pH-Dependent Coloring of Combination Effect Pigments with Anthocyanins from Brassica oleracea var. capitata F. rubra

Abstract

Mica-titania pearlescent pigments (MTs) were previously coated with organic molecules to obtain combination pigments (CPs) for achieving certain improvements or functionalities. Anthocyanins (ACNs) are molecules that can be extracted from natural resources and exhibit color changes via pH modifications of the enclosing medium. The purpose of the study was to produce a new series of CPs by depositing ACNs on MTs at different pH values, to observe the changes in color, and to associate these changes to thermogravimetrically determined deposition efficiencies in light of spectral differences. The extraction and deposition methods were based on aqueous chemistry and were straightforward. The ACN deposition generally increased with increasing pH and correlated with the consistency between the charges of the MT surfaces and the dominant ACN species at a specific pH value. The fluorescence of the CPs was inversely correlated with the deposition quantities invoking the possibility of a quenching effect.