Study of Diffusion of Organic Dyes in a Triblock Copolymer Micelle and Gel by Fluorescence Correlation Spectroscopy

Abstract

Fluorescence correlation spectroscopy (FCS) has been used to study translational diffusion of three fluorescent dyes in a micelle and a gel. It was demonstrated that a highly hydrophobic dye, DCM, remains confined to a particular micelle during the passage of the micellar aggregation through the confocal volume. As a result, DCM exhibits slow diffusion of the large micellar aggregate with a diffusion coefficient (D(t)) approximately 25 times slower compared with that of water. In contrast, a hydrophilic probe (C343 or C480) occasionally diffuses out of the micelle into bulk water and displays a large D(t) (twofold smaller in F127 and approximately six times smaller in the P123 micelle compared with that in bulk water). In a gel, diffusion of the individual micelles is completely arrested and hence, the autocorrelation in FCS arises solely from the diffusion of the dye in the gel. In this case, all the three dyes exhibit extremely slow diffusion (300, 45, and 20 times slower than that in water for DCM, C480, and C343 in F127 gel, respectively). In a P123 and F127 gel, diffusion of DCM is respectively, seven and 29 times slower compared with that of the ionic probe C343. The relatively small value of red-edge excitation shift (REES) of the emission maximum, suggests that DCM is confined within the core of the triblock copolymer micelles and gels. The hydrophilic probes (C343 or C480) exhibit fast diffusion in the micelles and gels. However, their REES is very different. The large REES of C480 suggests that it is distributed over a large region of the micelle, whereas the low REES of C343 indicates that it is located primarily in the peripheral corona region.

How does bile salt penetration affect the self-assembled architecture of pluronic P123 micelles? – light scattering and spectroscopic investigations

“…62 In this section, the interaction of P123 and different bile salts has been investigated through the fluorescence correlation spectroscopic technique. 77 In this study, we have also observed a lower diffusion coefficient (31.991 mm 2 S À1 ) for DCM in the P123 micelle (Table 4). In this study, our aim is to investigate the influence of bile salt on the core, corona and peripheral region of the P123 micelle.…”

“…62,77,78 Recently, our group has also reported the translational diffusion of R6G in vesicular systems. Now-a-days, the FCS technique is used extensively to investigate the diffusion of organic dyes and to study the aggregation behavior of the surfactants in non-aqueous and aqueous medium.…”

Single-Molecule Investigations of Morphology and Mass Transport Dynamics in Nanostructured Materials

“…These same measurements have since been employed in studies of nanoporous alumina (64), mesoporous silica particles (55,65,66), monoliths (67,68), films (43,(69)(70)(71)(72)(73), and thermotropic (74)(75)(76)(77)(78)(79)(80) and lyotropic (67,81,82) LCs. As a representative example, Zhong et al (65) studied the diffusion and adsorption of rhodamine 6G (R6G) molecules within C18-modifed silica particles incorporating 10-nm pores, under conditions that mimic reversed-phase liquid-chromatographic separations.…”

Probing Dynamic Heterogeneity in Nanoconfined Systems: The Femtosecond Excitation Wavelength Dependence and Fluorescence Correlation Spectroscopy

“…Using farfield microscopy, Moerner et al monitored the Brownian motion of a single dye molecule in a polyacrylamide gel [36]. Recently, many groups have used FCS to study the mobility and diffusion constants of fluorescent probes in different systems, including vesicles and membranes [37], colloidal particles [38] [45]. They used a non-covalent probe instead of a covalent one because the motion of a dye molecule covalently attached to a macromolecule is dominated by the superimposed motion of the macromolecule.…”

“…As a result, DCM reports slow diffusion of the large micellar aggregate with a diffusion coefficient (D t ¼ 12-14 mm 2 s À1 ) $25 times slower compared with water (D t ¼ 300 mm 2 s À1 ). 45 For C480 and C343 (hydrophilic probe), the D t values in the two micelles are found to be lower than those in water by a much small factor ($2-6-fold). The large value of D t in this case (and also for other probes in neutral micelles) may arise from the occasional escape of the dye from a particular micelle into bulk water during diffusion through the confocal volume.…”