Writing and erasing hidden optical information on covalently modified cellulose paper.

An unprecedented strategy for preparing photoresponsive cellulose paper enabling the storage of short-lived optical data by covalent photopatterning is disclosed. An ab initio design hinting that the covalent grafting of coumarins on the paper could yield valuable photoresponsive units was first performed. Second, light sensitive paper that can be reversibly altered upon irradiation at a specific wavelength was prepared by covalent surface functionalization with coumarins. Third, the validity of this strategy is demonstrated using the photolithography of several gripping patterns such as a dynamic QR code.