Quenching of pyrene fluorescence by cesium ions in micellar systems. Protection by surface-active crown ethers

Cesium chloride is found to quench the first excited singlet state of pyrene with a rate constant of 9.7 × 10⁷ M^-1 s^-1 in aqueous solution. When pyrene is sequestered in micelles of a surface-active crown ether, nonionic Brij 35 micelles, or anionic SDS micelles the quenching efficiency depends critically upon the nature of the aggregate. Although cesium ions bind to the micelles of the crown ether, the pyrene singlet state is protected from the quencher in this system. Similar results are obtained for the quenching of the surfactant probe 6-indole-11. The quenching of the pyrene fluorescence was found to occur via heavy atom induced intersystem crossing to the triplet state.