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The aim of this study is the improvement of the photostability of several natural anionic dyes, carmine (CM), carthamus yellow (CY), and annatto dye (ANA), by complexation with hydrotalcite. The composite of the dyes and hydrotalcite is prepared by the coprecipitation method. CM is successfully intercalated in the hydrotalcite layer when the amount of introduced CM is large. The photostability of CM in CM/HT composites is superior to the CM adsorbed on silica surface. The effect of the stability enhancement is larger when the amount of introduced CM exceeds 0.23 g/g-host, or when the layer charge density of the hydrotalcite is larger. CY is also stabilized by complexation with hydrotalcite, whereas ANA is not stabilized by complexation with hydrotalcite. The photostability of an anionic natural dye can be improved by intercalation into the hydrotalcite layer, if the dye has a hydrophilic nature and a rather planar structure. The intercalated dye is stabilized by the protection from the attack of the atmospheric oxygen. In addition, contribution of the electrostatic interaction between the positively charged hydrotalcite layer and the intercalated anionic dye is also proposed.

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Super ionic conductor Li3InBr6 (σ=10−3Scm−1 at 297 K) due to lithium ions was synthesized and characterized by temperature dependence of the 7Li NMR T1. The substitution effect of the cation and the temperature behavior of T1 suggested that the high ionic conductivity resulted from the considerably disordered state of the cationic sublattice.

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.

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19The stability of the naturally occurring annatto dye against irradiation with visible light 20 was enhanced by intercalation into octyl trimethylammonium and dodecyl 21 trimethylammonium montmorillonite. The intercalated dye exhibited improved light fastness. 22