Polypyrrole Thin Films Research Articles

Novel chemical synthesis of polypyrrole thin film electrodes for supercapacitor application

Present investigation describes the cost-effective, novel and simple chemical synthesis of polypyrrole (PPy) thin films for supercapacitor application. These PPy films are characterized by different techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The XRD pattern reveals the amorphous nature of PPy thin film, which is highly feasible for supercapacitors. Further, FTIR study confirms the formation of PPy. The surface morphological study exhibit the coverage of uniform and smooth morphology on thin film. The electrochemical supercapacitive properties of PPy thin films are evaluated using cyclic voltammetry (CV) in 0.5M H2SO4 electrolyte, which exhibits the maximum specific capacitance of 329Fg−1 at the scan rate of 5mVs−1. Additionally, an equivalent series resistance (ESR) of PPy thin films is found to be 1.08Ω using electrochemical impedance measurement.

Electrophoretic nanotechnology of graphene–carbon nanotube and graphene–polypyrrole nanofiber composites for electrochemical supercapacitors

Thin films of multiwalled carbon nanotubes (MWCNT), graphene and polypyrrole (PPy) nanofibers were prepared by cathodic electrophoretic deposition (EPD) from aqueous suspensions, containing safranin (SAF) as a new dispersant. The results of Fourier transform infrared spectroscopy, UV–Vis spectroscopy studies and sedimentation tests, coupled with deposition yield and electron microscopy data showed that SAF adsorbed on MWCNT, graphene and PPy, provided their dispersion and charging in the suspensions and allowed efficient EPD. The deposition yield can be controlled by the variation of SAF concentration in the suspensions and deposition time. The use of SAF as a co-dispersant for MWCNT, graphene and PPy, allowed controlled EPD of composite graphene–MWCNT and graphene–PPy films. The proposed approach for the deposition of PPy paves the way for EPD of neutral polymers using organic dyes as dispersing and charging agents. The composite films were investigated for application in electrochemical supercapacitors (ES). The graphene–MWCNT and graphene–PPy films showed significant increase in capacitance, decrease in resistance and increase in capacitance retention at high charge–discharge rates compared to the films of individual components. The analysis of electrochemical testing results and electron microscopy data provided an insight into the influence of composite microstructure on electrochemical performance. The composites, prepared by EPD are promising materials for electrodes of ES.

Influences of aniline, carbazole, indole, and pyrrole monomers and polymers on formic acid oxidation at Pt electrodes

The effects of aniline, carbazole, indole, and pyrrole on formic acid oxidation at Pt electrodes are compared with those of their corresponding polymers. While thin films of polyaniline, polycarbazole, polypyrrole, and polyindole all promote the direct oxidation (i.e. the pathway that does not involve carbon monoxide as an intermediate) of formic acid at low potentials on Pt, only aniline exhibits a similar effect when added to the formic acid solution. At +0.25V vs. SCE, current enhancements over bare Pt by factors of 4.0, 3.0, 3.4, 5.2, 6.8, respectively, were observed. Interestingly, drop coating of a Pt electrode with carbazole also promoted the direct pathway, although adsorption of carbazole from solution only inhibited formic acid oxidation. The promotion of the direct pathway by aniline adsorbed from solution followed a dependence on surface coverage that suggests inhibition of poisoning by adsorbed carbon monoxide. It is argued that the diversity of these effects indicates that the mechanism by which the direct pathway becomes favoured does not involve any specific chemical functionality of the modifier. However, it must be dependent on the orientation of the modifier relative to the Pt surface. A recent literature model, in which the direct pathway is shown to be favoured by disruption of the H-bonding network of water at the water/metal interface, is invoked to explain this. According to this model, the reaction pathway is determined by the orientation of the formic acid molecule as it adsorbs, which can be changed by other adsorbed species (formate in the model) that create a local hydrophobic region. It is suggested that the modifiers used here can play a similar role.

Nucleation of metals on conductive polymers: Electrodeposition of silver on thin polypyrrole films

The electrodeposition of silver was examined under conditions that excluded a possibility of electroless formation of polypyrrole and silver crystallites. The polymer layers were appropriately prepared; after finishing the polymerization and before the silver reduction they were oxidized. A comparison of the theoretical chronoamperograms with the experimental data, appropriately corrected for the induction time, revealed that the progressive nucleation took place for all examined polymer films and deposition potentials. For lower overpotentials the Ag nuclei were mainly formed under the polymer layer and in its pores. An explanation was given for why the Ag crystallites cannot be completely oxidized from the polypyrrole films.

Hexavalent chromium removal mechanism using conducting polymers

We report detoxification of Cr(VI) into Cr(III) using electrochemically synthesized polyaniline (PANI), polypyrrole (PPY), PANI nanowires (PANI-NW) and palladium-decorated PANI (PANI-Pd) thin films. Percent Cr(VI) reduction was found to be decreased with an increase in pH from 1.8 to 6.8 and with initial Cr(VI) concentration ranging from 2.5 to 10mg/L. Efficacy of PANI increased at higher temp of 37°C as compared to 30°C. PANI-Pd was found to be most effective for all three initial Cr(VI) concentrations at pH 1.8. However, efficacy of PANI-Pd was significantly reduced at higher pHs of 5 and 6.8. Efficacy of PANI and PANI-NW was found to nearly the same. However, there was a significant reduction in effectiveness of PANI-NW at 10mg/L of Cr(VI) at all the three pHs studied, which could be attributed to degradation of PANI-NW by higher initial Cr(VI) concentration. PPY and PANI-NW were found to be highly sensitive with respect to pH and Cr(VI) initial concentration. Chromium speciation on PANI film was carried out by total chromium analysis and XPS, which revealed Cr(III) formation and its subsequent adsorption on the polymer. PANI-Pd and PANI are recommended for future sensor applications for chromium detection at low pH.

Flexible and high surface area composites of carbon fiber, polypyrrole, and poly(DMcT) for supercapacitor electrodes

Thin films of polypyrrole (Ppy) and poly-2,5-dimercapto-1,3,4-thiadiazole (poly(DMcT)) are electrochemically deposited on pieces of carbon fiber (CF) cloth, yielding flexible and high surface area composites that are characterized as electrodes for supercapacitors. A bilayered polymeric composite (CF/poly(DMcT)/Ppy) is obtained by depositing a nanometric layer of Ppy on CF already supporting a poly(DMcT) film. Electrochemical stability tests indicate that the Ppy film acts as a barrier that prevents the loss of the poly(DMcT) electroactive material, thus improving the charge-storage characteristics of the bilayered film even after 1000 cycles. Specific capacitance values of 460±50 and 1130±100Fg−1 are observed for electrodes made of the CF/Ppy and CF/poly(DMcT)/Ppy composites, respectively. Comparatively to similar Ppy composite materials used for supercapacitors, the bilayered film electrode here reported presents a significantly improved specific capacitance value.

Structural and Morphological modification of 100 MeV, silver (Ag8+) Swift Heavy Ions Irradiated Polypyrrole

Polypyrrole (PPY) is a conducting polymer that displays rich variety in morphology, partially crystalline, and partially disordered. Investigations are still being pursued to make them more conducting and crystalline. In the present investigation, conducting polymer polypyrrole (PPY) thin films have been prepared by the electrochemical polymerization technique and were irradiated by 100 MeV, silver (Ag8+), swift heavy ions (SHI) at various fluences of 1010, 1011 and 1012 ions / cm2 . A comparative study of samples before and after irradiation has been performed by using various techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Atomic force microscopy (AFM), X-ray diffraction (XRD). With increase in fluence, the surface structure of PPY films becomes smoother, the crystallinity increases and the conductivity increases by two orders. The present investigations open up the scope for the applicability of irradiated conducting polymers with defined conductivity for sensor applications.

Behaviors of Polypyrrole Soft Actuators in LiTFSI or NaCl Electrolyte Solutions Containing Methanol

Organic soft linear actuators were fabricated using galvanostatic electropolymerization of the polypyrrole (PPy) thin film using a methyl benzoate electrolyte solution of N,N-Diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide. The electrochemical deformation behaviors of the PPy actuators were investigated in aqueous solutions of an electrolyte, lithium bis (trifluoromethanesulphonyl) imide (LiTFSI) or sodium chloride (NaCl), containing different concentrations of methanol. The actuating strain of approximately 9% was achieved when the actuator was driven by a potential between –1 and 1 V with the potential sweep rate of 10 mV/s corresponding to 0.0025 Hz in the LiTFSI electrolyte containing 40% to 50% of methanol under a load stress of 0.3 MPa. However, the PPy actuator could not catch up with the higher frequency. On the other hand, the PPy actuator caught up with the potential sweep up to 0.1 Hz in the NaCl solutions with a methanol concentration between 40% and 60% with the expense of the actuating strain to approximately 1%.

Synthesize, Characterization, and Corrosion Inhibition of Polypyrrole Thin Films on Copper

Polypyrrole (PPy) coatings were synthesized on copper by electrochemical polymerization of pyrrole monomer in aqueous acidic and basic solutions by cyclic voltammetry. The coatings were characterized with CV, UV-visible absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) techniques. The corrosion protection aspects of PPy coatings have been investigated using the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The potentiodynamic polarization measurements show that the PPy coating has ability to protect the copper against corrosion. It was concluded that a complete corrosion protective PPy film could not be obtained through direct electro-oxidation procedure. This may be due to copper dissolution in the monomer oxidation potential range.

Amperometric biosensor based on polypyrrole and tyrosinase for the detection of tyramine in food samples

An electrochemical tyrosinase electrode for detection of tyramine was developed via cross-linking immobilization method over phosphate-doped polypyrrole film. The enzyme tyrosinase immobilized over the polypyrrole thin film preserves well its biocatalytic activity. Tyramine was determined by the direct reduction of biocatalytically formed dopaquinone at −0.250V. The analytical characteristics of this biosensor, including linear range, detection limit, repeatability and storage stability are described. The kinetics of the enzymatic reaction fitted into a Michaelis–Menten type kinetic, as confirmed by the h parameter close to 1 obtained from the Hill's plot. Under the optimum conditions, the current response had a linear relationship with the concentration of tyramine in the range of 4–80×10−6M, with a sensitivity of 0.1069AM−1 and a limit of detection of 5.7×10−7M. The biosensor exhibited high repeatability and long term stability. Determination of tyramine in real samples showed good recovery. The selective detection is related to specific action of tyrosinase toward phenolic group from tyramine (1-hydroxy-4-ethylaminobenzene). The developed biosensor was applied to the determination of the tyramine content in sauerkraut samples.

Optical and Electrical Properties of Thin Films of Polyaniline and Polypyrrole

Optical and Electrical Properties of Thin Films of Polyaniline and Polypyrrole

Electrochemical polymerization and Raman study of polypyrrole and polyaniline thin films

In this paper we present thin films of polypyrrole (PPY) and polyaniline (PANi) which have been synthesized electrochemically on Gold electrode by direct oxidation of pyrrole and aniline in Acetonitrille using three electrodes. Raman spectroscopy results were analyzed in terms of normal modes, and spectra were obtained using 633 nm He-Ne laser. It was found that Raman spectra depend on the doping level of PPY and PANi. DFT force field has been calculated at the B3LYP/6-311+ G* level. General assignments of the vibrational spectra of polypyrrole and polyaniline have been proposed and were compared with those of pyrrole and aniline in order to determine the vibrational modes. Key words: Electropolymerization, polypyrrole, polyaniline, vibrational analysis modes, comparison of DFT functional, Raman spectroscopy.

Investigation of morphology, a.c. electrical and optical properties of nanostructured thin film of polypyrrole–bromoaluminium phthalocyanine

In this research, nanocomposite polypyrrole (PPy) + 30 % bromoaluminium phthalocyanine (BrAlPc) was prepared in our laboratory. Optical absorption and field emission scanning electron microscopy characterized the thin films. The powder of nanocomposite was characterized by X-ray diffraction. The nanocomposite PPy + 30 % BrAlPc thin film deposited on pre-cleaned glass substrate with a thickness of 100 nm, which was deposited in a high vacuum device of electron-beam gun in the pressure of 10−5 mbar. The capacitance and the dissipation factor were measured in a.c. electrical and in the range of 102–105 Hz frequency and 303–413 K temperatures. The nanoparticles are spherical in shape with an average size about 25–37 nm. Their UV–Vis spectra of the nanocomposite (PPy + 30 % BrAlPc) is typically described by two strong Q and Soret bands 600–700 and 300–400 nm. The results showed a sharp diffraction peak appeared in 2θ = 8.72 (d = 10.1296 A) and grian size D = 8.991 nm. The results can be described by the theory of Goswami–Goswami for sandwich devices.

Optical absorption and dispersion analysis based on single-oscillator model of polypyrrole (PPy) thin film

In this work, polypyrrole samples were synthesized by chemical oxidative polymerization technique with Iron (III) chloride as an oxidant. Thin films of PPy were prepared by spin coating technique. The molecular structure of polypyrrole film was characterized by Fourier transform infrared spectroscopy (FTIR). The optical properties of the PPy films were studied using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500nm. The recorded absorption measurements in the UV–vis region show two well defined absorption bands. The analysis of the spectral behavior of the absorption coefficient (α), in the absorption region revealed two direct transitions. The dispersion parameters were determined and discussed based on the single oscillator model. According to the analysis of dispersion curves, the parameters, namely; dispersion energy (Ed), oscillator energy (Eo), high frequency dielectric constant (ɛ∞) and lattice dielectric constant (ɛL) were evaluated. Discussion of the obtained results and their comparison with the previous published data were also given.

Conducting Plasma Polymerized Polypyrrole Thin Films as Carbon Dioxide Gas Sensors

AbstractThis paper describes the production of conducting polypyrrole (PPy) thin films by plasma‐enhanced chemical vapor deposition (PECVD) and its posterior use for sensing applications of carbon dioxide (CO2). Since PECVD yields the non‐conducting form of PPy, a doping process consisting of exposure to iodine vapor is required to obtain electrically conducting samples. Differences in the chemical state and topography between the doped and undoped systems are studied and characterized to demonstrate the doping effect on the polymer. Furthermore, changes in conductivity after exposure to CO2 gas are measured to evaluate the use of these thin films as chemical sensors. The results suggest that plasma polymerized films show a good sensitivity and reproducibility in the analyte detection. magnified image

Dopant-dependent variation in the distribution of polarons and bipolarons as charge-carriers in polypyrrole thin films synthesized by oxidative chemical polymerization

A study on the distribution of polarons vs. bipolarons as charge carriers in polypyrrole thin films doped with different dopant anions (chloride, p-toluenesulfonate and anthraquinone-2-sulfonate) is presented in this paper. The polypyrrole thin films synthesized by oxidative chemical polymerization have comparable thickness in the range of 80–100nm. However, with the variation of the dopant anion, the conductivity of the polypyrrole thin films can differ by three orders of magnitude. The conductivity of polypyrrole thin films doped with chloride, p-toluenesulfonate and anthraquinone-2-sulfonate is 0.64S/cm, 7.1S/cm and 120S/cm, respectively. The Raman spectroscopy and electron spin resonance (ESR) spectroscopy results show that (i) both polarons and bipolarons are present in the three types of polypyrrole thin films and (ii) the distribution of polarons vs. bipolarons as charge carriers in polypyrrole varies with the dopant anion used. The overall study reveals that the charge carriers in the anthraquinone-2-sulfonate-doped polypyrrole thin film are mainly spinless bipolarons, whereas the charge carriers in the chloride-doped polypyrrole thin film are dominated by paramagnetic polarons.

In-Situ Monitoring the Growth of Polypyrrole Films at Liquid/Solid Interface Using a Combination of Polarized Infrared Spectroscopy and Reflectance Anisotropy Spectroscopy

Polarized infrared reflection measurements in an ellipsometric set-up and reflectance anisotropy spectroscopy (RAS) were used for the first time for combined in-situ characterization of the electrochemical growth (potentiostatic pulse method) of thin polypyrrole (PPy) films on Si(110). Both methods can monitor material and thickness related changes during deposition and are shown as sensitive tools for studying time development of PPy growth under varying potential. In detail polarized infrared spectroscopy delivered information on the chemical structure of the as-deposited film and RAS gave information on the quality of the interface and deposition rate. The identified polymerisation mechanism is in agreement with literature and valid for all times of deposition. For deposited films rough surfaces and partially inhomogeneous thicknesses (35 ± 10 nm and 120 ± 10 nm) were found. At present state it is not possible to simulate the in-situ RAS and IR-spectra in simple coherent optical layer models.

All-organic polymer-dispersed liquid crystal light-valves integrated with electroactive anthraquinone-2-sulfonate-doped polypyrrole thin films as driving electrodes

All-organic PDLC (polymer-dispersed liquid crystal) light-valves using all-polymer conductive substrates containing thin films of polypyrrole doped with anthraquinone-2-sulfonate (AQSA −) as the driving electrodes were fabricated in this study. The all-polymer conductive substrates were prepared under ambient conditions by in situ depositing polypyrrole thin films on blank flexible poly(ethylene terephthalate), or PET, substrates from aqueous media in which oxidative polymerization of pyrrole was taking place. The obtained flexible all-polymer conductive substrates were semi-transparent with cohesive coatings of AQSA −-doped polypyrrole thin films (thickness ∼55 nm). The all-polymer flexible conductive substrates had sheet resistivity ∼40 kΩ □ −1and T% transparency against air ∼78% at 600 nm. The light-valves fabricated using the above all-polymer conductive substrates showed ∼50% transparency against air at 600 nm when 4 V μm −1 electric field was applied.

Polypyrrole Thin Film: Room Temperature Ammonia Gas Sensor

Polypyrrole thin films were synthesized in situ by chemical polymerization. The morphological studies by Scanning Electron Microscopy showed formation of uniform granular structure with average grain size of 0.6 μm. Fourier transform infrared spectroscopy revealed formation of polypyrrole. The film composition was also characterized by UV-Vis Spectroscopy. These films were investigated for their sensing behavior towards NH3, C2H5OH and CH3OH gases at room temperature. It has been observed that these films are selective for ammonia gas, and the sensitivity exhibited a linear response in range of 5-100 ppm. These studies show that polypyrrole films can be used as room temperature ammonia sensors.

Amperometric tyrosinase based biosensor using an electropolymerized phosphate-doped polypyrrole film as an immobilization support. Application for detection of phenolic compounds

An amperometric biosensor was constructed by immobilization of enzyme, tyrosinase, in an electrochemically synthesized phosphate ion-doped polypyrrole film on a Pt disk electrode. The tyrosinase maintains its bioactivity well within the polypyrrole thin film. A clearly defined reduction current proportional to the phenolic compounds concentration was observed in cyclic voltammetry, which attributed to the reduction of enzymatically produced quinone at the electrode surface. Phenolic compounds were quantitatively estimated in aqueous medium by the direct electrochemical reduction of enzymatically liberated quinone species at −0.05 V by chronoamperometry. For the all six phenolic compounds analyzed, the kinetics of the enzymatic reaction fitted into a Michaelis–Menten type kinetics, as demonstrated by the h parameter close to 1 obtained from the Hill's plot. The sensitivity followed the decreasing order catechol > phenol > 2-bromophenol > 2-chlorophenol > 2-iodophenol > 2-fluorophenol. The greater value of I max and the lowest K M a p p was found for catechol. The detection limits were in the range of 0.84–8.54 μM. The lowest detection limits were found for catechol and the highest for 2-fluorophenol.