Fluorescence Analysis of Single and Mixed Micelle Systems of SDS and DTAB

Abstract

Structural features of the single and mixed micellar systems of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) were characterized using the fluorescence probe 6-propionyl-2-(dimethylamino)naphthalene (Prodan). In particular, our investigations capitalized on the spectral sensitivity of Prodan to its environment as well as the extensive solubility of Prodan in solvents of varying polarity and/or hydrophobicity to effectively use a three-mode factor analysis technique to resolve the coincident emission from Prodan in multiple microenvironments of single and mixed micelle systems. Our investigations reveal parameters of Prodan fluorescence that reflect the relative polarities of the surfaces of SDS and DTAB micellar cores, the permeability of the SDS micelle interface, and the heterogeneity of SDS−DTAB mixed micellar systems. In particular, we observe a strong affinity of Prodan for both SDS and DTAB micelles at the water−surfactant interface with the emission λmax of Prodan consistent with greater water accessibility in the SDS interfacial region. Reduction in SDS head-group repulsion upon the addition of both an alkali metal series of counterions (Li+ → Na+ → K+) and a tetrasubstituted ammonium series of counterions (NH4 + → N(CH3)4 + → N(CH3CH2)4 + → N(CH3CH2CH2CH2)4 +) appears to induce a more nonpolar environment for Prodan. Each one-phase and two-phase region of the dilute aqueous binary SDS−DTAB pseudoternary diagram is identified by distinct Prodan λmax values. Evidence is presented for the presence of SDS−DTAB mixed micelle systems.

Changes in Asphaltene Microenvironments Evidenced by Fluorescence Solvatochromism

“…Karukstis et al 45 proposed the use of PRODAN as a novel and powerful probe to study the presence of different microenvironments in aqueous and nonaqueous solutions. The structure of PRODAN is presented in Fig.…”

Univalent salts as modifiers in micellar capillary electrophoresis

“…These changes can include variations in both the size and shape of the micelle, as well as variations in their chemical properties. Fluorescence investigations using a variety of probes have shown that the interiors of surfactant micelles display increased hydrophobic character in the presence of salt concentrations as low as 5 mM [17][18][19]. Previous work in our laboratory has indicated that the addition of small amounts of NaCl to BGEs containing SDS can have a significant impact on the separation of complex mixtures [20].…”

Submicellar aggregates in aqueous sodium dodecyl sulphate solutions: Investigations by dynamic light scattering and water penetration through porous media

“…The formation of mixed micelles for aqueous mixtures of C12TAB and SDS is discussed in various reports [31][32][33][34][35][36][37]. A strong electrostatic interaction between anionic SDS and cationic DTAB leads to formation of spherical mixed micelles at dilute conditions and equal molar ratios, which transform to stable large vesicles at specific molar ratio of surfactant components [37].…”