Polyaniline Film Surface Research Articles

A dual-functional polyaniline film-based flexible electrochemical sensor for the detection of pH and lactate in sweat of the human body.

A flexible dual functional electrochemical sensor based on macroscopic polyaniline (PANI) film is reported. The PANI film is prepared by interfacial synthesis without any additional templates and surfactants, and is easily transferred from the water surface to any substrate. The surface of PANI film is flat and has a certain degree of crystallization. The PANI film exhibits good electrochemical properties, which is attributed to the order structure of PANI. The flexible sensor based on PANI film exhibits good electrochemical performances to pH and lactate. And the flexible PANI sensor has good reproducibility, selectivity and long-term stability. Meanwhile, the PANI sensor is also applied to detect the actual sample (such as food and human sweat), and the results are in accordance with the commercial pH meter, indicating the reliability of the PANI sensor.

Biofield-effect protein-sensor: Plasma functionalization of polyaniline, protein immobilization, and sensing mechanism

We report the fabrication of a biofield-effect protein-sensor (BioFEP) based on atmospheric-pressure plasma (AP) treatment of a conducting polyaniline (PANI) film. Successive H2 and O2 AP (OHAP) treatment generated dominant hydrophilic –OH and O=CO– functional groups on the PANI film surface, which served as strong binding sites to immobilize bovine serum albumin (BSA) protein molecules. The output current changes of the BioFEP as a function of BSA concentration were obtained. The resistance of the OHAP surface could be sensitively increased from 2.5 × 108 Ω to 2.0 × 1012 Ω with increasing BSA concentrations in the range of 0.025–4 μg/ml. The results suggest that the method is a simple and cost-effective tool to determine the concentration of BSA by measuring electrical resistance.

Facile Route for the Synthesis of a Vertically Aligned ZnO–PANI Nanohybrid Film for Polyphenol Sensing

Vertically aligned zinc oxide (ZnO) nanorods have been fabricated on a polyaniline (PANI) film template after electrochemical seeding and hydrothermal growth in a nutrient medium at a low temperature of 65 °C. Dense c-oriented [0001], hexagonal-shaped, vertically aligned ZnO nanorods are obtained on the PANI film surface, which is confirmed by X-ray diffraction and scanning electron microscopy studies. The nanohybrid film used as the working electrode has been characterized for sensing catechin polyphenol in different tea varieties through cyclic voltammetry. Principal component analysis shows enhancement in the classification ability of the nanohybrid film for various concentrations of catechin standard and tea infusions.

Mycotoxin detection on antibody-immobilized conducting polymer-supported electrochemically polymerized acacia gum

Electrochemical polymerization of acacia gum (AG) was initiated by electroactive polyaniline (PANI) monomers by radical cation formation and their coupling reactions with AG molecules. RCT values obtained from electrochemical impedance spectroscopy analysis at various AG concentrations with PANI were drastically decreased, confirming formation of conducting AG complexes with PANI. Quantitative analysis of ochratoxin-A (OTA) detection in electrolyte was carried out on rabbit antibody-immobilized PANI and PANI–AG matrices. The observed sensitivities of 50, 150, and 250mg AG-added PANI matrix-based platforms were 3.3±0.5, 10.0±0.5, and 12.7±0.5μA/ng/ml, respectively. The sensitivity of only PANI electrodes was 2.6±0.3μA/ng/ml, which was relatively lower than AG-added PANI. This increase was due to the presence of glycan functional groups in AG molecules that supported the retention of activity of antibodies. In addition, enhanced electron transportation at AG–PANI film surface was observed due to formation of an electroactive polymer film of two different electroactive functions to contribute toward enhancement in the detection sensitivity.

Silver nanoparticles dispersed in polyaniline matrixes coated on titanium substrate as a novel electrode for electro-oxidation of hydrazine

Silver nanoparticles dispersed in polyaniline matrixes coated on titanium substrate, as a novel electrode, was easily synthesized by electro-polymerization of aniline on titanium and then electrodeposited silver nanoparticles on PAni electrode. The electrochemical behavior and electro-catalytic activity of silver nanoparticles/PAni/Ti electrodes were characterized by cyclic voltammetry. The morphology of silver nanoparticles on PAni/Ti electrodes were characterized by scanning electron microscopy and energy-dispersive X-ray techniques, respectively. Results indicated that silver nanoparticles with a diameter of about 40–70 nm were homogeneously dispersed on the surface of polyaniline film. The silver nanoparticles/PAni/Ti electrodes were examined for electro-catalytic activity toward oxidation of hydrazine. The results show that these modified electrodes are highly active for electro-catalytic oxidation of hydrazine.

Electrochemical fabrication of polyaniline films containing gold nanoparticles deposited on titanium electrode for electro-oxidation of ascorbic acid

Polyaniline films prepared on titanium were employed as substrate for the electrodeposition of gold. The modified electrode was used as anode for the electro-oxidation of ascorbic acid. The electrochemical behavior and electro-catalytic activity of Au/PAni/Ti electrode were characterized by cyclic voltammetry. The morphology of the polyaniline film and gold coating on PAni/Ti electrode were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) techniques, respectively. Results indicated that gold nanoparticles were homogeneously dispersed on the surface of polyaniline film. The electro-oxidation of ascorbic acid is found to proceed more facile on Au/PAni/Ti electrode than on bare gold electrode. The irreversible oxidation current of ascorbic acid exhibits a linear dependence on the ascorbic acid concentration in the range of 1–5 mM.

Investigation on cell biocompatible behaviors of polyaniline film fabricated via electroless surface polymerization

Considering for the potential application in tissue engineering, polyaniline (PANi) film was fabricated via a two-step route: a self-assembled monolayer of C 6H 5NHC 3H 6Si(OMe) 3 was firstly formed on the single-crystal Si substrate; the conducting PANi film was then prepared through electroless surface polymerization of the aniline molecules on the aniline monolayer-bearing silane surface in an acidic aqueous solution. The formation of PANi film on Si surface was confirmed by characterizations of X-ray photoelectron spectroscope (XPS) and specular reflectance Fourier transform infrared (SR-FTIR) spectrum, etc. At last, the proliferation behaviors of PC-12 cells on the PANi film surface were studied by the [3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) colorimetric assays, acridine orange fluorometric staining, and scanning electron microscope (SEM) observation, etc. The results demonstrate that the as-prepared PANi film provides high ability for cell proliferation, exhibiting promising potentials as surface coating to cultivate neuronal cells for applications in the tissue engineering.

Suppression of pH effect on the electrochemical deformation in polyaniline film

pH effect on the electrochemical deformation of freestanding polyaniline (PANi) film was investigated by means of electrochemomechanical deformation (ECMD) measurement. The maximum anodic expansion was found in PANi at around pH = 1.5 in aqueous acid consisted of HCl and NaCl. The deformation vs. redox charge ( D−Q) plots revealed the critical differences in the deformation characteristics below and above pH = 1.5. The similar pH dependences were also observed in other acidic media. Against these results, we investigated the surface coating effect of PANi film on deformation behaviors. It was revealed that the PPy coating on PANi film successfully reduced the pH dependence of the PANi/PPy film deformation. The results indicate that the buffer layer coated on the PANi film surface decreases the ion concentration effects on the PANi deformation. The result indicates the extensive usage of PANi actuator in wide pH aqueous media.

Adsorption kinetics of optochemical NH 3 gas sensing with semiconductor polyaniline films

Polyaniline (PANI) shows electrical as well as optical property changes when it is in contact with oxidant/reductor gas. In this work, the optical transmittance changes in PANI coatings originated by their exposure to the ammonia gas were detected by a nulling optical transmittance bridge. The adsorption and desorption curves were carefully analysed using Langmuir kinetic theory for the adsorption of ammonia gas on PANI single and PANI–PMMA composite coatings. Because of the inhomogeneous nature of the PANI film surface adsorption isotherms were the best described by Freundlich model. From the numerical fitting equations it is suggested that there may be two energetically different adsorption sites on the PANI surface for NH 3 molecules, which corroborates with the no-uniform positive charge distribution on the nitrogen atoms of the PANI backbone chains. The activation energy of adsorption and the heat of adsorption were estimated to be about 0.3–0.5 eV at a NH 3 gas concentration of 10–1000 ppm.

Surface Modification of Polyaniline Film by Plasma-Graft Polymerization and Its Effect on the Redox Reaction

Poly(vinylsulfonic acid) chains having cation-exchangeable groups are introduced onto a surface of polyaniline film by means of plasma-graft polymerization, and the redox reaction mechanism of the plasma-grafted polyaniline film is investigated with a combination of electrochemical and microgravimetric techniques. It becomes apparent from the surface analyses of the polyaniline film that poly(vinylsulfonic acid) chains are plasma-grafted. The graft area is not covered on all the surface of the film and is formed locally here and there on the surface. The plasma-grafted film exhibits both anion and cation migrations which take place in order to maintain electroneutrality of the film during the redox process in an electrolyte. The cation migration takes place predominantly through thickening of the graft layer composed of poly(vinylsulfonic acid) chains and extending of the graft area.

The morphology of different metals electrodeposited onto polyaniline films

The process of electrochemical deposition/dissolution and the morphology of obtained deposits of cadmium and copper onto polyaniline films of different thickness have been investigated by linear sweep voltammetry, the potentiostatic pulse technique and in situ microscopic monitoring. It was shown that both metals can be deposited onto polyaniline films, although cadmium deposits at the potentials where the polymer is non-conductive while copper deposits at the potentials where the polyaniline is partially oxidized (conductive). Cadmium was found to deposit only into the open pores of the polymer onto glassy carbon substrate at particular places of the polyaniline surface, so that a compact layer of cadmium cannot be obtained. It was also shown that the whole amount of deposited cadmium cannot be dissolved at the potential of “normal” dissolution of cadmium, and the rest of the deposit dissolves at potentials of polyaniline oxidation. In contrast, a compact layer of copper of a desired thickness can readily be deposited onto a polyaniline film surface. It was suggested that in situ microscopic monitoring of the morphology of deposits of metals depositing onto reduced (non-conductive) polymer films can be used as a method for determination of the porosity of polymer films.