We have enhanced the stability of some derivatives of a flavylium dye, a model compound of a natural anthocyanin dye, by incorporating them between the interlayer of a clay mineral, montmorillonite K10. The incorporation procedure is simply mixing the solution of the flavylium dyes with the clay powder. The resulting colored powder shows excellent stability under increased temperature (up to 353 K) , alkaline environment (pH 9) , and visible light irradiation, compared to the original flavylium dyes. This material can be a candidate for an environmentally friendly coloring material.

UV-Vis spectra of FV/BN with different amounts of FV. Loading amounts of FV were a 0.01, b 0.03, c 0.12, d 0.25, e 0.50, f 0.75, g 1.00 and h 1.25 mmol/g, respectively. The absorbance was normalized at respective λmax. Fluorescence emission spectra of A FV aqueous solution 1.0 10 4 M and B FV/BN samples. The amounts of FV loading are a 0.01, b 0.03, c 0.12, d 0.25, e 0.50 mmol/g, respectively. Excitation light was 470 nm.