Influence of the Incorporation of CeO_2 Nanoparticles on the Ion Exchange Behavior of Dodecylsulfate Doped Polypyrrole Films: Ac-Electrogravimetry Investigations

摘要

Cerium oxide (CeO_2) nanoparticles (NPs) possessing defined size and crystallinity have been synthesised by a co-precipitation method. The effect of several parameters, such as the nature of the solvent and the calcination process, on the crystallite size was studied by XRD, TEM and BET methods. These CeO_2 nanoparticles were then incorporated in dodecylsulfate (DS) doped PPy films during their electrodeposition in potentiodynamic conditions in order to produce PPy-DS/CeO_2 NPs nanocomposite thin films on gold coated quartz crystals. Simultaneous EQCM experiments revealed successful incorporation of increasing amounts of cerium oxide nanoparticles in the polypyrrole matrix during each of the consecutive CV scans. This was confirmed using FEG-SEM and EDS microanalysis. The ion exchange phenomena occurring in the resulting nanocomposite materials were studied by ac-electrogravimetry in NaCl aqueous electrolyte. PPy-DS films appear to be mainly cation exchangers, independently from the incorporation of CeO_2 nanoparticles (NPs), even though chloride anions in smaller amounts, and free water molecules, are simultaneously transferred at the film/electrolytic solution interface. This study also reveals that the kinetics of Cl~- ion insertion occurring at the film/electrolyte interface upon oxidation is persistently slower in PPy-DS/CeO_2 NPs films than in PPy-DS films through-out the entire potential window of investigation. However, the relative concentration changes of Cl~- ions in PPy-DS/CeO_2 NPs films is about two times greater than that occurring in pristine PPy-DS films. Such conclusion tends to demonstrate that CeO_2 NPs have the ability to modify the morphology of electrodeposited PPy-DS thin films as well as their subsequent permeability towards ions contained in the electrolytic solution, possibly via the perturbation of polymer chain interactions and organisation.