Characterization and reactivity of organic monolayers on gold and platinum surfaces
The focus of this study is to understand how the immobilization, dielectric, orientation, composition, coverage, and structure of self-assembled organic monolayers on metal surfaces affects the surface reactivities and properties of these films in order to facilitate the construction of desired films;Two model systems used: tiols at gold and aromatic acids at platinum. Both methyl-and carboxylic acid-terminated thiolate monolayers were formed at evaporated gold films by the self-assembly technique via the thiol moiety of thiols. The phenylcarboxylic acid and pyridylcarboxylic acid monolayers were formed at platinum electrodes cleaned electrochemically in 1 N H[subscript]2SO[subscript]4 aqueous solution;Several surface analysis technologies (including contact angle measurement, electrochemistry, ellipsometry, infrared reflection absorption spectroscopy (IRRAS), and x-ray photospectroscopy) have been used to study the formation, composition, structure, surface properties and reactivity of self-assembled organic monolayers on gold and platinum surfaces;IRRAS, contact angle measurements, and an electrochemistry methods were used to determine the surface pK[subscript] a of phenylcarboxylic acids and pyridylcarboxylic acids monolayers on platinum;These techniques were also used to determine the orientation of polymethylene chain axis and the carboxylic follow the structural evolution of the chains and end group of the thiolate monolayers during formation;In addition, IRRAS was used to asses the carboxylic acid group in terms of its possible existence as the non-hydrogen-bonded species, the hydrogen-bonded dimeric group, and the hydrogen-bonded polymeric group. The existence of these different forms of the end group were also followed as a function of coverage and as well as their influence a reactivity as a function of solution pH;IRRAS and contact angle measurements were used to calculate the rate constant of the esterification of carboxylic acid-terminated monolayers on gold.