Nano-identification for the cleavage of disulfide bond during the self-assembly processes of unsymmetric dialkyl disulfides on Au(111)

Abstract

The formation of striped phases of unsymmetric hexyl octadecyl disulfide (CH3(CH2)5SS(CH2) 17CH3, HOD) and 1-hydroxyundecyl octadecyl disulfide (CH3(CH2)17SS(CH2)11OH, HUOD) on Au(111) and graphite has been investigated by scanning tunneling microscopy (STM)'to understand the self-assembly processes of dialkyl disulfides. STM imaging clearly shows the formation of striped phases having corrugation periodicities that are nearly consistent with the molecular length of alkanethiolate moieties formed after the S-S bond cleavage of dialkyl disulfide on a gold surface. On the other hand, self-assembled monolayers (SAMs) of dialkyl disulfides on a graphite surface displayed long-range, well-ordered monolayers with one striped pattern that shows periodicity as a function of molecular length via nondissociative adsorption. From a nonbscopic viewpoint, we have clearly demonstrated that dialkyl disulfide SAMs on gold form via S-S bond cleavage of disulfide.