Enhancement of the photostability of flavylium dye adsorbed on mesoporous silicate

Flavylium dye, a model compound of natural anthocyanin, has a defect that its color stability is very poor. We have tried to complex the flavylium dye with several mesoporous silicas (FSM-16, MCM-41 and HMS) and succeeded to enhance the photostability of the dye against visible light irradiation. We have found that the light fastness is enhanced when the dye is incorporated into the mesoporous silicas exhibiting solid acidity that derives from an aluminum impurity. The solid acidity plays a role to stabilize the cationic flavylium dye, while the mesopore structure hinders the attack of oxygen to the incorporated dye molecules. Because of its enhanced color stability, the flavylium dye incorporated in the acidic mesoporous silicas can be a candidate for an environmentally friendly coloring material.