EXAFS STUDY OF PROBE MOLECULES IN MICELLAR SOLUTIONS

EXAFS and XANES measurements were systematically performed on various systems containing brominated hydrocarbons and remarkable differences were found in the bromine K-edge spectra recorded in polar or nonpolar media. This suggests that molecules with suitable probe atoms can be used to monitor the polarity of the medium in which they are buried and, consequently, provide information about the interactions between probe atoms and several systems such as micelles, macromolecules, membranes, solvent molecules, and host molecules in inclusion compounds. Structural features of such systems can be inferred. Brominated hydrocarbons in different solvents and in aqueous micellar solutions of rubidium deoxycholate were investigated. Here we present EXAFS and Fourier transform calculated functions that are in satisfactory agreement with the observed ones. Plausible and reasonable models are proposed. In particular, potential energy calculations of the interaction model between the rubidium deoxycholate micellar aggregate and a brominated hydrocarbon agree with the EXAFS data and indirectly confirm the helical structure previously verified for this salt. The simultaneous study of two probe atoms on the same sample could allow the detection of possible structural changes of the micelle caused by the probe molecule.