Photocatalytic colour switching of redox dyes for ink-free light-printable rewritable paper.

The invention of paper as writing materials has greatly contributed to the development and spread of civilization. However, its large-scale production and usage have also brought significant environment and sustainability problems to modern society. To reduce paper production and consumption, it is highly desirable to develop alternative rewritable media that can be used multiple times. Herein we report the fabrication of a rewritable paper based on colour switching of commercial redox dyes using titanium oxide-assisted photocatalytic reactions. The resulting paper does not require additional inks and can be efficiently printed using ultraviolet light and erased by heating over 20 cycles without significant loss in contrast and resolution. The legibility of prints can retain over several days. We believe this rewritable paper represents an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental protection.