Electrochemical and surface analytical studies of self-assembled monolayers of three aromatic thiols on gold electrodes

Three thiols with three aromatic rings and different structure - terphenyl- 4-methanethiol (TPMT), terphenyl-4-thiol (TPT), and anthracene-2-thiol (AT) have been used to form self-assembled monolayers (SAM) on vapour-deposited and flame-annealed Au films on glass substrates. All three SAMs effectivel y block the anodic formation of Au oxide, indicating densely packed layers which prevent the access of water and hydrated ions through the organic lay er to the metal surface. The film improves its inhibiting properties with d uration of exposure to the thiol solutions. reaching completion after 1 hou r [1]. The charge-transfer reaction of the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) syst em is blocked for TPMT films with an insulation of the pi -electron system from the Au surface by the methylene group. TPT and especially AT films sho w the current density of the redox reactions. It is proposed that the charg e transfer occurs via the aromatic molecules of the SAMs to the Au surface.