Capillary zone electrophoresis of quantum dots dispersed in mixed micelles: New evidence of the concentration effect

CZE was applied to characterizing a nanoparticle/micellar system, in which CdSe nanoparticles dispersed in a mixture of non-ionic and ionic surfactants are introduced into a capillary to form the sample zone that migrates being sandwiched by the background electrolyte (BGE). Parameters that affect the migration of the surface-modified CdSe nanoparticles and conditions under which they are focused within the micellar zone (or released from it into bulk BGE) were explored, including the sample composition, sample plug length, and applied voltage. The observed migration behavior was analyzed within the framework of a concept of formation of a mixed pseudomicellar system, according to which a nanoparticle coated with an ionic surfactant is treated as a micelle-like entity. It was found out that the nanoparticles are subject to transformation that results in building-up a mixed pseudomicellar system (with regular micelles), with a consequence of exhibiting distinctive migration phenomena. Particularly observed and brought into focus is the event of focusing of the nanoparticles.