Potentiometric sensors based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonated calixarene and calixresorcarenes
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Potentiometric ion sensors have been prepared by galvanostatic electrosynthesis of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-sulfonated calixarene (CS) and p-methylsulfonated calixresorcarenes (R n S) with alkyl substituents of different chain length (R1=CH3; R2=C2H5; R3=C6H13). The bowl-shape of these doping ions makes them suitable as ionic recognition sites, and their bulky character is expected to prevent them from leaching out of the conducting polymer membrane. For comparison, sensors based on PEDOT doped with poly(styrene sulfonate) (PSS) and poly(vinyl sulfonate) (PVS) were also constructed. The resulting GC/PEDOT electrodes were conditioned in 0.01 mol L−1 AgNO3 and their performance as Ag+ ion-selective electrodes (ISEs) studied. Results reveal that selectivity and lifetime of the electrodes is affected by the doping anion structure, although all electrodes show selectivity towards Ag+ ions. Interaction of Ag+ with sulfur atoms present in the conducting polymer backbone is considered to be the main reason for this behavior. A second set of electrodes was constructed and conditioned in 0.1 mol L−1 KCl. These electrodes were tested in chloride solutions of quaternary ammonium cations, showing that CS and R2S exhibit significant sensitivity towards pyridinium.
KeywordsIon-selective electrode Silver Calixarene Calixresorcarene Conducting polymer
The authors are grateful to the ERASMUS exchange student Jens Künnemeyer for experimental assistance. Financial support from the National Technology Agency (TEKES) and the Academy of Finland are gratefully acknowledged. This work is part of the activities at the Åbo Akademi Process Chemistry Centre within the Finnish Centre of Excellence Programme (2000–2005) by the Academy of Finland.
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