SELF-ASSEMBLED MONOLAYER FILMS OF C(60) ON CYSTEAMINE-MODIFIED GOLD

Self-assembled monolayer films (SAMs) of C60 on cysteamine-modified an d cysteamine/ethanethiol-modified Au are reported. The monolayers were characterized via contact angle measurements, X-ray photoelectron spe ctroscopy, electrochemistry, and quartz crystal microbalance (QCM) mea surements. C60 surface coverage (2.0 X 10(-10) mol/cm2) for a film for med on pure cysteamine was determined by QCM measurements and compares remarkably well with monolayer coverage (1.9 x 10(-10) mol/cm2) predi cted by a model based on crystallographic data for C60. These experime nts demonstrate the utility of the QCM in characterizing and monitorin g the growth of fullerene SAMs. C60 SAMs formed on pure cysteamine yie ld strikingly different electrochemical responses than those formed on prelayers consisting of varying ratios of ethanethiol and cysteamine and previously reported monolayers of C60 on (aminopropyl)silanized ox ide surfaces. Although the C60 SAMs are stable under ambient condition s, the fullerenes may be desorbed from the surface through electrochem ical reduction of the films for extended periods of time (>10 min).