Photochromic Properties of 3-Deoxyanthocyanidin Pigments in Nontoxic Solvents.

The photochromic properties of some naturally occurring 3-deoxyanthocyanidin pigments were investigated in various nontoxic solvents. When luteolinidin, a representative 3-deoxyanthocyanidin, was dissolved in a mixture of weakly acidic water and an organic solvent with a relative permittivity between 20 and 34, it was possible to repeatedly induce coloration via ultraviolet irradiation and decoloration under light-shielded conditions. 1,3-Butanediol and ethanol, which are approved for use in foods, cosmetics, and household goods, were found to be appropriate organic solvents for this process.

Photostability enhancement of anionic natural dye by intercalation into hydrotalcite.

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.

Color sensors for indole vapors based on Ehrlich-type reactions.

A sensitive and simple color sensor for indole vapors has been developed based on the Ehrlich-type reaction in solid polymer film. Upon 60-min exposure of the film sensor to the air containing 5 - 100 ppb of indole vapors, pink or magenta color could be recognized by the naked eyes. Alternatively, a trial gas detector tube has been prepared by mixing the reagents with sea sand.