Polypyrrole Nanofibers Research Articles

Controllable anchoring of gold nanoparticles to polypyrrole nanofibers by hydrogen bonding and their application in nonenzymatic glucose sensors

An enzymeless glucose biosensor based on polypyrrole nanofibers-supporting Au nanoparticles (Au/PPyNFs) was investigated in this study. The Au/PPyNFs heterogeneous composite materials were synthesized in-situ via hydrogen bonding interactions for the assembly of polyethyleneimine (PEI) on the surface of polypyrrole nanofibers (PPyNFs). By changing the molar ratio of PPy to HAuCl4, Au/PPyNFs with different Au loadings were obtained. The morphology and composition of Au/PPyNFs were characterized using SEM, TEM, FTIR, XRD and XPS, respectively. The hybrids exhibited a high electrocatalytic activity toward glucose oxidation, which is prerequisite for the catalysts to be applied in amperometric glucose sensors. By using the nonenzymatic glucose sensor based on Au/PPyNFs, 0.2–13mM glucose can be detected with a sensitivity of 1.003μAcm−2mM−1 and a good linearity (R2=0.9993) between current density and glucose concentration. The proposed glucose sensor provides a promising strategy to construct fast, sensitive, and anti-interfering amperometric sensors for early diagnosis and prevention of diabetes.

The electrical properties of a sandwich of electrodeposited polypyrrole nanofibers between two layers of reduced graphene oxide nanosheets

A sandwich of polypyrrole (PPy) nanofibers between two electrodeposited reduced graphene oxide (RGO) layers was prepared by an electrochemical method. The structure and compositions were characterised by field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FT-IR) spectroscopy. The electrical properties were studied by electrochemical impedance spectroscopy (EIS). The FESEM results confirmed synthesis of a sandwich structure with PPy nanofibers between two electrodeposited RGO layers (RGO/PPy/RGO). The mean width of PPy nanofibers was approximately 76±16nm. The EIS results showed that the charge transfer resistance of the coated glassy carbon electrode (GCE) with a sandwich structure of RGO/PPy/RGO was significantly decreased in comparison with coated GCE with PPy nanofibers. This was because the RGO with many small band gaps is more favourable for electron conduction. The comparison of EIS results shows that diffusion of active species through the RGO layers is increased in the presence of the second layer of RGO. The simulation results indicate a high interfacial capacitance (Cdl) of 2170.60μFcm−2 for the coated GCE with RGO/PPy/RGO compared with 360.77μFcm−2 for coated GCE with PPy/RGO. This difference in capacitance can be attributed to the highly accessible specific surface area of graphene and its high efficiency towards electrolyte ion absorption.

Nitrogen‐Doped Porous Carbon Nanofiber Webs as Anodes for Lithium Ion Batteries with a Superhigh Capacity and Rate Capability

Nitrogen-doped carbon nanofiber webs (CNFWs) with high surface areas are successfully prepared by carbonization-activation of polypyrrole nanofiber webs with KOH. The as-obtained CNFWs exhibit a superhigh reversible capacity of 943 mAh g(-1) at a current density of 2 A g(-1) even after 600 cycles, which is ascribed to the novel porous nanostructure and high-level nitrogen doping.

Preparation and characterization of electrospun polyurethane–polypyrrole nanofibers and films

AbstractPolyurethane (PU)–polypyrrole (PPy) composite films and nanofibers were successfully prepared for the purpose of combining the properties of PU and PPy. Pyrrole (Py) monomer was polymerized and dispersed uniformly throughout the PU matrix by means of oxidative polymerization with cerium(IV) [ceric ammonium nitrate Ce(IV)] in dimethylformamide. Films and nanofibers were prepared with this solution. The effects of the PPy content on the thermal, mechanical, dielectric, and morphological properties of the composites were investigated with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR)–attenuated total reflection (ATR) spectroscopy, dielectric spectrometry, and scanning electron microscopy. The Young's modulus and glass‐transition temperatures of the composites exhibited an increasing trend with increases in the initially added amount of Py. The electrical conductivities of the composite films and nanofibers increased. The crystallinity of the composites were followed with DSC, the mechanical properties were followed with DMA, and the spectroscopic results were followed with FTIR–ATR spectroscopy. In the composite films, a new absorption band located at about 1650 cm−1 appeared, and its intensity improved with the addition of Py. The studied composites show potential for promising applications in advanced electronic devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Facile synthesis of polypyrrole nanofiber and its enhanced electrochemical performances in different electrolytes

A porous nanocomposite based on polypyrrole (PPy) and sodium alginate (SA) has been synthesized by easy, inexpensive, eco-friendly method. As prepared nanocomposite showed fibrillar morphology in transmission electron microscopic (TEM) analysis. The average diameter of ~100 nm for the nanofibers was observed from scanning electron microscopic (SEM) analysis. As prepared nanofiber, was investigated as an electrode material for supercapacitor applica- tion in different aqueous electrolyte solutions. PPy nanofiber showed enhanced electrochemical performances in 1 M KCl solution as compared to 1 M Na2SO4 solution. Maximum specific capacitance of 284 F/g was found for this composite in 1 M KCl electrolyte. It showed 76% specific capacitance retention after 600 cycles in 1 M KCl solution. Electrochemical Impedance Spectra showed moderate capacitive behavior of the composite in both the electrolytes. Further PPy nanofiber demonstrated higher thermal stability as compared to pure PPy.

Au nanoplate/polypyrrole nanofiber composite film: preparation, characterization and application as SERS substrate

Without any other additives or additional energy, Au nanoplates have been successfully prepared and integrated simultaneously with the dedoped polypyrrole nanofiber film via the in situ reduction of AuCl4– on the film surface. The morphology and structure of the as‐prepared composite film are characterized, and its application for surface‐enhanced Raman scattering is also investigated. It has been found that the morphology of as‐prepared Au nanoplates is dependent on the reaction duration, while the density is dependent on the concentration of AuCl4– ions in the reaction process. It is suggested that polypyrrole plays dual reducing and structure‐directing roles during the formation of Au nanoplates. Surface‐enhanced Raman scattering study shows that the Au nanoplates give an intensive and enhanced Raman scattering when 4‐aminothiophenol is used as a probing molecule. The employed approach may shed some light on simultaneously fabricating and immobilizing other noble metal micro/nanostructures with unique morphology. Copyright © 2011 John Wiley & Sons, Ltd.

Swift heavy ion irradiation-induced structural and conformational changes in polypyrrole nanofibers

In the present paper, we report a detailed analysis of the fluence-dependent conformational and structural changes induced in the polypyrrole nanofibers (PPy NFs) upon swift heavy ion (SHI) irradiation. PPy NFs, synthesized using a cationic surfactant cetyltrimethylammonium bromide-assisted micellar polymerization technique, have been irradiated with 90 MeV O7+ ions at normal beam incidence with fluence varying from 3×1010 to 1×1012 ions/cm2 using a 15UD Pelletron accelerator under ultra-high vacuum. X-ray diffraction studies reveal a decrease in the domain length and an increase in the strain upon SHI irradiation. A decrease in the integral intensity upon SHI irradiation indicates the amorphization of the material. Micro-Raman (μR) studies confirm amorphization of the PPy NFs and also show that the PPy NFs get de-doped upon SHI irradiation. μR spectroscopy also reveals a benzenoid to quinoid transition in the PPy chain upon SHI irradiation.

QCM based mercury vapor sensor modified with polypyrrole supported palladium

Polypyrrole (PPy) nanofibers loaded with either palladium (II) acetate (PPy/Pd(O 2CCH 3) 2) or palladium (II) nitrate (PPy/Pd(NO 3) 2) were characterized by TEM, SEM, EDX, Raman and FTIR techniques prior to their use as sensing materials for QCM based mercury vapor sensors. The QCM based sensor loaded with PPy/Pd(O 2CCH 3) 2 nanofibers was observed to perform better over that of the PPy/Pd(NO 3) 2 loaded QCM and is postulated to be due to the lack of Pd salt reduction in the PPy/Pd(O 2CCH 3) 2 matrix. The developed sensor was observed to operate with a response precision of ±5% over a 16 h testing period, and can withstand the presence of different levels of humidity at an operating temperature of 28 °C. Furthermore, the PPy/Pd(O 2CCH 3) 2 based sensor was found to have a response time ( t 90) of ∼45 min towards a Hg vapor concentration of 10.55 mg/m 3 balanced in either dry nitrogen or in streams containing up to 38% RH at near room temperature (28 °C). The stability of the developed sensor over 50 h of continuous testing towards Hg vapor under varying humidity levels indicates that a PPy/Pd(O 2CCH 3) 2 thin layer is a good choice for near room temperature Hg vapor sensing applications.

Dielectric spectroscopy for probing the relaxation and charge transport in polypyrrole nanofibers

Conductivity relaxation and charge transport mechanisms in polypyrrole (PPy) nanofibers synthesized using a micellar polymerization technique with varying surfactant concentration has been investigated by dielectric relaxation spectroscopy. TEM micrographs depict that the increasing surfactant concentration leads to the reduction of the nanofiber diameter. X-ray diffraction studies show that domain length in the PPy nanofibers decreases with decreasing fiber diameter whereas the strain caused due to dislocations and point defects increases. The permittivity spectra reveal that the relaxation mechanism in PPy nanofibers are dominated by hopping of trapped charges. Two relaxation peaks in the impedance spectra are attributed to the two-phase structure in the PPy nanofibers; the lower frequency peak is ascribed to the phase of oxidized repeat units and the higher frequency peak to the reduced repeat units of PPy nanofibers. The occurrence of relaxation peaks at different frequencies in the impedance and modulus spectra indicates a non-Debye relaxation with a wide distribution of relaxation times. The ac conductivity has been interpreted as a power law of frequency. The decrease of the parameter s with increasing temperature indicates that correlated barrier hopping is the dominant charge transport mechanism. Existence of polarons as major charge carriers has been confirmed by the low values of polaron binding energy.

DNA immobilization on a polypyrrole nanofiber modified electrode and its interaction with salicylic acid/aspirin

A double-stranded calf thymus DNA (dsDNA) was physisorbed onto a polypyrrole (PPy) nanofiber film that had been electrochemically deposited onto a Pt electrode. The surface morphology of the polymeric film was characterized using scanning electron microscopy (SEM). The electrochemical characteristics of the PPy film and the DNA deposited onto the PPy modified electrode were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Then the interaction of DNA with salicylic acid (SA) and acetylsalicylic acid (ASA), or aspirin, was studied on the electrode surface with DPV. An increase in the DPV current was observed due to the oxidation of guanine, which decreased with the increasing concentrations of the ligands. The interactions of SA and ASA with the DNA follow the saturation isotherm behavior. The binding constants of these interactions were 1.15×10(4)M for SA and 7.46×10(5)M for ASA. The numbers of binding sites of SA and ASA on DNA were approximately 0.8 and 0.6, respectively. The linear dynamic ranges of the sensors were 0.1-2μM (r(2)=0.996) and 0.05-1mM (r(2)=0.996) with limits of detection of 8.62×10(-1) and 5.24×10(-6)μM for SA and ASA, respectively.

Green-nano approach to nanostructured polypyrrole

Bulk quantities of polypyrrole nanofibers and nanospheres can be synthesized with a facile, one-step "green-nano" chemical oxidative polymerization approach, by simply using different reaction media.

Electrorheological properties of thermo-oxidative polypyrrole nanofibers

Using a chemical oxidative polymerization, polypyrrole (PPy) nanofibers were synthesized. After further thermo-oxidative treatment in air, the conductivity of PPy nanofibers was adjusted to a suitable level for use as a non-conventional nanofiber-based electrorheological (ER) suspension. Under electric fields, rheological properties of thermo-oxidative PPy nanofiber suspension were characterized. It showed that the nanofiber suspension possessed notable ER effect and low current density. Especially, the yield stress and shear modulus of nanofiber suspension were stronger than that of conventional granular suspension at the same volume fraction though the off-field viscosity of former was lower than that of latter. The ER effect and current density of thermo-oxidative PPy nanofiber suspension depended on the thermo-oxidative time and the nanofibers obtained after treatment for 3–5 h at 240 °C exhibited the optimal ER performances. It also showed that the thermo-oxidative PPy nanofiber suspension could maintain good ER properties within a wide operating temperature range of 25–115 °C.

Polypyrrole nanofibers synthesized via reactive template approach and their NH 3 gas sensitivity

The synthesis of polypyrrole (PPy) nanofibers has been achieved via a simple reactive template approach. The reactive template of FeCl 3 and methyl orange (MO) leads to the formation of uniform PPy nanofibers. Moreover, the fabrication of PPy nanofibers with high yield is realized, suggesting that this methodology is appropriate for the large-scale production of the corresponding nanomaterials. In contrast to the NH 3 gas sensor based on bulk PPy, the gas sensor based on the as-prepared PPy nanofibers exhibits greatly improved performances.

Synthesis and characterization of polypyrrole nanofibers with different dopants

AbstractNanostructures of polypyrrole (PPy) were synthesized in the presence of different dopants including hydrochloric acid (HCl), ferric chloride (FeCl3), p‐toluene sulfonic acid (p‐TSA), camphor sulfonic acid (CSA), and polystyrene sulfonic acid (PSSA), using a simple interfacial oxidative polymerization method. The method is a reliable non‐template approach with relatively simple instrumentation, ease of synthesis, and economic viability for synthesizing PPy nanostructures. Morphology of synthesized PPy structures was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which indicate the formation of one‐dimensional (1D) nanofibers with average diameter of 75–180 nm. Energy dispersive spectrum (EDS) of the PPy nanofibers indicates the attachment of the dopants to the PPy backbone; the fact is further confirmed by the Fourier transform infrared (FTIR) spectra of PPy nanostructures. Thermal stabilities of the nanostructures explored using thermal gravimetric analysis (TGA) follow the order PPy‐p‐TSA > CSA > HCl > FeCl3 > PSSA. It is noticed that the electrical conductivity (EC) of PPy nanostructures depends upon the nature of dopant (PPy‐p‐TSA > CSA > HCl > FeCl3 > PSSA), PPy‐p‐TSA nanofibers showing the highest EC of 6 × 10−2 Scm−1. Copyright © 2009 John Wiley & Sons, Ltd.

Templating fabrication of polypyrrole nanorods/nanofibers

Nanostructured polypyrrole have been fabricated in high yield by chemical oxidation polymerization using one-dimensional rod-like aggregates of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS 4) as a template. This aggregate has the advantages of both soft and hard template such as stable, good versatility (for hard template), cheap, and easy removal (for soft template). Also, the molar ratio of TPPS 4 and pyrrole monomer could be as low as 1:1000, showing a high efficiency of the template. Polypyrrole nanorods with variational size have been achieved successfully by using this versatile template and cooperating with the oxidants with different redox potentials. Moreover, in the presence of TPPS 4 template and polyvinylpyrrolidone (PVP), Polypyrrole (PPy) nanofibers were obtained even though using a weak oxidant. The formation of PPy nanorods/nanofibers was discussed and their properties including conductivity and thermalstability were evaluated.

Template-Free Electrochemical Synthesis of Superhydrophilic Polypyrrole Nanofiber Network

In this work, a superhydrophilic polypyrrole (PPy) nanofiber network is electrochemically synthesized in an aqueous solution by using phosphate buffer solution (PBS) in the absence of templates, surfactants and structure-directing molecules. FESEM, X-ray diffraction, UV−visible absorption, and contact angle measurement were employed to characterize the nanofiber network. The effect of synthetic conditions including pH, oxidation potential and concentrations of phosphate, pyrrole (Py) and dopant ClO4− on the PPy nanostructure is systematically investigated. A mechanism for the nanofiber formation in an aqueous solution without assistance of any “hard” and “soft” template is proposed, in which the presence of the hydrogen bonding between phosphate and Py oligomers is essential to producing the 1D nanofiber structure, and the electrostatic interactions between ion dopant and Py oligomers lead to an irregular nanostructure. This is a simple, environmentally friendly and one-step approach to fabricate a PPy film with unique nanostructure and chem-physical properties, which can have great potential in various applications such as sensors, electronics, and energy source systems.

Toward an Understanding of the Formation of Conducting Polymer Nanofibers

Introducing small amounts of additives into polymerization reactions to produce conducting polymers can have a profound impact on the resulting polymer morphology. When an oligomer such as aniline dimer is added to the polymerization of aniline, the nanofibers produced are longer and less entangled than those typically observed. The addition of aniline dimer can even induce nanofiber formation under synthetic conditions that generally do not favor a nanofibrillar morphology. This finding can be extended to both the synthesis of polythiophene and polypyrrole nanofibers. The traditional oxidative polymerization of thiophene or pyrrole only produces agglomerated particles. However, when minute amounts of thiophene or pyrrole oligomers are added to the reaction, the resulting polymers possess a nanofibrillar morphology. These results reveal important insights into a semirigid rod nucleation phenomenon that has hitherto been little explored. When polyaniline nucleates homogeneously, surface energy requirements necessitate the formation of ordered nuclei which leads to the directional polymerization of aniline. This ultimately leads to the one-dimensional nanofibrillar morphology observed in the final product. The synthetic procedures developed here are simple, scalable, and do not require any templates or other additives that are not inherent to the polymer.

Polypyrrole nanofiber surface acoustic wave gas sensors

Abstract We present for the first time, to the best of authors’ knowledge, surface acoustic wave (SAW) gas sensors featuring polypyrrole nanofibers as the active component for hydrogen (H2) and nitrogen dioxide (NO2) detection at room temperature. Polypyrrole nanofibers were synthesized through a template-free chemical route by introducing bipyrrole as an initiator to speed up the polymerization of pyrrole in the presence of iron (III) chloride (FeCl3) as the oxidizing agent. Polypyrrole nanofibers were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopic (FT-IR) techniques which indicated that the average diameter of the nanofibers was 18 nm with lengths in the order of several microns. The polypyrrole nanofibers were dispersed onto the surface of a ZnO/36°YX LiTaO3 SAW transducer. Gas testing towards H2 and NO2 was conducted in an enclosed environmental cell at room temperature. Measured frequency shifts due to sensor responses were 20 kHz towards 1% of H2 and 4.5 kHz towards 2.1 ppm NO2, respectively. The sensor performance was assessed during a five-day period and repeatable results were obtained.

Non-enzymatic glucose biosensor based on overoxidized polypyrrole nanofiber electrode modified with cobalt(II) phthalocyanine tetrasulfonate

An enzymeless biosensor, based on electrodeposition of overoxidized polypyrrole nanofiber onto pencil graphite electrode and modified with cobalt(II) phthalocyanine tetrasulfonate (CoPcTS), was investigated in this study. CoPcTS showed electrocatalytic activity for the oxidation of glucose in alkaline solution. The electrochemical performance of the modified electrodes was investigated by differential pulse voltammetric (DPV) method. The resulting biosensor exhibited excellent performance for glucose determination with a wide linear range (0.25–20 mM), a highly reproducible response (R.S.D. of 2.7%), low percentage of the interferences and long-term stability. The calculated detection limit was 0.1 mM at 3 σ. In order to verify the reliability of the biosensor, it was applied to the determination of glucose in serum samples. The results were satisfactory and agreed closely with those measured in a hospital.

Conductometric Hydrogen Gas Sensor Based on Polypyrrole Nanofibers

Polypyrrole nanofibers are synthesized through a template-free chemical route and used as the active component for hydrogen gas sensing at room temperature. The synthesis of polypyrrole nanofibers was achieved by using bipyrrole as an initiator to speed up the polymerization of pyrrole with FeCl as the oxidizing agent. Scanning and transmission electron microscopy studies indicate that the resulting polypyrrole forms a nanofibrous mat with average nanofiber diameter of 18 nm. Fourier transform infrared spectroscopy and elemental analysis confirms that the structure of the nanofibers is comparable to bulk polypyrrole. Gas sensing properties of polypyrrole nanofibers were investigated by depositing nanofiber dispersions on an interdigited conductometric transducer. The sensor performance was tested through programmable exposure towards different concentrations of hydrogen gas diluted in synthetic air in an environmental cell at different temperatures. A short response time of 43 s was observed upon exposure to a concentration of 1% hydrogen with a decrease in film resistance of 312 at room temperature. The sensor sensitivity was analyzed with gradual elevation of the operating temperature.