Structures of Self-Assembled Monolayer Films of Organosulfur Compounds Adsorbed on Gold Single Crystals: Electron Diffraction Studies

摘要

Transmission electron microscopy and diffraction have been used to study the packing arrangements of docosyl thiol (RSH), didocosyl sulfide (RSR), and didocosyl disulfide (RSSR) on gold single crystal foils. The specimens include gold films in (100) and (111) orientations. Docosyl thiol and didocosyl disulfide adsorbed on (111) faces assemble in coincidence lattice structures yielding hexagonal overlayers c(7 x 7) in which the short interchain distance indicates freely rotating methylene chains. On a (100) surface both alkyl groups exhibit an in-plane structure consisting of a base-centered square array in which the interchain distance implies a hindered chain movement. We have presented evidence that substrate crystallography does control the packing of monolayer alkyl sulfides adsorbed from the solution phase.