Quantification of dopant ions in polypyrrole films with electrochemical ICP-atomic emission spectrometry and comparison to electrochemical quartz crystal microbalance studies

Quantification of electroinactive dopants in conductive polypyrrole (PPY) f ilms was performed with electrochemistry combined on-line with inductively coupled plasma-atomic emission spectrometry (EC/ICP-AES). Anion (HSO4-) eje ction out of a PPY film was first chosen as a model system and the results obtained with EC/ICP-AES were found to be comparable with values deduced by electrochemical quartz crystal microbalance (EQCM). The EC/ICP-AES approac h was then extended to cases where EQCM findings become difficult to interp ret (i.e. simultaneous insertion,of Na+ into and ejection of HSO4- out of P PY film). It is demonstrated that EC/ICP-AES can simultaneously quantify bo th cationic and anionic species involved in the PPY redox switching. This i s in contrast with EQCM studies that can only detect the net mass change fr om the two competing processes. This study shows that EC/ICP-AES is a viabl e technique for providing accurate information concerning the doping/dedopi ng processes without the necessity of removing the polymer-modified electro de from the electrochemical flow cell. More importantly, the species invest igated do not need to be electroactive. It is clear that the comparative st udy between the two techniques can be powerful in unraveling relatively com plicated redox reactions and ion-transport processes in conductive polymer films. (C) 2001 Elsevier Science B.V. All rights reserved.