Effects of Subzero Temperatures on Fluorescent Probes Sequestered within Aerosol-OT Reverse Micelles

We report on the effects of temperature (+30 to −100 °C) and water loading on the steady-state fluorescence from four fluorescent probe molecules when they are sequestered within the interior of sodium bis(2-ethyl-1-hexyl) sulfosuccinate (Aerosol OT, AOT) reverse micelles. Each probe locates itself to different average microenvironments within the reverse micelle, and these individual microenvironments behave differently to changes in the molar ratio of water-to-AOT ( R ) and temperature. Changes in probe steady-state fluorescence emission spectra or fluorescence anisotropy indicate that “freezing” occurs within the water pool at temperatures between −10 and −60 °C. The lowest freezing points are generally observed at the lowest R values.