Electrochemistry and structure of the isomers of aminothiophenol adsorbed on gold

The self-assembled monolayers (SAMs) of the three isomers of aminothiopheno l, ATP, have been studied by means of electrochemistry, in-situ STM and XPS . We find that the isomers are organized differently. The organization is p resumably governed by their intermolecular and surface interactions. Moreov er, the chemical and physical characteristics of the interface are signific antly and differently affected by the isomers comprising the SAMs. The elec trochemistry of the modified surface as well as the bare gold surface in co ntact with the thiol-containing electrolyte, copper deposition and palladiu m(II) extraction have been studied for the 2-, 3- and 4-ATP monolayers. The organization of the layers has been investigated by STM. In essence, we fi nd that the different isomers are likely to adopt an orientation that is pe rpendicular to the surface. While 4-ATP forms the densest monolayer, 2-ATP probably interacts with the gold surface with both the amino and the mercap to groups. Moreover, STM images indicate the partial formation of more than a monolayer. This is supported by XPS measurements and electrochemistry an d can be attributed to the SAM modification solution, i.e. sulfuric acid, w hich allows the formation of sulfate-bridged ATP bilayers. The chemical and physical characteristics of the interfaces are governed by the different o rganization as well as by the individual chemical properties of each isomer . (C) 2000 Published by Elsevier Science B.V. All rights reserved.