SPECTROSCOPIC AND ELECTROCHEMICAL ANALYSES OF ELECTRON-TRANSFER AND MASS-TRANSFER ACROSS THE MICRODROPLET SOLUTION INTERFACE

A laser trapping - spectroscopy - electrochemistry method has been applied to study electron transfer and mass transfer across the microdroplet/water interface. Electron transfer from Fe(III) produced electrochemically at an optically transparent SnO2 electrode in water to ferrocene (FeCp) in an oil droplet was directly measured by both fluorometric and coulometric methods. The rate determining step of the FeCp oxidation was the electron transfer process across the droplet/water interface and the relevant rate constant was determined for individual micrometer droplets. As a model of color developing reactions in photographic emulsions, cyan dye formation reaction in a single oil droplet was also investigated. Mass transfer of a reagent across the droplet/water interface and subsequent dye formation reaction in the droplet were demonstrated. The yield and the rate constant of the dye formation reaction in single droplets were also discussed.