Observation of adsorbate coverage with electrogenerated chemiluminescence imaging

Abstract

The spatial distribution of poly(phenylene oxide) on platinum electrodes was studied using the technique of electrogenerated chemiluminescence (ECL) imaging. The polymer was deposited on electrodes through the electrooxidation of phenol in aqueous solution. Electrochemical oxidation of phenol itself was effectively inhibited by the film, as was the electrogenerated chemiluminescen of luminol in alkaline peroxide. Using a sensitive microscopic imaging system, light from the ECL reaction was collected and used to show where film coverage occurred on the surface. At partial coverages of poly(phenylene oxide), some regions of the electrode were still able to support electron transfer and therefore the ECL images exhibited heterogeneity. Images showed that the nature and extent of coverage of poly(phenylene oxide) on the surface was a factor of phenol oxidation potential. The potential dependence of coverage was consistent with an isotherm that accounts for a high degree of attraction between adsorbed molecules, so that coverage increased abruptly over a relatively small potential range.