Assembly of dithiocarbamaten-anchored monolayers on gold surfaces in aqueous solutions

摘要

Dithiocarbamates (DTCs) can be formed by the in situ condensation of polar alkylamines with CS2, and assembled into dithiocarbamate-anchored monolayers (DAMs) on Au substrates in aqueous solutions. Primary and secondary amines can both be used to prepare DTCs, but have significant differences in their reactivities and product stabilities. Ultraviolet absorption spectroscopy provides a convenient method for monitoring in situ DTC formation as well as the formation of potential byproducts. The kinetics of DAM assembly on An substrates as measured by second harmonic generation (SHG) indicated first-order rate processes and saturation coverages similar to those of alkanethiols on Au. However, the rate of adsorption did not change with DTC concentration in a manner expected of Langmuir kinetics, and is attributed to the competitive adsorption of alkylammonium counterions to the freshly oxidized Au substrate. These analyses establish a practical range of conditions for preparing DAMs from polar amines using in situ DTC formation.