Template-free enzymatic synthesis of electrically conducting polyaniline using soybean peroxidase

Synthesis of polyaniline (PANI) catalyzed by soybean peroxidase at 1 °C in either aqueous or partially organic media, was studied as a function of pH and reaction media. Kinetic studies indicated that, unlike chemical polymerization, enzymatic polymerization of aniline showed neither induction period nor auto acceleration. The redox reversibility and chemical structure of the synthesized PANI was strongly dependent on the starting pH of the reaction medium. UV-vis, FT-IR, WAXD and TGA analysis are used to explain how the enzymatic reaction conditions influence both the chemical structure and physical properties of the PANI. Optimal reaction conditions are outlined for the direct enzymatic synthesis of electrically conductive emeraldine salt with yield as high as 71%.     

血红蛋白生物催化合成导电聚苯胺

利用血红蛋白在十二烷基磺酸钠阴离子表面活性剂胶束体系中生物催化合成水溶性导电聚苯胺/十二烷基磺酸复合物(PANI/SDS), 讨论了不同反应体系及溶液pH值对聚合反应产物的影响. 结果表明该反应具有明显的pH值依赖性, pH (1.0～4.0)是合成导电聚苯胺所必需的, 其最适pH值为3.0, 聚苯胺由导电的翠绿亚胺盐转变为本征态发生在pH 10.4. 用元素分析法、紫外-可见分光光度法、FT-IR、循环伏安法、粘度测试、电导率测试、热重分析法等对PANI/SDS复合物表征, 结果表明该复合物具有较好的热稳定性和可逆的电化学活性.     

Au nanoparticles and polyaniline coated resin beads for simultaneous catalytic oxidation of glucose and colorimetric detection of the product

In this letter, we report the synthesis of Au nanoparticles (NPs) and polyaniline (PANI) on the same cation-exchange resin beads and demonstrate their use in catalyzing the oxidation of glucose to gluconic acid by Au NPs and simultaneously in detecting the formation of the acid by the color change of PANI. The synthesis was carried out by exchanging the cations of the resins with HAuCl4 and anilinuium chloride and then reducing the metal ions by NaBH4 to produce Au NPs followed by polymerization of aniline using H2O2. The green emeraldine salt form of PANI thus obtained was treated with NaOH to be converted to blue emeraldine base before use. The deposition of Au NPs was confirmed by a change in color of the bead, visible spectroscopy, X-ray diffraction, and scanning electron microscopic measurements. On the other hand, the presence of PANI was confirmed by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. The formation of gluconic acid from glucose was confirmed by FTIR spectroscopy. We could detect the presence of glucose of a minimum 1.0 mM concentration in water, using the present method. Our experimental observations demonstrate the possibility of the incorporation of multifunctional components on the surfaces of resins for carrying out a chemical reaction as well as detection of the product.     

Polyurethane/polyaniline and polyurethane‐poly(methyl methacrylate)/polyaniline conductive core‐shell particles: Preparation,morphology, and conductivity

Polyurethane/polyaniline (PU/PANI) and polyurethane‐poly(methyl methacrylate)/polyaniline (PU‐PMMA/PANI) conductive core‐shell particles were synthesized by a two‐stage polymerization process. The first stage was to produce a core of PU or PU‐PMMA via miniemulsion polymerization using sodium dodecyl sulfate (SDS) as the surfactant. The second stage was to synthesize the shell of polyaniline over the surface of core particles. Hydrogen chloride (HCl) and dodecyl benzenesulfonic acid (DBSA) were used as the dopant agents. Ammonium persulfate (APS) was used as the oxidant for the polymerization of ANI. Different concentrations of HCl, DBSA, and SDS would cause different conformations of PANI chains and thus different morphologies of PANI particles. UV–visible spectra revealed that the polaron band was blue‐shifted because of the more coiled conformation of PANI chains by increasing the concentration of DBSA. Besides, with a high concentration of DBSA, both spherical‐ and rod‐shape PANI particles were observed by transmission electron microscope, and the coverage of PANI particles onto the core surfaces was improved. The key point of formation of rod‐type PANI particles was that DBSA was served with a high concentration accompanied with the existence of HCl or SDS. The better coverage of PANI particles over the core surfaces by charging higher DBSA concentrations resulted in a higher conductivity of hybrid particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3902–3911, 2007     

Synthesis and characterization of single‐wall‐carbon‐nanotube‐doped emeraldine salt and base polyaniline nanocomposites

Nanocomposites of polyaniline (PANI) and single‐wall carbon nanotubes (SWNTs) were prepared and characterized via resonance Raman and electronic absorption spectroscopy (ultraviolet–visible/near‐infrared). The chemical synthesis of PANI was performed in the presence of SWNTs in concentrations ranging from 10 to 50 wt % (SWNT/PANI). The obtained materials were hydrophilic, homogeneous composite compounds. The chemical interaction between PANI (in the conducting emeraldine salt form and in the insulating emeraldine base form) and metallic and semiconducting nanotubes was investigated. The emeraldine salt form of the polymer was significantly stabilized in the composite in comparison with plain PANI. A selective electronic interaction process between PANI and metallic SWNTs was found. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 815–822, 2005     

Polyaniline Film Based Amperometric pH Sensor Using A Novel Electrochemical Measurement System

A polyaniline based amperometric pH sensor has been developed using a novel electrochemical measurement system. A polyaniline film (PANI) coated pencil graphite electrode (PGE) is connected in series between the working and counter electrodes of a potentiostat, and immersed in the solution together with a reference electrode. When an external potential is applied, the resulting current varies with the solution pH, which provides the basis for the amperoemtric pH sensor. Equations describing the measurement principle are presented. Based on pH dependent emeraldine salt–emeraldine base transition of PANI film, the pH sensor exhibits high stability, accuracy, selectivity, sensitivity and a short time.     

Micelle-assisted synthesis of polyaniline/magnetite nanorods by in situ self-assembly process

Polyaniline/magnetite nanocomposites consisting of polyaniline (PANI) nanorods surrounded by magnetite nanoparticles were prepared via an in situ self-assembly process in the presence of PANI nanorods. The synthesis is based on the well-known chemical oxidative polymerization of aniline in an acidic environment, with ammonium persulfate (APS) as the oxidant. An organic acid (dodecylbenzenesulfonic acid, DBSA) was used to replace the conventional strong acidic (1 M HCl) environment. Here, dodecylbenzenesulfonic acid is used not only as dopant, but also as surfactant in our reaction system. So, DBSA can excellently control the morphology and size of PANI nanorods and magnetite particles. Magnetite particles were formed simultaneously during sedimentation, and the formed nanorods were also decorated by the particles. The resulting PANI/magnetite composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). It is found that PANI/magnetite nanorod composites have uniform size, superparamagnetism and a small mass fraction of magnetite, thermal stabilization even at a higher temperature.     

Novel polyaniline/titanium nitride nanocomposite: controllable structures and electrical/electrochemical properties

We first present the preparation of a new class of polyaniline (PANI)/titanium nitride (TiN) nanocomposites by in situ chemical polymerization in the presence of TiN nanoparticles. It was found that nanocrystalline TiN with an average diameter of approximately 20 nm incorporated and dispersed homogeneously within the polymer matrix, leading to enhanced conductivity and electrochemical activity. The interaction between nanocrystalline TiN and the polymer matrix was characterized by XRD, FTIR, and UV-vis spectra. Interestingly, the morphology and structure of the PANI/TiN were controlled by the content of TiN nanoparticles in the composites. Structural changes are observed at TiN > or = 30 wt %, where the in situ synthesis results in rod-shape composite particles. The electrical and electrochemical properties of the nanocomposites were also affected by the structure. The mechanisms of the property changes with the TiN contents are discussed. The structural difference was used to explain the different activation energies for the conductance process in emeraldine base (EB)/TiN composites.     

Facile synthesis of polyaniline nanofibers using chloroaurate acid as the oxidant

This work demonstrated a facile route to the synthesis of polyaniline (PANI) nanofibers by polymerization of aniline using chloroaurate acid (HAuCl(4)) as the oxidant. The reduction of AuCl(4)(-) is accompanied by oxidative polymerization of aniline, leading to uniform PANI nanofibers with a diameter of 35 +/- 5 nm and aggregated gold nanoparticles which can precipitate from the liquid phase during the reaction. The resultant PANI nanofibers and gold particles were characterized by means of different techniques, such as UV-vis, FTIR spectroscopy, and scanning and transmission electron microscopy methods. It is found that the gold aggregates are capped with polyaniline, and the conductivity of the fibers is around 0.16 S/cm.     

Inkjet printable polyaniline nanoformulations

Aqueous polyaniline (PANI) nanodispersions doped with dodecylbenzenesulfonic acid (DBSA) were synthesized and successfully inkjet-printed using a piezoelectric desktop printer. This paper examines the optimization and characterization of the nanoparticulate formulation for optimal film electrochemistry and stability. PANI nanoparticle synthesis was optimized in terms of the ratio of monomer (aniline) to oxidant (ammonium persulphate, APS) and dopant (DBSA). Particle size, UV-vis spectroscopy, electrochemical, and conductivity analyses were performed on all materials. Optimal synthesis conditions were found to be at a molar ratio of 1.0:0.5:1.2 aniline/APS/DBSA. This resulting nanodispersion showed a uniform particle size distribution of approximately 82 nm, and UV-vis analysis indicated a high doping level. These synthetic conditions resulted in the highest conductivity, and the electrochemistry of the resulting films was well-defined and stable. Surface tension analysis and rheological studies demonstrated that the aqueous nanodispersions were suitable for inkjet printing. Successful inkjet printing of these polyaniline nanoparticulate formulations is demonstrated.     

Electrically conductive,melt‐processed ternary blends of polyaniline/dodecylbenzene sulfonic acid,ethylene/vinyl acetate,and low‐density polyethylene

Although polyaniline (PANI) has high conductivity and relatively good environmental and thermal stability and is easily synthesized, the intractability of this intrinsically conducting polymer with a melting procedure prevents extensive applications. This work was designed to process PANI with a melting blend method with current thermoplastic polymers. PANI in an emeraldine base form was plasticized and doped with dodecylbenzene sulfonic acid (DBSA) to prepare a conductive complex (PANI–DBSA). PANI–DBSA, low‐density polyethylene (LDPE), and an ethylene/vinyl acetate copolymer (EVA) were blended in a twin‐rotor mixer. The blending procedure was monitored, including the changes in the temperature, torque moment, and work. As expected, the conductivity of ternary PANI–DBSA/LDPE/EVA was higher by one order of magnitude than that of binary PANI–DBSA/LDPE, and this was attributed to the PANI–DBSA phase being preferentially located in the EVA phase. An investigation of the morphology of the polymer blends with high‐resolution optical microscopy indicated that PANI–DBSA formed a conducting network at a high concentration of PANI–DBSA. The thermal and crystalline properties of the polymer blends were measured with differential scanning calorimetry. The mechanical properties were also measured. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3750–3758, 2004     

Dendritic polyaniline nanoparticles synthesized by carboxymethyl chitin templating

Dendritic polyaniline (PANI) nanoparticles were synthesized via oxidative polymerization of aniline, using ammoniumperoxodisulfate as an oxidant, and CM-chitin as a template. The reaction was performed under acidic conditions and the template was removed after the polymerization was completed. Molecular characterization (including UV-vis, FTIR, TGA, and XRD) suggests that the structure of the synthesized dendritic PANI nanoparticles is identical to that of the emeraldine form of PANI, synthesized by the conventional route (without the addition of the CM-chitin template). SEM images reveal that the dendritic PANI nanoparticles have an average diameter in the nanometer range, and are globular in shape, with radially oriented PANI dendrites; in contrast, irregularly-shaped aggregates of PANI are obtained using the conventional synthesis. It was further found that the size of the dendritic PANI nanoparticles is dependent on the CM-chitin content. The higher the CM-chitin concentration, the smaller is the size of the dendritic PANI nanoparticles obtained. An interpretation of these observations and a possible formation mechanism are proposed based on self-assembly between the CM-chitin chains and the aniline monomer.     

Adsorption of sulfonated dyes by polyaniline emeraldine salt and its kinetics

A method for the removal of anionic (sulfonated) dyes from aqueous dye solutions using the chemical interaction of dye molecules with polyaniline is reported. Polyaniline (PANI) emeraldine salt was synthesized by chemical oxidation. Sulfonated dyes undergo chemical interactions with the charged backbone of PANI, leading to significant adsorption of the dyes. This phenomenon of selective adsorption of the dyes by PANI is reported for the first time and promises a green method for removal of sulfonated organics from wastewater. The experimental observations from UV-vis spectroscopy, X-ray diffraction, and conductivity measurements rule out the possibility of secondary doping of polyaniline salt by sulfonated dye molecules. A possible mechanism for the chemical interaction between the polymer and the sulfonated dye molecules is proposed. The kinetic parameters for the adsorption of sulfonated dyes on PANI are also reported.     

Chromatic changes in the blends of electroactive polymers with comb-shaped flexible polymers

The effect of blending of alkylated polymers, which have different backbone structures, was investigated in order to improve the electronic properties of conducting polymers. Comb-shaped flexible polymer, poly(octadecyl acrylate) (PODA), was blended with rigid alkylated conducting polymers, poly(3-dodecyl-thiophene)(PDDT), and polyaniline emeraldine base (PANI)/p-dodecyl-benzenesulfonic acid (DBSA) complex, respectively, to investigate the effect of long alkyl chain of flexible polymer on the conformational mode change of rigid backbones and the effect of intermolecular interaction between these alkylated polymers. Optical microscopy was applied to observe the morphology change and obtain the phase diagrams of these blends. The intermolecular interactions that occurred in these blends were explained for each different characteristic peak obtained with FT-IR spectra. Solvatochromism (red-shift) of PDDT/PODA binary blends in solid state due to the planarity change of rigid backbone in the presence of PODA and electrochromism of PANI(DBSA)₄/PODA ternary blends due to the hydrogen bonding between the nitrogen cation of PANI complex and carbonyl group of PODA are observed in UV-Vis-NIR spectra. Interestingly, the increase of conductivity was observed in the presence of 5 wt% of PODA in PDDT/PODA binary blends and a homogeneous smectic liquid crystalline structure was clearly confirmed by cross polarized optical microscopy in PANI(DBSA)₄/PODA ternary blends.     

Doping of polyaniline films with organic sulfonic acids in aqueous media and the effect of water on these doped films

Polyaniline (PANI) films in the form of emeraldine salt (ES) doped with aqueous organic sulfonic acids such as camphorsulfonic acid (CSA), p-toluenesulfonic acid (p-TSA) and dodecylbenzenesulfonic acid (DBSA) were studied. The ES films were obtained by treating the PANI in the form of emeraldine base (EB) with the aqueous solution of the acids. The dopant weight fraction (w), which is related to the mass gain during the redoping of EB, was in situ determined using a quartz crystal microbalance (QCM). The behaviour of PANI doping with different acids indicates that the uptake shows a slow diffusion process. The kinetics of the doping reaction is dominated by Fickian diffusion kinetics. The diffusion coefficients (D) of the dopant ions into the PANI chains were determined and were found to vary within the range of (1.6-18) × 10⁻¹⁵ cm² s⁻¹. Moreover, the effect of water on these doped ES films was studied. The starting point is the fact that PANI-coated the electrode of QCM shows significant frequency shifts on exposure to water. The changes in the frequency as a function of treatment time in water were quantitatively measured. The response of the device suggests that the mass decrease under water exposure is due to dopant ions release. The latter films were dedoped by exposure to ammonia solution to obtain the EB film form. A further decrease in the mass of the films was observed. The percentage of the mass loss due to water exposure is found to be less than w determined during the dedoping process.     

Preparation and characterization of polyaniline-containing Na-AlMCM-41 as composite material with semiconductor behavior

Composite material formed from a mesoporous aluminosilicate, Na-AlMCM-41, with conducting polyaniline (PANI) has been synthesized by an in situ polymerization technique. Studies of aniline adsorption over mesoporous Na-AlMCM-41 synthesized in our laboratory allowed us to find the modes in which aniline interacts with the active sites of Na-AlMCM-41. In order to obtain the best reaction conditions to polymerize aniline onto Na-AlMCM-41, aniline was first polymerized to produce pure PANI. Hence, the oxidative in situ polymerization was carried out by two procedures, differing in the polymerization time and in static or stirring conditions. Studies of infrared spectroscopy and UV-vis spectroscopy indicated that higher polymerization time and static conditions allowed us to obtain mainly polyaniline in emeraldine form on the host. The N(2) isotherm of the polyaniline/Na-AlMCM-41 composite (PANI/MCM) indicated that the shape was similar to that of MCM, but the shift to saturation transition to lower partial pressure shows that the channels are occupied by PANI and they are now narrowed. The thermal properties of PANI, Na-AlMCM-41, and composite were investigated by TGA analyses and we found that the polymer shows higher thermal stability when it is forming the composite. Scanning electron microscopy indicated that PANI is not on the outer surface of the host. Conductivity studies show that PANI/Na-AlMCM-41 exhibits semiconductor behavior at room temperature and its conductivity was 7.0 x 10(-5) S/cm, smaller than that of pure polyaniline. PANI/Na-AlMCM-41 conductivity shows an increase as temperature increases. Magnetic measurements at room temperature confirmed that the composite has paramagnetic behavior; at lower temperatures the composite became diamagnetic.     

多级树状纳米结构聚苯胺的电化学制备

建立一种无模板的恒电位电聚合方法,可在室温下制备对甲基苯磺酸（p-TSA）掺杂的多级树状纳米结构聚苯胺（PANI）.根据电聚合曲线分析了PANI的聚合机理.扫描电镜（SEM）、透射电镜（TEM）观察表明制备的PANI具有均匀的多级树状纳米结构.紫外可见吸收光谱（UV-Vis）和红外光谱（FTIR）则显示所制备的PANI为掺杂态.该电沉积方法具有简便、易操作的特点,还可应用于其他纳米结构导电聚合物的可控制备.     

A polyaniline-containing filter paper that acts as a sensor, acid, base, and endpoint indicator and also filters acids and bases

In this paper we report a new idea for synthesizing polyaniline in an ordinary filter paper. The synthesis was carried out by a process in which aqueous acidic aniline solution and the oxidizing agent H(2)O(2) was added to the paper drop by drop and in sequence. Uniform polymerization could be obtained with the addition of reagents in either sequence. The polymer formation led to a green coloration of the paper. Formation of the emeraldine salt of polyaniline was confirmed by UV-vis and FTIR spectroscopy. Scanning electron microscopic measurements were made for surface characterization of the polymer formed in the paper. The same paper was used as a sensor for ammonia in vapor and in solution, for acid and base as well as endpoint indication, and also to filter acids and bases. We found that, using the polymer-containing paper, ammonia concentrations in a solution as low as 14 ppm could be measured.     

Conducting polymer diffraction gratings on gold surfaces created by microcontact printing and electropolymerization at submicron length scales

Conducting polymer diffraction gratings on Au substrates have been created using microcontact printing of C18-alkanethiols, followed by electropolymerization of either poly(aniline) (PANI) or poly(3,4-ethylenedioxythiophene) (PEDOT). Soft-polymer replicas of simple diffraction grating masters (1200 lines/mm) were used to define the alkanethiol template for polymer growth. Growth of PANI and PEDOT diffraction gratings was followed in real time, through in situ tapping-mode atomic force microscopy, and by monitoring diffraction efficiency (DE) as a function of grating depth. DE increased as grating depth increased, up to a limiting efficiency (13-26%, with white light illumination), defined by the combined optical properties of the grating and the Au substrate, and ultimately limited by the loss of resolution due to coalescence of the polymer films. Grating efficiency is strongly dependent upon the grating depth and the refractive index contrast between the grating material and the surrounding solutions. Both PEDOT and PANI gratings show refractive index changes as a function of applied potential, consistent with changes in refractive index brought about by the doping/dedoping of the conducting polymer. The DE of PANI gratings are strongly dependent on the pH of the superstrate solution; the maximum sensitivity (DeltaDE/DeltapH) is achieved with PANI gratings held at +0.4 V versus Ag/AgCl, where the redox chemistry is dominated by the acid-base equilibrium between the protonated (emeraldine salt) and deprotonated (emeraldine base) forms of PANI. Simulations of DE were conducted for various combinations of conducting polymer refractive index and grating depth, to compute sensitivity parameters, which are maximized when the grating depth is ca. 50% of its maximum obtainable depth.     

Raman based pH measurements with polyaniline

The reversible acid–base equilibrium between the emeraldine salt (ES) and the emeraldine base (EB) form of thin electropolymerized films of polyaniline (PANI) has been studied between pH 2 and 9 with in situ Raman spectroscopy using the 514, 633 and 780 nm laser excitation wavelengths. The electropolymerization of PANI was done with cyclic voltammetry in a flow cell from a solution consisting of 50 mM aniline and 1.0 M HCl. It is shown that the Raman signal of the CN stretching vibration at 1439 cm⁻¹, originating from the quinoid units of the EB form, can be used for pH measurements between pH 3 and 6 with the 633 nm laser. This vibration is strongly resonance enhanced by the 633 nm laser and its intensity grows therefore considerably in the pH interval where the ES–EB transition mainly takes place (pH 3–6). The influence of the film conditioning pH was also studied as well as the reproducibility of the Raman spectra when pH was changed several times from pH 6 to 3.