Ultrafast torsional dynamics in nanoconfined water pool: Comparison between neutral and charged reverse micelles

Abstract

Abstract Photophysical properties and the ultrafast excited state torsional dynamics of an amyloid fibril sensing dye, Thioflavin-T, have been investigated in Triton X-100 reverse micelle as a function of water content. This study has been undertaken to comprehend the effect of interfacial charge on the ultrafast torsional dynamics of Thioflavin-T in nanoconfined reverse micellar system. The emission intensity and the fluorescence lifetime of Thioflavin-T increases considerably in the nonionic reverse micellar system as compared to bulk water indicating a strong confinement effect on the photophysical behavior of the probe. The photophysical parameters of Thioflavin-T in Triton X-100 reverse micelle is found to be almost invariant with the increasing water content, which is in sharp contrast to its behavior in ionic reverse micelles (Journal of Physical Chemistry 113 (2009) 8532, Chemical Communication 47 (2011) 6912). This behavior has been rationalized on the basis of the differences in the localization sites of the probe in the nonionic and ionic reverse micelles. Photophysical properties of Thioflavin-T in triethyleneglycol monomethyl ether, which mimic the interior of the Triton X-100 reverse micelle, at different water content also confirms the site of localization of the probe in the nonionic reverse micelle. Present result in combination with that reported in ionic reverse micelles suggest that the reaction dynamics of the probe in the nanoconfined water pools of reverse micelle are strongly influenced by interfacial charge, which in fact control the location of the probe in the reverse micellar systems.