title: How does the surface charge of ionic surfactant and cholesterol forming vesicles control rotational and translational motion of rhodamine 6G perchlorate (R6G ClO₄)?
abstract: The rotational dynamics and translational diffusion of a hydrophilic organic molecule, rhodamine 6G perchlorate (R6G ClO4) in small unilamellar vesicles formed by two different ionic surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), with cholesterol have been investigated using fluorescence spectroscopic methods. Moreover, in this article the formation of vesicle using anionic surfactant, SDS at different cholesterol-to-surfactant molar ratio (expressed by Q value (Q = [cholesterol]/[surfactant])) has also been reported. Visual observation, dynamic light scattering (DLS) study, turbidity measurement, steady state fluorescence anisotropy (r0) measurement, and eventually microscopic images reveal the formation of small unilamellar vesicles in aqueous solution. Also, in this study, an attempt has been made to observe whether the cationic probe molecule, rhodamine 6G (R6G) experiences similar or different microenvironment in cholesterol-SDS and cholesterol-CTAB assemblies with increase in cholesterol concentration. The influence of cholesterol on rotational and translational diffusion of R6G molecules has been investigated by monitoring UV-vis absorption, fluorescence, time-resolved fluorescence anisotropy, and finally fluorescence correlation spectroscopy (FCS) measurements. In cholesterol-SDS assemblies, due to the strong electrostatic attractive interaction between the negatively charged surface of vesicle and cationic R6G molecules, the rotational and diffusion motion of R6G becomes slower. However, in cholesterol-CTAB aggregates, the enhanced hydrophobicity and electrostatic repulsion induces the migration of R6G from vesicle bilayer to aqueous phase. The experimental observations suggest that the surface charge of vesicles has a stronger influence than the hydrophobicity of the vesicle bilayer on the rotational and diffusion motion of R6G molecules.
authors: Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, West Bengal, India.
authors: Surajit
authors: S
authors: Ghosh
authors: Arpita
authors: A
authors: Roy
authors: Debasis
authors: D
authors: Banik
authors: Niloy
authors: N
authors: Kundu
authors: Jagannath
authors: J
authors: Kuchlyan
authors: Anjali
authors: A
authors: Dhir
authors: Nilmoni
authors: N
authors: Sarkar
mesh_terms: D002784:Cholesterol / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D010316:Particle Size; D012235:Rhodamines / Q000737:chemistry*; D012399:Rotation; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D007477:Ions; D012235:Rhodamines; D013501:Surface-Active Agents; C026188:rhodamine 6G; D002784:Cholesterol