Conducting polymer‐coated, palladium‐functionalized multi‐walled carbon nanotubes for the electrochemical sensing of hydroxylamine

Electrochemical sensors of hydroxylamine were fabricated on glassy carbon electrodes (GCEs) by the electropolymerization of 3,4‐ethylenedioxypyrrole (EDOP) and 3,4‐ethylenedioxythiophene (EDOT) on palladium (Pd) nanoparticles attached to thiolated multi‐walled carbon nanotubes (MWCNTs), denoted as PEDOP/MWCNT‐Pd/GCE and PEDOT/MWCNT‐Pd/GCE. The sensors were characterized by field emission scanning electron microscopy and electrochemical impedance spectroscopy. They showed strong catalytic activity toward the oxidation of hydroxylamine. Cyclic voltammetry and amperometry were used to characterize the sensors' performances. The detection limits of hydroxylamine by PEDOP/MWCNT‐Pd/GCE and PEDOT/MWCNT‐Pd/GCE were 0.22 and 0.24 μM (S/N = 3), respectively. The sensors' sensitivity, selectivity, and stability were also investigated.     

Charge re-distribution and ZT in PEDOT-related thermoelectrics

Recently it has been reported that poly(3,4-ethylenedioxythiphene (PEDOT))-related polymers can attain values of ZT comparable to their inorganic counterpart. In particular, it was shown that the thermal conductivity κ could be lowered to a value found in nano-structured semiconductors. In this work we studied the charge transport properties of PEDOT-related polymers and examined how the materials parameters were linked to κ and ZT based on data reported in the open literature. Using a two-region model and taking into account charge migration from the more conducting PEDOT islands to the resistive PSS sheaths in poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), we were able to demonstrate that ZT in the PSS sheaths could increase by orders of magnitude. Furthermore, ZT could approach a value of 20 or more when σ the bandwidth of the density of states of the transport sites was very small (<3 meV). Outward charge migration from the islands can in theory be enhanced by adding negatively-charged oxygen ions to the sheaths as observed in oxidized Poly(3,4-ethylenedioxythiophene-tosylate). This lowers the barrier height for holes and enhances ZT in the sheaths.     

导电聚3,4-乙撑二氧噻吩的制备及性能

以水为溶剂,分别选用对甲苯磺酸钠、高氯酸锂、硫酸钠为支持电解质,用电化学法合成聚3,4-乙撑二氧噻吩(PEDOT)膜。采用线性扫描伏安法(LSV)确定了合适的聚合电位;采用循环伏安法(CV)、电化学交流阻抗谱(EIS)研究了PEDOT膜的电化学行为。结果表明,掺杂阴离子种类对膜的循环伏安特性、EIS曲线等有很大的影响;此外研究了掺杂不同阴离子的PEDOT膜对电极的粘接性能,发现粘接性能也与阴离子种类有关。     

Experimental study of culture for mouse fibroblast used conductive polymer films

The purpose of this study is to develop electrodes for electrical stimulation of the nervous system using conductive polymers, polypyrrole (PPy) and/or poly(3,4-ethylenedioxythiophene), PEDOT. We evaluated biocompatibility in fibroblast and/or myoblast of mouse. Cultured cells on PPy and/or PEDOT extended their neuritis and survived over a week. These experiments have demonstrated that conductive polymers such as PPy, PEDOT, etc. have high biocompatibility, and PPy and/or PEDOT are applicable to nerve stimulation electrodes.     

Obvious enhancement in electrochemical capacitive properties for poly(3,4-ethylenedioxythiophene) electrodes prepared under optimized conditions

This work investigates the effect of preparation conditions on the supercapacitive performances of the poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes electrodeposited detailedly. These preparation conditions include electrode substrates, electrodeposition modes, parameters, and counter anions. Electrochemical characterizations indicate an evident impact of electrode substrates on the electrochemical behaviors of the PEDOT electrodes prepared. Graphite foils (GF) as the electrode substrate show better electrochemical capacitive properties relative to conductive glasses (CG). This can be ascribed to lower sheet resistance and better adhesion to the PEDOT films for the former. Moreover, SEM and AFM tests indicate that different electrodeposition modes, parameters, and counter anions would result in different morphologies and roughness for the PEDOT electrodes obtained, consequently affecting their supercapacitive performances. Among numerous preparation conditions, the polystyrene sulfonic acid salt-doped PEDOT deposited on GF substrates prepared with potentiostatic mode at 0.9 V shows the best supercapacitive behaviors, delivering the specific capacitance of 108.2 mF cm^?2 at 0.2 mA cm^?2, also exhibiting good rate capability and superior cycle performance (keeping 93.4% of initial capacitance after 10,000 cycles). This work indicates that the supercapacitive properties of PEDOT electrodes can be substantially enhanced by changing their preparation conditions.

     

Attenuated Glial Reactivity on Topographically Functionalized Poly(3,4‐Ethylenedioxythiophene):P‐Toluene Sulfonate (PEDOT:PTS) Neuroelectrodes Fabricated by Microimprint Lithography

Following implantation, neuroelectrode functionality is susceptible to deterioration via reactive host cell response and glial scar‐induced encapsulation. Within the neuroengineering community, there is a consensus that the induction of selective adhesion and regulated cellular interaction at the tissue–electrode interface can significantly enhance device interfacing and functionality in vivo. In particular, topographical modification holds promise for the development of functionalized neural interfaces to mediate initial cell adhesion and the subsequent evolution of gliosis, minimizing the onset of a proinflammatory glial phenotype, to provide long‐term stability. Herein, a low‐temperature microimprint‐lithography technique for the development of micro‐topographically functionalized neuroelectrode interfaces in electrodeposited poly(3,4‐ethylenedioxythiophene):p‐toluene sulfonate (PEDOT:PTS) is described and assessed in vitro. Platinum (Pt) microelectrodes are subjected to electrodeposition of a PEDOT:PTS microcoating, which is subsequently topographically functionalized with an ordered array of micropits, inducing a significant reduction in electrode electrical impedance and an increase in charge storage capacity. Furthermore, topographically functionalized electrodes reduce the adhesion of reactive astrocytes in vitro, evident from morphological changes in cell area, focal adhesion formation, and the synthesis of proinflammatory cytokines and chemokine factors. This study contributes to the understanding of gliosis in complex primary mixed cell cultures, and describes the role of micro‐topographically modified neural interfaces in the development of stable microelectrode interfaces.     

Enhanced thermoelectric metrics in ultra-long electrodeposited PEDOT nanowires

The Seebeck coefficient, S, and the electrical conductivity, σ, of electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires and thin films are reported. PEDOT nanowires were prepared by electropolymerizing 3,4-ethylenedioxythiophene (EDOT) in aqueous LiClO(4) within a template prepared using the lithographically patterned nanowire electrodeposition (LPNE) process. These nanowires were 40-90 nm in thickness, 150-580 nm in width, and 200 μm in length. σ and S were measured from 190 K to 310 K by fabricating heaters and thermocouples on top of arrays of 750 PEDOT nanowires. Such PEDOT nanowire arrays consistently produced S values that were higher than those for PEDOT films: up to -122 μV/K (310 K) for nanowires and up to -57 μV/K (310 K) for films. The sample-to-sample variation in S for 14 samples of PEDOT nanowires and films, across a wide range of critical dimensions, is fully explained by variations in the carrier concentrations in accordance with the Mott equation. In spite of their higher |S| values, PEDOT nanowires also had higher σ than films, on average, because electron mobilities were greater in nanowires by a factor of 3.     

Electrical conduction through self-assembled monolayers in molecular junctions: Au/molecules/Au versus Au/molecule/PEDOT:PSS/Au

We fabricated and characterized a large number of octanedithiol (denoted as DC8) molecular devices as vertical metal–molecule–metal structure with or without using an intermediate conducting polymer layer of poly (3,4-ethylenedioxythiophene) stabilized with poly(4-styenesulfonic acid) (called as PEDOT:PSS). The electronic transport properties of DC8 molecular devices with and without PEDOT:PSS layer were statistically compared in terms of current density and device yield. The yields of the working molecular devices were found to be ~ 1.75% (84 out of 4800 devices) for Au/DC8/Au junctions and ~ 58% (74 out of 128 devices) for Au–DC8/PEDOT:PSS/Au junctions. The tunneling decay constants were obtained with the Simmons tunneling model and a multibarrier tunneling model for two kinds of molecular devices with and without PEDOT:PSS layer.     

Interfacial scattering at electrochemically fabricated atom-scale junctions between thin gold film electrodes in a microfluidic channel

Atom-scale junctions were formed between two Au thin-film electrodes by a combination of lithography, microfluidics, and electrochemistry. Two Au thin-film electrodes with a small (0.25-25 microm) gap between them were lithographically defined such that the gap fell in the center of a 100-microm-wide microfluidic channel in poly(dimethylsiloxane). Directional electrodeposition between the Au thin-film electrodes, accomplished by applying a potential between the thin-film electrodes, caused Au to etch from the anode and deposit on the cathode, thereby closing the gap. Current through the gap was monitored continuously, and the directional electrodeposition was terminated when a current near that corresponding to the conductance quantum, G(0) = 2e(2)/h, was reached. To regenerate the device, the atom-scale junction was broken with a potential sweep, the microfluidic channel was rinsed, and the junction was re-formed with a subsequent comparator-terminated directional electrodeposition. Alternating current impedance was measured while hexadecanethiol (HDT) was chemisorbed onto the atom-scale junction. The interfacial scattering from chemisorption of the Lewis base HDT on the atom-scale junction caused a normalized impedance change of 71 +/- 1%, the noise level being equivalent to a population fluctuation of five HDT molecules.     

An All‐Plastic Field‐Effect Nanofluidic Diode Gated by a Conducting Polymer Layer

The design of an all‐plastic field‐effect nanofluidic diode is proposed, which allows precise nanofluidic operations to be performed. The fabrication process involves the chemical synthesis of a conductive poly(3,4‐ethylenedioxythiophene) (PEDOT) layer over a previously fabricated solid‐state nanopore. The conducting layer acts as gate electrode by changing its electrochemical state upon the application of different voltages, ultimately changing the surface charge of the nanopore. A PEDOT‐based nanopore is able to discriminate the ionic species passing through it in a quantitative and qualitative manner, as PEDOT nanopores display three well‐defined voltage‐controlled transport regimes: cation‐rectifying, non‐rectifying, and anion rectifying regimes. This work illustrates the potential and versatility of PEDOT as a key enabler to achieve electrochemically addressable solid‐state nanopores. The synergism arising from the combination of highly functional conducting polymers and the remarkable physical characteristics of asymmetric nanopores is believed to offer a promising framework to explore new design concepts in nanofluidic devices.     

Poly(3,4-ethylenedioxythiophene) nanotubes as electrode materials for a high-powered supercapacitor

We report the fast charging/discharging capability of poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes during the redox process and their potential application to a high-powered supercapacitor. PEDOT nanotubes were electrochemically synthesized in a porous alumina membrane, and their structures were characterized using electron microscopes. Cyclic voltammetry was used to characterize the specific capacitance of the PEDOT nanotubes at various scan rates. A type I supercapacitor (two symmetric electrodes) based on PEDOT nanotube electrodes was fabricated, and its energy density and power density were evaluated by galvanostatic charge/discharge cycles at various current densities. We show that the PEDOT-nanotube-based supercapacitor can achieve a high power density of 25?kW?kg(-1) while maintaining 80% energy density (5.6?W?h?kg(-1)). This high power capability is attributed to the fast charge/discharge of nanotubular structures: hollow nanotubes allow counter-ions to readily penetrate into the polymer and access their internal surfaces, while the thin wall provides a short diffusion distance to facilitate the ion transport. Impedance spectroscopy shows that nanotubes have much lower diffusional resistance to charging ions than solid nanowires shielded by an alumina template, providing supporting information for the high charging/discharging efficiency of nanotubular structures.     

Synergistic catalytic effect of a composite (CoS/PEDOT:PSS) counter electrode on triiodide reduction in dye-sensitized solar cells

Inorganic/organic nanocomposite counter electrodes comprised of sheetlike CoS nanoparticles dispersed in polystyrenesulfonate-doped poly(3,4-ethylenedioxythiophene (CoS/PEDOT:PSS) offer a synergistic effect on catalytic performance toward the reduction of triiodide for dye-sensitized solar cells (DSSCs), yielding 5.4% power conversion efficiency, which is comparable to that of the conventional platinum counter electrode (6.1%). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry measurements revealed that the composite counter electrodes exhibited better catalytic activity, fostering rate of triiodide reduction, than that of pristine PEDOT: PSS electrode. The simple preparation of composite (CoS/PEDOT:PSS) electrode at low temperature with improved electrocatalytic properties are feasible to apply in flexible substrates, which is at most urgency for developing novel counter electrodes for lightweight flexible solar cells.     

Potential Stability of All-Solid-State Ion-Selective Electrodes Using Conducting Polymers as Ion-to-Electron Transducers

Demanding analytical applications such as on-line process analysis and clinical analysis require robust, reliable, and maintenance-free ion sensors of high potential stability. In this work the stability of the electrode potential of all-solid-state ion-selective electrodes using conducting polymers as ion-to-electron transducers is critically evaluated by using chronopotentiometry and electrochemical impedance spectroscopy. This study is focused on the relationship between the potential stability of the electrode and the capacitance of the solid contact where ion-to-electron transduction takes place. The influence of this capacitance on the potential stability of all-solid-state ion-selective electrodes is studied experimentally by using conducting polymer layers of different thickness as solid contacts in potassium ion-selective electrodes based on a solvent polymeric membrane. Because of its excellent environmental stability, the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is used as a model compound for the solid contact material. Chronopotentiometry is found to be a convenient and fast experimental method to critically evaluate the potential stability of different types of ion-selective electrodes.     

PEDOT-PSSA as an alternative support for Pt electrodes in PEFCs

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (styrene sulphonic acid) (PSSA) supported platinum (Pt) electrodes for application in polymer electrolyte fuel cells (PEFCs) are reported. PEDOT-PSSA support helps Pt particles to be uniformly distributed on to the electrodes, and facilitates mixed electronic and ionic (H⁺-ion) conduction within the catalyst, ameliorating Pt utilization. The inherent proton conductivity of PEDOT-PSSA composite also helps reducing Nafion content in PEFC electrodes. During prolonged operation of PEFCs, Pt electrodes supported onto PEDOT-PSSA composite exhibit lower corrosion in relation to Pt electrodes supported onto commercially available Vulcan XC-72R carbon. Physical properties of PEDOT- PSSA composite have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. PEFCs with PEDOT-PSSA-supported Pt catalyst electrodes offer a peak power-density of 810 mW cm⁻² at a load current-density of 1800 mA cm⁻² with Nafion content as low as 5 wt.% in the catalyst layer. Accordingly, the present study provides a novel alternative support for platinized PEFC electrodes.     

Universal scaling of the charge transport in large-area molecular junctions

Charge transport through alkanes and para-phenylene oligomers is investigated in large-area molecular junctions. The molecules are self-assembled in a monolayer and contacted with a top electrode consisting of poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonic acid) (PEDOT:PSS). The complete set of J(V,T) characteristics of both saturated and π-conjugated molecules can be described quantitatively by a single equation with only two fit parameters. The derived parameters, in combination with a variation of the bulk conductivity of PEDOT:PSS, demonstrate that the absolute junction resistance is factorized with that of PEDOT:PSS.     

Water-processable polymer-nanocrystal hybrids for thermoelectrics

We report the synthesis and thermoelectric characterization of composite nanocrystals composed of a tellurium core functionalized with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Solution processed nanocrystal films electronically out perform both PEDOT:PSS and unfunctionalized Te nanorods while retaining a polymeric thermal conductivity, resulting in a room temperature ZT ～ 0.1. This combination of electronic and thermal transport indicates the potential for tailored transport in nanoscale organic/inorganic heterostructures.     

An Efficiently Doped PEDOT:PSS Ink Formulation via Metastable Liquid−Liquid Contact for Capillary Flow-Driven,Hierarchically and Highly Conductive Films

With commercial electronics transitioning toward flexible devices, there is a growing demand for high-performance polymers such as poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS). Previous breakthroughs in promoting the conductivity of PEDOT:PSS, which mainly stem from solvent-treatment and transfer-printing strategies, remain as inevitable challenges due to the inefficient, unstable, and biologically incompatible process. Herein, a scalable fabrication of conducting PEDOT:PSS inks is reported via a metastable liquid−liquid contact (MLLC) method, realizing phase separation and removal of excess PSS simultaneously. MLLC-doped inks are further used to prepare ring-like films through a compromise between the coffee-ring effect and the Marangoni vortex during evaporation of droplets. The specific control over deposition conditions allows for tunable ring-like morphologies and preferentially interconnected networks of PEDOT:PSS nanofibrils, resulting in a high electrical conductivity of 6,616 S cm⁻¹ and excellent optical transparency of the film. The combination of excellent electrical properties and the special morphology enables it to serve as electrodes for touch sensors with gradient pressure sensitivity. These findings not only provide new insight into developing a simple and efficient doping method for commercial PEDOT:PSS ink, but also offer a promising self-assembled deposition pattern of organic semiconductor films, expanding the applications in flexible electronics, bioelectronics as well as photovoltaic devices.     

Sustainable Solid‐State Supercapacitors Made of 3D‐Poly(3,4‐ethylenedioxythiophene) and κ‐Carrageenan Biohydrogel

3D‐Poly(3,4‐ethylenedioxythiophene) (PEDOT) electrodes are prepared using the multi‐step template‐assisted approach. Specifically, poly(lactic acid) nano‐ and microfibers collected on a previously polymerized PEDOT film are used as templates for PEDOT nano‐ and microtubes, respectively. Morphological analysis of the samples indicates that 3D‐PEDOT electrodes obtained using a low density of templates, in which nano‐ and microtubes are clearly identified, exhibit higher porosity, and specific surface than conventional 2D‐PEDOT electrodes. However, a pronounced leveling effect is observed when the density of templates is high. Thus, electrodes with microtubes still present a 3D‐morphology but much less marked than those prepared using a low density of PLA microfibers, whereas the morphology of those with nanotubes is practically identical to that of films. Electrochemical studies prove that solid supercapacitors prepared using 3D‐PEDOT electrodes and κ‐carrageenan biohydrogel as electrolytic medium, exhibit higher ability to exchange charge reversibly and to storage charge than the analogues prepared with 2D‐electrodes. Furthermore, solid devices prepared using 3D‐electrodes and κ‐carrageenan biohydrogel exhibit very similar specific capacitances that those obtained using the same electrodes and a liquid electrolyte (i.e., acetonitrile solution with 0.1 M LiClO₄). These results prove that the success of 3D‐PEDOT electrodes is independent of the electrolytic medium.

     

Conducting‐Polymer Nanotubes Improve Electrical Properties,Mechanical Adhesion,Neural Attachment,and Neurite Outgrowth of Neural Electrodes

An in vitro comparison of conducting‐polymer nanotubes of poly(3,4‐ethylenedioxythiophene) (PEDOT) and poly(pyrrole) (PPy) and to their film counterparts is reported. Impedance, charge‐capacity density (CCD), tendency towards delamination, and neurite outgrowth are compared. For the same deposition charge density, PPy films and nanotubes grow relatively faster vertically, while PEDOT films and nanotubes grow more laterally. For the same deposition charge density (1.44 C cm^?2), PPy nanotubes and PEDOT nanotubes have lower impedance (19.5 ± 2.1 kΩ for PPy nanotubes and 2.5 ± 1.4 kΩ for PEDOT nanotubes at 1 kHz) and higher CCD (184 ± 5.3 mC cm^?2 for PPy nanotubes and 392 ± 6.2 mC cm^?2 for PEDOT nanotubes) compared to their film counterparts. However, PEDOT nanotubes decrease the impedance of neural‐electrode sites by about two orders of magnitude (bare iridium 468.8 ± 13.3 kΩ at 1 kHz) and increase capacity of charge density by about three orders of magnitude (bare iridium 0.1 ± 0.5 mC cm^?2). During cyclic voltammetry measurements, both PPy and PEDOT nanotubes remain adherent on the surface of the silicon dioxide while PPy and PEDOT films delaminate. In experiments of primary neurons with conducting‐polymer nanotubes, cultured dorsal root ganglion explants remain more intact and exhibit longer neurites (1400 ± 95 µm for PPy nanotubes and 2100 ± 150 µm for PEDOT nanotubes) than their film counterparts. These findings suggest that conducting‐polymer nanotubes may improve the long‐term function of neural microelectrodes.     

Composite supercapacitor electrodes made of activated carbon/PEDOT:PSS and activated carbon/doped PEDOT

In this paper, we report on the high electrical storage capacity of composite electrodes made from nanoscale activated carbon combined with either poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) or PEDOT doped with multiple dopants such as ammonium persulfate (APS) and dimethyl sulfoxide (DMSO). The composites were fabricated by electropolymerization of the conducting polymers (PEDOT:PSS, doped PEDOT) onto the nanoscale activated carbon backbone, wherein the nanoscale activated carbon was produced by ball-milling followed by chemical and thermal treatments. Activated carbon/PEDOT:PSS yielded capacitance values of 640 F g^?1 and 26 mF cm^?2, while activated carbon/doped PEDOT yielded capacitances of 1183 F g^?1 and 42 mF cm^?2 at 10 mV s^?1. This is more than five times the storage capacity previously reported for activated carbon–PEDOT composites. Further, use of multiple dopants in PEDOT improved the storage performance of the composite electrode well over that of PEDOT:PSS. The composite electrodes were characterized for their electrochemical behaviour, structural and morphological details and electronic conductivity and showed promise as high-performance energy storage systems.