Aldehyde modified nanocellulose-based fluorescent hydrogel toward multistage data security encryption

In view of the insecurity of encode information storage based on fluorescence switch single-stage encryption, a fluorescent hydrogel for multistage data security encryption were proposed, named as polyvinyl alcohol/dialdehyde cellulose nanofibrils/carbon quantum dots hydrogel. Herein, the interpenetrating network was formed by chemically crosslinking between polyvinyl alcohol (PVA) and dialdehyde cellulose nanofibrils (DACNF). Additionally, nitrogen-doped carbon quantum dots (CDs) synthesized by one-step hydrothermal method were introduced into the above hydrogel system by hydrogen bonds. The resultant fluorescent hydrogels possessed high stretchability up to 530 %, good strength of 0.96 MPa, Fe3+-responsive fluorescence quenching, fluorescence recovery triggered by ascorbic acid and borax-triggered shape memory. Moreover, various complex 3D hydrogel geometries were fabricated by folding/assembling 2D fluorescent hydrogel sheets, extending data encryption capability from 2D plane to 3D space. More remarkably, the 3D data encryption-erasing process of fluorescent hydrogel was realized by the strategy of alternating treatment of Fe3+ solution and ascorbic acid solution. This work provided a facile and general strategy for constructing high security important information encryption and protection.