Multicolor and fast electrochromism of nanoporous NiO/poly(3,4-ethylenedioxythiophene) composite thin film

We report a nanoporous NiO/poly(3,4-ethylenedioxythiophene) (PEDOT) composite film using a highly porous NiO film as a template by the combination of chemical bath deposition and electro-polymerization methods. The as-prepared NiO/PEDOT composite film has an interconnecting reticular morphology with nanometer sized pores ranging from 20–150 nm. The NiO/PEDOT composite film exhibits multicolor electrochromism with reversible color changes from purple to light blue brown and presents a transmittance variation of 31% at 600 nm. Fast switching speed is achieved in this composite film, and the response time for oxidation and reduction is 500 and 600 ms, respectively.     

Micro-patterning of vapor-phase polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) using ink-jet printing/soft lithography

Highly conductive and transparent poly(3,4-ethylenedioxythiophene) (PEDOT) thin films can be prepared effectively via vapor-phase polymerization (VPP) with the addition of imidazole (Im) based derivatives. The addition of Im that has one and/or two alkyl substituents significantly improved the electrical conductivity of PEDOT thin films. In an effort to develop a facile PEDOT micro-patterning method, we investigated ink-jet printing and soft lithography. The procedure of oxidant patterning with a weak base followed by VPP of a 3,4-ethylenedioxythiophene (EDOT) monomer provides an effective and simple method for micro-patterning of an intrinsic conductive polymer (ICP).     

Electrosynthesis of a multilayer film stacked alternately by poly(3,4-ethylenedioxythiophene) and reduced graphene oxide from aqueous solution

Multilayer films stacked alternately by poly(3,4-ethylenedioxythiophene) and reduced graphene oxide were synthesized electrochemically from a single aqueous solution containing 3,4-ethylenedioxythiophene (EDOT) and graphene oxide (GO) by repeatedly oxidizing EDOT and reducing GO on a conductive substrate. Using the proposed technique, the thickness of the different layers could be easily tuned by varying the electrolysis time, and the number of layers could be increased simply by repeating the sequence of potential steps.     

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.     

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.     

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.     

Electrosynthesis and characterization of poly(hydroxy-methylated-3,4-ethylenedioxythiophene) film in aqueous micellar solution and its biosensing application

A new and efficient synthetic route to hydroxymethylated-3,4-ethylenedioxylthiophene（EDOT-MeOH） was developed by a simple four-step sequence,and its global yield was approximately 41.06%.The poly（hydroxymethylated-3, 4-ethylenedioxylthiophene）（PEDOT-MeOH） film was electrosynthesized in aqueous sodium dodecylsulfate micellar solutions and characterized by different methods.The EDOT-MeOH possessed better water solubility,and lower onset oxidation potential than EDOT.The as-obtained PEDOT-MeOH film displayed good reversible redox activity,stability and capacitance properties in a monomer-free electrolyte,especially the good solubility of PEDOT-MeOH film in strong polar organic solvents such as dimethyl sulfoxide and tetrahydrofuran created a potential application in many different fields. Fluorescent spectra indicated that PEDOT-MeOH was a yellow-green-light-emitter with maximum emission at 568 nm.The as-formed PEDOT-MeOH film had good biocompatibility and was used for fabricating the electrochemical vitamin C biosensor.The proposed biosensor showed a linear range of 3×10^-6 mol/L to 1.2×10^-2 mol/L with the detection limit of 1μmol/L,a sensitivity of 95.6μA（mmol/L）^-1 cm^-2,and a current response time less than 10 s and a fairly good stability (The relative standard deviation was 0.43%for 20 successive assays,the proposed biosensor still retained 93.5%of bioactivity after 15 days storage.This result indicated that the prepared PEDOT-MeOH film as immobilization matrix of biologically-active species could be a promising candidate for the design and application of biosensor.     

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.     

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.     

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.     

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.     

Thermal ageing of poly(ethylene oxide)/poly(3,4-ethylenedioxythiophene) semi-IPNs

The thermal stability study of a conducting semi-IPN has been reported. The thermo-oxidation of poly(ethylene oxide) (PEO)/poly(3,4-ethylenedioxythiophene) (PEDOT) semi-Interpenetrating Polymer Network (semi-IPN) was studied at 80 °C in open air. The degradation was followed by spectrophotometry in the visible and near infrared range, cyclic voltamperometry and thermogravimetric analysis. Fluorescence spectrophotometry allowed for the identification of OH by-product originated in the PEO network degradation by the use of a chemiluminescent probe, typically terephthalic acid. The formation of hydroxyl radicals damaged the PEDOT chains as checked by infrared spectroscopy. The mechanism of degradation is further confirmed (i) by introducing a radical scavenger or (ii) by performing a thermal ageing under inert atmosphere; in both cases the semi-IPN life-time is tremendously increased.     

Layer-by-layer assembly of UV-resistant poly(3,4-ethylenedioxythiophene) thin films

The layer-by-layer assembly technique was used to create electrically conductive films with poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT-PSS) and branched polyethylenimine (BPEI). Titanium dioxide (TiO(2)) and carbon black were used to prevent UV-degradation of these PEDOT-PSS thin film assemblies. Film growth and conductivity were studied, while varying composition and examining the effect of UV absorbing particles on the electrical conductivity. All films showed similar initial sheet resistances, but after exposure to 365 nm UV light for 9 days (correlating to approximately 4 years of sunlight), the films containing TiO(2) were up to 250 times more conductive. Additionally, the TiO(2) containing films were 27% more optically transparent than films made with PEDOT in the absence of TiO(2). The addition of colloidal titania allows the useful life of the PEDOT films to be extended without the detrimental effects of decreased transparency. Doping the PEDOT with dimethylsulfoxide produced eight bilayer films that were almost 6 times more conductive. However, the degradation rate for the doped PEDOT films without TiO(2) was 10 times greater than the doped films with TiO(2).     

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.     

Highly sensitive poly(3,4-ethylenedioxythiophene) modified electrodes by electropolymerisation in deep eutectic solvents

Deep eutectic solvents are evaluated as media for the electropolymerisation of 3,4-ethylenedioxythiophene (EDOT) for the first time. PEDOT modified glassy carbon electrodes (GCEs) were characterised by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. PEDOT modified GCEs prepared from choline chloride–urea (reline) and choline chloride–ethylene glycol (ethaline) exhibited interesting electrocatalytic and morphological characteristics. Fixed potential sensing of ascorbate at 0.0 V showed a greater electrocatalytic effect, significantly higher sensitivity and lower detection limit than at hitherto reported PEDOT modified electrodes.     

Electrochemical behaviour of poly(3,4-ethylenedioxythiophene) in a room-temperature ionic liquid

The cyclic voltammetry responses and the redox switching dynamics of poly(3,4-ethylenedioxythiophene) (PEDOT) in a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (EMImTf₂N), were investigated. The shape of the cyclic voltammograms showed two anodic and two cathodic peaks. These peak currents varied linearly with the scan rate indicating a thin-layer behaviour. No memory effects were observed during the cyclic voltammetry experiments in this ionic liquid. On the other hand, the redox switching dynamics of PEDOT were studied by means of potential step experiments. The analysis of chronocoulograms in term of RC-circuits indicated that the time dependence of the charge transferred during the potential step showed two time constants. These results were consistent with the postulated structure or morphology of the PEDOT film which contained two types of coexisting zones: a compact and an open structures.     

Time-scale- and temperature-dependent mechanical properties of viscoelastic poly(3,4-ethylenedioxythiophene) films

The viscoelastic properties of thin films of poly(3,4-ethylenedioxythiophene) (PEDOT) have been studied using the method of acoustic impedance. The films were deposited on the Au electrodes of 10 MHz AT-cut quartz thickness shear mode resonators and exposed to acetonitrile solutions of 0.1 M TEABF4 and LiClO4. For p-doped films, admittance spectra as a function of potential (E), temperature (T), and time scale (frequency, via harmonics, in the range 10-110 MHz) were acquired. Shear modulus components extracted from these responses surprisingly showed virtually no variation with E (and thus film solvation) or with T, but the variation with frequency was dramatic. This qualitative behavior and the numerical values of the shear moduli contrast strongly with recently reported data for the related poly(3-hexylthiophene) system, which shares the same conducting spine but differs substantially in the substitution pattern. Accordingly, the models and interpretation for PEDOT are quite different: film dynamics are determined by free-volume effects, and side-chain motion is not a significant factor. Qualitatively similar potential and time-scale effects were seen for n-doped PEDOT, but the scope of the measurements was limited by film stability.     

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.     

Synthesis of calibrated poly(3,4-ethylenedioxythiophene) latexes in aqueous dispersant media

The synthesis of spherical poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles with a narrow size distribution was achieved in a dispersant aqueous medium. Various oxidants such as ammonium persulfate, iron(III) p-toluenesulfonate, and iron(III) trichloride were tested. A series of end-functionalized poly(ethylene oxide) (PEO) such as alpha-(3,4-ethylenedioxythiophene) PEO, alpha-( N-methyl pyrrole) PEO, alpha-(fluorene) PEO, alpha,omega-( N-methyl pyrrole) PEO, alpha,omega-(thiophene) PEO, and alpha,omega-(fluorene) PEO were compared as reactive stabilizers. The molar mass and the functionality of these reactive PEOs were found to be important parameters with respect to the control of particle size and size distribution. PEDOT samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), size exclusion chromatography (SEC), and conductivity measurements.     

Poly(pyrrole) versus poly(3,4-ethylenedioxythiophene): amperometric cholesterol biosensor matrices

Two conducting polymers, poly(pyrrole) (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) were used as immobilization matrices for cholesterol oxidase (ChOx). The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H₂O₂ at +0.7 V in the absence of a mediator. Kinetic parameters, such as K _m and I _max, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. K _m values are found as 7.9 and 1.3 mM for PPy and PEDOT enzyme electrodes, respectively; it can be interpreted that ChOx immobilized in PEDOT shows higher affinity towards the substrate.