of the SPAn film changes from blue via green to transparent yellow as the applied potential decreases from 0.80 to −0.20 V (Ag/AgCl with saturated KCl solution), and this change is reversible. Based on the result from the cyclic voltammogram, SPAn in the non-aqueous solution has a good electrochemical activity and a fast charge transfer characteristic. The XPS spectrum of SPAn indicates that polyaniline in the concentrated sulfuric acid can be sulfonated.     

De-doped polyaniline nanofibres with micropores for high-rate aqueous electrochemical capacitor

Polyaniline nanofibres have been prepared without any template or surfactant. Although the morphology of polyaniline is well kept after dealing with aqueous ammonia, de-doped polyaniline nanofibres with micropores are of better electrochemical capacitor performances in 1 M H₂SO₄ aqueous solution. Its specific capacitance is 593 F g^?1 at a constant current density of 2.5 A g^?1, and can be subjected to charge/discharge over 5000 cycles in the voltage range of 0–0.65 V. Moreover, its capacitance retention ratio reaches circa 87% with the current densities increasing from 2.5 A g^?1 to 15 A g^?1.     

High charge/discharge rate polypyrrole films prepared by pulse current polymerization

Polypyrrole (PPy) films doped by p-toluenesulfonic (PTS) ion were prepared by pulse current polymerization (PCP PPy) and direct current polymerization (DCP PPy) in aqueous solution. During polymerization of DCP PPy films, the sustained high anodic potentials can result in overoxidation and –CH₂– formation at pyrrole rings, which was confirmed by the FTIR spectroscopy. PCP PPy films exhibited more homogeneous and smoother appearance than DCP PPy films. The apparent diffusion coefficient of PCP PPy films was one order of magnitude bigger than that of DCP PPy films, which was closely correlated with the more ordered structure of PCP PPy films confirmed by XRD. When the scanning rate reached up to 500 mV s^?1, the CV curves of PCP PPy films showed rectangular shape within voltage range of ?0.8 V to +0.8 V. High charge/discharge rate of PCP PPy films can be attributed to well wettability, very small charge transfer resistance, high electronic conductivity and ions apparent diffusion coefficient. After 50,000 charge/discharge cycles, the specific capacitance of PCP PPy films only decreased by 14% at a charge/discharge current of 20 A g^?1 within voltage range of 0–0.4 V.     

Investigation of polyaniline co-doped with Zn2+ and H+ as the electrode material for electrochemical supercapacitors

Polyaniline co-doped with Zn²⁺ and H⁺ was synthesized in aqueous HCl solution containing ZnCl₂, and tested for its supercapacitive behavior in three-electrode or two-electrode system with 1.0 M H₂SO₄ as electrolyte by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) techniques were employed for characterization of polyaniline co-doped with Zn²⁺ and H⁺. Compared with polyaniline doped with H⁺, it shows a larger specific capacitance of 369 F g^?1. Moreover, the specific capacitance remains 90% after 1000 cycles at a current density of 0.5 A g^?1, indicating good cycleability.     

Microwave study of chemically synthesized conducting polyaniline on alumina

Polyaniline (PANI) thin film on alumina was prepared by the chemical oxidation of aniline with ammonium peroxydisulphate in acidic aqueous medium. DC conductivity, microwave transmission and reflection, microwave conductivity, shielding effectiveness and microwave dielectric constant of the conducting PANI films are reported. DC conductivity was between 0.15 × 10^?3 and 3.13 × 10^?3 S/cm. Microwave conductivity was between 0.2 and 10 S/cm. The PANI films coated on alumina gave shielding effectiveness value of ?1 to ?4 db. The ?′ was between 2 and 350 whereas ?″ was between 437 and 60. Measurements have been carried over the frequency range of 8.2–18 GHz.     

Effect of Fenton reagent on the synthesis of polyaniline

Polyaniline has been prepared using Fenton reagent. The in situ visible spectra during the polymerization process show that the polymerization of aniline was carried out through an intermediate at 530 nm. The absorption band of the resulting product, polyaniline, appears at 700 nm. The conductivity of polyaniline prepared using Fenton reagent can reach 1.04×10⁻² S cm⁻¹, which is strongly dependent on the concentrations of FeSO₄, H₂SO₄ and polymerization time. The cyclic voltammogram of polyaniline prepared using Fenton reagent is much different from that of polyaniline prepared normally, and has the good electrochemical reversibility and a fast charge transfer characteristic in the solution with pH 4.0. The FTIR spectrum indicates that no absorption band attributed to N–H stretching vibrations is present in polyaniline.     

Electrical,structural and magnetic properties of polyaniline/pTSA-TiO2 nanocomposites

Polyaniline (PANI)/para-toluene sulfonic acid (pTSA) and PANI/pTSA-TiO₂ composites were prepared using chemical method and characterized by infrared spectroscopy (IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM). The electrical conductivity and magnetic properties were also measured. In corroboration with XRD, the micrographs of SEM indicated the homogeneous dispersion of TiO₂ nanoparticles in bulk PANI/pTSA matrix. Conductivity of the PANI/pTSA-TiO₂ was higher than the PANI/pTSA, and the maximum conductivity obtained was 9.48 (S/cm) at 5 wt% of TiO₂. Using SQUID magnetometer, it was found that PANI/pTSA was either paramagnetic or weakly ferromagnetic from 300 K down to 5 K with H_C ≈ 30 Oe and M_r ≈ 0.015 emu/g. On the other hand, PANI/pTSA-TiO₂ was diamagnetic from 300 K down to about 50 K and below which it was weakly ferromagnetic. Furthermore, a nearly temperature-independent magnetization was observed in both the cases down to 50 K and below which the magnetization increased rapidly (a Curie like susceptibility was observed). The Pauli susceptibility (χ_pauli) was calculated to be about 4.8 × 10^?5 and 1.6 × 10^?5 emu g^?1 Oe^?1 K for PANI/pTSA and PANI/pTSA-TiO₂, respectively. The details of these investigations are presented and discussed in this paper.     

Effect of boron doped fullerene C60 film coating on the electrochemical characteristics of silicon thin film anodes for lithium secondary batteries

In this work, boron doped fullerene (B:C₆₀) films were prepared by the radio frequency plasma assisted thermal evaporation technique for use as a coating material for the silicon thin film anode in lithium secondary batteries. Raman and XPS analyses revealed that the boron atoms were well inserted into the fullerene film lattices. The effect of the B:C₆₀ film on the electrochemical characteristics of the silicon thin film was studied by charge–discharge tests, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The B:C₆₀ coated silicon film exhibited a high reversible capacity of more than 1200 mAh g^?1 when cycled 50 times between 0 and 2 V at a current density of 1200 μA cm^?2 (1.5 C). The film also showed good rate capacity at different current densities and a more improved coulombic efficiency of 87.7% in the first cycle in comparison with that of the C₆₀ coated film electrode.     

Preparation of porous nanorod polyaniline film and its high electrochemical capacitance performance

Nano-sized polyaniline (PANI) films were electrochemically deposited onto an ITO substrate by a pulse galvanostatic method (PGM) in an aqueous solution. The morphology of the as-prepared PANI film was characterized using a field emission scanning electron microscope (FESEM). It was observed that the as-prepared PANI films were highly porous, and showed a nano-sized rod-like or coralline-like morphology depending on the charge loading performed in the electropolymerization process. Furthermore, the PANI films were electrochemically measured by the galvanostatic charge–discharge (GCD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests in 1 mol L^?1 HClO₄ solution. The results showed that such PANI films had a favorable electrochemical activity and an excellent capacitance. The rod-like PANI film prepared with the charge loading of 1000 mC showed the highest discharge capacitance of 569.1 F g^?1 at a low current density of 1 A g^?1. The discharge capacitance retained 97.7% after 1000 cycles at a large current density of 10 A g^?1.     

Preparation and enhanced stability of flexible supercapacitor prepared from Nafion/polyaniline nanofiber

Polyaniline nanofibers were used to produce a flexible supercapacitor electrode with a specific capacitance of 235 F g^?1. Cycle life and energy density were enhanced after encapsulating the polyaniline nanofiber electrode in Nafion. A specific capacitance of 195 F g^?1 was obtained over 10,000 charge–discharge cycles.A fully flexible, stand alone capacitor comprising two polyaniline nanofiber based electrodes and a PVDF separator was constructed. An initial specific capacitance of 125 F g^?1 (100 mV s^?1) was obtained. This decreased to 95 F g^?1 over 10,000 cycles.     

The reduction of silver nitrate to metallic silver inside polyaniline nanotubes and on oligoaniline microspheres

Polyaniline (PANI) reduces silver nitrate to metallic silver. Composites based on conducting polymer and silver have been prepared with equimolar proportions of reactants. Polyaniline bases having different morphologies – granular or nanotubular – and oligoaniline microspheres have been left to react with silver nitrate in acidic, neutral, and alkaline media. The content of silver, typically 20–30 wt.%, was determined by thermogravimetric analysis. Clusters of 40–80 nm silver particles are produced in the granular form of PANI. The formation of silver inside PANI nanotubes has been observed. With oligoaniline microspheres, silver was produced on their surface, and on PANI agglomerates accompanying them. The highest conductivity, 943 S cm^?1, was found with silver reduced by nanotubular PANI base in 0.1 M nitric acid at 17.3 wt.% silver content. The standard granular PANI, used as a reference material, yielded a composite having a much lower conductivity of 8.3 × 10^?5 S cm^?1 at 24.3 wt.% Ag. There is no simple correlation between the conductivity and silver content. Infrared and Raman spectroscopies have been used to study the changes in the molecular structure of the PANI bases of various morphologies before and after reaction with silver nitrate.     

Electrosynthesis of polyaniline films on titanium by pulse potentiostatic method

Polyaniline (PANI) was synthesized on titanium electrode from aqueous solution containing 0.3 mol L⁻¹ aniline and 1 mol L⁻¹ HNO₃ by pulse potentiostatic method. The chronoamperogram during polymerization process of aniline was recorded. The effects of the synthesis parameters, such as anodic pulse duration (t_a), cathodic pulse duration (t_c), lower limit potential (E_c) and upper limit potential (E_a), on the morphology and electroactivity of the PANI films were investigated by scanning electron microscopy (SEM) and cyclic voltammetry (CV). SEM results present that flake, mica-like, quasi-fibrous and nano-fibrous PANI film could be synthesized with various polymerization parameters. Under the following conditions, t_a = 0.8 s, t_c = 0.1 s, E_c = 0 V and E_a = 1.0 V, high quality nano-fibrous PANI film with the best electroactivity was obtained. The CV results show that the PANI films with different morphologies, which were prepared under the same anodic polymerization charge, have obvious different characteristics. This means that the PANI films with different morphologies have different electrochemical activity.     

Synthesis and characterization of polyaniline–Fe3O4 nanocomposite: Electrical conductivity,magnetic, electrochemical studies

Fe₃O₄ nanoparticles were prepared by hydrolysis reaction of urea in ethylene glycol as solvent at 160 °C. The prepared Fe₃O₄ nanoparticles were incorporated into polyaniline (PANI) matrix during in situ chemical oxidative polymerization of aniline with different molar ratios of aniline:Fe₃O₄ (19:1, 16:1, 12:1, 9:1) using (NH₄)₂S₂O₈ as oxidant in aqueous solution of sodium dodecylbenzene sulphonic acid under N₂ atmosphere. Room temperature conductivities of the synthesized PANI, PANI/Fe₃O₄ (19:1) and PANI/Fe₃O₄ (9:1) are 3.2 × 10^?4, 1.8 × 10^?5 and 1.0 × 10^?5 S/cm, respectively, indicating decrease of conductivity with increase of Fe₃O₄ in PANI. Saturation magnetizations of Fe₃O₄, PANI/Fe₃O₄ (19:1), and PANI/Fe₃O₄ (9:1) are 27.5, 5.5 and 6.3 emu/g, respectively, indicating an increase of ferromagnetic interaction with more incorporation of Fe₃O₄ in PANI matrix, whereas PANI is diamagnetic. Electrochemical studies shows that Zn-PANI/Fe₃O₄ (9:1) battery had delivered maximum discharge capacity (78.6 mAh/g) as compared to Zn-PANI battery (50.1 mAh/g) at constant current of 0.5 mA cm^?2. At constant resistance of 1000 Ω, discharge capacities of Zn-PANI/Fe₃O₄ and Zn-PANI battery are 73.37 and 50.8 mAh/g, respectively.     

Supercapacitive behavior of electrosynthesized marygold-like structured nickel doped iron hydroxide thin film

Herein, we report the electrosynthesized marygold-like structured nickel doped (5 at.%) iron hydroxide thin film from the aqueous solution of 0.1 M iron sulphate using galavanostatic mode of electrodeposition method for supercapacitor application. The compositional analysis of film was studied by AAS. Amorphous structure of nickel doped iron hydroxide film revealed from XRD analysis. The formation of elemental bands of iron hydroxide was confirmed from FTIR study. The SEM images and surface wettability showed marygold-like structure with contact angle 79° with surface of film. The supercapacitive properties of film using cyclic voltammetry and galvanostatic charge–discharge showed the highest specific capacitance 287 F g^?1 in 1 M Na₂SO₃ electrolyte at the scan rate of 10 mV s^?1. The supercapacitive parameters such as, specific energy (S.E.), specific power (S.P.) and coulomb efficiency (η%) are 8.32 Wh kg^?1, 2.5 kW kg^?1 and 92%, respectively.     

Transmembrane redox reactions through polyaniline membrane doped with fullerene C60

Polyaniline (PANI)-C₆₀ membranes were chemically synthesized with fullerene C₆₀ content of 0.2, 0.5, 1, 2 and 3 mol% (relative to aniline fragment) respectively, and then systematically characterized with FTIR, field emission scanning electron microscopy (FESEM), XPS and electrochemical impedance spectroscopy (EIS). It is demonstrated that electron/ion coupled transport across PANI-C₆₀ membrane is possible in the presence of oxidizing agent at one side of the membrane and reducing agent at the other side. If 0.05 M acidic solution of FeCl₃ was used as the oxidizing agent and 0.3 M ascorbic acid as the reducing agent, a typical value of transmembrane transport rate of redox equivalents was 3.1 × 10⁻⁸ mol s⁻¹ cm⁻² with the membrane containing 0.5% C₆₀. This value was one order higher than that for HCl doped PANI membrane at identical conditions, which can be explained by superimposed C₆₀ doping and acid doping. The 0.5% content of C₆₀ is optimal and at higher content the rates of transmembrane redox transport decrease.     

The carbonization of granular polyaniline to produce nitrogen-containing carbon

Polyaniline (PANI) was prepared by the oxidative polymerization of aniline. The deprotonated product, a PANI base, was carbonized in an inert atmosphere at temperatures up to 800 °C for various times. The mass decreased to 40–50 wt.% at temperatures above 600 °C. The progress of molecular structure during carbonization was followed by infrared and Raman spectroscopies. The carbonization at 650 °C for 1 h is suggested for the optimum conversion of PANI to carbon. The product retained the original globular structure of PANI. The conductivity of the carbonized material was low for carbonizations below 600 °C, <10^?10 S cm^?1, and increased to 10^?4 S cm^?1 after treatment at 800 °C. The content of nitrogen, ～10 wt.%, was not affected appreciably by the carbonization.     

Morphology and electrical properties of hybrid and sulphonated oxalic acid-doped polyaniline

Polyaniline–polyethylene glycol2000 (PAni–PEG2000) hybrid and sulphonated polyaniline (SPAni) were prepared using oxalic acid as dopant and potassium permanganate as oxidant. The properties of these two conductive polymers were studied in comparison with pure polyaniline (PAni) prepared using the same conditions. The investigated polymers were characterized using FTIR, UV–vis, TGA, TEM, SEM, XRD and their electrical conductivities were also investigated. The morphology of pure polymer was found to be flat ribbon-like form, while presence of polyethylene glycol led to the formation of separate nanospheres. The three polymer samples have different degrees of crystallinity, the highest degree is for SPAni. Unexpectedly, electrical conductivity is in the order SPAni > PAni–PEG2000 > PAni, aging of PAni increases gradually the conductivity of the polymer from 0.0056 to 0.023 S cm^?1 and the increase of temperature gradually decreases the conductivity.     

Chemical polymerization of pyrrole with disulfide structure and the application to lithium secondary batteries

An intramolecular cyclic disulfide-containing polypyrrole was prepared by the chemical-oxidative polymerization of 4,6-dihydro-1H-[1,2]dithiino[4,5-c]pyrrole (MPY), and the electrical properties were investigated as the cathode active material in lithium secondary batteries. Oxidizing agents and solvents for the chemical-oxidative polymerization were examined to prevent over-oxidation of the polypyrrole backbone. The conductivity of poly(MPY), the polymer prepared using FeCl₃ in ethylene glycol, was around 10⁻⁴ S/cm. Poly(MPY) showed very little over-oxidation, good redox properties, and a high discharge capacity of 398 mAh/g based on the redox response of the disulfide.     

Fabrication of LiMn2O4 thin film cathode from chitosan-containing solution

Thin film of spinel LiMn₂O₄ was obtained by spin coating the chitosan-containing precursor solution on a platinumized Si substrate, followed by a two-step annealing procedure at 300 and 700 °C, respectively. It was demonstrated that the addition of the appropriate amount of chitosan to the precursor solution enhanced the deposition of LiMn₂O₄ films. The thickness of the deposited film from chitosan-containing precursor solution is about 5.2 μm after five-time spin coating under a spinning speed of 2500 rpm. Without the addition of chitosan in precursor solution, the deposited film was as thin as 0.16 μm under the same processing parameters. Furthermore, the electrochemical behavior for the deposited LiMn₂O₄ film calcined at 700 °C for 1 h was characterized by the charge–discharge test. The result shows that the 1st discharge capacity is 56.31 μAh cm⁻² μm⁻¹ at a discharge rate of C/2 and the fading rate of the discharge capacity is only 0.19% cycle⁻¹ after 50 cycles.