Integrate nanoscale assembly and plasmonic resonance to enhance photoluminescence of cellulose nanocrystals for optical information hiding and reading

•Assembled cellulose nanocrystals (CNCs) intometal-organic framework(MOF).•Enhanced assembly-induced emission via introducing plasmonic resonance in MOF.•An invisible ink based on MOF@CNC presented a bright blue color under UV light. Assembling cellulose nanocrystals (CNCs) can induce photonic emission. It is free of photobleaching and aggregation-induced quenching, which has great potential in the application of information security. However, the emission suffers a low emission quantum yield (EQY), and the assembly mediate (solvents) can affect the assembly or the emission. Herein, we established a strategy of nanoscale assembly to integrate emission enhancement methods and improve the assembly induced emission. Via controlling the CNC assembly in the nanoscale space of metal-organic frameworks (MOFs), the EQY of CNC array primarily increased by 50 %. When carbon nanodots were further incorporated in MOF, their plasmonic resonance could enhance the emission coupling rate and offset the loss in emission intensity from the extinction of MOF particles, leading to a 6.9-time increase in EQY (to 64.84 %). Such a high EQY from two emission enhancement mechanisms make this nanomaterial able to hide and present photonic information effectively.