Optical properties of voltage sensitive hemicyanine dyes of variable hydrophobicity confined within surfactant micelles

• Published in: Materials research express Vol. 4; no. 11; pp. 115402 - 115408
• Main Authors: Naeem, Kashif, Naseem, Bushra, Shah, S S, Shah, Syed W H
• Format: Journal Article
• Language: English
• Published: IOP Publishing 15.11.2017
• Subjects: anionic surfactant; hemicyanine dyes; hydrophobic interaction; UV-visible absorption spectroscopy
• ISSN: 2053-1591; 2053-1591
• DOI: 10.1088/2053-1591/aa9798

The optical properties of amphiphilic hemicyanine dyes with variable hydrophobicity, confined within anionic micelles of sodium dodecylbenzenesulfonate (NaDDBS) have been studied by UV-visible absorption spectroscopy. The confinement constant, Kconf has been determined for each entrapped dye. The ion-pair formation between dye and surfactant causes a decline in electronic transition energy (ΔET) when dye alkyl chains are smaller due to stabilization of both the ground and excited state. ΔET values gradually increase with increase in dye hydrophobicity that hampers the electrostatic interaction with dialkylammonium moiety and consequently excited state stabilization is compromised. The average number of dye molecules trapped in a single micelle was also determined. The negative values of Gibbs free energy indicate that the dye entrapment within micelles is energetically favored. These findings have significance for developing functional materials with peculiar luminescent properties, especially for more effective probing of complex biological systems.