Electrochemical Transducer Based on Nanostructured Polyaniline Films Obtained on Functionalized Self Assembled Monolayers of 4-Aminothiophenol (original) (raw)
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Amplified Electrochemical DNA Sensor Based on Polyaniline Film and Gold Nanoparticles
Electroanalysis, 2013
In this work, an electrochemical DNA biosensor, based on a dual signal amplified strategy by employing a polyaniline film and gold nanoparticles as a sensor platform and enzyme-linked as a label, for sensitive detection is presented. Firstly, polyaniline film and gold nanoparticles were progressively grown on graphite screen-printed electrode surface via electropolymerization and electrochemical deposition, respectively. The sensor was characterized by scanning electron microscopy (SEM), cyclic voltammetry and impedance measurements. The polyaniline-gold nanocomposite modified electrodes were firstly modified with a mixed monolayer of a 17-mer thiol-tethered DNA probe and a spacer thiol, 6-mercapto-1-hexanol (MCH). An enzyme-amplified detection scheme, based on the coupling of a streptavidin-alkaline phosphatase conjugate and biotinylated target sequences was then applied. The enzyme catalyzed the hydrolysis of the electroinactive a-naphthyl phosphate to a-naphthol; this product is electroactive and has been detected by means of differential pulse voltammetry. In this way, the sensor coupled the unique electrical properties of polyaniline and gold nanoparticles (high surface area, fast heterogeneous electron transfer, chemical stability, and ease of miniaturisation) and enzymatic amplification. A linear response was obtained over a concentration range (0.2-10 nM). A detection limit of 0.1 nM was achieved.
Influence of charged tail groups of self-assembled monolayers on electrodeposition of polyaniline
Electrochimica Acta, 2004
Self-assembled monolayers (SAMs) of thiols with three different tail groups, −COOH, −SO 3 Na, and −NH 2 , were used to modify the Au substrates for electrodepositing polyaniline (PANI). Electrochemical quartz crystal microbalance (EQCM) results indicated a slower rate of deposition of PANI on a SAM surface consisting of positively charged amine groups compared to polymerization on bare gold and on a SAM of carboxyl acid groups. The properties of the SAM layers are dependent on the pH value of the solutions, and are effective only at very low pH values (pH < 2). A layer of the positively charged amino groups in acidic solution acted as a barrier for electron transfer in electro-oxidation of aniline monomer. The positively charged SAM of amine groups also increased repulsion between the coupled aniline species and the electrode surface and in this way hindered electrodeposition. Modification of the surface with pre-patterned SAMs have been demonstrated to be a convenient and practical way to fabricate selectively deposited thin films of polyaniline.
In situ electrochemical SERS studies on electrodeposition of aniline on 4-ATP/Au surface
Journal of Solid State Electrochemistry, 2006
The electrochemical polymerization of 0.01 M aniline in 1 M H 2 SO 4 aqueous solution on roughened Au surface modified with a self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) has been investigated by in situ electrochemical surface-enhanced Raman scattering spectroscopy (SERS). The repeat units and possible structures of the electrodeposited polyaniline (PANI) film were proposed; i.e., aniline monomer is coupled in head-to-tail predominately at the C 4 of aniline and amine of 4-ATP, and the thin PANI film is orientated vertically to substrate surface. Simultaneous Raman spectra during potential scanning indicate clearly that the ultrathin PANI film (in initial growth of the film) consists of semiquinone radical cation (IP + ), para-disubstituted benzene (IP and IP + ) and quinine diimine (NP) while it is oxidized, and without quinine diimine and semiquinone radical cation while reduced. Meanwhile, the results confirm that 4-ATP monolayer shows a strong promotion on the electrodeposition of aniline monomer, and a possible polymerization mechanism was proposed.
Two-Dimensional Polyaniline Thin Film Electrodeposited on a Self-Assembled Monolayer
Journal of the American Chemical Society, 1998
A two-dimensional conducting polyaniline (PAN) monolayer has been formed on an electrically insulating monolayer. The approach is based on the electrochemical polymerization of surface-confined anilinium ions that were electrostatically attached to a negatively charged self-assembled monolayer of ω-mercaptodecanesulfonate (MDS), HS(CH 2) 10 SO 3-, on a gold surface. The formation and characterization of the two-dimensional film and the MDS monolayer have been examined by cyclic voltammetry, Fourier transform IR spectroscopy, X-ray photoelectron spectroscopy, wettability, and scanning electrochemical microscope. The formation of a capacitor-like assembly, in which electron transfer was blocked between PAN and the gold surface, was accomplished by electrochemically incorporating hexadecanethiol (C 16) into the MDS monolayer. The PAN monolayer exhibits properties similar to those of a thin polymer film.
An amperometric enzyme biosensor fabricated from polyaniline nanoparticles
…, 2005
The biosensor described here uses a novel aqueous-based nanoparticulate polyaniline (PANI), doped with dodecylbenzenesulfonic acid (DBSA). The nanoparticles were applied to a glassy carbon electrode surface by electrodeposition techniques, and horseradish peroxidase (HRP) was subsequently electrostatically adsorbed to the nanoparticle-modified surface. This biosensor format was demonstrated for H 2 O 2 sensing. Electrodeposited polymer nanoparticles resulted in highly ordered conductive nanostructured films, which were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), profilometry and spectroelectrochemistry. The surface of the films were characterized by a uniform array of nanoparticulate PANI (nanoPANI/DBSA) nodules and were shown to have a thickness of 350 nm. Physical techniques have shown that the nanofilms possess properties which allow for uniform electrostatic adsorption of protein to take place. This effective biosensor format, exhibits higher signal-tobackground ratios and shorter response times than previous PANI biosensor configurations.
Thin Solid Films, 2008
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.
Electrochemical Preparation and Sensor Properties of Conducting Polyaniline Films
A polyaniline-glucose oxidase electrode was prepared by the electrochemical polymerization of aniline on a Pt electrode that was already pre-adsorbed by the enzyme (glucose oxidase) at a potential of 1 V vs. Ag/AgCl. Then, the amperometric responses of the enzyme electrode to the electroactive hydrogen peroxide formed by the enzyme-catalyzed reaction of the substrate (glucose) with oxygen were measured at a potential of 0.7 V in PBS solution. The effects of electrochemical polymerization (i.e., concentrations of monomer and electrolyte, film thickness) and amperometric measurement parameters (i.e. pH, temperature) on the amperometric response characteristics to glucose of the resultant enzyme electrode were systematically investigated and all these parameters were optimized. The prepared polymeric sensor exhibited a fast steady-state amperometric response time (4-5 s), a linear amperometric response up to 6 mM glucose through with poor stability. Also, it was found that the sensor responded successfully to glucose injections in the presence of some interfering substances such as ascorbic acid, oxalic acid, lactose, sucrose and urea.
Electrochemical preparation and electrical characterization of polyaniline as a sensitive biosensor
Microsystem Technologies, 2018
Electrochemical biosensor has been developed for detection of danazol (Dz) based on electrochemical polyaniline (PANI) electrode. Electrochemical PANI films were prepared by electrochemical polymerization technique. The Fourier transform infrared spectroscopy and X-ray diffraction were performed to identify the characteristic peaks and the degree of crystallinity of the prepared films. Cyclic voltammetry (CV) studies have been investigated for the electrochemical polyaniline films onto carbon electrode to determine the appropriate electro-active films to be used as electrochemical biosensor. CV of electrochemical polymerization of polyaniline films at different doping concentrations of 1, 1.2 and 1.5 M. CV results shown, the maximum peak current was 44.67 mA/cm 2 at 0.2 V/SCE for 1 M HCl. The prepared electrodes were used for detecting Dz using differential pulse voltammetry (DPV) technique and electrochemical impedance spectroscopy (EIS). The current peak of DPV produced inside solution containing Dz of concentration 2 nM is about 1.671 mA. Also, EIS showed that the charge transfer resistance (R ct) was increased with different Dz concentration.