MULTILAYER SELF-ASSEMBLY OF AMPHIPHILIC CYCLODEXTRIN HOSTS ON BARE AND MODIFIED GOLD SUBSTRATES - CONTROLLING AGGREGATION VIA SURFACE MODIFICATION

Self-assembled multilayers of the three modified cyclodextrins is(2,3- O-hexyl-6-deoxy-6-amino)-alpha-cyclodextrin (1), kis(2,3-O-hexyl-6-deo xy-6-amino)-beta-cyclodextrin (2), and is(2,3-O-hexyl-6-deoxy-6-amino) -gamma-cyclodextrin (3)) on bare gold, as well as on gold surfaces mod ified with mercaptopropionic (4) and mercaptooctanoic (5) acid, were i nvestigated by cyclic voltammetric, contact angle, FT-IR, and quartz c rystal microbalance measurements in neutral aqueous media. The level o f organization of the aggregates formed by the three CD derivatives (1 -3) on the negatively charged surface of the mercaptopropionic and mer captooctanoic acid modified gold electrodes proved to be substantially better than that on bare gold electrodes. This finding suggests that although the amphiphilic character of compounds 1-3 can induce aggrega tion on a gold surface, the electrostatic interaction between the carb oxylic acid groups and the positively charged cyclodextrins is the pri mary force leading to the formation of well-organized aggregates.