Electrodeposited Polyaniline Films Research Articles

Influence of surfactant on conductivity, capacitance and doping of electrodeposited polyaniline films

The electrodeposition of polyaniline films is usually carried out in acid solutions such as hydrochloric acid, perchloric acid or sulfuric acid, and more rarely in organic acids such as camphorsulfonic acid (CSA). In this study, the impact of the presence of a surfactant in the electrolytic solution based on hydrochloric acid or CSA was evaluated by successively using anionic (sodium dodecyl sulfate, SDS), cationic (cetyltrimethylammonium bromide, CTAB), and non-ionic (Tritonx100) surfactants. Whatever the surfactant and the acid used, the electrochemical oxidation of aniline has successfully led to the formation of a thick polyaniline (PANI) film through a quasi-reversible reaction controlled by the diffusion of aniline monomers. The nature of the surfactant was shown to affect physico-chemical properties of the film, in particular its morphological features (morphology, thickness, roughness), electrochemical activity, specific capacitance, and conductivity. For example, PANI films containing SDS had a spongy morphology when PANI films containing Tritonx100 had a more fibrous and compact structure. Glow Discharge Optical Emission Spectroscopy (GDOES) experiments also highlighted differences depending on the acid used since chloride anions, from HCl, were present only on the top surface of the PANI films when camphorsulfonate anions were present everywhere throughout the polymer film, which impacts the doping process and electrochemical activity of the films. Moreover, the specific capacitance of the PANI/CSA films is higher and more sensitive to current density variation than the one of PANI/HCl films. Finally, electrochemical impedance experiments evidenced that the conductivity of PANI films electrodeposited from CSA solutions was much higher than the one of PANI films prepared from HCl solutions, and highly dependent on the nature of the surfactant, the most conductive films being obtained in the presence of SDS and Tritonx100. Therefore, the originality of this work comes from the possibility of modulating the conductivity, capacitance and electroactivity of electrodeposited polyaniline films using surfactants of different polarity, and from the determination of the distribution of ions in the films using the GDOES technique, which is rarely used to characterise organic films.

RBD-Modified Polyaniline-Based Label-Free Immunosensor for Sensitive Impedimetric Detection of Anti-SARS-CoV-2 Antibodies

The emergence of the SARS-CoV-2 virus and the associated pandemic has affected the entire human population. Human susceptibility to the virus has highlighted a tremendous need for affordable diagnostic systems to manage the pandemic and monitor the effectiveness of vaccination. We have developed a simple and label-free electrochemical immunosensor for the detection of human anti-SARS-CoV-2 IgG antibodies, which consists of a supporting screen-printed carbon electrode (SPCE) modified with an electrodeposited polyaniline film and glutaraldehyde, allowing effective immobilization of the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) as a biorecognition element. The impedimetric immunosensor showed a linear response over a wide concentration range of 0.01–10 μg mL−1, that is, 67 pM–6.7 nM, with a low detection limit of 25.9 pM. A dual working electrode configuration with a built-in negative control unit was demonstrated for practical field applications. The immunosensor was successfully used in a real serum sample from an infected patient and showed good reproducibility and fair agreement with ELISA. An optional amplification step with secondary goat anti-human IgG antibodies was demonstrated, resulting in an extended linear range and a detection limit as low as 0.93 pM.

Electrochemical Aptasensor for Ultralow Fouling Cancer Cell Quantification in Complex Biological Media Based on Designed Branched Peptides.

The rapid, convenient, and selective assaying of clinical targets directly in complex biological media brings with it the potential to revolutionize diagnostics. One major hurdle to impact is retention of selectivity and a tight control of nonspecific surface interactions or biofouling. We report herein, the construction of an antifouling interface through the covalent attachment of designed branched zwitterionic peptides onto electrodeposited polyaniline film. The antifouling capability of the designed branched peptide significantly outperforms that of the commonly used PEG and linear peptides. The interfaces modified with branched peptides are exceptionally effective in reducing a nonspecific protein and cell adsorption, as verified by electrochemical and fluorescent characterization. The derived sensors with mucin1 protein (MUC1) aptamer as the recognition element detect MUC1-positive MCF-7 breast cancer cells in human serum with high sensitivity and selectivity. The linear response range of the cytosensor for the MCF-7 cell is from 50 to 106 cells/mL, with a limit of detection as low as 20 cells/mL. More importantly, the assaying performances remain unchanged in human serum owing to the presence of branched antifouling peptide, indicating feasibility of the cytosensor for practical cancer cell quantification in complex samples.

An in situ electrochemical fabrication of layer by layer graphenized graphite polyaniline as a stable solid-phase microextraction fiber coating for trace environmental analysis.

A layer by layer graphenized graphite/polyaniline coating was fabricated on commercial pencil lead substrate by an in situ facile, fast and efficient electrochemical procedure. The electrodeposited polyaniline film on surface-confined graphene structure can integrate the advantages of the both layers and was used for solid-phase microextraction. Effective experimental parameters in electrochemical production of graphene nanosheets and electropolymerization of aniline were optimized. The prepared fiber was used for extraction and determination of four polycyclic aromatic hydrocarbons: phenanthrene, anthracene, fluoranthene and pyrene in aqueous samples by high performance liquid chromatography. The fiber coating was characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. Under the optimized conditions, the coating provided good linear ranges (0.10-25 μg/L for phenanthrene, 0.05-12.5 μg/L for anthracene, 0.825-99μg/L for fluoranthene and 0.625-75 μg/L for pyrene (R2 =0.999)) and limits of detection, 0.016 to 0.275μg/L. The produced coating has several attractive features such as high stability, low cost and long operation time.

Capacitance Properties of Electrodeposited Polyaniline Films on Stainless Steel Substrate

Polyaniline (PANI) thin films were successfully synthesized from a mixed solution of 1M aniline and two different concentration solutions of H2SO4 on a stainless steel substrate. The capacitance properties of polyaniline (PANI) films, have been determined and examined in the selected media of two different concentrations of H2SO4 acid using cyclic volammetry technique. Cyclic voltammetric measurements have shown that PANI films grown by cycling the potential between -0.2V and 1 V in 1M H2SO4 and 2M H2SO4 on SS electrode. The electrochemical characterization of the electrode was carried out by means of cyclic voltammetry. The results show that polyaniline has a high specific capacitance of 702.1 F.g-1 and 810.5 F.g-1 at 10 mV s-1 in 1M H2SO4 and 2M H2SO4 respectively. This indicates that the promising feasibility of the polyaniline used as an electrochemical capacitor material in the sulphuric acid solutions.

Application of original assemblies of polyelectrolytes, urease and electrodeposited polyaniline as sensitive films of potentiometric urea biosensors

Original assemblies were prepared for use as sensitive films of potentiometric enzyme urea sensors, and compared to identify the more efficient structure with respect to stability. These films included electrodeposited polyaniline, used as transducer, urease, used as catalyst, and biocompatible polyelectrolytes, used as a matrix to preserve the integrity of the enzyme in the sensitive film. Two kinds of assemblies were done: the first one consisted in the adsorption of urease onto a polyaniline film followed by the adsorption of a chitosan-carboxymethylpullulan multilayer film, while the second one consisted in the adsorption of a urease-chitosan multilayer film onto an electrodeposited polyaniline film. The morphological features and growth of these assemblies were characterized by scanning electron microscopy and quartz crystal microbalance, respectively. This allowed us to demonstrate that the assemblies are successfully formed onto the electrodes of the sensors. The potentiometric responses of both assemblies were then measured as a function of urea concentration using a home-made portable potentiostat. The electrochemical response of resulting sensors was fast and sensitive for both types of assemblies, but the stability in time was much better for the films obtained from alternative adsorption of urease and chitosan onto a layer of urease adsorbed over electrodeposited polyaniline.

Glow discharge optical emission spectroscopy: a complementary technique to analyze thin electrodeposited polyaniline films

Glow Discharge Optical Emission Spectroscopy (GDOES) has been developed to perform depth profiles of thick metallic films, in tens of microns range. GDOES spectroscopy can also be used to analyze thin organic polymer films since this technique has a great potential thanks to its high depth resolution, multi-element capability, sensitivity, and adaptability to solids or films and to conducting or non-conducting samples. In particular thin electrodeposited conducting polymer films remain an unexplored field of investigation for GDOES technique. However GDOES was used in this work to analyze electrodeposited polyaniline films, in addition to other techniques such as profilometry, electron microscopy and X-ray diffraction (XRD). More precisely polyaniline thin films were electrodeposited from HCl solutions and the presence of an anilinium chloride excess at the top surface of the polymer film was demonstrated using GDOES and XRD. Rinsing of these films with water led to the removal of this excess and to the partial dedoping of the polymer film due to the porous structure of polymer films. Polyaniline thin films were also electrodeposited from H2SO4 solutions and an anilinium hydrogen sulfate was similarly observed at the top surface of the polymer. This excess was removed by rinsing, contrary to hydrogen sulfate anions incorporated into the polymer film during the electrochemical polymerization that were not completely expulsed from the polyaniline films as proved using GDOES.

Organic Solar Cells Based on Electrodeposited Polyaniline Films

Polyaniline thin films as hole transporting layers were fabricated on transparent indium–tin-oxide electrodes by electrodeposition of aniline in an aqueous H2SO4 electrolyte solution. Emerald-green polyaniline films were obtained, which showed stable redox waves. A mixed solution of polythiophene and fullerene derivative was spin-coated onto the electrodeposited polyaniline film. After the modification of titanium oxide film on the surface of the polythiophene/fullerene layer, an aluminum electrode was fabricated by vacuum deposition. The obtained solar cells generated stable photocurrent and photovoltage under light illumination.

Elaboration and characterization of polyaniline films electrodeposited on tin oxides

This paper presents the electrochemical synthesis of polyaniline films on fluorine tin oxide (FTO) and indium tin oxide (ITO) in acidic medium by both potentiodynamic and potentiostatic methods. The use of potentiodynamic deposition showed that conductive polyaniline films were synthesized by the same process than on noble metals and allowed the determination of the electrodeposition potential used for further potentiostatic electrodepositions. The electropolymerization was then performed by chronoamperometry and appeared easier on ITO than on FTO. The electrodeposited polyaniline films were extensively characterized in terms of chemical nature, electrochemical growth, thickness, roughness and morphology. The chemical nature of the films was identified through infrared spectroscopy and X-ray diffraction analyses. The roughness and the morphology of the polymer coatings, determined by profilometry, scanning electron microscopy and atomic force microscopy, were correlated to the calculated thickness of each polyaniline film and to the nature of the substrate.

Urea potentiometric enzymatic biosensor based on charged biopolymers and electrodeposited polyaniline

A potentiometric biosensor based on urease was developed for the quantitative determination of urea concentration in aqueous solutions for biomedical applications. The urease was either physisorbed onto an electrodeposited polyaniline film (PANI), or immobilized on a layer-by-layer film (LbL) assembled over the PANI film, that was obtained by the alternate deposition of charged polysaccharides (carboxymethylpullulan (CMP) and chitosan (CHI)). In the latter case, the urease (Urs) enzyme was either physically adsorbed or covalently grafted to the LbL film using carbodiimide coupling reaction. Potentiometric responses of the enzymatic biosensors were measured as a function of the urea concentration in aqueous solutions (from 10 −6 to 10 −1 mol L −1 urea). Very high sensitivity and short response time were observed for the present biosensor. Moreover, a stability study showed a higher stability over time for the potentiometric response of the sensor with the enzyme-grafted LbL film, testifying for the protective nature of the polysaccharide coating and the interest of covalent grafting.

Electrochemical polymerization of an aniline-terminated self-assembled monolayer on indium tin oxide electrodes and its effect on polyaniline electrodeposition

Indium tin oxide (ITO) transparent electrodes were surface modified by a self-assembled monolayer of N-phenyl-γ-aminopropyl-trimethoxysilane (PAPTS). Cyclic voltammetry of the PAPTS monolayer in aniline-free aqueous electrolyte showed the typical shape of a surface-confined monomer, due to the oxidation of the aniline moieties. This process resulted in a two-dimensional polyaniline film with uniform thickness of 1.3 nm, as measured by atomic force microscopy. X-ray photoelectron and UV–visible spectroscopic techniques confirm the formation of a conjugated polymer film. The influence of the surface modification of ITO electrodes on polyaniline electrochemical deposition was also studied. The initial oxidation rate of aniline increased in the PAPTS-modified ITO electrodes, although the overall film formation rate was lower than that of unmodified ITO electrodes. The morphology of the electrodeposited polyaniline films on PAPTS-modified and unmodified ITO electrodes was studied by atomic force microscopy. Films of smaller grain were grown in the PAPTS-modified ITO as compared to films grown on unmodified ITO. A blocking effect due to the propyl spacer is proposed to explain the reduced electron transfer in PAPTS-modified electrodes.

Synthesis and characterization of novel nano size electroactive poly 4,4′‐diaminodiphenyl sulphone

AbstractThe modification of electrodeposited polyaniline film by subsequent electrodeposition of 4,4′‐diaminodiphenyl sulfone (DDS) leads to a new material having nanostructure. The coated polymer films were treated with various pH solutions. The film adherent characteristics and surface morphology were studied using SEM. The electrochemically synthesized polyDDS revealed good redox behavior. The DDS was also polymerized by the chemical oxidation method using potassium persulphate. The polymer was characterized by UV‐Vis and FTIR spectral studies. The formation of polymer through the NH group was understood from the single NH stretching vibrational frequency at 3459 cm−1. The X‐ray diffraction studies revealed the formation of nano sized (28 nm) crystalline polymer. The conductivity of the polymer was determined to be 1.07 × 10−4 S.cm−1. The solubility of the chemically polymerized powder was ascertained, and polyDDS showed good solubility in DMF and DMSO. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1702–1707, 2005

Evidence of a Free Pt Surface under Electrodeposited Polyaniline (PANI) Films: CO Adsorption and Methanol Oxidation at PANI/Pt without Metal Particles

Differential electrochemical mass spectrometry (DEMS) and Fourier transform infrared spectroscopy (FTIRS) are used to provide evidence of the existence of a free metal surface under electrodeposited polyaniline (PANI) films. With this purpose, both methanol oxidation and CO adsorption are studied on Pt electrodes modified by electrodeposited polyaniline films (PANI/Pt). Using the DEMS signal for CO2 (m/z = 44) to follow the oxidation of adsorbed CO to CO2, the exposed Pt surface area under the film is evaluated to reach ∼30% of the clean Pt electrode. CO adsorption on a PANI/Pt electrode is clearly detected by FTIRS through the bands at 2080 and 1820 cm-1 for linear and bridge bonded CO, respectively. The free area seems to behave differently than clean Pt toward methanol oxidation. The in-situ FTIR spectra present only a band at 2343 cm-1 due to CO2 formation, but not those due to CO adsorption, suggesting a change in the oxidation mechanism.

Preparation and characterisation of polyaniline electrode modified with diamino-methylbenzoate

The modification of electrodeposited polyaniline film by subsequent electrodeposition of diamino-methylbenzoate leads to a new material of interesting electrochemical, electrical and spectroscopic properties. The electronically conductive parent polymer can be transformed into a redox polymer, however, the electrochemical behaviour, the colour and the conductivity of the polymer during the modification procedure can be easily regulated, therefore, the required properties can be finely tuned. The formation and the properties of the new polymeric films were studied by electrochemical microgravimetric and spectroelectrochemical techniques.

Dynamic scaling analysis of scanning force microscopy images of electrochemically formed polyaniline films in the oxidized form scale-dependent roughening kinetics

The morphology of the oxidized form of electrodeposited polyaniline films (PANI) grown on platinum under potentiodynamic cycling has been studied by scanning force microscopy (SFM). For average film height 〈h〉 1000 nm, a highly branched deposit was produced. The dynamic scaling analysis of the granular-deposit SFM image scans revealed the characteristic features of a self-affine fractal surface with two sets of roughness exponents α and β, depending whether the length of the SFM scan, Ls, involved in the analysis was smaller or larger than the average grain size ds of the polymer film. For Ls < ds, α(I)= 0.90 and β(I)= 0.4, whereas for ds⩽Ls⩽ 1000 nm, α(II)= 0.4 and β(II)= 0.6 were obtained. Both high values of β are consistent with the contribution to the growth process of a directional electric field, which at advanced stages of growth leads to the development of the highly branched deposit. A correlation between the analysis of PANI morphology and potentiostatic PANI electroformation current transient data is also presented.

Photoacoustic Spectroscopy of Polyaniline Films

Photoacoustic spectra as well as optical absorption spectra were measured to study the heat generation by nonradiative processes in electrodeposited polyaniline films in the wavelength range of 310 to 800 nm. The shapes of both spectra depend on the pH for polymerization of electrodeposited polyaniline films. The shapes of infrared spectra also show the pH dependence. Photoacoustic spectra show that the changes of signal intensity are different from those of optical absorption spectra, suggesting the character of lattice relaxation of a low-dimensional system.

The electrochemical actuator using electrochemically-deposited poly-aniline film

Electrochemomechanical polymer actuators were fabricated by using the electro-deposited poly-aniline film. Using LASER displacement meter, we can easily get the in-situ observation of the displacement and the cyclic voltammogram[1]. At the redox reaction from leuco-emeraldine salt to emeraldine salt(ES), PANI film showed large deformation. On the other hand, at the redox reaction from ES to pernigraniline salt, PANI film showed the slight contraction.