Spectral study of dye-surfactant interactions in relation to dye indicator structures

Abstract

Anionic azo dyes with structural variations such as V-acid, <i>p</i>-nitrophenyl-, <i>p</i>-chlorophenyl-, <i>p-</i> sulphonicphenyl-, <i>p</i>-sulphonic- and <i>m</i>-sulphonic- salicylic acids have been used to study the structural effects on the behaviour of anionic and cationic surfactants. The substituents – NO₂and - SO₃H, make dyes more anionic and hence the system even with cationic surfactants behaves as an anionic one promoting micellisation and solubilisation with increasing light intensity. However, with electropositive hyperconjugative - CH₃ group, anionic character is decreased with decrease in absorbance intensity.