Cation-Selective Color Sensors Composed of Ionophore−Phospholipid−Polydiacetylene Mixed Vesicles

Supramolecular assemblies of vesicles composed of ionophores and phospholipids embedded in a matrix of polymerized diacetylene [PDA] lipids are shown to undergo visible color changes in the presence of ions in solution. The blue-to-red color transitions of the vesicles are directly related to binding of the cations to the ionophores, and their association with the lipids. The system detects cations in submillimolar concentrations and demonstrates a significant ionic selectivity, in particular between the physiologically important ions Na+ and K+.