Structural study of self-assembled monolayer of 22-mercapto-1-docosanoic acid on silver (111)

22-mercapto-1-docosanoic acid spontaneously forms a compact self-assembled (SA) monolayer on the silver (111) surface. Surface X-ray diffraction shows that the in-plane structure of this monolayer is close-packed hexagonal with an interchain spacing of approximately 4.77 Å and a chain tilt angle of 0 ± 5° from the surface normal. The monolayer is incommensurate with the substrate and exhibits rotational epitaxy. The rotational epitaxy angle also depends monotonically on the interchain spacing and varies from 0 to ±10° with respect to the Ag(211) direction as the spacing varies from 4.80 to 4.73 Å. Based on comparisons with other structures we conclude that the S atom is bound to the surface.