Controlled optical transition rates in nanodroplets

The time-resolved fluorescence measurements of 3,3′-diethyl-5,5′-dichloro-9-phenylthiacarbocyanine (DDPT) in bulk solvents and methanol-in-oil reverse micellar systems is presented which include nano-sized methanol droplets stabilized with anionic surfactant aerosol-OT (AOT) in n-heptane, at room temperature. Relative fluorescence intensities of DDPT increase with a factor of 16 in m/o reverse micelles in comparison to those in bulk methanol. The radiative and nonradiative rate constants decreases in methanol dispersions, indicating that internal motions of DDPT in the droplets is reduced due to strong electrostatic interactions between the positively charged DDPT and the negatively charged sulfonate head-groups of AOT.