Monitoring Supramolecular Self-Assembly using Time-Resolved Fluorescence Spectroscopy

Time-resolved fluorescence spectroscopy is used to observe subtleties in supramolecular structure during the self-assembly of polymers in solution. Lifetime distribution analysis of the fluorescence decay kinetics of the solvent-sensitive fluorescent probe 1-anilino-8-naphthalene sulfonic acid associated with the di-block copolymer poly(2-vinylpyridine)41–poly(ethylene oxide)204 (P2VP-PEO) as it self-assembles enabled identification of three microdomains, distinguishable on the basis of micropolarity. These microdomains can be assigned to different supramolecular substructures: the micelle corona (high polarity), the micelle core and the P2VP globule (both low polarity), and the core–corona interface and the globule–PEO junction (both intermediate polarity). Changes in the relative population distributions of these sub-structures as a function of P2VP-PEO pinpoint the onset of micellization corresponding to the critical micelle concentration (CMC) of the copolymer, but indicate significant variation in supramolecular structure, including micelle formation, well below the CMC. This suggests that supramolecular self-assembly in polymeric systems has characteristics of a second order phase transition.

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Characterization of Plasma-Modified Fluoropolymer Surfaces Using Steady-State and Time-Resolved Fluorescence Spectroscopy

Applied Spectroscopy ◽

10.1366/0003702944924826 ◽

1994 ◽

Vol 48 (5) ◽

pp. 630-637 ◽

Cited By ~ 3

Author(s):

Ming Li ◽

Michaeleen L. Pacholski ◽

Frank V. Bright

Keyword(s):

Steady State ◽

Fluorescence Spectroscopy ◽

Sulfonyl Chloride ◽

Sodium Dodecylsulfate ◽

Covalent Immobilization ◽

Ambient Conditions ◽

Time Resolved Fluorescence ◽

Decay Kinetics ◽

Time Resolved

Poly(hexafluoropropylene-co-tetrafluoroethylene) (FEP) has been widely used in biotechnology because of its unique surface properties and biocompatibility. Recent work from our group has shown that plasma discharge-modified FEP can be used as the substratum for development of a very stable immunosensor. This result has prompted us to study further this new surface under ambient conditions. In this paper, we report on the covalent immobilization of a pyrene residue (-Py) onto FEP-APS (FEP-aminopropyl silane) surfaces and the characterization of FEP-APS-Py using steady-state and time-resolved fluorescence spectroscopy. Among the immobilization schemes tested, we found that the covalent coupling of pyrene-sulfonyl chloride to FEP-APS is the easiest and yields the most photostable FEP-APS-Py derivative. Steady-state emission spectra of FEP-APS-Py in contact with H2O, β-cyclodextrin (β-CD), and sodium dodecylsulfate (SDS) aqueous solutions differ considerably from those of Py-SO3 in solution. Time-resolved fluorescence spectroscopy of FEP-APS-Py demonstrates that the decay kinetics are strongly affected by the presence of ionic quenchers and molecular oxygen, as well as β-CD and SDS. The results are consistent with the suggestion that the APS-Py moiety undergoes a slow time-dependent reconfiguration at the FEP/APS interface.

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