DIRECT ANALYSES OF AN ELECTROCHEMICALLY INDUCED DYE FORMATION REACTION ACROSS A SINGLE-MICRODROPLET WATER INTERFACE

The rate and the yield of the cyan dye formation reaction in single mi crodroplets dispersed in water were determined for the first time by a laser trapping-spectroscopy-electrochemistry method. The rate-determi ning step was shown to be the interfacial coupling reaction between el ectrochemically generated 4-N,N-diethyl-2-methylquinonediimine (QDI) i n the water phase and a phenol derivative in an oil droplet. The dye f ormation efficiency in an individual droplet was also demonstrated to be controlled by the distance between the microdroplet and the electro de. The results were explained in terms of the concentration gradient of QDI between the droplet and the electrode, which was generated by b oth diffusion and side reactions of QDI in the water phase. Simulation of QDI diffusion in the water phase supported the conclusion as well.