Full Length ArticleUltrafast excited state deactivation channel of thioflavin T adsorbed on SDS micelle: A combined femtosecond fluorescence and transient absorption study

•Dual TICT state of thioflavin T has been verified in the Stern layer of SDS micelle.•LE-TICT1 and LE-TICT2, both the rotation found to be hindered in micelle.•Rotation of dimethylaniline moiety of ThT is controlled by medium viscosity.•Rotation of dimethylamino group in the excited state possesses an intrinsic potential energy barrier.

In this contribution, we have presented the dynamics of molecular rotor dye thioflavin T (ThT) in Stern layer of sodium dodecyl sulfate (SDS) micelle using femtosecond fluorescence up-conversion and broadband transient absorption spectroscopy. ThT being a positively charged molecule is expected to remain in the Stern layer of micelle due to columbic attraction with the negatively charged surfactant head groups. The restriction imposed by the environment slows down the rotation of molecular fragments, which increases its quantum yield ∼8 times compared to pure water. We have confirmed the dual relaxation channel of ThT (LE → TICT1 and LE → TICT2) and found that the lifetime of the three states namely LE, TICT1 and TICT2 are 0.5, 3.1 and 15.7 ps respectively in 40 mM SDS.

Graphical abstractDownload high-res image (175KB)Download full-size image