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Conjugated polymer-polyelectrolyte blends combine and couple electronic semiconductor functionality with selective ionic transport, making them attractive as the active material in organic biosensors and bioelectronics, electro-chromic displays, neuromorphic computing, and energy conversion and storage. Although extensively studied and explored, fundamental knowledge and accurate quantitative models of the coupled ion-electron functionality and transport are still lacking to predict the characteristics of electrodes and devices based on these blends. We report on a two-phase model, which couples the chemical potential of the holes, in the conjugated polymer, with the electric double layer residing at the conjugated polymer-polyelectrolyte interface. The model reproduces a wide range of experimental charging and transport data and provides a coherent theoretical framework for the system as well as local electrostatic potentials, energy levels, and charge carrier concentrations. This knowledge is crucial for future developments and optimizations of bioelectronic and energy devices based on the electronic-ionic interaction within these materials. [ABSTRACT FROM AUTHOR]

Morphology of the conducting polymer PEDOT:TOS (poly(3,4-ethylenedioxythiophene) doped with molecular tosylate) and its crystallization in aqueous solution were studied using atomistic molecular dynamics simulations. It was found that (a) PEDOT comprises crystallite aggregates consisting of 3–6 π–π stacked chains. The crystallites are linked by interpenetrating π–π stacked chains such that percolative paths in the structure are formed. (b) The size of the crystallites depends on the water content, but the π–π stacking distance is practically independent of the chain length, charge concentration and water content. (c) TOS counterions are located either on the top of the chains or on the side of the crystallites and their distribution depends on the charge concentration but is practically independent of the water content; (d) PEDOT chains and crystallites exhibit bending that depends on their length and water content. [ABSTRACT FROM AUTHOR]

The monitoring of phenolic compounds in wastewaters in a simple manner is of great importance for environmental control. Here, a novel screen printed laccase-based microband array for in situ , total phenol estimation in wastewaters and for water quality monitoring without additional sample pre-treatment is presented. Numerical simulations using the finite element method were utilized for the characterization of micro-scale graphite electrodes. Anodization followed by covalent modification was used for the electrode functionalization with laccase. The functionalization efficiency and the electrochemical performance in direct and catechol-mediated oxygen reduction were studied at the microband laccase electrodes and compared with macro-scale electrode structures. The reduction of the dimensions of the enzyme biosensor, when used under optimized conditions, led to a significant improvement in its analytical characteristics. The elaborated microsensor showed fast responses towards catechol additions to tap water – a weakly supported medium – characterized by a linear range from 0.2 to 10 μM, a sensitivity of 1.35 ± 0.4 A M −1 cm −2 and a dynamic range up to 43 μM. This enhanced laccase-based microsensor was used for water quality monitoring and its performance for total phenol analysis of wastewater samples from different stages of the cleaning process was compared to a standard method. [ABSTRACT FROM AUTHOR]

Abstract: The spectra of conducting polymers obtained using ultraviolet photoelectron spectroscopy (UPS) exhibit a typical broadening of the tail σUPS ≈ 1 eV, which by an order of magnitude exceeds a commonly accepted value of the broadening of the tail of the density of states σDOS ≈ 0.1 eV obtained using transport measurements. In this work, an origin of this anomalous broadening of the tail of the UPS spectra in a doped conducting polymer, PEDOT (poly(3,4‐ethylenedioxythiophene)), is discussed. Based on the semiempirical approach and using a realistic morphological model, the density of valence states in PEDOT doped with molecular counterions is computed. It is shown that due to a disordered character of the material with randomly distributed counterions, the localized charge carriers in PEDOT crystallites experience spatially varying electrostatic potential. This leads to spatially varying local vacuum levels and binding energies. Taking this variation into account the UPS spectrum is obtained with the broadening of the tail comparable to the experimentally observed one. The results imply that the observed broadening of the tail of the UPS spectra in PEDOT provides information about a disordered spatially varying potential in the material rather than the broadening of the DOS itself. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is the most studied and explored mixed ion-electron conducting polymer system. PEDOT:PSS is commonly included as an electroactive conductor in various organic devices, e.g., supercapacitors, displays, transistors, and energy-converters. In spite of its long-term use as a material for storage and transport of charges, the fundamentals of its bulk capacitance remain poorly understood. Generally, charge storage in supercapacitors is due to formation of electrical double layers or redox reactions, and it is widely accepted that PEDOT:PSS belongs to the latter category. Herein, experimental evidence and theoretical modeling results are reported that significantly depart from this commonly accepted picture. By applying a two-phase, 2D modeling approach it is demonstrated that the major contribution to the capacitance of the two-phase PEDOT:PSS originates from electrical double layers formed along the interfaces between nanoscaled PEDOT-rich and PSS-rich interconnected grains that comprises two phases of the bulk of PEDOT:PSS. This new insight paves a way for designing materials and devices, based on mixed ion-electron conductors, with improved performance. [ABSTRACT FROM AUTHOR]

Electronic plants, e-Plants, are an organic bioelectronic platformthat allows electronic interfacing with plants. Recently we have demonstrated plants with augmented electronic functionality. Using the vascular system and organs of a plant, we manufactured organic electronic devices and circuits in vivo, leveraging the internal structure and physiology of the plant as the template, and an integral part of the devices. However, this electronic functionality was only achieved in localized regions, whereas new electronic materials that could be distributed to every part of the plant would provide versatility in device and circuit fabrication and create possibilities for new device concepts. Here we report the synthesis of such a conjugated oligomer that can be distributed and form longer oligomers and polymer in every part of the xylem vascular tissue of a Rosa floribunda cutting, forming long-range conducting wires. The plant's structure acts as a physical template, whereas the plant's biochemical response mechanism acts as the catalyst for polymerization. In addition, the oligomer can cross through the veins and enter the apoplastic space in the leaves. Finally, using the plant's natural architecture we manufacture supercapacitors along the stem. Our results are preludes to autonomous energy systems integrated within plants and distribute interconnected sensor-actuator systems for plant control and optimization. [ABSTRACT FROM AUTHOR]

Spatiotemporal control of the complexchemical microenvironmentis of great importance to many fields within life science. One wayto facilitate such control is to construct delivery circuits, comprisingarrays of dispensing outlets, for ions and charged biomolecules basedon ionic transistors. This allows for addressability of ionic signals,which opens up for spatiotemporally controlled delivery in a highlycomplex manner. One class of ionic transistors, the ion bipolar junctiontransistors (IBJTs), is especially attractive for these applicationsbecause these transistors are functional at physiological conditionsand have been employed to modulate the delivery of neurotransmittersto regulate signaling in neuronal cells. Further, the first integratedcomplementary ionic circuits were recently developed on the basisof these ionic transistors. However, a detailed understanding of thedevice physics of these transistors is still lacking and hampers furtherdevelopment of components and circuits. Here, we report on the modelingof IBJTs using Poisson’s and Nernst–Planck equationsand the finite element method. A two-dimensional model of the deviceis employed that successfully reproduces the main characteristicsof the measurement data. On the basis of the detailed concentrationand potential profiles provided by the model, the different modesof operation of the transistor are analyzed as well as the transitionsbetween the different modes. The model correctly predicts the measuredthreshold voltage, which is explained in terms of membrane potentials.All in all, the results provide the basis for a detailed understandingof IBJT operation. This new knowledge is employed to discuss potentialimprovements of ion bipolar junction transistors in terms of miniaturizationand device parameters. [ABSTRACT FROM AUTHOR]

The authors demonstrate the triggering of surface plasmons at the interface of a metal grating and a photovoltaic bulk heterojunction blend of alternating polyfluorenes and a fullerene derivative. An increased absorption originating from surface plasmon resonances is confirmed by experimental reflection studies and theoretical modeling. Plasmonic resonances are further confirmed to influence the extracted photocurrent from devices. More current is generated at the wavelength position of the plasmon resonance peak. High conductivity polymer electrodes are used to build inverted sandwich structures with top anode and bottom metal grating, facilitating for triggering and characterization of the surface plasmon effects. [ABSTRACT FROM AUTHOR]