Interfacial structure and dynamics.

Thin nanoporous metallic films have been prepared by electrochemical deposition around spherical polystyrene particles deposited on gold substrates. The characterisation of both the polystyrene templates and the films were carried out by in situ electrochemical quartz crystal microbalance (EQCM) and atomic force microscopy. The formation of the polystyrene template significantly depends on the deposition conditions (sedimentation time and rate of solvent evaporation). The resultant metallic films mirror the morphology of the polystyrene arrays. The frequency shifts for films in air and in water indicate only partial fluid filling of the hemispherical voids left by the dissolved polystyrene templates. EQCM measurements were made during the p-, n- and sequential p-and n-doping of PEDOT films exposed to a range of electrolytes in two different solvents. The films were acoustically thin, so the EQCM response was simply gravimetric. Dopant ion and solvent fluxes were determined by the use of time differentials obtained from the current and mass response. Normalisation of the flux data as a function of potential or charge lead to mechanistic information. For the case of p-doping of PEDOT films exposed to LiClO4/CH3CN, during both the doping and un-doping half cycles, all fluxes normalised with respect to scan rate. However, the responses in the two directions are not mirror images suggesting the two processes have different mechanistic paths. Comparison of data obtained for a PEDOT film cycled in two different solvents showed distinct differences. The normalisation procedure works well for both sets of data, but illustrates that they have different mechanisms. Both sets of data showed a mechanistic switch occurring during both the doping and un-doping half cycles. There was significant solvent transfer for PEDOT films cycled in the n-doping region, but the direction was cation dependent. The fluxes normalised with respect to scan rate, indicating no kinetic or transport limitations. Considerable hysteresis between the responses suggested that polymer reconfiguration occurs. Extension of the potential range to include both p- and n-doping regimes, showed additional features appear on the edge of the two doping peaks, signalling the release of trapped charge.