Conductimetric immunosensor based on poly(3,4-ethylenedioxythiophene)

A conductimetric reagentless immunosensor using the biospecific binding pair of goat antirabbit IgG and rabbit IgG has been designed and fabricated using poly (3,4-ethylenedioxythiophene) as the immobilization matrix-cumtransducer.     

Synthesis and characterization of p-toluenesulfonate incorporated poly(3,4-ethylenedioxythiophene)

Poly(3,4-ethylenedioxythiophene) (PEDOT), a conducting polymer, was electrochemically synthesized with p-toluenesulfonate (TSNa) as a dopant on gold surface. The electrochemical properties of the polymer were studied by impedance spectroscopy and cyclic voltammetry (CV). It was found that the impedance magnitude of the electrode significantly decreased over a wide range of frequency from 10⁰ to 10⁴ Hz after the polymer deposition. The CV demonstrated enhanced reversibility of the PEDOT film. The surface morphology was investigated by scanning electronic microscope (SEM) and atomic force microscope (AFM). Due to the effect of TSNa structure, nano-fungus was observed. Polymerization time was optimized and 30 min deposition resulted in the highest charge capacity, showing the highest electroactive surface area, possibly due to its porous structured polymer. Moreover, the high specific surface area could be favorable for cell attachment. The stability of PEDOT in glutathione (GSH), a common biologically relevant reducing agent, was studied with polypyrrole (PPy) as a baseline. It showed that the former had much better stability than the latter and it could be an excellent candidate for potential applications of in vivo neural devices.     

Novel label-free DNA sensors based on poly(3,4-ethylenedioxythiophene)

We report on the design and development of a novel label-free DNA sensor based on conducting poly(3,4-ethylenedioxythiophene) for the direct detection and quantification of target ssDNA.     

Simultaneous determination of N-acetyl-p-aminophenol and p-aminophenol with poly(3,4-ethylenedioxythiophene) modified glassy carbon electrode

A sensitive and selective method was developed for the determination of N-acetyl-p-aminophenol (APAP) and p-aminophenol (PAP) using poly(3,4-ethylenedioxythiophene) (PEDOT)-modified glassy carbon electrode (GCE). Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical reaction of APAP and PAP at the modified electrode. Both APAP and PAP showed quasireversible redox reactions with formal potentials of 367 mV and 101 mV (vs. Ag/AgCl), respectively, in phosphate buffer solution of pH 7.0. The significant peak potential difference (266 mV) between APAP and PAP enabled the simultaneous determination both species based on differential pulse voltammetry. The voltammetric responses gave linear ranges of 1.0 × 10⁻⁶-1.0 × 10⁻⁴ mol L⁻¹ and 4.0 × 10⁻⁶-3.2 × 10⁻⁴ mol L⁻¹, with detection limits of 4.0 × 10⁻⁷ mol L⁻¹ and 1.2 × 10⁻⁶ mol L⁻¹ for APAP and PAP, respectively. The method was successfully applied for the determination of APAP and PAP in pharmaceutical formulations and biological samples.     

Characterization of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) adsorption on cellulosic materials

The interaction between poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) and cellulosic fibers was characterized in order to obtain further understanding of the conductivity properties of the modified cellulosic fiber material. Microcrystalline cellulose (MCC) was used as a model surface to study the adsorption behavior at various pH and salt concentrations, while samples of low-conductivity paper, normally used for the production of electrical insulation papers, were dipped into PEDOT:PSS dispersion and air-dried for X-ray photoelectron spectroscopy (XPS) studies. The results showed a strong interaction between the MCC and PEDOT:PSS, which implied a broad molecular distribution of the conducting polymer. With increasing pH, less amount of the conducting polymer was adsorbed whereas the amount adsorbed passed through a maximum value with varying salt concentration. Zeta potential measurement and polyelectrolyte titration were used to determine the surface charge of both suspended MCC particles and dispersed PEDOT:PSS at various pH levels and salt concentrations. Dip-coated paper samples exhibited two peaks in the S(2p) XPS spectra at 168–169 and 164–165 eV which correspond to the sulfur signals of sulfonate (in PSS) and in thiophene (in PEDOT), respectively. It was found that the PEDOT:PSS with a ratio of 1:2.5 was adsorbed more in the base paper than that with a ratio of 1:6. The PEDOT:PSS ratio on the surface of the cellulosic material was higher than that in the bulk liquid for all samples. The results indicated that PEDOT was preferentially adsorbed rather than PSS. The degree of washing of the conducting polymer did not significantly affect the PEDOT enhancement on the surface.     

Electrochemical sensor for nitrobenzene based on carbon paste electrode modified with a poly(3,4-ethylenedioxythiophene) and carbon nanotube nanocomposite

A sensitive and selective electrochemical sensor for the determination of nitrobenzene (NB) was developed based on a carbon paste electrode (CPE) modified with a nanocomposite prepared from the conducting polymer poly(3,4-ethylenedioxythiophene) and carbon nanotubes. The modified CPE exhibits good conductivity, a large surface area, and excellent catalytic activity towards the electrochemical reduction of NB. Under optimal conditions, the modified CPE is capable of detecting NB in the 0.25 to 43 μM concentration range and with a detection limit at 83 nM. Moreover, the sensor is highly stable and reusable, and free of interferences by other commonly present nitro compounds. It was used to determine NB in wastewater samples.

Quasi-solid-state dye-sensitized solar cells assembled with polymeric ionic liquid and poly(3,4-ethylenedioxythiophene) counter electrode

Poly(3,4-ethylenedioxythiophene) nanofibers (PEDOT-NF) with high catalytic activity were synthesized and employed as a counter electrode in dye-sensitized solar cells (DSSCs). A polymeric ionic liquid (PIL) was used as a gelling agent and an iodide source for making a highly conductive gel polymer electrolyte. A quasi-solid-state DSSC assembled with this PIL-based gel polymer electrolyte and PEDOT-NF counter electrode exhibited high conversion efficiency of 8.12% at 100 mW cm^− 2.     

Amperometric nitrite sensor based on a glassy carbon electrode modified with electrodeposited poly(3,4-ethylenedioxythiophene) doped with a polyacenic semiconductor

Microchimica Acta - The paper describes an electrochemical nitrite sensor based on the use of a nanocomposite consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polyacenic...     

Simultaneous determination of dopamine and ascorbic acid on poly (3,4-ethylenedioxythiophene) modified glassy carbon electrode

Detection of dopamine (DA) in the presence of excess of ascorbic acid (AA) has been demonstrated using a conducting polymer matrix, poly (3,4-ethylenedioxythiophene) (PEDOT) film in neutral buffer (PBS 7.4) solution. The PEDOT film was deposited on a glassy carbon electrode by electropolymerization of EDOT from acetonitrile solution. Atomic force microscopy studies revealed that the electrodeposited film was found to be approximately 100 nm thick with a roughness factor of 2.6 nm. Voltammetric studies have shown catalytic oxidation of DA and AA on PEDOT modified electrode and can afford a peak potential separation of ∼0.2 V. It is speculated that the cationic PEDOT film interacts with the negatively charged ascorbate anion through favorable electrostatic interaction, which results in pre-concentration at a less anodic value. The positively charged DA tends to interact with the hydrophobic regions of PEDOT film through hydrophobic–hydrophobic interaction thus resulting in favorable adsorption on the polymer matrix. Further enhancement in sensitivity to micro molar level oxidation current for DA/AA oxidation was achieved by square wave voltammetry (SWV) which can detect DA at its low concentration of 1 μM in the presence of 1000 times higher concentration of AA (1 mM). Thus the PEDOT modified electrode exhibited a stable and sensitive response to DA in the presence of AA interference.     

Potential-modulated, attenuated total reflectance spectroscopy of poly(3,4-ethylenedioxythiophene) and poly(3,4-ethylenedioxythiophene methanol) copolymer films on indium-tin oxide

We report the first application of a potential-modulated spectroelectrochemical ATR (PM-ATR) instrument utilizing multiple internal reflections at an optically transparent electrode to study the charge-transfer kinetics and electrochromic response of adsorbed films. A sinusoidally modulated potential waveform was applied to an indium-tin oxide (ITO) electrode while simultaneously monitoring the optical reflectivity of thin (2-6 equivalent monolayers) copolymer films of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-ethylenedioxythiophene methanol) (PEDTM), previously characterized in our laboratory. At high modulation frequencies the measured response of the polymer film is selective toward the fastest electrochromic processes in the film, presumably those occurring within the first adsorbed monolayer. Quantitative determination of the electrochromic switching rate, derived from the frequency response of the attenuated reflectivity, shows a linear decrease in the rate, from 11 x 10(3) s(-1) to 3 x 10(3) s(-1), with increasing proportions of PEDTM in the copolymer, suggesting that interactions between the methanol substituent on EDTM and the ITO surface slow the switching process by limiting the rate of conformational change in the polymer film.     

A screen-printed carbon electrode modified with gold nanoparticles,poly(3,4-ethylenedioxythiophene), poly(styrene sulfonate) and a molecular imprint for voltammetric determination of nitrofurantoin

A molecularly imprinted polymer (MIP) and a nanocomposite prepared from gold nanoparticles (AuNP) and poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) were deposited on a screen-printed carbon electrode (SPCE). The nanocomposite was prepared by one-pot simultaneous in-situ formation of AuNPs and PEDOT:PSS and was then inkjet-coated onto the SPCE. The MIP film was subsequently placed on the modified SPCE by co-electrodeposition of o-phenylenediamine and resorcinol in the presence of the antibiotic nitrofurantoin (NFT). Using differential pulse voltammetry (DPV), response at the potential of ~ 0.1 V (vs. Ag/AgCl) is linear in 1 nM to 1000 nM NFT concentration range, with a remarkably low detection limit (at S/N?=?3) of 0.1 nM. This is two orders of magnitude lower than that of the control MIP sensor without the nanocomposite interlayer, thus showing the beneficial effect of AuNP-PEDOT:PSS. The electrode is highly reproducible (relative standard deviation 3.1% for n?=?6) and selective over structurally related molecules. It can be re-used for at least ten times and was found to be stable for at least 45 days. It was successfully applied to the determination of NFT in (spiked) feed matrices and gave good recoveries.

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Graphical abstract Schematic representation of a voltammetric sensor for the determination of nitrofurantoin. The sensor is based on a screen-printed carbon electrode (SPCE) modified with an inkjet-printed gold nanoparticles-poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) nanocomposite and a molecularly imprinted polymer.

     

Click-functionalization of conducting poly(3,4-ethylenedioxythiophene) (PEDOT)

Efficient post-functionalization of conductive polymer films was achieved by Cu(+)-catalyzed "click"-cycloaddition of novel poly(azidomethyl-EDOT) and various functionalized terminal alkynes under mild heterogeneous conditions with high conversion efficiencies.     

Conducting poly(3,4-ethylenedioxythiophene)-montmorillonite exfoliated nanocomposites

Exfoliated nanocomposites formed by poly(3,4-ethylenedioxythiophene) and different concentrations of non-modified montmorillonite (bentonite), which range from 1% to 10% w/w, have been prepared by anodic electropolymerization in aqueous solution. Analyses of the electrochemical and electrical properties reveal that the electroactivity of the nanocomposites is higher than that of the individual homopolymer, while the electrical conductivity of the two systems is practically identical. On the other hand, the exfoliated distribution of the clay in the polymeric matrix and the morphology of the prepared materials have been characterized using transmission electron microscopy, X-ray diffraction and atomic force microscopy. The overall of the results represents a significant improvement with respect to other nanocomposites constituted by conducting polymers and clays, including those involving poly(3,4-ethylenedioxythiophene), and evidences the reliability of the preparation procedure employed in this work.     

ESR spectroelectrochemistry of poly(3,4-ethylenedioxythiophene) (PEDOT)

In situ ESR spectroelectrochemical studies of poly(3,4-ethylenedioxythiophene) (PEDOT) have been performed, in an attempt to take a closer look at species responsible for the conductivity of the polymer in the doped state. A series of ESR spectra at progressively changed potentials applied to the polymer film in the oxidation and subsequently, reduction half-cycles were recorded. The results reveal distinct ESR lines with a noteworthy concentration of spins in the reduced state of the polymer and marked changes in both the intensities and ΔB_pp widths of the ESR signal across the studied potential range, indicating non-trivial changes in the character of charge carriers with changing potential. Also, interesting phenomena like the potential hysteresis of the spin concentration and of ΔB_pp linewidths between the oxidation and reduction cycles of the polymer are observed. The presence of residual spins in the polymer in the reduced state may indicate that at least to some partial extent, PEDOT chains exist in the quinoid rather than benzoid configuration in the dedoped state. Hysteresis of spectroscopic parameters may imply that certain hindrance factors like slow anion expulsion speed accompany the dedoping process of the polymer.     

Synthesis and characterization of perfluorohexylated poly(3,4-ethylenedioxythiophene)

The perfluorohexylated 3,4-ethylenedioxythiophene 5 was prepared via Mitsunobu reaction of perfluorohexylatyed diol 2 with diethyl 3,4-dihydroxythiophenedicarboxylate followed by decarboxylation. The polymerization of 5 was conducted with both oxidative chemical and electrochemical polymerizations. The polymers were characterized by cyclic voltammogram, UV, IR, TGA and DSC.     

Novel flexible chemical gas sensor based on poly(3,4-ethylenedioxythiophene) nanotube membrane

Poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT NTs) flexible membrane was successfully fabricated by vapor deposition polymerization (VDP) mediated electrospinning for ammonia gas detection. PVA nanofibers (NFs) were electrospun as a core part and polyvinyl alcohol (PVA)/PEDOT coaxial nanocables (NCs) were prepared by VDP method via EDOT monomer adsorption onto the electrospun PVA NFs as templates. To obtain the PEDOT NTs membrane, the PVA NFs were removed from PVA/PEDOT coaxial NCs with distilled water. PVA/PEDOT coaxial NCs and PEDOT NTs had the conductivities of 71 and 61 S cm⁻¹ and were applied as a transducer for ammonia gas detection in the range of 1-100 parts per million (ppm) of NH₃ gas. They exhibited the minimum detectable level of ca. 5 parts per million (ppm) and fast response time (less than 1 s) towards ammonia gas. In a recovery time, the PEDOT NTs membrane sensor was ca. 30 s and shorter compared to that of the membrane sensor based on the PVA/PEDOT NCs (ca. 50 s). In addition, sensor performance of PEDOT NTs membrane was also undertaken as a function of membrane thickness. Thick membrane sensor (30 μm) had the enhanced sensitivity and the sensitivity on the membrane thickness was in the order of 30 μm > 20 μm > 10 μm at 60 ppm of NH₃ gas.     

Amperometric sensors based on poly(3,4-ethylenedioxythiophene)-modified electrodes: discrimination of white wines

The voltammetric responses on selected white wines of different vintages and origins have been systematically collected by three different modified electrodes, in order to check their effectiveness in performing blind analysis of similar matrices. The electrode modifiers consist of a conducting polymer, namely poly(3,4-ethylenedioxythiophene) (PEDOT) and of composite materials of Au and Pt nanoparticles embedded in a PEDOT layer. Wine samples have been tested, without any prior treatments, with differential pulse voltammetry technique. The subsequent chemometric analysis has been carried out both separately on the signals of each sensor, and on the signals of two or even three sensors as a unique set of data, in order to check the possible complementarity of the information brought by the different electrodes. After a preliminary inspection by principal component analysis, classification models have been built and validated by partial least squares-discriminant analysis. The discriminant capability has been evaluated in terms of sensitivity and specificity of classification; in all cases quite good results have been obtained.     

Memcapacitive properties of poly(3,4-ethylenedioxythiophene) modified electrodes

We study the capacitive properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin layer that shows memory effects. The capacitance vs. charge plot indicates the history-dependence of the electrochemical responses, for instance capacitance with memory or memcapacitance. The variation of the charge vs. potential exhibits a hysteresis loop that is related to the non-equilibrium properties of the redox switching. The calculation of the energy that can be added to and removed from the memcapacitance system during cycling shows a reactive behavior. This property is due to the electromechanical behaviors of PEDOT film that can store and transform electrochemical energy. Indeed, the charging–discharging processes during the redox switching induce a volume and conformational change of the polymer that in turn influences its electrochemical responses. In the context of bio-inspired information processing systems or bio-inspired circuits, a 3-terminal device exhibiting non-linearity and history-dependence responses is of interest for developing organic memory-circuit elements such as an electrochemical memcapacitance.     

Preparation of electrically conducting cellulose fibres utilizing polyelectrolyte multilayers of poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) and poly(allyl amine)

The primary goal with this work is to create electrically conductive cellulose fibres, this has been done to explore possible new applications for fibre based material. This research uses various methods to create polyelectrolyte multilayers (PEMs) on bleached softwood fibres and on SiO₂ model surfaces, by sequentially treating these materials with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS) and poly(allyl amine) (PAH). Paper sheets were then produced from the PEM-modified pulp and evaluated in terms of tensile strength, adsorbed amount of polymer, and electrical conductivity. To evaluate the influence of fibre charge on the measured paper properties, pulps of two different initial fibre charge densities were prepared via carboxymethylation. Because of the bluish colour of PEDOT:PSS, the build-up of PEM could be easily followed, since the fibres grew increasingly darker blue throughout the modification sequence. The conductivity of the fibre network increased by 2−3 orders of magnitude when the pulp of a higher fibre charge density was used. This suggests that it is more important to create a fibrous network with a high fibre-fibre joint strength and a large total joined area in the sheet rather than to maximize the adsorbed amount of PEDOT:PSS. A difference in conductivity could also be noted depending on the polyelectrolyte adsorbed in the outer layer, PAH lowered the conductivity compared to PEDOT:PSS. Evaluating the mechanical properties revealed that the use of PEDOT:PSS reduces the tensile strength of the paper. When five double layers had been adsorbed onto the carboxymethylated sample in which PEDOT:PSS formed the outer layer, calculations indicated a 25% decrease in tensile strength compared to that of reference material without PEMs. ESEM studies indicate that PEM treatment produces a significantly changed and somewhat smoother fibre surface.