Locations of methanol in methanol-containing AOT reverse micelles revealed by photophysics of IR125

Methanol has appeared in many publications reporting reverse micelles (RMs) formation, but it remains debate whether it can be effectively encapsulated by surfactant AOT to form RMs. In this work, we investigated the formation of methanol-containing AOT RMs in n-heptane solvents by using IR125 as a probe. We studied the photophysics of IR125 in methanol/AOT/n-heptane RMs at different loading methanol content (w′0w′0: w′0=[methanol]/[AOT]w′0=[methanol]/[AOT]) by means of steady-state absorption and fluorescence spectroscopies as well as time-resolved fluorescence spectroscopy. We obtained the absorption and fluorescence maxima, fluorescence lifetimes, and reorientation times of IR125 in methanol/AOT/n-heptane RMs at different w′0w′0. We found that the methanol can be effectively encapsulated by AOT in n-heptane solvents to form stable methanol/AOT/n-heptane RMs and the size of methanol/AOT/n-heptane RMs maintains constant with the increase of w′0w′0.

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► The formation of CH3OH/AOT/n-heptane RMs was explored using IR125 as a probe.
► The photophysics of IR125 in CH3OH/AOT/n-heptane RMs at different w′0w′0 was studied.
► The lifetime of IR125 in CH3OH/AOT/n-heptane RMs decreases upon increasing w′0w′0.
► The size of CH3OH/AOT/n-heptane RMs maintains constant as a function of w′0w′0.