Polymerized Polypyrrole Films Research Articles

Investigation of the effect of in-situ grown PPy on low frequency dielectric properties and other properties of PVA-PVP blend film

Present study is carried out to understand the effect of conducting polymer, polypyrrole (PPy) on structural, morphological, thermal and dielectric properties of bio-compatible polymer blend film of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP). The growth of PPy in the matrix of PVA–PVP was analyzed using XRD, FT-IR and SEM studies. The shifting in positions and broadening of XRD diffraction peaks of PVA–PVP-PPy from that of PVA–PVP indicates the structural modification and reduction in the crystallinity of the PVA–PVP due to incorporation of PPy. The SEM studies suggest scattered growth of PPy in PVA–PVP matrix at lower concentration of pyrrole monomer. As the monomer concentration is increased, the uniform and interconnected growth of PPy was observed in SEM micrographs. The TGA thermograms show faster thermal degradation of PVA–PVP- PPy films at lower temperature as compared to PVA–PVP films. The blend films of PVA–PVP- PPy exhibited enhanced values of dielectric constant and ac conductivity as compared to the virgin blend film which are observed to increase with increasing concentration of PPy. The high dielectric constant with high ac conductivity exhibited by PVA–PVP-PPy film suggests its possible application as flexible dielectric material for the development of biosensors, energy storage devices in field of green organic electronics.

Micro Organic Light Emitting Diode Arrays by Patterned Growth on Structured Polypyrrole

AbstractPatterning organic light emitting diodes (OLEDs) with several micrometers resolution is of importance in applications such as micro displays, virtual and augmented reality devices. Here a fabrication method of micro OLEDs is reported, using conducting polymer polypyrrole (PPy) as nucleation layer. The photolithographically patterned PPy films are used for patterned growth of hole transport layer to locally confine carrier injection. High‐resolution red, green, and blue micro OLED arrays are demonstrated. The green micro OLEDs with stacked structure of Al/Alq3/NPB/PPy/ITO exhibit a maximum current efficiency of 3.41 cd A−1, which is 80% in comparison to those devices on indium tin oxide glass.

Performance of Zn rechargeable cells having Polypyrrole cathodes doped with surfactant anion

Currently there exists a very high demand for electrochemical energy storage devices such as rechargeable cells and super capacitors due to massive increase in the use of portable electronics. At the moment this demand is mainly supplied by Li based cells. However due to high cost, rapid reactivity and issues in disposal of Li attention has diverted on non Li based cells. Zn has been identified as a good candidate to replace Li. Even though several Zn based rechargeable cells were reported, less work has been carried out on cells with conducting polymer cathode based Zn cells. In this study, performance of Zn rechargeable cells fabricated with conducting polymer Polypyrrole(PPy) doped with a surfactant anion is reported. PPy films were galvanostatically electro polymerized on to stainless steel disc and cells were assembled with a Polyvinylidenefluoride based gel polymer electrolyte having Zinc trifluoromethanesulfonate as the salt. Cells having different cathode thickness were fabricated and they were characterized using cyclic voltammetry, electrochemical impedance spectroscopy and continuous charge-discharge tests. Cells exhibit open circuit voltages between 0.9 -1.0 V. Cycling testes showed that cycleable capacity almost follow the thickness variation. Continuous charge-discharge tests revealed that the capacity decrement with the cycle number is higher in thinner films.

Integration of carbon nanotubes to three-dimensional C-MEMS for glucose sensors

The amperometric glucose biosensor utilizing glucose oxidase immobilized in polymerized polypyrrole film was constructed on multi-walled carbon nanotube (CNT) modified C-MEMS electrode. Dense coverage of CNTs was successfully integrated on the surface of the C-MEMS, which greatly increased the effective electro-active surface area thus resulting in higher loading of enzyme. Electrochemical studies reveal that the C-MEMS/CNT based glucose sensor displays linear response for glucose concentrations from 5 to 80mM with a sensitivity of 97.3mAM−1cm−2 with the response time less than 10s. The detecting sensitivity was proved to be increased more than 50 times compared with 1.7mAM−1cm−2 for the blank C-MEMS one.

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.

A rationally-designed synergetic polypyrrole/graphene bilayer actuator

The development of advanced actuator system strongly depends on the assorted use of unique materials and rational structure design. In the current work, a newly designed bilayer actuator based on a graphene film which has undergone O2 plasma pretreatment and the conducting polymer polypyrrole (PPy) doped with small anions has been presented. The antithetic expansion–contraction mechanisms of graphene and PPy films under a certain positive or negative potential offer the favorably synergetic function for driving the excellent actuation response of the resultant PPy/graphene bilayer actuator. In response to the variation of electrochemical potentials (e.g., ±0.8 V), the PPy/graphene actuator can move to and fro with a large bending angle of ca. 120° despite the limit of electrolyte surface, which is superior to that of the unitary graphene films demonstrated previously, and overcomes the relatively poor mechanical strength of PPy films. Calculations based on an ideal model by only considering the deformation of each constituent layer of the actuator reveal that the bending degree of PPy/graphene configuration could be up to ca. 1600°, suggesting that there is considerable room to further optimize the actuator configuration and improve the actuation performance.

Electrocatalytic Reduction of HNO2 by a Silicomolybdate Polyanion: A Differential Electrochemical Mass Spectrometry Study

AbstractElectrocatalytic activities towards the reduction of important analytes such as nitrite, bromate, chlorate and hydrogen peroxide have been demonstrated for numerous heteropolyanions (HPAs). In this paper, the behavior of a Keggin‐type HPA, SiMo12O, on the one hand in solution and on the other hand immobilized in a conducting polymer, polypyrrole (PPy), in the presence of nitrous acid (HNO2) is examined. It is shown that the PPy films codoped with SiMo12O and HSO ions could be used as sensitive part of an amperometric sensor even if the response is limited by HNO2 diffusion into the PPy film. Differential electrochemical mass spectrometry (DEMS) was used to determine the gas formed during nitrous acid reduction by H2SiMo12O. Under an applied cathodic potential, when both HNO2 and SiMo12O are present in the medium, NO gas is produced whereas, when SiMo12O ions are immobilized in a PPy film, N2O evolves and the NO concentration, notably due to the disproportionation of HNO2, decreases.

Electrodeposited (Cu–In–Se)/polypyrrole PV structures

Hybrid PV structures based on polycrystalline photoabsorber Cu–In–Se (CISe) and electrically conductive polymer polypyrrole (PPy) were prepared using the electrodeposition technique. The PPy is considered as p-type barrier layer on n-CISe in the cell structure. Photoactive CISe thin films of various compositions were deposited electrochemically onto glass/ITO substrates from aqueous solutions containing CuSO 4, In 2(SO 4) 3 and SeO 2. All the obtained polycrystalline CISe films were annealed in vacuum to improve the crystalline structure and etched in 10% KCN to remove the additional phases. In order to prepare the PV structures, thin PPy films doped with β-naphthalene sodium sulfonate were galvanostatically electrodeposited onto the CISe films. Appropriate parameters of electrodeposition were selected experimentally. The morphology and thickness of the prepared film layers were determined using the SEM technique. The chemical composition of the CISe films was determined by energy dispersive X-ray spectroscopy (EDS). To investigate the electrical properties of the obtained structures, current–voltage and impedance characteristics were measured. The best structure showed an open-circuit voltage of 138 mV and a short-circuit current density of 2.55 mA/cm 2 under white light illumination with an intensity of 100 mW/cm 2.

The sensitivity of 4-ethylbenzenesulfonic acid-doped plasma polymerized polypyrrole films to volatile organic compounds

We have investigated the volatile organic compounds (VOCs) gas sensing properties of high conducting polypyrrole thin films prepared by plasma polymerization and doped with 4-ethlbenzenesulfonic acid (EBSA). Upon exposure to VOCs gas, the resistance of EBSA-doped plasma polymerized polypyrrole (PPPy) films decreases. The films exhibit higher sensitivities to polar analytes such as formaldehyde and acetaldehyde, but show little response to toluene and benzene. Moreover, the EBSA-doped PPPy films are hardly affected by humidity.

Hybrid copper–indium disulfide/polypyrrole photovoltaic structures prepared by electrodeposition

Abstract Photovoltaic structures on the basis of photoactive polycrystalline CuInS2 (CIS) in combination with electrically conductive polymer polypyrrole (PPy) were prepared using the electrodeposition technique. In order to prepare stable PPy films with a good adherence to the surface of CIS, the appropriate concentrations of reagents, current densities and electrodeposition potentials were selected experimentally. Electrochemical polymerization of pyrrole to PPy on the CIS surface is faster under white light irradiation, and the polymerization starts at a lower potential than in the dark. Significant photovoltage and photocurrent of the fabricated CIS/PPy structures have been observed under standard white light illumination. The best structure showed an open-circuit voltage of 509 mV, a short-circuit current density of 6.45 mA/cm2, fill-factor 0.47 and photoconversion efficiency of 1.53% under white light illumination of 100 mW/cm2.

Indicator Free DNA Hybridization Detection by Impedance Measurement Based on the DNA‐Doped Conducting Polymer Film Formed on the Carbon Nanotube Modified Electrode

AbstractA new biosensing strategy for direct electrochemical detection of DNA hybridization by AC impedance measurement is described. The indicator or label free approach was developed on the basis of the carbon nanotubes coupled with a conductive polymer polypyrrole (PPy). Multi‐walled carbon nanotubes functionalized with carboxylic group (MWNTs‐COOH) were modified on the glassy carbon electrode (GCE) and the oligonucleotide probes were doped within the electro‐polymerized PPy films by serving as the sole counter anion during the growth of the conducting films. Before and after hybridization reaction with the complementary DNA sequences, a decrease of impedance values was observed as a result of the reduction of the electrode resistance. Hybridization amounts of the one‐base, two‐base and three‐base mismatched sequences were obtained only in a 51%, 18% and 8.2% response when compared to that for the complementary matched sequence. Such unique response is attributed to the concomitant conductivity changes of the PPy‐polymerized carbon nanotubes, and offers great promise for reagentless DNA hybridization analysis.

Effects of discharge power on the structure and electrical properties of plasma polymerized polypyrrole films

We report on the effects of the discharge conditions on the structure and conductivity of the plasma polymerized polypyrrole films. Comparative studies of the infrared spectroscopy, elemental analysis and UV–VIS spectroscopy give information that the some pyrrole rings are remained in the PPPy films prepared with 10, 20 W discharge power, whereas almost all the pyrrole rings are cleaved in the PPPy films prepared with 50, 100 W discharge power and the three-dimensional crosslinked structure seems to have been formed. However, the different in the structure of the polymer backbone of the PPPy films does not crucially affect on the conductivity, the high conductivity is obtained under the wide discharge condition.

Analysis of the characteristics of electrochemically polymerized polypyrrole films by using QCA and AFM

In order to investigate dynamic properties of polypyrrole (Ppy) thin films in various electrolyte solutions, NaCl, NaClO 4, NaNO 3, NaDS, LiClO 4, KClO 4, resonant frequency and resistance were measured through electrical polymerization process using a quartz crystal analyzer (QCA). The surface structure was observed by using atomic force microscopy (AFM). A diagram of the resonant frequency and resistance (F-R diagram) was used to interpret the results and compared with AFM photograph. When the Ppy film is polymerized onto the AT-cut quartz electrode crystal, it behaves as a rigid elastic layer at the initial stage. Then, it turns into a viscoelastic layer as polymerization. This is due to the penetration of electrolytes into the film. The size, mass and mobility of the hydrated cation and anion of the electrolyte affected the degree of the viscoelastic change of the polypyrrole thin films.

Electrical stimulation alters protein adsorption and nerve cell interactions with electrically conducting biomaterials

Electrical charges have been shown to enhance nerve regeneration; however, the mechanisms for this effect are unclear. One hypothesis is that an electrical stimulus alters the local electrical fields of extracellular matrix molecules, changing protein adsorption. We have investigated this hypothesis — that electrical stimulation increases the adsorption of serum proteins, specifically fibronectin (FN), to the electrically conducting polymer polypyrrole (PP), thereby, increasing neurite extension. PP was used because electrical stimulation of PP has been shown to significantly enhance neurite outgrowth, and more importantly, PP can be formed into conduits to guide nerve regeneration in vivo. Here, we looked at the effects of electrical stimulation on protein adsorption when an electrical current was applied to PP (1) during protein adsorption (immediate stimulation) and (2) several hours after protein adsorption (delayed stimulation). We found that immediate stimulation of PP increases FN adsorption from purified FN and serum-containing solutions. Correspondingly, PC-12 cells grown on PP films that had been previously adsorbed with FN during immediate stimulation expressed longer neurites. However, for delayed stimulation, no significant differences in adsorption or neurite outgrowth were observed. These studies suggest that increased FN adsorption with immediate electrical stimulation may explain enhanced neurite extension on electrically stimulated PP.

The principle and applications of piezoelectric crystal sensors

The principle, construction, and applications of piezoelectric crystal sensors as universal sensor are reviewed. A historical overview and basic piezoelectric crystal physics as well as design considerations for different sensor system are reviewed. Most of previous reviews were treated with gas phase application, but this review is focused mainly on the liquid phase application, such as monitoring the dynamic microrheology phenomena of liquid crystal, lipid thin films, and electrochemical polymerized polypyrrole film.

Synthesis and characterization of polypyrrole-hyaluronic acid composite biomaterials for tissue engineering applications.

New tissue engineering technologies will rely on biomaterials that physically support tissue growth and stimulate specific cell functions. The goal of this study was to create a biomaterial that combines inherent biological properties which can specifically trigger desired cellular responses (e.g., angiogenesis) with electrical properties which have been shown to improve the regeneration of several tissues including bone and nerve. To this end, composites of the biologically active polysaccharide hyaluronic acid (HA) and the electrically conducting polymer polypyrrole (PP) were synthesized and characterized. Electrical conductivity of the composite biomaterial (PP/HA) was measured by a four-point probe technique, scanning electron microscopy was used to characterize surface topography, X-ray photoelectron spectroscopy and reflectance infrared spectroscopy were used to evaluate surface and bulk chemistry, and an assay with biotinylated hyaluronic acid binding protein was used to determine surface HA content. PP/HA materials were also evaluated for in vitro cell compatibility and tissue response in rats. Smooth, conductive, HA-containing PP films were produced; these films retained HA on their surfaces for several days in vitro and promoted vascularization in vivo. PP/HA composite biomaterials are promising candidates for tissue engineering and wound-healing applications that may benefit from both electrical stimulation and enhanced vascularization.

Characterization of a urea optical sensor based on polypyrrole

A new optical sensor for urea determination is presented. It is based on the enzymatic reaction with urease, which is first photoimmobilized with polyacrylamide onto a chemically polymerized polypyrrole (PPy) film. The main advantage of this sensor is that no indicator dye or pH indicator is needed, because PPy itself acts as the support and the indicator. These PPy films show an absorbance spectrum in the near IR range which is pH dependent. The variation of absorbance is thus directly related to the change of pH caused during the enzymatic reaction, which is also dependent on the urea concentration. The linear range of the sensor is from 0.06 to 1 M of urea, which is the common level of urea concentration found in blood and urine samples.

Effect of Dopants on Characteristics of Polypyrrole as a Liquid Crystal Alignment Layer

Electrochemically polymerized polypyrrole (PPy) films with different dopants showed different surface energies. The films were used as alignment layers of liquid crystal displays (LCDs). The PPy films doped with ClO4 − (PPy/ClO4) and PF6 − (PPy/PF6) showed surface energies of 43.2 and 32.3 mJ/m2, respectively, while the pretilt angles of 4-cyano-4′-pentylbiphenyl on the films were 5.6 ± 0.3 and 14.0 ± 2.2 degrees, respectively. The electro-optic response time measured by light transmittance through the twisted nematic(TN) LCDs on switch-on was shorter for the display with PPy/PF6 than for that with PPy/ClO4. However, the turn-off response time was shorter for the display with PPy/ClO4 than for that with PPy/PF6. The total response time, which is the sum of the turn-on and turn-off response times, was 75 and 120 msec at 3.0 V pp for the displays with PPy/ClO4 and PPy/PF6, respectively.

Formation of Polypyrrole Fine Wires by “Electropolymerization LB Technique”

Electrically conducting wire of (1.5pm width and of 50μm length was formed ovcr the electrically insulation gap formed on the ITO substratc by “electropolymeriation LB technique”; the combination of clctropolymerization of conducting polymer and the deposition of Langmuir-Blodgctt fi Ims. The conductivity of the wire was estimated to be about 200Skm from thc I-V characteristics and the value was not infenor to the reported conductivity of the electrochemically polymerized polypyrrole film.

Characteristics of aluminium solid electrolytic capacitors using a conducting polymer

In order to form an electrochemically polymerized polypyrrole film on an electrically insulated dielectric layer surface, a conductive precoating layer was first deposited, at the expense of electrical conductivity. Using the precoating layer as the anode, a polypyrrole layer was then deposited electrochemically in preparation for the fabrication of a solid electrolytic capacitor in which the composite conducting polymer layer was used as a solid electrolyte. Soluble polyaniline could be used as a conductive precoating layer as well as polypyrrole formed by chemical oxidizing polymerization. The capacitor using the composite solid electrolyte presented excellent impedance frequency and temperature characteristics; moreover, the solid electrolyte showed ‘self-healing’ and non-polar behaviour.