Monitoring of Dissolving Processes of Amphipathic Molecules from Aqueous Surface by Laser-Induced Two-Photon Ionization

Laser two-photon ionization technique has been applied to monitor dissolving processes of probe molecules from solution surfaces. The time courses of the photoionization charge decay were measured by changing the properties of the bulk phase after the addition of the amphipathic molecules. The dissolving rate of pyrenebutyric acid, aminopyrene and pyrenesulfonic acid was strongly depended on pH in the bulk solution. The dissociation equilibrium of the conjugated acid-base system governed the solubility of the amphipathic molecules. Effects of surfactants were also observed in the dissolving process of pyrenedecanoic acid.