Photoionization of Ru(bpy)32+ ions in aqueous solutions containing sodium dodecyl sulfate. Influence of ion binding

Sodium dodecyl sulfate (SDS) augments the yield of biphotonic ionization of tris-2,2′-bipyridyl ruthenium(II) ions (3.75×10−5 mol dm−3) in aqueous solution at room temperature to different extents at two different concentration ranges: by a factor 4 at [SDS] just below the critical concentration for precipitation (4.5×10−4 mol dm−3) and by a factor 1.4 at [SDS] above the critical micellar concentration (8×10−3 mol dm−3). The augmentation of the photoionization yield is explained in terms of ion binding, i.e. electrostatic interaction between Ru(bpy)32+ ions and dodecyl sulfate ions which results in a partial charge neutralization with the consequence of a decrease in the ionization potential.