Monolayer phase transitions due to ultraviolet irradiation of sequentially-adsorbed 9,10-anthracene dicarboxylic acid and octanethiol on Au(111)

Abstract

Abstract Sequential adsorption of 9,10-anthracenedicarboxylic acid (AnDCA) and 1-octanethiol create a multicomponent self-assembled monolayer on Au(111). The presence of AnDCA does not alter the size of close-packed octanethiol domains, but can be found in separate close-packed domains. Successive exposure to 375 nm ultraviolet radiation causes organizational rearrangement of the adsorbed components. Sections of close-packed up-right phase, ϕ , octanethiol with ( 3 × 3 )R30 ∘ packing and a density of 21.6\xa0A 2 /molecule or 4.63 molecules/nm 2 transition to a combination of lower density striped β and ( 5 × 2 ) phase with a density of 35.9\xa0A 2 /molecule or 2.79 molecules/nm 2 . Small domains of AnDCA exhibit a packing density of 0.90 molecules/nm 2 or 110\xa0A 2 /molecule after 20 minutes of UV exposure. After 60 minutes of UV exposure, AnDCA exhibits a similar packing density of 0.91 molecules/nm 2 or 110\xa0A 2 /molecule. Ultimately the domain boundaries become less defined as the β and ( 5 × 2 ) packing dominates the self-assembled monolayer, and adjacent areas of longer-range ordered hydrogen-bonded regions of AnDCA are observed.