ORIENTATION OF SURFACTANTS ADSORBED ON A HYDROPHOBIC SURFACE

While it is generally accepted that surfactants adsorb at the interfac e between water and a hydrophobic surface with their nonpolar parts in contact with the hydrophobic surface and their polar regions oriented toward the water, this orientation has never been experimentally veri fied. In this paper, infrared-visible sum-frequency spectroscopy is us ed to demonstrate that dodecanol adsorbs from aqueous solution onto a hydrophobic surface (a monolayer of octadecanethiol on gold) with the terminal methyl group of the dodecanol oriented toward the hydrophobic surface.