Fabrication of Robust Spatially Resolved Photochromic Patterns on Cellulose Papers by Covalent Printing for Anticounterfeiting Applications

Despite its millennial age, cellulose paper remains the preferred material for domestic and professional printings, covering applications from simple office paperwork to fiducial solutions such as bills, passports, and head letters. The creation of robust photochromic patterns on cellulose papers for anticounterfeiting applications is an important and still partially unaddressed challenge. In this contribution, we report the covalent printing of dibenzothienylethenes as photochromic compounds through a spatially controlled light-mediated thiol-X ligations. Photophysical and theoretical studies provide evidence for a reversible photochromism behavior, not affected significantly by the polar environment of the cellulose matrix, and demonstrates a high fatigue resistance over 18 successive write-erase cycles. The strong coloration-discoloration switch can be easily followed by a direct naked-eye readout.