Surface modification of conducting substrates. Existence of azo bonds in the structure of organic layers obtained from diazonium salts

This paper analyzes the structures of organic layers that are obtained on metals or carbon by electrochemical reduction of diazonium salts or by simple dipping of the substrate in a diazonium solution. There is a general agreement in the literature on the polyphenylene structure of these layers. But, previous results based on XPS data have indicated the possible presence of azo groups in these layers. IR and TOF-SIMS experiments demonstrate the existence of these azo groups included in the polyphenylene chains. A mechanism is presented that accounts both for the growth of polyphenylene chains and the inclusion of azo bonds in these chains.