An attenuated total internal reflectance spectroscopy study of ET(30) at the free oil-water interface

Abstract

Visible attenuated total internal reflectance (ATR) spectroscopy has been used to measure the mean solvent microenvironment at free "oil"-water interfaces using the solvatochromic and acid-base properties of 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridino)phenoxide (ET(30)). From the wavelength maximum of the solvatochromic visible absorption band of ET(30), the effective interfacial dielectric constants of a range of oil-water interfaces have been determined to be ≈8. Titration of the interfacially located probe from high to low pH leads to the creation of a positive electrostatic surface potential which can be largely accounted for using simple Gouy-Chapman theory. Complete agreement, however, ..