Waterborne fluorescent dual anti-counterfeiting ink based on Yb/Er-carbon quantum dots grafted with dialdehyde nano-fibrillated cellulose.

Nanofibrillated cellulose (NFC) is becoming popular in the field of anti-counterfeiting material due to its favorable biocompatibility, renewability, and easy modification properties, which give it great potentials as carrier of carbon quantum dots (CQDs). Herein, we report an effective method to fabricate Yb and Er doped CQDs grafted onto dialdehyde NFC (DANFC). Owning to special rheological properties of NFC, a waterborne fluorescent dual anti-counterfeiting ink was rationally designed and successfully prepared by adding NFC to waterborne ink to form a stable network structure and increase the thixotropy and yield stress. The resulting CQDs exhibited both photoluminescence (PL) and up-conversion luminescence (UCPL), emitting blue and green fluorescence at excitation wavelengths of 370 and 980 nm, respectively. The study provides a novel method to prepare the waterborne fluorescent dual anti-counterfeiting ink based on Yb and Er doped CQDs/DANFC composites, which provides a reference for its application in printing and packaging industry.