Light stability of pyrazolotriazole azamethine dyes at oil/aqueous interfaces

Chetan K. Parmar, Garry Rumbles, Christopher J. Winscom

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Film and dispersion coatings of two pyrazolotriazole azamethine (PT) dyes are used to study the effect of increasing the surface-area-to-volume (SA : V) ratio of the oil/aqueous (solvent/gelatin) interface on non-oxidative and oxidative fade characteristics. High concentration solutions of the dyes in a poly(vinyl acetate)-dicyclohexylphthalate mixture as solvent are coated on glass substrates with a gelatin overcoat to produce thin film coatings and are also dispersed in gelatin to create "oil-in-gelatin" dispersion coatings. It is calculated that the dispersion coatings possess a SA : V ratio of approximately 20× greater than the film coatings. In non-oxidative fade conditions both the film and dispersion samples possess similar quantum yields of fade, implying that the presence of a solvent/gelatin interface does not significantly affect any electron transfer fade mechanisms. However, in oxidative fade conditions increasing the SA : V ratio of the interface by 20× leads to an increase in the quantum yield of fade of only a factor of 1.5-2. This disproportionate increase in the fade kinetics in dispersion coatings is explained by a kinetic scheme modelling oxygen diffusion through the coatings. It shows that the rate determining step for dye fade starts to become the diffusion of oxygen through the air/gelatin interface, and explains why changes in the SA : V ratio are not fully transferred to the quantum yield of fade.

Original languageEnglish
Pages (from-to)1815-1823
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume7
Issue number8
DOIs
Publication statusPublished - Apr 21 2005

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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