A comparative photophysical investigation of styryl dye in cationic and anionic miceller environments

In the present study, we examine the impact of micellization by ionic surfactants on the photophysical properties of a styryl dye, 4-[4(dimethylamino)styryl]pyridine (DMASP), through steady-state absorption, fluorescence emission, and time-resolved fluorescence emission measurements and DFT studies. The spectroscopic results reveal that the photophysical behavior of DMASP is significantly influence by the charge, structure of the surfactant head group, and length of the alkyl chain of the surfactants. The binding constant and partition coefficient values indicate a more favorable interaction of DMASP with cationic surfactant Cetyltrimethylammonium bromide (CTAB) compare to the anionic surfactant Sodium dodecyl sulfate (SDS). Moreover, the higher average decay time of DMASP in CTAB is attributed to the increased viscosity and more hydrophobic core of the CTAB micelle, compared to SDS micelle. DFT studies further support the greater stability of the DMASP-CTAB complex over the DMASP-SDS complex based on by binding energy calculation. These finding demonstrate that DMASP is highly sensitive to the micellar environment, suggesting its potential as a useful probe to understand the structure of different biological microenvironments.