Stuttgart 2012 – scientific programme

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MO: Fachverband Molekülphysik

MO 12: Femtosecond Spectroscopy III

MO 12.4: Talk

Tuesday, March 13, 2012, 15:00–15:15, V38.03

Ultrafast solvation dynamics of ferulic acid at a micellar surface — •Mayra Stuhldreier¹, Michal Malicki¹, Hendrik Böhnke¹, Kathleen Oehlke², Karin Schwarz², and Friedrich Temps¹ — ¹Institute of Physical Chemistry, Christian-Albrechts-University Kiel, D-24118 Kiel — ²Department of Food Technology, Christian-Albrechts-University Kiel, D-24118 Kiel

The solvation dynamics of the anti-oxidant ferulic acid (FA) in buffered aqueous solution and in the palisade layer of CTAB micelles have been investigated by means of femtosecond time-resolved broadband fluorescence spectroscopy. Since the dipole moment of the molecules increases significantly upon electronic excitation, the solvent shell around the excited molecule in solution will rearrange to reach the energetically most favourable position according to the new dipole moment. This reorganization can be monitored by recording the emission spectra shortly after excitation, as they show a time-dependent red-shift corresponding to the stabilization of the solvated excited molecule. The time that is needed to reach the equilibrium structure of the solvated excited molecule and hence to complete the fluorescence shift is directly related to the mobility of the solvent molecules and therefore to the structure of the microenvironment of the solvated molecule. Compared with the dynamic red-shift of the emitted fluorescence in bulk water, a deceleration of the solvation dynamics of FA in micellar environment is clearly observable. This difference is attributed to the fast reorientation of the water molecules around the excited solutes, which is sterically hindered at the micellar surface.