Electrofluorescence of dye-tagged sepiolite
| Autor: | G. W. Middleton, B. R. Jennings |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Fluorophore
Chemistry Light switch Transition dipole moment Analytical chemistry 020101 civil engineering 02 engineering and technology Fluorescence in the life sciences 010502 geochemistry & geophysics Polarization (waves) 01 natural sciences Ray Molecular physics Fluorescence 0201 civil engineering chemistry.chemical_compound Geochemistry and Petrology Surface charge 0105 earth and related environmental sciences |
| Zdroj: | Clay Minerals. 26:1-9 |
| ISSN: | 1471-8030 0009-8558 |
| DOI: | 10.1180/claymin.1991.026.1.01 |
| Popis: | A B S T R A C T: In electric fields, anisodiametric minerat particles in suspension orientate and align. When tagged with fluorescent molecules, the alignment is accompanied by changes in the intensities of the polarized components of the emitted fluorescence. By measuring these changes under specific experimental conditions, any non-random directional coincidence of the absorption and emission transition moments associated with the dye molecules can be evaluated and the spatial array of the dyes estimated. From such measurements, the binding of the optical brightening agent FBA1, a triazinylaminostilbene compound, to sepiolite has been studied. A fluorophore is an active fluorescent group which absorbs linearly polarized light of a suitable wavelength. The absorption is optimal when the polarization azimuth is parallel to the absorption transition moment (a-) of the group. Light of a longer wavelength is emitted polarized parallel to an emission transition moment (e-) which may not be coincident with d. The fluorescent beam is thus generally depolarized even when the fluorophore has been held stationary during the fluorescence interaction. The depolarization can be characterized by the measurement of four polarized components of fluorescence, Ff; where F = V or H for vertically and horizontally polarized incident light, respectively, and f = v or h for the similar polarization states of the emitted beam (Parker, 1968). Optical brighteners are fluorescent compounds which absorb radiation in the violet or ultra-violet spectral region, and emit their fluorescence within the visible range. They are added to paints, pigments, inks, colourants and cleansing agents. Occasionally, they supply spectral output at wavelengths where natural absorption may occur with other materials present. Their compatibility with the supplementary dyestuffs, or with fabrics and surfaces in the case of cleansing agents, is also of commercial importance. Colloidal particles may embrace fluorescent groups within their structure. Alternatively, owing to the surface charge generally associated with them, fluorescent dyes may be adsorbed or chemically bound to the particles. In materials where the arrangement of surface sites and the surface topography of the particles are favourable, the dye molecules may bind with a highly directional order relative to the particle morphology. In such examples, alignment of the relatively large colloidal particles in an external force field imposes a high degree of alignment on the active fluorophores and their transition moments. The changes in the four polarized components of fluorescent (Abe) on the application of the external force field can thus be used either as the basis of an electrofluorescent light switch (Jennings & Ridler, 1980), or as a means of estimating the average directions of the transition moments (~ and e-) relative to the colloid anisotropic geometry. |
| Databáze: | OpenAIRE |
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