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Electrochemical ion transfer with thin films of poly(3-octylthiophene)

Published inAnalytical chemistry, vol. 88, no. 13, p. 6939-6946
Publication date2016
Abstract

We report on the limiting conditions for ion-transfer voltammetry between an ion-exchanger doped and plasticized poly(vinyl chloride) [PVC] membrane and an electrolyte solution that was triggered via the oxidation of a poly(3-octylthiophene) (POT) solid-contact (SC), which was unexpectedly related to the thickness of the POT SC. An electropolymerized 60 nm thick film of POT coated with a plasticized PVC membrane exhibited a significant sodium transfer voltammetric signal whereas a thicker film (180 nm) did not display a measurable level of ion-transfer due to a lack of oxidation of thick POT beneath the membrane film. By contrast, this peculiar phenomenon was not observed when the POT film was in direct contact with an organic solvent-based electrolyte. This evidence is indicative of three key points: i) the coated membrane imposes a degree of rigidity to the system, which restricts the swelling of the POT film and its concomitant p-doping; ii) this phenomenon is exacerbated with thicker POT films due to an initial morphology (rougher comprising a network of large POT nanoparticles), which gives rise to a diminished surface area and electrochemical reactivity in the POT SC; iii) the rate of sodium transfer is higher with a thin POT film due to a smoother surface morphology made up of a network of smaller POT nanoparticles with an increased surface area and electrochemical reactivity. A variety of techniques including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) were used to elucidate the mechanism of the POT thickness/POT surface roughness dependency on the electrochemical reactivity of the PVC/POT SC system.

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Citation (ISO format)
CUARTERO BOTIA, Maria et al. Electrochemical ion transfer with thin films of poly(3-octylthiophene). In: Analytical chemistry, 2016, vol. 88, n° 13, p. 6939–6946. doi: 10.1021/acs.analchem.6b01800
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