How the type of interface can alter the behavior of an aprotic ionic liquid-water mixture entrapped in different reverse micelles: An exploratory study using an enzymatic reaction as a sensor

Abstract

In this work, we decipher how an aprotic Ionic Liquid (IL)-water mixture structure can be altered upon confinement in different reverse micelles (RMs) media. Thus, the effect of the polar pseudophase composition in RMs formulated by anionic or cationic surfactants was monitored using the well-known enzymatic hydrolysis reaction of 1-naphthyl phosphate (1-NP) with alkaline phosphatase (AP). Water and an aqueous mixture formed by the IL 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4C1im, TfO]) as the polar pseudophase were used. As surfactants, the anionic sodium diethylhexyl sulfosuccinate (AOT) and the cationic benzyl-n-hexadecyldimethylammonium chloride (BHDC) were employed. The effect of the nanoconfinement, as well as the impact of the polar solvent content and the type of interface, were analyzed by determining the Michaelis-Menten parameters. In homogeneous media, the catalytic efficiency of the hydrolysis reaction is strongly dependent on the amount of water in the mixtures evaluated. In RMs the catalytic efficiency is dependent on both, the polar content and the type of surfactant used. Thus, by using a model reaction with an enzyme entrapped inside different RMs it was possible to learn that an aprotic IL:water mixture can be strongly disturbed when it is confined in a cationic or anionic RMs. This particular behavior can produce a deep impact on the technological applications of these organized systems.