Assembly-Induced Emission of Cellulose Nanocrystals for Hiding Information

Fluorescent-labeled cellulose nanocrystal (CNC) films have been used to record and protect information in paper materials, whereas the fluorescent materials usually suffer photobleaching. Herein, a strategy of solid-state emission induced by the vertical assembly of CNCs was established. The assembly-induced emission starts from the structural diffraction of CNC, whose wavelength is adjusted into the ultraviolet (UV) region for hiding information under natural light. The small diameter (≈10 nm) of CNCs then promotes the resonance between the vertically assembled CNCs and the UV light, leading to a strong blue emission with an emitting quantum efficiency as high as 13.90%. By introducing the vertical-assembly film with a specific pattern into paper materials, an anti-counterfeiting image is obtained under a UV radiation. Since CNCs are a kind of cellulose with high crystallinity, this material can be a wear-resistant anti-counterfeiting material for banknotes or other paper applications.