Most of them are synthetic in nature, made up of two key components: the chromophore, responsible for the color, and the auxochrome
, that not only supplement the chromophore but also render the solubility of molecule in water and give enhanced affinity to attach the fiber .
Dyes must carry one or more functionalities giving the dye color, called chromophores, as well as an electron withdrawing or donating substituents that cause or intensify the color of the chromophores, called auxochrome
. The chromophore group can be a base for dye classification.
Flavonoids is a crystalline solid, a few (such as flavone glycosides) amorphous powder, color of flavonoids and molecular whether there cross conjugated system and auxochrome
group (- Oh, - OC[H.sub.3]) category, number and position of substitution on.
Generally, there are two important components in the dye molecules: chromophore component that is responsible for producing the color and the auxochrome
component which increases the affinity of the dye towards cellulose fibers [14, 43].
It is designed with the dye structure containing hard segment (chromophore) and soft segment (auxochrome
) to get higher dyeing fastness.
It contains azo (-N=N-) group as chromophore and sulfonate (- SO3H) group as auxochrome
. The color of Direct Red-28 dye alters in acidic and basic pH conditions from blue (at pH 2.0 -4.0) to red (at pH 12.0).