A new surfactant-fluorescence probe for detecting shape transitions in self-assembled systems

A surfactant type fluorescence probe for detecting micellar growth

“…12-DAN-ADA was synthesized from 12-aminolauric acid and dansyl chloride according to the reported method [27]. Sodium dodecyl sulfate (SDS) was purchased from Acros and was used directly without further purification.…”

“…At the beginning where no salt was added, the micelles are ellipsoidal [29] which allows the anisotropy of 0.012 for 12-DAN-ADA; whereas the anisotropy increases about 1.5 times as the micelles become long worms of 4240 Å. One should notice that the fluorescence anisotropy values for the worm-like micelles are actually much lower if they are compared with those for vesicles [27], which indicates that the molecular packing in micelles is much looser than that in vesicles. This suggests two possibilities: (1) the 12-DAN-ADA molecule is not sensitive enough in detecting the growth of SDS micelles; (2) the quantity of the free 12-DAN-ADA molecules in the bulk solution which in equilibrium with the SDS micelles is rather large, so that signals from these free 12-DAN-ADA molecules mask the real response of those tethered in the SDS micelles.…”

“…The experimental results revealed that the emission maximum and the fluorescence anisotropy vary significantly as a transition between micelles and 0021-9797/$ -see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2010.10.037 vesicles in catanionic surfactant systems occurs, whereas the characteristic I 1 /I 3 value of pyrene, or the anisotropy of DPH hardly give significant responsiveness [27]. This extremely high sensitivity may be related to the deep location of the fluorescent group of our FLA molecules in the self-assemblies.…”

“…In our design, the fluorescent group, dansyl, was linked to the tail of an anionic surfactant (12-aminolauric acid), which is abbreviated as 12-DAN-ADA in the following text [27]. We were surprised to find that such a FLA is much more sensitive in detecting the micelle-vesicle transition than other commonly used fluorescence probes, such as pyrene and DPH [27]. The experimental results revealed that the emission maximum and the fluorescence anisotropy vary significantly as a transition between micelles and 0021-9797/$ -see front matter Ó 2010 Elsevier Inc. All rights reserved.…”

Making sense of luminescence from GRAS optical probes

“…Intensity increases of $100-fold compared to solution have been observed in microorganized environments such as micelles, liposomes, or inclusion complexes [33,34]. Steady state and time resolved luminescence techniques can thus be used to investigate a wide variety of colloidal characteristics such as droplet shape, size, structure and microviscosity [35][36][37].…”