Atomic force microscopic study of the chemical oxidation of silver crystals immobilized on platinum and on quartz

When silver crystals immobilized on a platinum surface are oxidized with a diluted aqueous solution of bromine, the morphological reaction scenario resembles very much that of the electrochemical oxidation described earlier [U. Hasse, F. Scholz, Electrochem. Commun. 6 (2004) 409–412], i.e., the oxidation can be described by a nucleation–growth kinetics via an oversaturated solution. In that reaction the platinum serves as local cathode for bromine reduction and the silver as the local anode. When the silver crystals are immobilized on an electronic insulator like quartz, the loci of reducing the bromine and oxidizing the silver are obviously the silver crystals. In that case one observes for sub-micrometer size Ag crystals that each crystal is converted to a silver bromide crystal. However, crystals of micrometer size leave ring-shaped structures of silver bromide.