Polypyrrole Nanostructures Research Articles

The Controlled Preparation of Polypyrrole Nanostructures via Tuning the Concentration of Acrylic Acid

Two types of nanostructures, nanowires and nanoribbons were prepared with polypyrrole (PPy) by controlling the concentration of acrylic acid (AA) in systems containing cationic surfactant, cetyltrimethylammonium bromide (CTAB) at about 12 degrees C. The effect of reaction conditions involving the concentration of AA, CTAB, pyrrole as well as the reaction temperature was systematically studied on the final structures of prepared PPy. The results revealed that the polymerization of AA, resulting in PAA, played a key role in the evolution of PPy nanostructures. A possible mechanism was briefly discussed on the formation of these two nanostructures, nanowires and nanoribbons.

Polypyrrole/silver composites prepared by single-step synthesis

Polypyrrole/silver composites were prepared by single-step chemical oxidative polymerization of pyrrole using silver nitrate as an oxidant in aqueous medium at room temperature. The oxidant-to-monomer mole ratio was varied in these experiments. The time needed for yield to be higher than 70% has been estimated to at least several days. The silver content was 70–80wt.%, the conductivity of composites was of the order of 1000Scm−1. The morphology of composites was demonstrated by scanning electron microscopy and that of individual components by transmission electron microscopy. Silver is present mainly as nanoparticles of 50–100nm size, but also as larger objects. Among polypyrrole nanostructures, nanotubes are the most interesting. The molecular structure of polymer component was characterized by FTIR and Raman spectroscopies, and polypyrrole structure was confirmed. Surface-enhanced Raman scattering at PPy–silver interface was observed. Optical microscopy demonstrated the presence of macroscopic silver plates in the composites and thus illustrated the macroscopic heterogeneity of composites.

Counter electrodes from double-layered polyaniline nanostructures for dye-sensitized solar cell applications

Counter electrodes from polypyrrole (PPy) and polyaniline (PANi) nanostructures were fabricated by chemical and electrochemical approaches for dye-sensitized solar cell (DSSC) applications. It was found that double-layered PANi consisting of a nanoparticle layer and a nanofiber layer was formed by an electrodeposition route, given significantly increased active sites and solar cell performances. The solar-to-electricity conversion efficiency of the double-layered PANi-based DSSC was 6.58% under 100 mW cm−2 (AM 1.5), which was much higher than those of PPy and chemically deposited PANi or Pt-based DSSCs. The enhancement in the conversion efficiency was due to the design of double-layered nanostructures, which resulted in an increased charge transfer kinetics and higher electrocatalytic activity for the I−/I3− redox reaction.

Screening Conditions for Rationally Engineered Electrodeposition of Nanostructures (SCREEN): Electrodeposition and Applications of Polypyrrole Nanofibers using Microfluidic Gradients

A rapid screening method for optimizing electrochemical deposition conditions of polypyrrole (PPy) nanostructures is reported. An electrochemical cell is integrated within a low-cost microfluidic system, in which electrochemical deposition is carried out across a linear concentration gradient of a reaction parameter. The protocol, refered to as the screening of conditions for rationally engineered electrodeposition of nanostructures (SCREEN), allows rapid screening of conditions for the production of specific morphologies by characterizing the electrodeposited samples produced within a chemical gradient. To demonstrate the utility of the SCREEN method, applications in tunable optical coatings and superhydrophobic surfaces are presented.

Enhanced photoconductive properties of a simple composite coaxial nanostructure of zinc oxide and polypyrrole

The coaxial nanostructures of zinc oxide (ZnO) and polypyrrole (PPy) are synthesized through the low-temperature solution processes. Compared with the reference structures, the enhanced photoconductive properties with high on–off ratio comparable to 104 are found for the coaxial nanostructures. The use of the depletion layer at the interface of the composites leads to the significant changes of photoconductivity. The results indicate that the simple composites and nanostructures lead to the enhanced performance applicable for photoswitches and photodetectors.

Electroplated porous polypyrrole nanostructures patterned by colloidal lithography for drug-delivery applications

Porous nanostructures of polypyrrole (Ppy) were fabricated using colloidal lithography and electrochemical techniques for potential applications in drug delivery. A sequential fabrication method was developed and optimized to maximize the coverage of the Ppy nanostructures and to obtain a homogeneous layer over the substrate. This was realized by masking with electrophoretically-assembled polystyrene (PS) nanospheres and then electroplating. Drug/biomolecule adsorption and the release characteristics for the porous nanostructures of Ppy were investigated using rhodamine B (Rh-B). Rh-B is an easily detectable small hydrophobic molecule that is used as a model for many drugs or biological substances. The porous Ppy nanostructures with an enhanced surface area exhibited higher Rh-B loading capacity than bulk planar films of Ppy. Moreover, tunability of surface morphology for further applications (e.g., sensing, cell adhesion) was demonstrated.

Influence of dopant anions on properties of polypyrrole nanocoated poly(styrene- co-methacrylic acid) particles

Nanostructures of polypyrrole (PPy) were synthesized on poly(styrene- co-methacrylic acid) particles with iron (III) p-toluensulfonate hexahydrate (FeTS), sodium p-toluensulfonate (NaTS), 5-sulfosalicylic acid dihydrate (SSA), iron(III) chloride hexahydrate or p-toluensulfonic acid (TSA) as dopants. A doping level between 0.25 and 0.29 in all samples was determined by X-ray photoelectron spectroscopy (XPS). FTIR analysis shows the effective covering of core samples and that no degradation of PPy has taken place. Conductivity decay study establishes that aromatic sulfonic acid anions provide better performance to the conducting polymer when are present as the only dopants. The chloride anions have a detrimental effect over conductivity and stability of the PPy shell.

Chemical synthesis of high density and long polypyrrole nanowire arrays using alumina membrane and their hydrogen sensing properties

Polypyrrole nanowire arrays were synthesized through chemical polymerization inside the nanochannels of alumina membrane. By optimizing the polymerization time and applying appropriate oxidant:monomer molar ratio with proper concentrations, the pores filling and also the continuity of the obtained polypyrrole inside the nanochannels improved and therefore after dissolution of the host membrane, high density and long nanowire arrays appeared. The obtained nanostructures were characterized by SEM, FTIR and BET techniques. The synthesized nanostructures had high surface areas of 75.66–172.90m2/g. Since nanowires are attractive for gas sensing applications owing to their high surface areas, their hydrogen gas sensing was investigated at room temperature. The results show that the electrical resistance of the polypyrrole nanostructure arrays reduced upon exposure to hydrogen gas.

Synthesis and characterization of poly (indene‐co‐pyrrole) nanofibers

AbstractNanofibers of poly (indene‐co‐pyrrole) (CInPy) have been synthesized, using a facile chemical oxidative polymerization reaction. The effect of copolymerization was examined in view of the individually synthesized homopolymer nanostructures of polyindene (PIn) and polypyrrole (PPy). Morphological details of CInPy, studied using scanning electron microscopy (SEM) and transmission electron microscopy, (TEM) reveal the appearance of dense cottony mess, comprising of fine fibers with an average diameter of 5–10 nm. Chemical structural analysis of CInPy, conducted using ultraviolet‐visible (UV‐Vis), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectroscopic techniques, reveals that both PIn and PPy are involved in the formation of copolymer organization. Fluorescence properties of nanosized copolymer are observed in the blue region, with emission λmax placed at 395 nm. Conductivity of copolymer nanofibers (2.4 × 10−3 S/cm) is consistent with the morphology and thermal stability properties of integral homo‐polymers. Improved thermal stability and processability along with the enhanced optical and electrical properties of copolymer nanostructures outfit it as a better promising material in optoelectronic and light emitting nanodevices, with reference to nanosized PIn and PPy. Copyright © 2009 John Wiley & Sons, Ltd.

Facile Synthesis of Water-Dispersible Conducting Polymer Nanospheres

Water-dispersible polypyrrole nanospheres with diameters of less than 100 nm were synthesized in high yield without any templates, surfactants, or functional dopants by the introduction of 2,4-diaminodiphenylamine as an initiator into a reaction mixture of pyrrole monomer, oxidant, and acid. The initiator plays a critical role in tailoring the nanostructures of polypyrrole. 2,4-Diaminodiphenylamine interacts with acid to form cations, which combine with various anions to self-assemble resulting in different size nanomicelles. These nanomicelles, stabilized by initiator molecules, act as templates to encapsulate pyrrole and oxidant leading to the formation of nanospheres during polymerization. When smaller acids are used, smaller diameter sphere-like polypyrrole nanostructures are obtained. The as-synthesized polypyrrole nanospheres can then be used to fabricate highly conducting nitrogen-doped carbon nanospheres with controllable sizes of 50-220 nm with monodispersities up to 95% after pyrolysis. The size of the carbon nanospheres decreases by 20-30 nm due to carbonization when compared to the original polymer nanospheres. The molecular structures, morphologies, and electrical properties along with the formation mechanism of the polypyrrole and carbon nanospheres are discussed.

Synthesis, Properties and Applications of Conducting Polymer Nano-Objects

Two different approaches are used to produce conducting polymer nano-objects. One is a “top-down” approach which involves laser ablation of conducting polymer films using laser light interference patterns (direct laser interference patterning, DLIP) to produce various surface shapes, including nanowires and nanodots. Polyaniline(PANI) and polypyrrole (PPy) nanostructures could be easily produced by ablation of films, previously formed by in-situ polymerization of the aromatic monomers. The other is a “bottom-up” approach involving the controlled nucleation and growth during monomer polymerization. This is achieved by performing the polymerization at the interface of two immiscible solvents. Both kinds of nanomaterials are characterized using dynamic light scattering, TEM, EDAX, FTIR, UV-vis and fluorescence spectroscopy. The structures are studied by SEM-FIB, optical and fluorescence microscopy along with water contact angle. It is shown that nanometric sized structures can be made by both methods. The chemical structures are quite similar or identical to that of the bulk polymer. While PANI nanofibers are dispersed in acid media, due to the surface charge related with chain protonation, they agglomerate in neutral media. In the interest of biological applications, different soluble polymers are used to help disperse the nanofibers at neutral pH. Both the dispersing agent and PANI nanofibers have to be innocuous to biological cells and higher organisms, like frog larvae. The successful intake of PANI nanofibers into cancer line cells and frog larvae prompts its application as NIR radiation absorbers in photothermal or photoacoustic tumor therapy and/or tomography.

Effects of Reaction Sequence on the Colloidal Polypyrrole Nanostructures and Conductivity

The relationship between nanoscaled morphology and macroscopic electrical conductivity of polypyrrole (PPy) nanostructures was qualitatively investigated. The PPy nanostructures were prepared via microemulsion polymerization using ionic surfactants. The morphology of PPy was influenced by both the type of ionic surfactants and reaction sequences; specifically, the PPy structures were highly influenced by the reaction sequence when anionic surfactant of SDS was used. By changing reaction sequence, a gel-like PPy was formed influencing on the macroscopic electrical conductivity. The results indicate that the macroscopic conductivity of PPy is affected by its nanoscaled structures as determined by the reaction conditions.

Electrochemical polymerization and characterization of polypyrrole nanowires and nanotubules

Polypyrrole nanostructure arrays, including simultaneously large quantities of nanowires and small quantities of partially filled nanotubules have been electrochemically synthesized in home-made etched ion-track polycarbonate (PC) templates. Diameter of the prepared nanostructures varies from 45 to 320 nm with their lengths up to 30 microns. Morphological studies of these nanostructures were performed by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. While optical absorption properties were studied by ultraviolet–visible–near infrared spectrophotometry (UV–vis–NIR). It has been observed that the absorption maximum of polypyrrole shifts to the longer wavelength side as the diameter of these nanostructures (nanowires and nanotubules) increases.

Photoactive Nanostructures of Polypyrrole

The creation of nanostructures of the photoactive polymer polypyrrole (PPy) on glass substrates with the spin-coating method is described. No additional post-production treatment is necessary to obtain uniformly distributed photoactive nanostructures on macroscopically scaled substrates. Based on X-ray reflectivity measurements, the critical solution concentration of PPy below which these nanostructures develop is determined. The PPy nanostructures are displayed with atomic force microscopy (AFM) measurements, which prove that the nanostructures form directly on the substrate. With UV/Vis spectroscopy the absorption behavior of the nanostructures is probed in comparison to PPy films and PPy solutions. A linear dependence of the absorption of the nanostructure on the surface coverage measured with AFM is detected. The influence of confinement on the conjugation length results in a modified absorption behavior of the nanostructures.

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.

Template-free one-step electrochemical formation of polypyrrole nanowire array

Oriented polypyrrole nanowire (nanorod) array readily forms using one-step pyrrole electropolymerization without using a template. These nanostructures having diameter in the range of 40–120 nm are obtained by electrogenerating polypyrrole in the presence of jointly non-acidic and weak-acidic anions. The latter are essential, their presence leads to the formation of an overoxidized polypyrrole thin layer that surrounds the polypyrrole nanostructure base. This simple and convenient method allows direct polymer nanowire array fabrication on various conductive substrates, the length of nanostructures being controlled by the polymerization time . Finally, a reaction mechanism involving oxidation of pyrrole and water and polypyrrole overoxidation is discussed.

Molecular imprinted polypyrrole nanowires for chiral amino acid recognition

Abstract Recognition and separation of chiral molecules is of great importance in the field of biotechnology, especially on pharmaceutics. Molecular imprinted polymers (MIP) have been proved as a powerful tool for the separation of target molecules. In this paper, polypyrrole (PPy) nanowires with an average diameter of ca. 100 nm and few micrometers in length were successfully prepared by electrochemical polymerization, in which enantiomeric camphorsulfonic acid ( d - or l -CSA) molecule acted as both the dopant and molecular imprinting pseudo-template. Both electrochemical impedance spectra (EIS) and circular dichroism (CD) spectra were employed to demonstrate the enantioselective interaction between de-doped PPy nanowires imprinted with CSA enantiomers (MIP-PPy) and chiral phenylalanine ( d - or l -Phe). EIS leads to the characterization of interfacial electron resistance of the PPy coated electrode, while CD spectra provides spectral evidence for the enantioselective recognition event. Both methods proved that MIP-PPy nanowires have the capability for the recognition and separation of chiral phenylalanine. The sensitivity of the chiral recognition was further investigated by using various concentrations of chiral Phe and adsorption time. This approach provides a potential route for fabricating enantioselective recognition polypyrrole nanostructures that could be employed in enantiomeric sensoring or separating various chiral molecules.

Polypyrrole Nanostructures Self-Assembled in Magnetic Ionic Liquid as a Template

Nanostructured conducting polypyrrole and poly(N-methylpyrrole) were successfully synthesized by simply adding monomers into a magnetic ionic liquid, bmim[FeCl4]. In this process, self-organized conducting polymer nanostructures such as particles and tubes were formed without and with magnetic field. The shape of polypyrrole nanoparticles synthesized at room temperature was almost spherical with their size ranging around 60 nm with a relatively narrow size distribution. The conductivity of pelletized particles was 101−2 S/cm. From the N-methylpyrrole monomer, more attractive nanostructured polymers were obtained. Tubes with nanoscaled inner holes and walls were synthesized using a self-assembly process for the first time. The self-assembled local structures in the solvent ionic liquid are likely to serve as templates of highly organized nanostructured polymers. External magnetic field seems to affect these local structures and hence the resultant polymer nanostructures. This research provides a new method...

Tailoring the gold–polypyrrole nanostructures at water–toluene interphase

A method is described to obtain gold–polypyrrole nanostructures by reacting gold chloride with pyrrole at toluene–water interphase. By adjusting the concentration of the stabilizer, namely, pyridine-3-sulphonate, the shape of the nanostructures formed at the interphase can be tailored. This novel method facilitates the fabrication of Au–Ppy composite material that gives wider scope for biosensing applications.

Magnetic Properties of Conducting Polymer Nanostructures

Magnetic susceptibility measurements on conducting polyaniline and polypyrrole nanostructures with different dopant type and doping level as functions of temperature and magnetic field are reported. The susceptibility data cannot be simply described as Curie-like susceptibility at lower temperatures and temperature-independent Pauli-like susceptibility at higher temperatures; some unusual transitions are observed in the temperature dependence of susceptibility, for example, paramagnetic susceptibility decreases gradually with lowering temperature, which suggests the coexistence of polarons and spinless bipolarons and possible formation of bipolarons with changing temperature or doping level. In particular, it is found that the direct current magnetic susceptibilities are strongly dependent on applied magnetic field, dopant type, and doping level.