Glucose oxidase electrodes based on microstructured polypyrrole films

Highly sensitive glucose oxidase (GOD) electrodes were fabricated on the basis of microstructured polypyrrole (PPy) films. The microstructures of the PPy films had a morphology like cups and were arranged in a density of approximately 4000 units/cm². GOD was immobilized in microstructured PPy films coated on a Pt or stainless steel (SS; AISI 321) substrate electrode. The GOD/PPy/Pt electrode showed a linear response to glucose concentrations in the range of 0–17 mM at a potential of 0.4 V (vs a saturated calomel electrode). Its sensitivity was measured to be approximately 660 nA/(mM cm²) at 15°C, and the response time (t_95%) was approximately 20 s. In comparison, the sensitivity of the GOD/PPy/Pt electrode based on a flat PPy film was only approximately 330 nA/(mM cm²) under the same conditions. The sensitivity of the microstructured GOD/PPy/Pt electrode could be increased to as high as approximately 2400 nA/(mM cm²) at 37°C. The microstructured GOD/PPy/SS electrode had a sensitivity of approximately 550 nA/(mM cm²) and a t_95% value of approximately 30 s at 15°C and 0.4 V. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2550–2554, 2005     

Investigation of electropolymerized polypyrrole composite film: Characterization and application to gas sensors

Polypyrrole–Polymethylmethacrylate (PMMA + PPy) composite films were prepared electrochemically by means of codeposition at constant potential. The films were characterized by using Infrared spectroscopy, wide‐angle X‐ray diffraction analysis, and scanning electron microscopy. The appearance of standard and some new absorption bands for PPy and PMMA confirms the composite formation. The mechanical properties of the conducting PMMA+ PPy films were studied and found to be improved with respect to the control PPy films. The electrical conductivity of the PMMA + PPy film was measured by using standard four‐ and two‐probe methods. The conductivity of the films was found to depend on the pyrrole content. These conducting composites were further used as gas sensors by observing the change in the current when exposed to ammonia gas. The film gives a fast and reproducible response towards ammonia gas. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88:22–29, 2003     

Potassium persulfate-mediated preparation of conducting polypyrrole/polyacrylonitrile composite fibers: Humidity and temperature-sensing properties

Conducting polypyrrole (PPy)/polyacrylonitrile (PAN) composite fibers were prepared by the polymerization of pyrrole in the presence of PAN fibers with potassium persulfate in an acidic aqueous solution. We obtained composite fibers containing concentrations of PPy as high as 1.14% and having surface resistivities as low as 0.6 kΩ/cm² by changing the polymerization parameters, including the temperature and concentrations of pyrrole and oxidant. The tensile strength of 10.02 N/m² and breaking elongation of 32.68% for the pure PAN fiber increased up to 10.45 N/m² and 33.23%, respectively, for the composite fiber containing 0.13% PPy. The change in the resistivity of the PPy/PAN composite fiber during heating–cooling cycles in the temperature range of +5 to 120°C was examined. Scanning electron microscopy and optical microscopy images of the composite fibers showed that the PPy coating was restricted to the surfaces of the PAN fibers. Surface resistivity measurements, Fourier transform infrared spectroscopy, and thermogravimetric analysis techniques were also used to characterize the composite fibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and properties of conducting polypyrrole,polyalkylanilines, and composites of polypyrrole and poly(2‐ethylaniline)

Conducting polymers of alkylanilines, pyrrole, and their conducting composites were synthesized by oxidation polymerization. The oxidants used were KIO₃ and FeCl₃ for the polyalkylanilines and polypyrrole (PPy), respectively. Among the polyalkylanilines synthesized with KIO₃ salt, the highest conductivity was obtained with poly(2‐ethylaniline) (P2EAn) with a value of 4.10 × 10^?5 S/cm. The highest yield was obtained with poly(N‐methylaniline) with a value of 87%. We prepared the conducting composites (PPy/P2EAn and P2EAn/PPy) by changing synthesis order of P2EAn and PPy. The electrically conducting polymers were characterized by IR spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis, and X‐ray diffraction spectroscopy. From the results, we determined that the properties of the composites were dependent on the synthesis order of the polymers. The thermal degradation temperature of PPy was observed to be higher than that of the other polymers and composites. We determined from X‐ray results that the structures of the homopolymers and composites had amorphous regions (88–95%) and crystal regions (5–12%). From the Gouy balance magnetic measurements, we found that the polymers and composites were bipolaron conducting mechanisms. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 241–249, 2006     

Chemical synthesis,characterization, and direct‐current conductivity studies of polypyrrole/γ‐Fe2O3 composites

The in situ polymerization of pyrrole was carried out in the presence of γ‐Fe₂O₃ to synthesize polypyrrole/γ‐Fe₂O₃ composites by a chemical oxidation method. The polypyrrole/γ‐Fe₂O₃ composites were synthesized with various compositions, including 10, 20, 30, 40, and 50 wt % γ‐Fe₂O₃ in pyrrole. The polypyrrole/γ‐Fe₂O₃ composites were characterized with X‐ray diffractometry and infrared spectroscopy. The surface morphology of these composites was studied with scanning electron microscopy. The direct‐current conductivity was studied from 40 to 200°C. The dimensions of the γ‐Fe₂O₃ particles in the matrix had a greater influence on the conductivity values. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2797–2801, 2007     

Application of polypyrrole to flexible substrates

Conducting polymers such as polypyrrole may be useful in smart packaging products, provided application methods can be developed that circumvent the insolubility and infusibility of these materials. Experiments were conducted in five research areas relevant to the application of polypyrrole to nonrigid substrates. The studies reveal that application of polypyrrole from the liquid phase, either by deposition from depleted bulk solution or inkjet printing dispersions, is unlikely to give films as regular as those produced by vapor phase polymerization. Using the latter approach, two potential methods of applying patterned polypyrrole films to nonrigid substrates were developed. The first used hypochlorite to pattern a continuous film of polypyrrole, previously applied by vapor phase polymerization. The second used inkjet printing to apply an oxidant solution, whose pH had been raised with a volatile base, to nonrigid substrates. The higher pH reduced corrosion of the print head, increasing the lifetime of printers exposed to oxidative compounds. The base was subsequently evaporated by heating, and the dried oxidant used as a template for vapor phase polymerization of polypyrrole. This method gave smooth, shiny and adherent polypyrrole films on papers and polyester transparency, with high resolution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3938–3947, 2007     

In situ polymerizations of thiophene on TiO2 films using the semiconductors as initiators

In this work, we prepare the TiO₂ nanoparticle film and anatase TiO₂ nanoarray film, and we achieve the polymerizations of thiophene using the photoexcited TiO₂ film as the initiators. It is measured that the in situ polymerizations of thiophene take place on the surfaces of the two films. The growth of polythiophene (PTh) on the TiO₂ nanoarray is monitored using Fourier‐transform Raman spectroscopy. The TiO₂ nanoarray is found to strongly interact with the PTh polymers. It is observed using scanning electron microscope that the microspores in the nanoarray are filled by the polymers after the reaction of 3 h, and the nanoarray is fully covered by the polymer layer when the polymerization lasts for 5 h. The PTh–TiO₂ nanoarray composite films are measured for the transient photocurrents and photocurrent‐voltage characteristics. The dependence of the photocurrents on the reaction time is revealed and discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40187.     

Raman spectroscopic studies on the structural changes of electrosynthesized polypyrrole films during heating and cooling processes

Polypyrrole films were electrochemically synthesized by direct oxidative polymerization of pyrrole in acetonitrile containing β‐naphthalene sulfonic acid or tetrabutylammonium tetrafluoroborate as an supporting electrolyte. We characterized the as‐grown polypyrrole films by resonance Raman spectroscopy in the temperature region of ?195 to 275°C. During the heating process, the Raman bands related to the oxidized species decreased gradually, due mainly to the affect of oxygen and moisture in the air, and, finally, the neutral polymer chains decomposed into disordered carbons. During the cooling process, polymer chains changed from disordered (coil‐like) to ordered (rodlike) structures and caused the elongation of the conjugated chain length. This results in a red shift of the absorption of the electron spectra of the polymer and the enhancements of the Raman bands related to the oxidized species. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3390–3395, 2003     

Flexible and conducting composites of polypyrrole and polydimethylsiloxane

Conductive and flexible polydimethylsiloxane (PDMS)/polypyrrole (PPy) composites were synthesized electrochemically. Electrochemical syntheses were performed at +1.10 V by using p‐toluene sulfonic acid (PTSA) as supporting electrolyte and water as solvent. Composites were characterized by cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy. Conductivity measurements and mechanical tests were also performed. The observed conductivities were in the range of 3.5–7.6 S/cm, indicating that the conductivities of PDMS/PPy composites and that of pure PPy were in the same order of magnitude. Tensile tests revealed that higher percent elongation was obtained by the addition of PDMS. Highly flexible and foldable PDMS/PPy composites were successfully synthesized, which have high conductivities and improved mechanical properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 736–741, 2004     

New composite systems on the base of polyethylene porous films covered by polypyrrole and polyacrylic acid

New composite systems were prepared by deposition of conducting polymer (polypyrrole) and polyacrylic acid onto polyethylene porous support. Polypyrrole layers were formed by oxidative polymerization from the gas phase of the monomer, and the layers of polyacrylic acid were deposited from a water solution. Morphology of the systems was studied by atomic force microscopy. Measurements of density, electric, and mechanical characteristics of composites were carried out. The interactions between components of systems were investigated by IR spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1410–1417, 2005     

Electronic properties of polypyrrole based TiO2 nanofiber composite

In this work, Polypyrrole (PPy), Titanium dioxide nanofiber (TiO₂‐nf) are prepared by oxidative polymerization and hydrothermal process respectively. The PPy/TiO₂‐nf composite is prepared by in situ oxidative polymerization in the presence of pyrrole monomer and TiO₂‐nf. The nanocomposite and TiO₂‐nf are then characterized by scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDX) techniques and XRD studies. Dielectric studies of PPy/TiO₂‐nf composite is carried out in the frequency range of 1 KHz‐3 MHz at varying temperature and it shows anomalous behavior at 1MHz, where its value reaches to its minimum value of 13 at room temperature and this dip remains even at higher temperature. Impedance study is used to understand the grain and grain boundary effects of the material; frequency dependent ac conductivity has two regions separated at 1MHz, which is being explained by hopping conduction and Maxwell‐Wagner type mechanism, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40036.     

Examining the use of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles to enhance the NH<Subscript>3</Subscript> sensitivity of polypyrrole films

Summary Polypyrrole (PPy) composite films with different contents of Fe₃O₄ were prepared by in-situ polymerization of pyrrole in aqueous solutions. The dependence of dc current changes on the response of the samples exposure to NH₃ vapor has been investigated. The results shows the composite films are more stable than the pristine ones after being exposed to NH₃ vapor. Meanwhile, the response time was reduced with increasing the Fe₃O₄ content in the films. The results might be originated from the structural changes in the PPy films caused by the addition of Fe₃O₄.     

Supercritical carbon dioxide assisted preparation of conductive polypyrrole/cellulose diacetate composites

Supercritical carbon dioxide (SC‐CO₂) has been used to assist the preparation of conductive polypyrrole/cellulose diacetate (PPy/CDa) composites by in situ chemical oxidative polymerization. The morphology and conductivity of resulted composites were investigated with scanning electron microscopy and four‐probe method, respectively. With the assistance of strong swelling effect of SC‐CO₂, composite films were obtained with a macroscopically homogeneous structure and conductivity up to 10^?1 S cm^?1 order of magnitude. Increasing the pressure of SC‐CO₂ increased conductivity, while increasing the temperature decreased conductivity. For comparison, PPy/CDa composite was also prepared with conventional oxidative method in aqueous solution. From the viewpoint of conductivity and environmental protection, the SC‐CO₂ method showed its superiority over the conventional one. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4575–4580, 2006     

Effects of an oxygen‐ion beam (O+7, 100 MeV) and γ irradiation on polypyrrole films

Nanostructured polypyrrole films doped with para‐toluene sulfonic acid were prepared by an electrochemical process, and a comparative study of the effects of swift heavy ions and γ‐ray irradiation on the structural and optical properties of the polypyrrole was carried out. Oxygen‐ion (energy = 100 MeV, charge state = +7) fluence varied from 1 × 10¹⁰ to 3 × 10¹² ions/cm², and the γ dose varied from 6.8 to 67 Gy. The polymer films were characterized by X‐ray diffraction, ultraviolet–visible spectroscopy, and scanning electron microscopy. The X‐ray diffraction pattern showed that after irradiation, the crystallinity improved with increasing fluence because of an increase in the crystalline regions dispersed in an amorphous phase. The ultraviolet–visible spectra showed a shift in the absorbance edge toward higher wavelengths, which indicated a significant decrease in the band gap of the polypyrrole film after irradiation. The scanning electron microscopy study showed a systematic change in the surface of the polymer. A similar pattern was observed with the γ irradiation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel route to pure and composite fibers of polypyrrole

An organic salt (FeAOT) is synthesized by the reaction of sodium 1,4‐bis(2‐ethylhexyl)sulfosuccinate (AOT) and ferric chloride. It is fabricated into fibers by manual drawing and electrospinning. Long polypyrrole (PPy) fibers are obtained for the first time by a vapor deposition reaction of pyrrole on the FeAOT fibers, and this technique is extended to the synthesis of PPy composite fibers with multiwalled carbon nanotubes (PPy–MWCNT fibers). The PPy and PPy–MWCNT fibers have a nanoporous morphology, a conductivity of 10–15 S cm^?1, and a tensile strength of 12–43 MPa. The electrochemistry and current–voltage characteristics of the PPy fibers are also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1490–1494, 2007     

Low temperature TiO2 based gas sensors for CO2

Monitoring the level of CO₂, especially in closed spaces, is more and more required in technological applications, or in human activities. Since most of the literature data reveal CO₂ detection materials with high sensitivities over 300 °C, here we have concentrated on the gas sensing abilities of Cr doped TiO₂ thin films in front of CO₂, close to the room temperature and at atmospheric pressure. The films were obtained by RF reactive sputtering. The undoped films contain a mixture of anatase and rutile phases. With the increase of Cr content, the crystallites size decreases, and the films become pure rutile for a 4 at% Cr concentration. We found out that these material based sensors are more sensitive to CO₂ for higher Cr concentration, the optimum operating temperature approaching to the room temperature, determining in fact low energy consumption. The explanation is related to the observed increase of oxygen vacancies number (which we have evidenced and clarified), and also to the presence of the rutile phase, whose higher dielectric constant (compared to anatase), and its finer crystallites, determine a better gas sensing. More, the surface active area in front of CO₂ increases, as the films become rougher for higher Cr contents. The increase of Cr³⁺ percentage enhance the power of interaction with the adsorbed species (O₂ and/or CO₂). A grain boundary model was proposed for the thermal activation of the electrical conductivity. The energy barrier height at the grain boundary, the impurities concentration (characteristic parameters of this model) were calculated and found to agree well with the data in the literature.     

Effect of K0.5Na0.5NbO3 filling particles on the charge carrier trap distribution of polyimide films

Polyimide (PI) films filled with K_0.5Na_0.5NbO₃ (KNN50) particles at different weight 0, 5, 10, and 15 wt % had been prepared by in‐situ dispersion polymerization process. The thermally stimulated current (TSDC) method was used to investigate the charge carrier trap levels and their distribution of the composite films. The TSDC spectra show that pure film has ‐peaks and ‐peak, but the composite films only have ‐peaks and an extraordinary peak at high temperature region. The trap parameters were calculated by an approximate model, and the results indicate that charge released of the shallow traps show a nonlinear behavior. The trap energies decrease from 0.879–0.968 eV to 0.549–0.839 eV with the increase of the KNN50 content. The surface and interface between KNN50 and PI matrix was considered to the variation of the trap levels. The extraordinary peak of the composite films was correlated with the phase transition of the KNN50 particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39828.     

染料敏化太阳能电池中的纳米TiO2多孔膜研究进展

介绍了染料敏化太阳能电池（DSSC）的工作原理;综述了应用于DSSC的纳米TiO2多孔膜制备方法以及掺杂改性方法。最后对用于DSSC的纳米TiO2多孔膜的发展方向进行了分析与展望。     

Synthesis and characterization of polypyrrole/TiO2 composites on mild steel

The anodic codeposition of polypyrrole and TiO₂ on AISI 1010 steel substrates in oxalic acid medium was studied from the standpoint of their use as protective coatings against corrosion. The influence of surface treatment, pH, stirring and current density (j) on the current efficiency () and pigment concentration incorporated in the polymer (C _c) were investigated. The highest C _c values (7.5%) were found at j = 5 mA cm^–2, pH 4 and stirred baths. The composites were characterized by adherence and surface roughness tests, XPS, EDX, SEM, FTIR and cyclic voltammetry.     

The preparation of Al2O3 based organic/inorganic composite films and the application in agricultural greenhouse

The work presented herein focuses on developing the Al₂O₃ based organic/inorganic multifunctional composite films via an internal addition method in the presence of dripping agent, antifogging agent, light stabilizer and insulation barrier agent. The resulting composite films were systematically characterized using scanning electron microscope, FTIR, differential scanning calorimetry, UV, and tensile testing machine. The morphology changed obviously after introducing the inorganic fillers. In addition, the results indicated that the contact angle of the activated Al₂O₃–10 film had the best stability and the film with ultrafine Al₂O₃ possessed the best anti-dripping performance. The time of the first water drop of the film containing 10 g activated Al₂O₃ (the activated Al₂O₃–10) was 7 min and 18 s, and the time of each ten-drops was less than 120 s. The simulated anti-aging period of the films with anti-aging agent was up to 423 days, which is superior to many other reported organic/inorganic composite films and can be applied to those extreme climate areas (such as Xinjiang, China).