Probing the location of methanol in methanol/AOT/n-heptane system: true microemulsion or bi-continuous medium?

Whether methanol can be effectively encapsulated within a reverse micellar core to form a true microemulsion is still a matter of debate. Thus, in this contribution, we have reported the modified photophysics of a potential chloride channel blocker 9-methyl anthroate (9-MA) in methanol/AOT/n-heptane reverse micelles and methanol/n-heptane binary mixture in order to assess the location of methanol by means of steady-state and time-resolved fluorescence spectroscopic techniques. By comparing the striking similarity between the photophysics of the probe in the methanol/AOT/n-heptane system and in the methanol/n-heptane binary mixture, we conclude that methanol does not form a true microemulsion but rather remains dissolved in the bulk nonpolar phase forming a bi-continuous medium owing to an appreciable mutual solubility between n-heptane and methanol.