| Abstract: | Plant‐derived 3‐deoxyanthocyanidins are photochromic materials that are coloured under ultraviolet (UV) irradiation and decoloured under light‐shielded storage. In this study, the optimised solvent composition is investigated to enhance the photochromic performance of luteolinidin, a 3‐deoxyanthocyanidin derivative. The visible absorbance ratio between the solution after UV irradiation and after storage in the dark, an index of photochromic performance, was found to be affected by the pH of the solution, and the value reached a maximum when the pH of the solution was 5.7. The type of organic solvent, which is necessary to dissolve luteolinidin, also affected the photochromic performance. When diethylene glycol or dipropylene glycol was used, the value of the absorbance ratio was especially large. Furthermore, this optimised solvent composition displayed excellent photochromic properties with an extract from the sorghum grain shell containing a large amount of 3‐deoxyanthocyanins. |
