Self-assembled monolayers on gold generated from aliphatic dithiocarboxylic acids

Self-assembled monolayers (SAMs) were prepared by the adsorption of aliphatic dithiocarboxylic acids (ADTCAs) onto the surface of gold. These new SAMs were characterized by optical ellipsometry, contact angle goniometry, and polarization modulation infrared reflection absorption spectroscopy. The data are consistent with a model in which the ADTCAs generate well-packed and highly oriented monolayer films. Comparison of the wettabilities of these new SAMs to those prepared from normal alkanethiols reveals an unusually large "odd-even" effect when hexadecane is used as the contacting liquid. The origin of this effect is attributed to chelation of the ADTCA headgroup to the surface of gold.