The Use of AOBH-DEHP Molecular Probe to Characterize BHDC Reverse Micelles Interfaces. Insights on the Interfacial Water Structure

Abstract

This work presents the use of the molecular probe: 3,6-bis(dimethylamino) acridinium bis-(2-ethylhexyl) phosphate salt, AOBH-DEHP. This probe is used to gain insights into the properties of the benzene/benzyl-n-hexadecyldimethylammonium chloride (BHDC)/water reverse micelles (RMs) interfaces. The techniques employed were absorption and emission spectroscopy in addition to the steady-state and, time-resolved fluorescence emission. For BHDC RMs without water addition, AOBH-DEHP can be used to determine the critical micellar concentration, CMC. Upon addition of water, we detect, at concentrations of BHDC lower < 1x10−2 M, a proton transfer process from the AOBH+ cation to the DEHP− anion producing AOB species. However, for [BHDC] > 10−2 M, when the RMs is completely formed this process is reverted because water molecules at the interface interact with the cationic polar head of BHDC through the oxygen non-bonding electron pair enhancing their hydrogen bond ability and acidity, hence it can easily transfer a proton to AOB species to form AOBH+.