Conducting Polymer Layer Research Articles

Fiber-in-tube solid-phase microextraction of caffeine as a molecular tracer in wastewater by electrochemically deposited layered double hydroxide.

Modified stainless-steel wires with a layer of polyaniline conductive polymer were coated by electrochemical deposition with Zn/Al layered double hydroxide to make solid-phase microextraction fibers. The coating layer was also electrochemically deposited on the inner surface of a stainless-steel tube. Then, ten prepared fibers were put inside the inner coated tube to make a fiber-in-tube solid phase microextraction device. The device was applied for the extraction of caffeine (1,3,7-trimethylxanthine) from domestic wastewater samples. Extraction conditions including extraction and desorption times, pH and ionic strength of the sample solution, and content of the organic desorption solvent were investigated and optimized. Under the optimized conditions, the fiber-in-tube solid phase microextraction exhibited excellent extraction efficiency toward caffeine. The precision of the method was evaluated. Average relative standard deviation of 5.7% (n=6) for intraday analysis and 8.3% (n=5) for interday analysis was obtained. The limits of detection and limits of quantification of the method (at signal to noise ratio of 3 and 10) were obtained as 0.14 and 0.37ng/mL, respectively. The current study can provide new prospective applications of layered double hydroxide conductive polymer fiber coatings.

Combination of copolymer film (PPy-PPyCOOH) and magnetic nanoparticles as an electroactive and biocompatible platform for electrochemical purposes

The process of obtaining the composite layer consisting of conductive copolymer, composed of unmodified pyrrole and pyrrole-3-carboxylic acid units (in various molar ratio) in combination with magnetic nanoparticles was investigated using voltammetry, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy and surface enhanced Raman scattering (SERS) spectroscopy. The SERS and voltammetric data demonstrate that the use of molar concentration ratio of monomers 75 (Py) to 25 mM (Py-COOH) results in the conductive polymer layer with the best bioelectrochemical properties. The ferritin attached covalently to such composite demonstrated the highest electroactivity. Thus, mixed conductive copolymer film containing Py and Py-COOH units, combined with magnetic nanoparticles could be further useful in developing bioactive conductive platforms for specific biomedical purposes.

Correlating the Seebeck coefficient of thermoelectric polymer thin films to their charge transport mechanism

Room temperature flexible heat harvesters based on conducting polymers are ideally suited to cover the energy demands of the modern nomadic society. The optimization of their thermoelectric efficiency is usually sought by tuning the oxidation levels of the conducting polymers, even if such methodology is detrimental to the Seebeck coefficient (S) as both the Seebeck coefficient and the electrical conductivity (σ) are antagonistically related to the carrier concentration. Here we report a concurrent increase of S and σ and we experimentally derive the dependence of Seebeck coefficient on charge carrier mobility for the first time in organic electronics. Through specific control of the conducting polymer synthesis, we enabled the formation of a denser percolation network that facilitated the charge transport and the thermodiffusion of the charge carriers inside the conducting polymer layer, while the material shifted from a Fermi glass towards a semi-metal, as its crystallinity increased. This work sheds light upon the origin of the thermoelectric properties of conducting polymers, but also underlines the importance of enhanced charge carrier mobility for the design of efficient thermoelectric polymers.

Fabrication of a Highly Sensitive Stretchable Strain Sensor Utilizing a Microfibrous Membrane and a Cracking Structure on Conducting Polymer

AbstractRecently, the detection of human motion has attracted considerable attention for the development of smart healthcare systems. Flexible or stretchable strain sensors are required to measure deformations on arbitrarily shaped human skin areas caused by human motion, and numerous studies have explored the development of such sensors. Here, a highly sensitive stretchable strain sensor is introduced, which consists of elastic fibrous membrane coated with conducting polymer. The membrane can be utilized to detect applied strain by measuring the conductance change caused by the change in the nanocracking structure on the coated conducting polymer layer. Furthermore, by collecting aligned microfibers as the fibrous membrane during electrospinning process, the sensor exhibits higher sensitivity (more than 40‐fold higher than the nonaligned version). Although limitations still remain in the repeatability and the applicability of the sensor, the developed sensor will demonstrate great potential for measuring applied strain and stress over a wide sensing range with high sensitivity is expected.

Biodegradable and electroconductive poly(3,4-ethylenedioxythiophene)/carboxymethyl chitosan hydrogels for neural tissue engineering

Electroconductive hydrogels with excellent electromechanical properties have become crucial for biomedical applications. In this study, we developed a conductive composite hydrogel via in-situ chemical polymerization based on carboxymethyl chitosan (CMCS), as a biodegradable base macromolecular network, and poly(3,4-ethylenedioxythiophene) (PEDOT), as a conductive polymer layer. The physicochemical and electrochemical properties of conductive hydrogels (PEDOT/CMCS) with different contents of PEDOT polymer were analyzed. Cell viability and proliferation of neuron-like rat phaeochromocytoma (PC12) cells on these three-dimensional conductive hydrogels were evaluated in vitro. As results, the prepared semi-interpenetrating network hydrogels were shown to consist of up to 1825±135wt% of water with a compressive modulus of 9.59±0.49kPa, a porosity of 93.95±1.03% and an electrical conductivity of (4.68±0.28)×10−3S·cm−1. Cell experiments confirmed that PEDOT/CMCS hydrogels not only had no cytotoxicity, but also supported cell adhesion, viability and proliferation. These results demonstrated that the incorporation of conductive PEDOT component into CMCS hydrogels endowed the hydrogels with enhanced mechanical strength, conductivity and kept the biocompatibility. Thus, the attractive performances of these composite hydrogels would make them suitable for further neural tissue engineering application, such as nerve regeneration scaffold materials.

Development of two-dimensional interdigitated center of pressure sensor

This paper presents the development of a two-dimensional (2D) flexible patch sensor to detect and monitor the center of pressure (CoP) location and the total magnitude of a spatially distributed pressure to the specific surface areas of engineering structures. The CoP sensor with the contact mode induced by a pressure distribution was formulated by force sensitive resistor technology and was mainly composed of a thin conductive polymer layer, adhesive spacers, and two interdigitated patterned electrode films with unique sensing aperture shadings. By properly mapping the interdigitated electrode patterns to the top and bottom surfaces of the conductive polymer, the proposed sensor ideally enables to measure an overall applied pressure level and its centroid location within a predetermined sensing region in real-time. The CoP sensor containing 36 sensing sections within a dimension of around 3 × 3 inches was prototyped and experimentally investigated to verify its capability to identify the CoP location and magnitude due to the presence of a permanent magnet-based local pressure distribution. Only five electric wires connected to the CoP sensor to inspect the pressure-sensing positions of 36 segments. The evaluation results of the measured sensor data demonstrate good agreements with the actual test parameters such as the total pressure and its centroid position with about 5% locational error. However, to provide accurate information on the overall pressure range, the compensation factors must be determined and applied to the individual sensing sections of the sensor.

Development of mono-component and tri-component fibres 100% polymer based piezoelectric PVDF to harvest energy

A first study focused on the realization of a 100% Polyvinylidene fluoride woven fabric. The multi-filaments produced by melt spinning and studied by FTIR, X-Ray and DSC, were optimized in the β-phase, 97%, thanks drawing ratio of λ=5, and the processing temperature, 90°C. When the polar β-phase achieves a certain level in PVDF, the woven material is poling with fields up to about 6kV. DMA tests coupled to a Keithley voltmeter allow the solicitation of PVDF fabrics. A variation of voltage is obtained in compression, with a maximum output voltage of up to 2,3V. The other part of the study explains premises of a tricomponent fibre development, PEHD/PVDF/PA12. Two layers of conductive polymers acting as electrodes are placed on either side of the PVDF layer. The interfacial adhesion between the three different layers is analysed by SEM. The maximum stretch on melt spinning was fixed at 2.5 and the β-phase of the PVDF measured by X-Ray.

Poly(3, 4-ethyleendioxythiophene) coated titanium dioxide nanoparticles in situ synthesis and their application for rechargeable lithium sulfur batteries

Poly (3, 4-ethyleendioxythiophene) (PEDOT) coated titanium dioxide (TiO2) nanoparticles were prepared through a soft chemistry approach-assisted in situ synthesis route. The as synthesized PEDOT/TiO2 nanocomposites (NCs) are characterized by XRD, Raman, BET, XPS, SEM, TEM and EDX analysis/elemental mapping. The formation mechanism of PEDOT/TiO2 NCs is also illustrated. The uniformly TiO2 nanoparticles dispersed in PEDOT matrix improving the electrochemical performance of the ternary PEDOT/TiO2/sulfur composite, which exhibits higher reversible capacity and better rate capability compared with the PEDOT/S and TiO2/S composites. The reversible capacity of PEDOT/TiO2 NCs can be up to 1110mAhg−1 and was retained 532.1mAhg−1 after 500 charge-discharge cycles at the rate of 1C, which confirms the good cycling behavior. The superior electrochemical performance of the PEDOT/TiO2 NCs could be attributed to the uniform conducting polymer layer and improving the electrical conductivity of TiO2, the lower charge-transfer resistance and larger lithium ion diffusion coefficient.

Integrated FeOOH nanospindles with conductive polymer layer for high-performance supercapacitors

The development of efficient electrode materials with high energy density and high power density is crucial to the assembly of high-performance storage device. One-dimensional (1D) coaxial nanostructured materials with large surface area and superior ion transport have shown great potential for enhancement of electrochemical performance. In this paper, we design a class of 1D PPy-sheathed FeOOH nanospindles (FeOOH@PPy) as integrated electrode for supercapacitors (SCs). The 1D coaxial nanostructures and elaborate integrated conductive layer endow them with excellent electrochemical performance. For example, the as-obtained FeOOH@PPy electrode exhibits a specific capacitance of 1140 F g−1 at a current density of 1 A g−1, which is two folds larger than that of the bare FeOOH. Furthermore, the as-assembled FeOOH@PPy//AC asymmetric supercapacitor (ASC) reveals a high specific energy density of 39.1 Wh kg−1 with a power density of 800.0 W kg−1. After 5000 cycling tests, the device retains 78.7% of the initial specific capacitance, showing its good stability. The present work represents an important step toward rational fabrication of iron-based supercapacitor electrodes with new horizons for fundamental and technological applications.

Electroenhanced Antimicrobial Coating Based on Conjugated Polymers with Covalently Coupled Silver Nanoparticles Prevents Staphylococcus aureus Biofilm Formation.

The incidence of hospital-acquired infections is to a large extent due to device-associated infections. Bacterial attachment and biofilm formation on surfaces of medical devices often act as seeding points of infection. To prevent such infections, coatings based on silver nanoparticles (AgNPs) are often applied, however with varying clinical success. Here, the traditional AgNP-based antibacterial technology is reimagined, now forming the base for an electroenhanced antimicrobial coating. To integrate AgNPs in an electrically conducting polymer layer, a simple, yet effective chemical strategy based on poly(hydroxymethyl 3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT-MeOH:PSS) and (3-aminopropyl)triethoxysilane is designed. The resultant PEDOT-MeOH:PSS-AgNP composite presents a consistent coating of covalently linked AgNPs, as shown by scanning electron microscopy and surface plasmon resonance analysis. The efficacy of the coatings, with and without electrical addressing, is then tested against Staphylococcus aureus, a major colonizer of medical implants. Using custom-designed culturing devices, a nearly complete prevention of biofilm growth is obtained in AgNP composite devices addressed with a square wave voltage input. It is concluded that this electroenhancement of the bactericidal effect of the coupled AgNPs offers a novel, efficient solution against biofilm colonization of medical implants.

Poly(3,4-ethylenedioxythiophene) (PEDOT) Derivatives: Innovative Conductive Polymers for Bioelectronics.

Poly(3,4-ethylenedioxythiophene)s are the conducting polymers (CP) with the biggest prospects in the field of bioelectronics due to their combination of characteristics (conductivity, stability, transparency and biocompatibility). The gold standard material is the commercially available poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). However, in order to well connect the two fields of biology and electronics, PEDOT:PSS presents some limitations associated with its low (bio)functionality. In this review, we provide an insight into the synthesis and applications of innovative poly(ethylenedioxythiophene)-type materials for bioelectronics. First, we present a detailed analysis of the different synthetic routes to (bio)functional dioxythiophene monomer/polymer derivatives. Second, we focus on the preparation of PEDOT dispersions using different biopolymers and biomolecules as dopants and stabilizers. To finish, we review the applications of innovative PEDOT-type materials such as biocompatible conducting polymer layers, conducting hydrogels, biosensors, selective detachment of cells, scaffolds for tissue engineering, electrodes for electrophysiology, implantable electrodes, stimulation of neuronal cells or pan-bio electronics.

Sensitive Potentiometric Determination of Amphetamine with an All-Solid-State Micro Ion-Selective Electrode

ABSTRACTThe development of amphetamine-ion-selective microelectrodes using electrochemical polymerization and microfabrication technologies is reported in this study. The microelectrodes include polypyrrole films electrochemically polymerized and doped with cosane anion ([3,3′-Co(1,2-C2B9H11)2]−) as the internal solid contact layer between the polymeric sensitive membrane and platinum working microelectrode. Several poly(vinyl chloride)-type membranes with different compositions of plasticizers/ionophore were drop casted on the conducting polymer layer, polypyrrole[3,3′-Co(1,2-C2B9H11)2]. Potentiometric measurements were performed to calibrate the response of the developed chemical sensors. The sensor was highly sensitive to amphetamine using a membrane composition of 26 wt% poly (vinyl chloride), 63 wt% di-butyl phthalate, 6 wt% sodium tetraphenylborate, and 5 wt% dibenzo-18-crown 6-ether. A high and linear response was demonstrated within the concentration range from 10−5 to 10−3 M with a slope of 53 mV/decade and a limit of detection of 4 × 10−5 M. A Reilley diagram shows that the sensor signal is stable for a working pH between 1.50 and 8.50. The chemical sensor was highly selective to amphetamine when compared to other interfering ions and compounds including K+, Na+, , D,L-phenylalanine, caffeine, (±)-epinephrine bitartrate salt, and N-formylamphetamine using the fixed interference method with coefficients of selectivity (Log ) from −1.40 to −1.15.

Simultaneous Determination of Na+, K+, Ca2+, Mg2+and Cl−in Unstimulated and Stimulated Human Saliva Using All Solid State Multisensor Platform

AbstractHuman saliva is one of the body fluids which collection method is relatively simple and non‐invasive. The article is dedicated to assess concentration (activity) of Na+, K+, Ca2+, Mg2+and Cl−in fresh, unstimulated or stimulated human saliva samples using single solid contact ion‐selective electrodes with conventional reference electrode and self‐made multisensor platform (MP) equipped with ion‐selective membranes for Na+, K+, Ca2+, Mg2+and Cl−and reference electrode made in solid state technology, based on dispersed KCl in the polymer. Both kind of electrodes, single ISE and miniaturized electrodes in multisensor platform (ISE‐MP) were made of glassy carbon. The electrode surfaces have been modified by conductive polymer (PEDOT) layer deposition; with the exception of Cl−electrode, in which conducting polymer was not applied. Potentiometric measurements were used to compare the changes of the ionic composition in various samples of saliva.

Fully-Polymeric pH Sensor Realized by Means of a Single-Step Soft Embossing Technique.

We present here an electrochemical sensor microsystem for the monitoring of pH. The all-polymeric device is comprised of a cyclic olefin copolymer substrate, a 200 nm-thin patterned layer of conductive polymer (PEDOT), and a 70 nm electropolymerized layer of a pH sensitive conductive polymer (polyaniline). The patterning of the fluidic (microfluidic channels) and conductive (wiring and electrodes) functional elements was achieved with a single soft PDMS mold via a single embossing step process. A post-processing treatment with ethylene glycol assured the functional enhancement of the electrodes, as demonstrated via an electrical and electrochemical characterization. A surface modification of the electrodes was carried out, based on voltammetric electropolymerization, to obtain a thin layer of polyaniline. The mechanism for pH sensing is based on the redox reactions of the polyaniline layer caused by protonation. The sensing performance of the microsystem was finally validated by monitoring its potentiometric response upon exposure to a relevant range of pH.

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.

A Versatile Method to Fabricate Highly In‐Plane Aligned Conducting Polymer Films with Anisotropic Charge Transport and Thermoelectric Properties: The Key Role of Alkyl Side Chain Layers on the Doping Mechanism

A general method is proposed to produce oriented and highly crystalline conducting polymer layers. It combines the controlled orientation/crystallization of polymer films by high‐temperature rubbing with a soft‐doping method based on spin‐coating a solution of dopants in an orthogonal solvent. Doping rubbed films of regioregular poly(3‐alkylthiophene)s and poly(2,5‐bis(3‐dodecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) yields highly oriented conducting polymer films that display polarized UV–visible–near‐infrared (NIR) absorption, anisotropy in charge transport, and thermoelectric properties. Transmission electron microscopy and polarized UV–vis–NIR spectroscopy help understand and clarify the structure of the films and the doping mechanism. F4TCNQ− anions are incorporated into the layers of side chains and orient with their long molecular axis perpendicular to the polymer chains. The ordering of dopant molecules depends closely on the length and packing of the alkyl side chains. Increasing the dopant concentration results in a continuous variation of unit cell parameters of the doped phase. The high orientation results in anisotropic charge conductivity (σ) and thermoelectric properties that are both enhanced in the direction of the polymer chains (σ = 22 ± 5 S cm−1 and S = 60 ± 2 µV K−1). The method of fabrication of such highly oriented conducting polymer films is versatile and is applicable to a large palette of semiconducting polymers.

Piezoelectric Micro- and Nanostructured Fibers Fabricated from Thermoplastic Nanocomposites Using a Fiber Drawing Technique: Comparative Study and Potential Applications

We report an all-polymer flexible piezoelectric fiber that uses both judiciously chosen geometry and advanced materials in order to enhance fiber piezoelectric response. The microstructured/nanostructured fiber features a soft hollow polycarbonate core surrounded by a spiral multilayer cladding consisting of alternating layers of piezoelectric nanocomposites (polyvinylidene enhanced with BaTiO3, PZT, or CNT) and conductive polymer (carbon-filled polyethylene). The conductive polymer layers serve as two electrodes, and they also form two spatially offset electric connectors on the fiber surface designed for the ease of connectorization. Kilometer-long piezoelectric fibers of sub-millimeter diameters are thermally drawn from a macroscopic preform. The fibers exhibit high output voltage of up to 6 V under moderate bending, and they show excellent mechanical and electrical durability in a cyclic bend-release test. The micron/nanosize multilayer structure enhances in-fiber poling efficiency due to the small distance between the conducting electrodes sandwiching the piezoelectric composite layers. Additionally, the spiral structure greatly increases the active area of the piezoelectric composite, thus promoting higher voltage generation and resulting in 10-100 higher power generation efficiency over the existing piezoelectric cables. Finally, we weave the fabricated piezoelectric fibers into technical textiles and demonstrate their potential applications in power generation when used as a sound detector, smart car seat upholstery, or wearable materials.

Hierarchically designed PEDOT encapsulated graphene-MnO2 nanocomposite as supercapacitors

A hierarchically designed ternary nanocomposite of PEDOT:Grp-MnO2 was synthesized as an electrode material for high performance supercapacitors. The binary composite of MnO2 nanoparticles decorated over graphene sheets (Grp-MnO2) were synthesized using a facile, one pot solvothermal method. Further, encapsulation of the binary composite was performed by wrapping with the conductive polymer layers of PEDOT. Structural morphology and oxidation states of Mangnese of the nanocomposite were studied using XRD, TEM, Raman spectroscopy and XPS. Supercapacitive behaviour of the nanocomposites was tested by using them as electrodes for electrochemical studies like cyclic voltammetry and charge-discharge. Highest specific capacitance value was found to be 213Fg−1 for the PEDOT:Grp-MnO2 (with the ratio of 1:3) with improved energy and power densities. AC impedance measurement was carried out to ascertain the pseudocapacitance arising from the redox reactions over the electrical double layer capacitance (EDLC) in the composite materials.

A potentiometric non-enzymatic glucose sensor using a molecularly imprinted layer bonded on a conducting polymer

A non-enzymatic potentiometric glucose sensor for the determination of glucose in the micomolar level in saliva was developed based on a molecularly imprinted polymer (MIP) binding on a conducting polymer layer. A MIP containing acrylamide, and aminophenyl boronic acid, as a host molecule to glucose, was immobilized on benzoic acid-functionalized poly(terthiophene) (pTBA) by the amide bond formation onto a gold nanoparticles deposited-screen printed carbon electrode (pTBA/AuNPs/SPCE). Aromatic boronic acid was incorporated into the MIP layer to stably capture glucose and create a potentiometric signal through the changed pKa value of polymer film by the formation of boronate anion-glucose complex with generation of H+ ions by the cis-diol reaction. Reversible binding and extraction of glucose on the sensor surface was observed using a quartz crystal microbalance. Each layer of the sensor probe was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The potentiometric response at the optimized conditions exhibited a wide linear dynamic range of 3.2×10−7 to 1.0×10−3M, with a detection limit of 1.9 (±0.15)×10−7M. The sensor probe revealed an excellent selectivity and sensitivity for glucose compared to other saccharides. In addition, the reliability of the proposed glucose sensor was evaluated in physiological fluid samples of saliva and finger prick blood.

Characterization and dynamic charge dependent modeling of conducting polymer trilayer bending

Trilayer bending actuators are charge driven devices that have the ability to function in air and provide large mechanical amplification. The electronic and mechanical properties of these actuators are known to be functions of their charge state making prediction of their responses more difficult when they operate over their full range of deformation. In this work, a combination of state space representation and a two-dimensional RC transmission line model are used to implement a nonlinear time variant model for conducting polymer-based trilayer actuators. Electrical conductivity and Young’s modulus of electromechanically active PEDOT conducting polymer containing films as a function of applied voltage were measured and incorporated into the model. A 16% drop in Young’s modulus and 24 times increase in conductivity are observed by oxidizing the PEDOT. A closed form formulation for radius of curvature of trilayer actuators considering asymmetric and location dependent Young’s modulus and conductivity in the conducting polymer layers is derived and implemented in the model. The nonlinear model shows the capability to predict the radius of curvature as a function of time and position with reasonable consistency (within 4%). The formulation is useful for general trilayer configurations to calculate the radius of curvature as a function of time. The proposed electrochemical modeling approach may also be useful for modeling energy storage devices.