Self-Assembly Process of Flatly Adsorbed Porphyrin Self-Assembled Monolayer on a Au(111) Surface Studied by ex situ Scanning Tunneling Microscopy and Electrochemical Reductive Desorption Measurements

Abstract

Self-assembly process of a porphyrin derivative [5,10,15,20-tetra-(m-mercapto-p-methoxyphenyl) porphyrin; TMMPP], which was designed and synthesized to be flatly adsorbed on a gold substrate surface, on a Au(111) single crystal surface was investigated by ex situ scanning tunneling microscopy (STM) and electrochemical reductive desorption measurements. A small number of TMMPP molecules were randomly but flatly adsorbed on the Au(111) surface when the deposition time was less than 1 h as the initial stage of the self-assembly process. When the deposition time was more than 20 h as the final stage of the self-assembly process, the densely-packed and flatly adsorbed TMMPP SAM formed on the Au(111) surface via a phase transition from a random to an ordered structure. These results indicated that we succeeded in the formation of the flatly adsorbed and well-defined porphyrin selfassembled monolayer (SAM) on the Au(111) surface.