Nanostructured Polyaniline Films Research Articles

Nanostructured Polyaniline Films Functionalized through Auxiliary Nitrogen Addition in Atmospheric Pressure Plasma Polymerization

Polyaniline (PANI) was synthesized from liquid aniline, a nitrogen-containing aromatic compound, through the atmospheric pressure (AP) plasma process using a newly designed plasma jet array with wide spacing between plasma jets. To expand the area of the polymerized film, the newly proposed plasma jet array comprises three AP plasma jet devices spaced 7 mm apart in a triangular configuration and an electrodeless quartz tube capable of applying auxiliary gas in the center of the triangular plasma jets. The vaporized aniline monomer was synthesized into a PANI film using the proposed plasma array device. The effects of nitrogen gas addition on the morphological, chemical, and electrical properties of PANI films in AP argon plasma polymerization were examined. The iodine-doped PANI film was isolated from the atmosphere through encapsulation. The constant electrical resistance of the PANI film indicates that the conductive PANI film can achieve the desired resistance by controlling the atmospheric exposure time through encapsulation.

Synthesis and Characterization of Conducting Polyaniline Nanostructured Thin Films for Solar Cell Applications

Optical-quality transparent, conducting polyaniline (PANI) thin films are suitable candidates for efficient counter electrodes for high-performance solar cells. In the first part of this work, the synthesis of highly uniform and homogenous nanostructured PANI films is reported. The film properties were assessed via scanning electron microscopy, atomic force microscopy, optical profilometry, spectrophotometry, and conductimetry. Simultaneous modeling, optimization and physical characterization of the PANI nanostructured films have not received much attention in the literature. Hence, in the second part, a multi-objective optimization approach with three objectives, namely minimum film thickness, maximum transparency, and maximum conductivity, was performed based on artificial neural network models with a novel k-fold cross-validation technique. The developed models can accurately predict the film characteristics in a wide range of design variables with most residuals remarkably less than 1.0%. Furthermore, after optimization, conductivity was increased three-fold (~ 2.2 × 10−1 S/cm) at a good level of transparency (~ 55%), which suit solar cell applications.

Metal-polymer interface influences apparent electrical properties of nano-structured polyaniline films.

The interface between the conductive polymer, polyaniline (PAn-Cl), and gold, platinum, or an interceding layer of electrodeposited platinum on gold or platinum, markedly influences the apparent electrical properties and the electronic to ionic transition in physiological buffers. Polyester-supported, sputter-deposited gold and platinum thin films were laser patterned to yield co-planar Thin Film Electrodes (TFEs) suitable for platinization and deposition of PAn-Cl nanofibers. Electrodeposition of platinum from chloroplatinic acid (50 mC cm-2) onto gold produced larger feature sizes and larger surface roughness (23.5 nm) when compared to platinization of platinum (15.2 nm) and both similarly reduced interfacial impedance in water and physiologically relevant buffers, PBS and HEPES. UV-Vis characterization produced absorption edges (DI water 2.36 eV, PBS 2.64 eV, and HEPES 2.66 eV) reflective of the ionic strength of the medium. Thin films (23 ± 2 μm) of PAn-Cl nanofibers were deposited onto Au, Pt, Au|Pt, Pt|Pt TFEs and each characterized by Electrical Impedance Spectroscopy (EIS) over the range 106-10-1 Hz at RT in air, DI water, PBS, and HEPES buffers and by multiple scan rate cyclic voltammetry (MSRCV) in PBS. Platinized gold and platinized platinum decorated with PAn-Cl behaved quite differently in these test environments confirming a role for the contacting surface roughness/nano-topography in influencing apparent electrical properties. Equivalent circuit modeling of EIS data revealed a modified Randles circuit (R(QR)) of low chi-square values (<0.05) that rationalized the capacitance and membrane resistance and confirmed that platinization of gold served to increase the PAn-Cl apparent resistance while platinization of platinum served to decrease the PAn-Cl apparent resistance.

Ion diffusion and optical switching performance of 3D ordered nanostructured polyaniline films for advanced electrochemical/electrochromic devices

Nanostructured polyaniline (PANI) has the ability of fast and reversible acid/base doping/dedoping, multi-color changes and electron-donating/accepting using surface or near-surface reactions. Here we report PANI films with 3D ordered nanostructures through template-assisted electrodeposition method and aim to study the ion diffusion behavior as well as optical switching properties. It is found the ion diffusion coefficient is greatly increased because of the chain and crystalline structural modulation of deposited polyaniline arising from the template confinement effect. The ion diffusion reversibility and ion storage of 3D ordered macroporous (3DOM) PANI is highly improved due to the interconnected porous structure, which benefits for the fast penetration of ions. The optical switching properties of 3DOM PANI are also highly enhanced especially in the infrared region mainly because of the extended optical transmission path associated with the interconnected porous structure. The outstanding ion/electron doping/dedoping performance and better interaction with lights shown here render the ordered porous polyaniline a promising candidate as high-density electrochemical/electrochromic energy materials.

Nanostructured polyaniline films on silicon for sensitive sensing of ammonia

Silicon (Si)–nanopolyaniline (PAni) conducting platform has been electrochemically developed for the sensitive sensing of ammonia. The nano PAni films are formed through the assembly of nano granules of the polymer. The average height of the film is in the range of 50nm. The electrical conductivity of the Si–PAni is influenced in the presence of ammonia. The response of this conductometric sensor is almost linear within 5–50ppm of ammonia. The response and the recovery times are observed to be 10 and 60s, respectively for 10ppm of ammonia. The response time of the sensor for other concentrations (viz. 20, 30, 40, 50 and 60ppm ammonia) is also in the range of 10±2s. However, the recovery of the sensor takes slightly longer time (70±3s) in case of higher concentrations (≥40ppm) of ammonia.

Synthesis of polyaniline nanostructures by electrochemical deposition on niobium

Nanostructured polyaniline films have been electrochemically synthesized on passivated niobium substrate by potentiodynamic method in 0.5 and 1 mol L−1 H2SO4 solution and different aniline/acid molar ratios. The niobium oxide particles formed during passivation induce the nucleation of polyaniline nanofibers via adsorbed phenazine nucleates. The infrared spectra of polyaniline nanofibers showed the presence of vibrations attributed to phenazine-units in the polymer chain which support the phenazine nucleates theory for polyaniline nanofiber growth. The morphology of polyaniline is also influenced by acid concentration and a branched structure consisting of polyaniline nanofibers with a mean diameter of 70 nm is observed for 1 mol L−1 sulfuric acid solution. The shape of the impedance spectra is controlled by charge transport through ion diffusion, with higher diffusion resistances for granular polyaniline. The capacitance increases with the polymer layer thickness and has higher values for nanofibrilar than for granular polyaniline.

Electrochemical Transducer Based on Nanostructured Polyaniline Films Obtained on Functionalized Self Assembled Monolayers of 4-Aminothiophenol

Gold(111) electrodes modified with Self Assembled Monolayers (SAMs) of 4-Aminothiophenol (4-ATP) functionalized with Pd(II) colloid nanoparticles, have been constructed, characterized and used as template for the electropolymerization of aniline (PANI) films. Cyclic voltammetry and UV-vis spectroscopy confirm the functionalization of the 4-ATP SAMs by Pd(II) complex nanoparticles. Atomic Force Microscopy (AFM) images and the cyclic voltammetry measurements reveal that polyaniline films grown on 4-ATP-Au(111) SAMs functionalized with Pd(II) complex nanoparticles, posses a nanostructured morphology constituted by globular structures of nanometric size. The electropolymerization of PANI driven by repeated potentiodynamic cycles produces structures with average diameters in a range of 20 to 60 nm.

Nanostructured polyaniline counter electrode for dye-sensitised solar cells: Fabrication and investigation of its electrochemical formation mechanism

Nanostructured polyaniline films with controlled thickness have been successfully grown on fluorine-doped tin oxide (FTO) glass substrates using the cyclic voltammetry (CV) method at room temperature. The formation mechanism of the polyaniline film is monitored by CV techniques, alternating current (AC) impedance spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). It is found that the accumulation of nanostructured polyaniline (>70 nm) on both the scattered and compact layers simultaneously increased the reactive interface, which supports charge transfer at the interface and resistance that hinders electronic transport in the film. By optimising the preparation conditions, the short-circuit photocurrent density of a dye-sensitised solar cell (DSSC) with a PANI counter electrode (CE) increased by 11.6% in comparison to a DSSC with an electrodeposited platinum CE.

Environmental responses of nanostructured polyaniline films based on polystyrene–polyaniline core–shell particles

This paper describes a simple method for fabricating nanostructured polyaniline (PANI) films from polystyrene (PS)–PANI core–shell particles and the environmental responses of the films. Monodisperse PS latex particles synthesized via surfactant-free emulsion polymerization were used as cores, onto whose surface aniline monomers adsorbed with the aid of sodium dodecyl sulfate and were polymerized by adding ammonium peroxydisulfate. The resulting suspensions of core–shell particles were then drop-cast onto substrates and dried. Films composed of fragments of thin PANI shells of tens of nanometers were obtained after the removal of PS by tetrahydrofuran extraction. Another kind of films was prepared by heating the core–shell particles above the glass transition temperature of PS for a short time before the extraction. The morphology was observed using scanning electron microscopy, and the UV–vis spectra were recorded by a spectrometer. Furthermore, we examined the resistance responses of the films to dry gas flow, ethanol vapor, hydrogen chloride, and ammonia. The high sensitivity and fast response should be due to the large surface area interacting with analytes and porosity that facilitates diffusion. In addition, the effect of the packing of PANI shells in the films on the responses was discussed.

Morphology and gas-sensing behavior of in situ polymerized nanostructured polyaniline films

Nanostructured polyaniline films could be easily in situ polymerized on microslides via rapidly mixing aniline with ammonium persulfate in acid solution. The influence of different conditions including aniline, acid concentration, reaction time and acid kinds on the morphology and thickness of the resulting films was studied. The gas-sensing behavior of the nanostructured films to 100 ppm of NH 3 was investigated through monitoring the change of the resistance.

Spectroelectrochemical and Morphological Studies of Nano-Structured Polyaniline Films Synthesized in the Presence of Polyamidosulfonic Acids of Different Nature

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