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Title: An investigation into the enhancement of fluorescence of disazo pigments by their synthesis in micellar solutions
Author: Hepburn, James
ISNI:       0000 0001 3553 8941
Awarding Body: University of Strathclyde, Pure and Applied Chemistry
Current Institution: University of Strathclyde
Date of Award: 2007
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The fluorescence of a series of commercially important yellow disazo pigments have been investigated with a view to enhancing fluorescence in the solid state. Solution absorption and fluorescence measurements in 1,2,4-trichloroben2;ene for some of the pigments was hampered by poor solubility. A comparison of the fluorescence intensities - normalised with respect to the amount of light absorbed - showed PY63 as being the most fluorescent in solution followed by PY12; PY14 and PY13. Fluorescence of the pigments in the solid state (as printed inks and aqueous dispersion~) showed that the relative intensities remained largely the same except that PY12 was found to be more fluorescent than PY63. The calculated absorption maxima by ZINDO/S and PPP-MO methods using the crystal structures showed good agreement with solution measurements. Comparison ofthe crystal structures of the pigments with fluorescence in the solid state showed that fluorescence correlates well with intermolecular stacking distances. It was also shown, however, that other distances, both intramolecular and interatomic, exhibit a similar trend and that the fluorescence intensities in the solid state may be incidental to, and not necessarily dependent on, the intermolecular stacking distances. It was observed that synthesis of the diarylides in micellar solutions of an amine surfactant, N,N'-dimethyldodecylamirie, brought about· an enhancement of fluorescence. of the pigments as inks printed on paper. This increase in fluorescence intensity was accompanied by an increase in crystallinity and particle size as evidenced -by powder x-ray diffraction, B.E.T. surface area and T.E.M. measurements. An investigation into the effect of pigment crystallinity on fluorescence by preparation of two model pigments, Pigments Yellow 12 and 14, at various stages of crystallinity, showed that even drastic changes in crystallinity had little effect on the fluorescence intensity. .It was found that particle size had much more of an influence on the fluort;::scence-.of the pigment. It was also found that the surfactant used was more effective at increasing fluorescence for PY12 than for PY14 and this was thought to be due to the different surface characteristics of the pigments as a consequence of their different crystal structures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available