Adsorption properties and stability of dihexadecyl phosphate vesicles

Abstract

The adsorption of the photochemical sensitizer tris(2,2'-bipyridine)ruthenium(II) on dihexadecylphosphate vesicles has been determined as a function of the pH and ionic strength of the dispersing medium. The adsorption density is a maximum at pH 7.5 ± 0.5 and with minimum ionic strength(pH adjusted by adding NaOH). The stability of the vesicles with respect to flocculation, in the presence of adsorbed sensitizer, is increased when the pH is raised from 3.3 to 7.5. The presence of an amine buffer at 5 x 10^-2 at pH 7.8 reduces the adsorption density by more than 90%. The relevance of these results to the interpretation of photochemistry experiments (in conjunction with photochemical hydrogen production from water) is discussed.