A single spectroscopic probe for the determination of both the interfacial solvent properties and electrostatic surface potential of model lipid membranes

Abstract

2,6-Diphenyl-4-(2,4,6-triphenyl-1-pyridinio)phenoxide, ET(30), has been investigated in order to ascertain its suitability as a probe for both the effective interfacial dielectric constant (εeff) and the electrostatic surface potential (ψ0) of model lipid membranes in aqueous solution. This work establishes that the solvatochromic visible absorption band for ET(30) can be used to provide a good estimate of the εeff for cationic micelles. It is also shown that the acid–base dissociation of ET(30) can be utilized to obtain a quantitative measure of the ψ0 in the case of cationic micelles. There are problems and uncertainties associated with the use of ET(30) in aqueous solutions of other types of charged self-assembled surfactant aggregates, and these are discussed.