Preconditioning gold substrates influences organothiol self-assembled monolayer (SAM) formation

Self-assembled monolayer (SAM) formation of alkanethiols with ionic, hydrop hilic terminal functionalities onto various O-2 plasma/ethanol pretreated g old substrates was characterized to explore the effect of gold surface oxid e on the SAM packing quality. Oxygen adsorption induced by the Au2O3 surfac e residuals are observed on the plasma-oxidized and O-2 plasma/ethanol-rins ed pretreated Au surfaces while no obvious adsorbed oxygen is found on fres hly coated and O-2 plasma/ethanol sonication pretreated Au substrates. A mo del for the formation of hydrophilic terminated SAMs, -OH, -COOH, and -PO3H 2 is proposed. According to this model, the ionic and/or other binding inte ractions between the surface Au2O3 and the alkanethiol hydrophilic terminal end as well as the interactions between the terminal SAM functionalities c ould cause the packing disorder found on these three SAMs formed on Au subs trates containing Au2O3 surface species. (C) 2001 Academic Press.