Self-Assembled Monolayers of Semifluorinated Alkaneselenolates on Noble Metal Substrates

Self-assembled monolayers (SAMs) formed from semifluorinated dialkyldiselenol (CF3(CF2)5(CH2)2Se−)2 (F6H2SeSeH2F6) on polycrystalline Au(111) and Ag(111) were characterized by high-resolution X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, near edge X-ray absorption fine structure spectroscopy, scanning tunneling microscopy, and contact angle measurements. The Se−Se linkage of F6H2SeSeH2F6 was found to be cleaved upon the adsorption, followed by the formation of selenolate−metal bond. The resulting F6H2Se SAMs are well-ordered, densely packed, and contamination-free. The packing density of these films is governed by the bulky fluorocarbon part, which exhibits the expected helical conformation. A noncommensurate hexagonal arrangement of the F6H2Se molecules with an average nearest-neighbor spacing of about 5.8 ± 0.2 Å, close to the van der Waals diameter the fluorocarbon chain, was observed on Au(111). The orientation of the fluorocarbon chains in the F6H2Se SAMs does not depend on the substratethe average tilt angle of these moieties was estimated to be about 21−22° on both Au and Ag.