Thermal undoping behavior of FeCl3-doped poly(3-octylthiophene)

Conductive Metal–Organic Frameworks as Ion-to-Electron Transducers in Potentiometric Sensors

“…Achieving stable and reliable measurements using SCEs hinges on four fundamental conditions: (i) reversible ion-to-electron signal transduction; (ii) non-polarizable interface with high exchange current density; (iii) absence of any side reactions; and (iv) absence of a thin water layer at the ISM/electrode interface. − Efforts to fulfill these combined criteria through the implementation of conductive polymers and porous carbon-based materials as ion-to-electron transducers have enabled major advancements in potentiometry, giving rise to the most stable and robust potentiometric devices to date. ,− Nonetheless, the existing classes of materials exhibit trade-offs and limitations in the context of SCEs. ,− Conductive polymerssuch as poly­(octylthiophene) (POT), poly­(3,4-ethylenedioxythiophene) (PEDOT), and polypyrrole (PPy)can provide hydrophobicity (contact angle of water of 50° and 100° measured on glassy carbon electrode (GCE) surface modified with either PEDOT–polystyrene sulfonate (PSS) or Ppy–perfluorooctanesulfonate, respectively) and high redox capacitance (10–200 μF) . However, their performance can also be diminished by: (i) variations in the crystallinity that can alter charge transport; (ii) dopant-dependent changes in glass-transition temperature that may affect the mechanical stability of the transducer layer; (iii) sensitivity to O 2 , CO 2 , pH, and light that can lead to potential drift; and (iv) dependence of conductivity upon conformational changes . Nanostructured carbon-based materials, such as carbon nanotubes (CNTs), graphene, fullerenes, and three-dimensional ordered mesoporous (3DOM) carbons have been recently shown to perform the function of ion-to-electron signal transduction via the formation of the electrical double layer at the membrane/electrode interface. ,, The inherent hydrophobicity of these materials, combined with excellent electrical conductivity and high capacitance (625 μF for 3DOM carbon and 302 μF for single-walled CNTs), reinforces the advantageous use of nanostructured materials as components for the development of SCEs.…”

“…19,22−27 Conductive polymerssuch as poly(octylthiophene) (POT), poly(3,4-ethylenedioxythiophene) (PEDOT), and polypyrrole (PPy)can provide hydrophobicity (contact angle of water of 50°and 100°measured on glassy carbon electrode (GCE) surface modified with either PEDOT−polystyrene sulfonate (PSS) 28 or Ppy−perfluorooctanesulfonate, 29 respectively) and high redox capacitance (10−200 μF). 30 However, their performance can also be diminished by: (i) variations in the crystallinity that can alter charge transport; 31 (ii) dopantdependent changes in glass-transition temperature that may affect the mechanical stability of the transducer layer; 32 (iii) sensitivity to O 2 , CO 2 , pH, and light that can lead to potential drift; 33 and (iv) dependence of conductivity upon conformational changes. 34 Nanostructured carbon-based materials, such as carbon nanotubes (CNTs), graphene, fullerenes, and three- dimensional ordered mesoporous (3DOM) carbons have been recently shown to perform the function of ion-to-electron signal transduction via the formation of the electrical double layer at the membrane/electrode interface.…”

Ion-Selective Electrodes with Colloid-Imprinted Mesoporous Carbon as Solid Contact

“…More importantly, conducting polymer films do not have a well-defined redox potential but instead exhibit a continuum of redox potentials (which manifests itself, e.g., by broad, scan rate independent peaks in cyclic voltammograms) . There are several causes for this energetic inhomogeneity, including the coexistence of crystalline and amorphous regions, slow conformational changes as the result of oxidation or reduction (often referred to as redox transformations, the slowness of which manifests itself in hysteresis), , changes in the glass transition temperature as a result of doping, the formation of intermolecular bonds between neighboring chains, and the dependence of the film morphology on the method of film fabrication. , Moreover, the penetrability of counterions and, concomitantly, the film capacitance depend on the counterion size and, likely, the local polymer morphology. Consequently, it is difficult to obtain high device-to-device reproducibility and to minimize long-term drift resulting from reactions of the conducting polymer with ambient redox-active species such as oxygen.…”