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Janaky C.,University of Szeged | Janaky C.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Rajeshwar K.,University of Texas at Arlington
Progress in Polymer Science | Year: 2015

Abstract Hybrid materials based on conducting polymers (CPs) and inorganic semiconductors (SCs) undoubtedly constitute one of the most promising classes of new materials. The spectacular progress in this research topic has been driven by the development of novel synthetic procedures and by the large variety of applications. Beyond scientific and fundamental interest, such hybrid assemblies are attractive from technological perspectives as well, for example, in energy conversion and storage, electronics, catalysis, and optics. This article is designed to be a critical overview for the polymer materials science community on how to employ electrosynthetic methods to obtain hybrid materials with well-designed composition and morphology. As this review illustrates, (photo)electrochemical approaches are versatile and powerful tools in the preparation of conjugated polymer-based composites, containing both elemental and compound semiconductors. Hybridization of CPs with metal oxides (TiO2, WO3, ZnO, NiO, Cu2O, CuO, V2O5, Fe2O3, Fe3O4, MnO2, SnO2, RuO2), metal chalcogenides (CdS, CdTe, CdSe, Bi2S3), and carbon nanomaterials (nanotubes, graphene, graphene oxide) is presented. We demonstrate that both composition and nanoscale architecture of the hybrid assemblies can be precisely controlled by employing carefully designed electrochemical methods. To achieve the goal of popularizing electro- and photoelectrosynthetic procedures, particular attention will be paid to compare the as-synthesized assemblies with their counterparts obtained from other procedures. The most prominent applications of these electrosynthesized materials are highlighted, with particular focus on energy related utilization pathways. © 2014 Elsevier Ltd. All rights reserved. Source


Samu G.F.,University of Szeged | Samu G.F.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Visy C.,University of Szeged | Rajeshwar K.,University of Texas at Arlington | And 4 more authors.
Electrochimica Acta | Year: 2014

Photoelectrochemical synthesis of TiO2/CdX/PEDOT [X: S, Se; PEDOT = poly(3,4-ethylenedioxythiophene)] ternary hybrids was carried out by exploiting the semiconductor (SC) nature of both the oxide and the chalcogenide component. To this end, TiO2 nanotube arrays were initially electrosynthesized on titanium foils by anodization in fluoride-containing aqueous media. CdS and CdSe quantum dots were subsequently deposited on the nanotubes using successive ionic layer adsorption and reaction (SILAR). The conjugated polymer, PEDOT, was then grafted using photoelectrochemical excitation of the SC matrix and potentiodynamic deposition, to ultimately afford the ternary hybrid architecture. The morphology, structural properties, and chemical composition of these assemblies were evaluated by scanning electron microscopy, diffuse reflectance UV-Vis spectrophotometry, and Raman spectroscopy, while their electroactivity was evaluated by cyclic voltammetry. Photoelectrochemical deposition of the conducting polymer was carried out both through selective excitation of the chalcogenide sensitizer and the collective photoexcitation of the two SC components. Two precursor molecules, namely, EDOT or bis-EDOT were compared and contrasted in terms of their relative proclivity to oligomer/polymer formation. The use of UV or visible spectral wavelength components allowed for discrimination between the various polymer formation and SC photoexcitation pathways. Source


Samu G.F.,University of Szeged | Samu G.F.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Pencz K.,University of Szeged | Janaky C.,University of Szeged | And 2 more authors.
Journal of Solid State Electrochemistry | Year: 2015

The aim of this study is to tailor the electrochemical synthesis of hybrid materials consisting of nanoporous tungsten trioxide (WO3) and polyaniline (PANI) for application as supercapacitor electrodes. Nanoporous WO3, synthesized by the anodization of tungsten foils, acted as the active material framework for this assembly. With the variation of the anodization voltage, host materials with different morphological features were prepared. Subsequently, electrodeposition of PANI was carried out by potentiodynamic cycling in highly acidic media. Through alteration of the number of deposition cycles, the amount of deposited PANI was varied. This parameter had a decisive impact on the morphology of the resulting hybrids as confirmed by SEM images. Cyclic voltammetry and galvanostatic charge–discharge measurements were carried out to characterize the charge storage properties of the synthesized hybrids. By comparing electrochemical data with structural properties, structure–property relationships were established, and under optimal conditions, 350 F g−1 and 200 mF cm−2 were obtained. © 2015, Springer-Verlag Berlin Heidelberg. Source


Endrodi B.,University of Szeged | Endrodi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Mellar J.,University of Szeged | Gingl Z.,University of Szeged | And 3 more authors.
Journal of Physical Chemistry C | Year: 2015

In this study, we investigated the impact of molecular and supramolecular structure of conducting polymers (CPs) on their thermoelectric properties. As a model system, poly(3-alkylthiophene)s (P3ATs) with different side-chain lengths were prepared through oxidative chemical polymerization and were recrystallized to a well-ordered lamellar structure, resulting in one-dimensional self-assembled nanofibers (evidenced by transmission electron microscopy, X-ray diffraction, and UV-vis spectroscopic measurements). Thermoelectric characterization was performed at different doping levels (precisely tuned by doping in the redox reaction with Ag+ and Fe3+ cations), and the highly doped samples exhibited the best performance for all studied polymers. By varying the length of the alkyl side chain, the supramolecular structure and consequently the electronic properties were varied. The highest electrical conductivity was measured for poly(3-butylthiophene), rooted in its densely packed structure. The established structure-property relationships, concerning the monotonous decrease of the electrical conductivity with the alkyl side chain length, highlight the importance of the supramolecular structure (interchain distance in this case). These findings may contribute to the rational design of organic thermoelectric materials. © 2015 American Chemical Society. Source


Endrdi B.,University of Szeged | Endrdi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Mellar J.,University of Szeged | Gingl Z.,University of Szeged | And 3 more authors.
RSC Advances | Year: 2014

Enhanced thermoelectric properties of poly(3-hexylthiophene) nanofiber networks, doped in their reaction with silver cations, are presented. The role of charge carrier concentration and mobility (influenced by the supramolecular structure and nanoscale morphology) is discussed. The nanonet structure leads to a six fold increase in the ZT value compared to the bulk polymer counterpart. This journal is © 2014 The Royal Society of Chemistry. Source

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