Formation of an Ordered Self-Assembled Monolayer of Docosaneselenol on Gold(111). Structure by Surface X-ray Diffraction

Docosaneselenol in solution spontaneously forms an ordered (self-assembled (SA)) monolayer on the gold(111) surface. The contact wetting angle of hexadecane (53-55°) on the SA monolayer coated Au surface is consistent with a surface exposing methyl groups which are at the end of the C22 chains. The in-plane structure of this SA monolayer was probed by surface X-ray diffraction. The SA monolayer forms an incommensurate structure with an oblique unit cell with a = 5.204 Å, b = 4.897 Å, and γ = 120°. The [formula omitted] axis is along the Au [202] direction. The correlation length obtained from the radial scan was approximately 60 Å. The tilt angle measured from the surface normal was 15° with the chains tilted along the Au [202] direction (i.e. R30°). The oblique structure of the unit cell represents a distorted hexagonal close packed lattice. © 1992, American Chemical Society. All rights reserved.