Novel photochromic system using methylene blue reduction with l-ascorbic acid.

A novel photochromic system was discovered, in which leucomethylene blue, reduced by l-ascorbic acid, was irradiated with 405 nm visible light, resulting in the solution undergoing a colorless-to-blue transition. The process was then repeated, with the solution returning to its colorless state when left undisturbed. This photochromic reaction is sensitive enough to be driven by a blue-violet LED lamp and enables figures to be drawn in solution with a laser pointer.