Photophysical Investigation of Styryl Dye in Ionic Liquid Micelles: Role of Micellar Polarity and Viscosity.

Authors

Ritika Sharma, Kanika Guleria, Debabrata Seth, Rabindranath Jana

Published in

The journal of physical chemistry. B. Jun 10, 2025. Epub Jun 10, 2025.

Abstract

In the present work, we investigate the influence of micellar polarity and viscosity induced by ionic liquids (ILs) on the photophysical properties of the styryl dye 4-[4-(dimethylamino)styryl]pyridine (DMASP). Using combined absorption, fluorescence emission, time-resolved fluorescence spectroscopy, and density functional theory (DFT) calculations, we demonstrate that the photophysical behavior of DMASP is strongly affected by the polarity and viscosity of the IL environment. Temperature-dependent variations in the absorption and emission spectra further indicate that the photophysical properties of DMASP are strongly influenced by the viscosity of the micellar structures. Partition coefficient measurements reveal a higher solubility of DMASP in 1-butyl-3-methylimidazolium octylsulfate ([BMIM][OS]) compared to 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]). The longer average lifetime of DMASP in [BMIM][OS] indicates the higher viscosity and greater hydrophobic micellar core of [BMIM][OS] relative to [BMIM][BF₄]. DFT calculations further support this observation, revealing greater stability of the [BMIM][OS]-DMASP complex based on binding energy analysis. Collectively, these results establish DMASP as a sensitive photophysical probe for assessing the structural features of complex biological microenvironments.

PMID:
40493807
Bibliographic data and abstract were imported from PubMed on 11 Jun 2025.

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