Guest-conditioned multicolor writing on cellulose nanocrystal canvases

Abstract

Attractive ion–ion interactions allow trapping the tetracationic host cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺) within solid matrices composed of negatively charged scaffolds, namely cellulose nanocrystals (CNCs). Through this supramolecular approach, we have fabricated CNC-CBPQT⁴⁺ films that change color upon sequenced guest uptake-molecular recognition. The evolution of color is conditioned to the selection of a guest and the self-assembly of an in-film host–guest complex. Here, we have used films and guests as synergetic paper and ink materials to generate responsive text and patterns that transform (disappear, change color, etc.) upon stimulation (temperature, pH, or competitive guests). This concept could be utilized for anticounterfeiting purposes, responsive inkjet printing, data encryption/decryption, and time-evolving patterns.