Self-doped Polyaniline Research Articles

High performance hybrid supercapacitor based on two nanostructured conducting polymers: Self-doped polyaniline and polypyrrole nanofibers

A hybrid asymmetric electrochemical supercapacitor is constructed by employing two different nanostructured conducting polymers of polypyrrole (PPy) and self-doped polyaniline (SDPA). Different electrochemical methods, including cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS), are performed to characterize the electrochemical performance of the supercapacitor. The maximal working potential window of 1.3V is associated with more than 97Fg−1 of total electrode materials. The cell maintains approximately 70% of its initial capacitance after 1000 cycles with an equivalent series resistance (ESR) below 1.6Ωcm2. Furthermore, the system shows high specific energy, specific power and maximum power values of 22.87Whkg−1, 570Wkg−1 and 45,193Wkg−1, respectively, at a current density of 5mAcm−2 in 1M KCl. Long-life cycling is achieved by removing dissolved oxygen and using a mild pH electrolyte, which limits the redox activity of the electrically conducting polymers (ECPs). Moreover, the proposed supercapacitor exhibits high capacitance retention of 89% at a higher current density (40mAcm−2), indicating good electrochemical stability and rate capability. The performance of the proposed hybrid supercapacitor has been compared with two other symmetric cells.

Electrocatalytic activity of self-doped polyaniline

Self-doped conducting polyaniline-modified indium tin oxide (ITO) electrodes were prepared by cyclic voltammetry on ITO substrates in aniline (AN) and o-aminobenzene sulfonic acid (OSA) mixed monomer solutions with AN/OSA mole ratios of 25/75, 50/50, and 75/25, followed by investigations on electrocatalytic activities of the copolymers to redox reactions of Fe(CN) 6 3−/4− as a probe in aqueous solutions of different pH using cyclic voltammetry. For a given pH, the P(25AN-co-75OSA)-modified ITO electrode demonstrated the highest current density, followed by the P(50AN-co-50OSA)- and by the P(75AN-co-25OSA)-modified ITO electrodes. It can be concluded that a higher content of OSA (sulfonate) in the copolymer exhibited a higher extent of self-doping in the copolymer, leading to a higher electrocatalytic activity to redox reactions of the probe. The electrocatalytic activities of the copolymers decreased with increasing pH. The P(25AN-co-75OSA)-modified ITO electrode was electroactive for sensing the redox reactions of the probe in aqueous solutions of up to pH 7, the P(50AN-co-50OSA)-modified ITO electrode was electroactive for up to only pH 5, but the P(75AN-co-25OSA)-modified ITO electrode was not electroactive in aqueous solution of pH even as low as 2.

On the catalytic oxidation of ascorbic acid at self-doping polyaniline films

Ascorbic acid molecules in either acid or conjugate base forms have been oxidized on self-doping carboxylated polyaniline thin films. The kinetic model proposed by Bartlett et al. has been successfully applied to the catalytic reactions. Active sites in the polymer have been identified as the rings having quinoid character. The existence of significant electrostatic repulsions between ionogenic groups at the self-doping polymer and negatively charged ascorbate molecules has been established thanks to the analysis of the pH dependence of the Michaelis constant. It has been found that in contrast to inorganic conductors the regeneration of active sites in polyaniline-based materials is slower at higher potentials. Such a behavior can be satisfactorily correlated with the potential dependence of the polymer electronic conductivity.

Electrocatalytic Behavior of Carbon Nanotubes in Electropolymerizations of Self-Doped Polyaniline Used as a Sensing Material

Electrochemically oxidative copolymerizations on indium tin oxide electrode of aniline (AN) and o-aminobenzene sulfonic acid (OSA) with mole ratio of 25/75 in the presence of carbon nanotubes (CNT) and acid-treated CNT (fCNT) were conducted to investigate the electrocatalytic effects of the nanotubes on the copolymerizations. The P(25AN-co-75OSA)/CNT and P(25AN-co-75OSA)/fCNT composites were subsequently investigated into their electrocatalytic activities to the redox reactions of Fe(CN)63−/4− as a probe in aqueous solutions of different pH and detection capacities for dopamine (DA) and ascorbic acid (AA) by cyclic voltammetry. The results revealed that CNT and fCNT both electrocatalyzed the oxidations during the copolymerizations of P(25AN-co-75OSA), with CNT having a higher electrocatalytic capacity than fCNT. The so-prepared composites exhibited electrocatalytic activity for the redox reactions of Fe(CN)63−/4− in solutions of up to pH 7, with fCNT having a higher electrocatalytic activity than CNT. The P(25AN-co-75OSA)/fCNT composite film was able to detect DA and AA, exhibiting diffusion-controlled electron transfer rate.

Self-doped polyaniline on functionalized carbon cloth as electroactive materials for supercapacitor

Carbon cloth was functionalized through cyclic voltammetric scans in 2M H2SO4 to afford functionalized carbon cloth (FC). The FC was characterized by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Self-doped polyaniline (SPAN) was deposited on FC through electro-co-polymerization of aniline and metanilic acid to get SPAN/FC which showed a specific capacitance of 408Fg−1 in 0.5M Na2SO4, based on a constant charge–discharge experiment at a current density of 1Ag−1. A symmetric model capacitor, SPAN/FC-SPAN/FC was assembled by using SPAN/FC as both of the electrodes and 0.5M Na2SO4 as the electrolyte. The charge storage property and charge–discharge cycling stability of SPAN/FC-SPAN/FC were investigated by galvanostatic experiment.

Morphology and electrical conductivity of self- doping polyanilines synthesized via self- assembly process

Copolymerization of self doping monomer aniline and oxalic acid (OA)/ acetic acid (AA) in different molar ratio via the self- assembly process were conducted to prepare self-doping polyanilines (SD-PANIs). In this polymerization process, AA or OA plays the roles of surfactant and dopant for the self-doping PANIs. The morphology, UV-Vis absorption behaviour, crystalline density and electrical conductivity of self-doped PANIs are investigated. Depending on molar ratio of aniline to OA/AA, nanotubes structure of polyaniline (PANI) can be formed. Higher concentration of OA leads to increase in the diameter of the tubes in which micelles act as the template in the self-assembly of PANI to form nanotube structures, whereas increase in concentration of AA leads to change the structure of polyaniline from microspheres to nanotubes. The nanotubular structure aggregates to form a bundle structure as the concentration of AA increases. More uniform structure is observed in case of OA than that of AA, which may be due to the bulky structure of OA than AA. Higher absorption intensity in UV-Vis spectra of self-doping PANIs was observed for lower concentration of OA/AA. The crystal structure for the synthesized self-doped PANIs is orthorhombic and the C-N-C angle is larger. High electrical conductivity of the self-doped PANIs was observed as a function of degree of doping. Copyright © 2011 VBRI press.

High performance battery–supercapacitor hybrid energy storage system based on self-doped polyaniline nanofibers

Nanostructured self-doped polyaniline (SDPA) is prepared from an aqueous solution of aniline and m-aminobenzoic acid using an electrochemical method onto a stainless steel electrode. This electrode employed as a positive shared electrode in the construction of a hybrid battery–supercapacitor energy storage system AC/SDPA/Zn. This hybrid system is constructed using a parallel combination of an asymmetric supercapacitor (AC/SDPA) and a secondary battery (Zn/SDPA) in a single cell configuration and same electrolyte. Different electrochemical methods including cyclic voltammetry, galvanostatic charge–discharge and rate charge–discharge studies are carried out to characterize electrochemical performances of the hybrid system. Based on the obtained results, the hybrid system shows specific capacity, specific energy, specific power and maximum power values of 215Ahkg−1, 204Whkg−1, 863Wkg−1 and 8909Wkg−1, respectively, at a current density of 2.5mAcm−2.

Polyaniline Nanoscaffolds for Colorimetric Sensing of Biomolecules via Electron Transfer Process

Biologically important analytes such as cysteine and vitamin-C were detected by electron transfer (ET) via naked eye colorimetric sensing using a tailor-made water-soluble self-doped polyaniline (PSPANa) as a substrate. Monomer (N-3-sulfopropylaniline) was synthesized via ring-opening of propane sultone with excess aniline and polymerized in water using ammonium persulfate to obtain green water-soluble polymer. Vitamin-C (ascorbic acid) and cysteine showed unexpected sharp and instantaneous color change from blue to colorless sensing action. The stoichiometry of the analyte to polymer was determined as 3:2 and 4:1 with association (or binding) constants of K = 2.1 × 10(3) and 1.5 × 10(3) M(-1) for vitamin-C and cysteine, respectively. Efficient electron transfer from vitamin-C (also cysteine) to the quinoid unit of the polyaniline base occurred in solution; as a result, the color of the solution changed from deep blue to colorless. Cyclic voltammetry analysis of PSPANa showed the disappearance of the cathodic peak at -0.21 V upon the addition of analytes (vitamin-C and cysteine) and confirms the electron transfer from the analyte to the polymer backbone. Dynamic light scattering (DLS) and zeta potential techniques were utilized to trace the molecular interactions in the electron transfer process. DLS histograms of the polymer samples confirmed the existence of nanoaggregates of 8-10 nm in diameter. The polymers possessed typical amphiphilic structure to produce micellar aggregates which facilitate the efficient electron transfer occurred between the analyte and polyaniline backbone.

Solution processable self-doped polyaniline as hole transport layer for inverted polymer solar cells

Polymer solar cells (PSCs) are a promising alternative for low-cost renewable energy due to their solution-process, flexibility and large-area fabrication. To improve power conversion efficiency (PCE) of PSC, a hole transport layer (HTL) is usually inserted between anode and active layer to enhance hole carrier collection. In this contribution, the utilization of solution processable self-doped sulfonic acid ring-substituted polyaniline (SPAN) thin film as the HTL in inverted PSC (i-PSC) composed of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction is demonstrated. The i-PSC with SPAN as the HTL exhibits an improvement over that with PEDOT:PSS (from 3.30 ± 0.14% to 3.54 ± 0.11%) due to higher conductivity and better film quality of SPAN relative to poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), suggesting that SPAN can be a promising alternative to PEDOT:PSS as the effective HTL for i-PSC.

Synergistic membrane of ZrO 2/self-doped polyaniline nanofibres fabricated by controllable electrodeposition for DNA hybridization detection

ZrO 2 microparticles and self-doped polyaniline nanofibres (nanoSPAN, copolymer of aniline and m-aminobenzenesulfonic acid) were utilized to fabricate synergistic membranes for the DNA hybridization sensing. The nanoSPAN was coated on the surface of glassy carbon electrode to form a negatively charged nanostructure monolayer. Then ZrO 2 microparticles with strong affinity toward the oxygen-containing groups were electrochemically deposited on nanoSPAN by using cyclic voltammetry, which acted as a bridge to link the –SO 3H group of the conducting polymer nanostructures and the phosphate group of the DNA. The architecture of the as-prepared ZrO 2/nanoSPAN, the immobilization and hybridization of DNA were characterized by scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetric technology, respectively. The charge transfer resistance observed for the Fe ( CN ) 6 3 - / 4 - redox marker was related to the adhered ssDNA and the hybridized dsDNA, which can be used as the highly sensitive label-free impedance sensing for the sequence-specific DNA detection. The transgenic fragment of phosphoenolpyruvate carboxylase (PEPCase) gene in transgenic rape was successfully detected by using this DNA electrochemical biosensor. The linear range was from 1.0 × 10 −12 M to 1.0 × 10 −6 M with a detection limit of 3.4 × 10 −13 M. This is the first application of nanoSPAN combined with ZrO 2 microparticles to fabricate a DNA electrochemical biosensor with a synergistic performance for the sensitive and rapid detection of DNA hybridization.

Three-step electrodeposition synthesis of self-doped polyaniline nanofiber-supported flower-like Au microspheres for high-performance biosensing of DNA hybridization recognition

A three-step electrodeposition method has been successfully adopted to fabricate morphology-controlled novel Au microspheres on self-doped polyaniline nanofibers (nanoSPAN) modified glassy carbon electrode. The deposition conditions, such as HAuCl4 concentration and deposition step, have significant influences on the morphologies and electrochemical properties of the resulted Au microspheres. Well hierarchical and homogeneously dispersed flower-like Au microspheres (HHFAu) were obtained under optimal conditions by the three-step electrodeposition strategy in 5.0mM HAuCl4 solution. HHFAu possess large surface area, excellent electron transfer ability and good biocompatibility. The DNA probe could be effectively attached to HHFAu and thus a high-performance DNA biosensor was constructed by using electrochemical impedance spectroscopy as detection method. A gene fragment of the cauliflower mosaic virus 35S gene, which is related to one of the screening genes for the transgenically modified plants, has been satisfactorily detected. The linear range was from 1.0×10−13M to 1.0×10−6M and the detection limit was 1.9×10−14M. This HHFAu/nanoSPAN-based impedance biosensing platform holds great promise for the detection of other biological and chemical molecules.

Controllable fabrication of Au micro/nanostructures on self-doped polyaniline nanofibers via electrochemical deposition and its application for DNA immobilization

Four electrochemical methods, cyclic voltammetric deposition, potentiostatic electrodeposition, multi-potential step electrodeposition and three-step electrodeposition, were used to fabricate Au micro/nanostructures on self-doped polyaniline nanofibers-coated glassy carbon electrodes (Au/nanoSPAN/GCEs). The Au micro/nanostructures deposited on the nanoSPAN-modified electrodes were shown by scanning electron microscopy to exhibit different morphologies, such as Au nanoparticle clusters, monodisperse nanoparticles and homogeneously dispersed flower-like microparticles, depending on the deposition method. This phenomenon demonstrates that control over the morphology of Au metal can be easily achieved by adjusting the electrodeposition method. The electrochemical behaviors of the Au/nanoSPAN/GCEs also varied with above four methods, which were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. In comparison with Au nanoparticle clusters and monodisperse Au nanoparticles, homogeneously dispersed flower-like Au microparticles had the largest surface area and obviously enhanced electrochemical response towards the redox reactions of [Fe(CN)6]3−/4− on the modified electrode. DNA immobilization on the Au/nanoSPAN/GCEs was investigated by differential pulse voltammetry using [Fe(CN)6]3−/4− as an indicator. The efficiency of DNA immobilization was inherently related to their different Au micro/nanostructure morphologies. The Au/nano-SPAN/GCE fabricated by three-step electrodeposition showed the largest capacity for immobilization of single stranded DNA, which makes it a promising DNA biosensor.

Self-doped polyaniline as new polyaniline substitute for solid-phase microextraction

This work is a first study on extraction efficiency and thermal stability of nano-structured self-doped polyaniline (SPAN) as a coating of solid-phase microextraction (SPME) fibers. SPAN-based fibers were prepared using electrochemical deposition on platinum wires. The particle sizes of prepared nano-structure were in the range of 50–100 nm. Extraction properties of the fiber to 1,4-dioxane were examined using headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-flame ionization detection (GC-FID). The results have proved higher thermal stability of the proposed fiber compared to common PANI fiber. The SPAN coating was proved to be very stable at relatively high temperatures (up to 350 °C) with high extraction capacity and long lifespan (more than 50 times). Therefore, it can be a good substitute of polyaniline (PANI) as a SPME coating. The extraction procedure was optimized by selecting the appropriate extraction parameters including extraction time, extraction temperature, salt concentration, stirring rate and headspace volume. Calibration graph was linear in the concentration range of 1–100 ng mL −1 ( R 2 > 0.993) with detection limit of 0.1 ng mL −1. Single fiber and fiber-to-fiber repeatability were lower than 6.0% and 10.4%, respectively. Different water samples were analyzed as real samples and good recoveries (98–120%) were obtained.

Synthesis and chemical properties of photoluminescent self-doped polyanilines

Fluorescent self-doped polyanilines (PAS-AntPy-a and PAS-AntPy-b) were obtained by the pyridinium sulfonation of poly(2-methoxyaniline-5-sulfonic acid) (PAS) with 4-(2-anthracene-9-yl-vinyl)pyridine (AntPy). The degrees of pyridinium sulfonation in PAS-AntPy-a and PAS-AntPy-b were 0.70 and 0.97, respectively. A neutral polyaniline with an AntPy side unit (PANI-AntPy) was synthesized by the oxidative polymerization of N-(2-aminophenyl)-4-(2-anthracene-9-yl-vinyl)pyridinium chloride. The UV-vis spectra of PAS-AntPy-a and PAS-AntPy-b exhibited an absorption due to the polaron band that was derived from the protonation of amine groups in the polyaniline backbone with the remaining sulfonic acid proton. In contrast, PANI-AntPy did not exhibit absorption due to the polaron band. PAS-AntPy-a, PAS-AntPy-b, and PANI-AntPy were photoluminescent in a solution. The electric conductivity of PAS-AntPy-a was σ = 1.5 × 10−7 S cm−1, which was higher than that of H2SO4 doped PANI (4.2 × 10−9 S cm−1) reported previously.

Conductive architecture of Fe2O3 microspheres/self-doped polyaniline nanofibers on carbon ionic liquid electrode for impedance sensing of DNA hybridization

A novel architecture was designed by combining the strong adsorption ability of Fe2O3 microspheres to the DNA probes and excellent conductivity of self-doped polyaniline (SPAN) nanofibers (copolymer of aniline and m-aminobenzenesulfonic acid) on carbon ionic liquid electrode (CILE) for electrochemical impedance sensing of the immobilization and hybridization of DNA. The formed conductive Fe2O3/SPAN membrane on the CILE was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using [Fe(CN)6]3−/4− as the indicator. The immobilization of the probe DNA on the surface of electrode and the sensitivity of DNA hybridization recognition were dramatically enhanced due to the unique synergistic effect of Fe2O3 microspheres, SPAN nanofibers and ionic liquid. The DNA hybridization events were monitored with a label-free EIS strategy. Under optimal conditions, the dynamic range of this DNA biosensor for detecting the sequence-specific DNA of phosphoenolpyruvate carboxylase (PEPCase) gene from transgenically modified rape was from 1.0×10−13 to 1.0×10−7mol/L, and the detection limit was 2.1×10−14mol/L. This work suggested a simple strategy to prepare a conductive interface for electrochemical detection of DNA hybridization and opened a way for the application of Fe2O3 in DNA electrochemical biosensing.

Electrochemical investigations of self-doped polyaniline nanofibers as a new electroactive material for high performance redox supercapacitor

Self-doped polyaniline (SDPA) nanofibers were deposited on platinum (Pt) electrode by reverse pulse voltammetric (RPV) method and their electrochemical performance was evaluated in an aqueous redox supercapacitor constituted as a two electrode cell in a weak acidic medium. Scanning electron micrographs clearly revealed the formation of nanofiber structures with diameters in range of 60–90nm under optimum experimental conditions. Different electrochemical methods including galvanostatic charge–discharge (CD) experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out in order to investigate the applicability of the system as a redox supercapacitor. Based on the charge–discharge results obtained, the SDPA represented high specific capacitance, specific power and specific energy values of 480Fg−1, 436Wkg−1 and 9.40Whkg−1, respectively, at a current density of 5mAcm−2. The present study introduces new nanofiber materials for electrochemical redox capacitors with advantages including low cost, long cycle-life and stable at low acidic solutions of pH 3.

Self-doped polyaniline films prepared by electropolymerization in the presence of sulfonated nickel phthalocyanine

It is shown that the addition of tetrasulfonated nickel phthalocyanine (NiTSPc) to an acidic solution of aniline results in an accelerated deposition of polyaniline (PANI) from such a solution using the electrochemical potential cycling method. The electrodeposited polyaniline includes NiTSPc to form a composite film that retains its electroactivity in a wide pH range due to the self-doping effect. The thus formed composite PANI-NiTSPc film exhibits catalytic activity toward the electrooxidation of ascorbic acid in a nearly neutral buffer (pH 7.4).

Hollow Self‐Doped Polyaniline Micro/Nanostructures: Microspheres, Aligned Pearls, and Nanotubes

AbstractHollow self‐doped polyaniline (SPAN) micro/nanostructures, such as hollow microspheres, aligned pearls, and nanotubes, have been synthesized by a one‐step chemical oxidation copolymerization of aniline (AN) and m‐aminobenzenesulfonic acid (SAN) using ammonium peroxydisulfate (APS) as the oxidant in aqueous solution. The process is facile and free of any template, surfactant, and external dopants. The shapes and sizes of the hollow SPAN micro/nanostructures can be controlled by adjusting the synthetic parameters, such as the molar ratios of AN and SAN, the concentrations of monomers, and the molar ratios of the monomer and APS. The formation of hollow SPAN micro/nanostructures is possibly related to the self‐assembly of SPAN oligomers at the early stage of the copolymerization reaction. The molecular structures of the SPAN micro/nanostructures were determined by FT‐IR spectroscopy, which reveales that SO groups are bonded to the aromatic rings in SPAN chains.magnified image

Molecular assembled crosslinked self-doped polyaniline nano-thin films in application of electrochromic devices

Crosslinked self-doping polyaniline (SPANI) nano-thin films were prepared by using the molecular assembly process coupled with the copolymerization of aniline (AN) with the self-doping monomers DABSA (2,5-diaminobenzenesulfonic acid). DABSA were also used as surfactants and the di-amino groups rendered as chain extension/crosslinked sites in the simultaneous copolymerization and molecular assembly process. TEM and SEM results indicated that the morphology changes from micelles to nano-films. This SPANI nano-film is promising for the application in electrochromic devices.

Self-Doped Polyaniline Nanoparticle Dispersions Based on Boronic Acid−Phosphate Complexation

Poly(anilineboronic acid)/phosphate nanoparticle dispersions are produced in high yields using the reactivity of the boronic acid moiety with phosphate in the presence of fluoride. The poly(anilineboronic acid)/phosphate dispersions have been characterized using spectroscopic, microscopic and electrochemical techniques. According to 11 B NMR studies, the formation of anionic tetrahedral boronate group in phosphoric acid in the presence of fluoride forms the basis of self-doped, stabilized PABA nanoparticle dispersion. Transmission electron microscope images show that 25-50 nm diameter PABA nanoparticles are formed under these conditions. UV-vis, FT-IR-ATR spectroscopic and cyclic voltammetric results confirm the formation of the conducting form of PABA. Films produced from these particles exhibit enhanced redox stability and potential dependant conductivity under neutral and basic pH conditions due to the formation of a boron- phosphate complex containing fluoride, which results in a self-doped form of the polymer.