Bolaform surfactants with polyoxometalate headgroups and their assembly into ultra-smallmonolayer membrane vesicles

摘要

Surfactants are indispensable in established technologies as detergents or emulsificationagents, and also in recent studies for controlling the growth of nanoparticles or for creatingnanocarriers. Although the properties of conventional, organic surfactants are thoroughlyexplored, strong interest persists in surfactants that possess unique features inaccessible forordinary systems. Here we present dipolar, bolaform surfactants with a head group comprising of 11 tungsten atoms. These novel compounds are characterized by an exceptionallylow critical self-organization concentration, which leads to monolayer vesicles with a diameter of only 15 nm, that is, substantially smaller than for any other system. The membraneof the vesicles is impermeable for water-soluble and oil-soluble guests. Control over releasekinetics, which can be followed via the quantitative fluorescence quenching of confinedfluorophores, is gained by means of pH adjustments.