Title: Geminate Labels Programmed by Two-tone Microdroplets Combining Structural and Fluorescent Color

Author: Lang Qin, Xiaojun Liu, Kunyun He, Guodong Yu, Hang Yuan, Ming Xu, Fuyou Li, Yanlei Yu*

Journal: Nat. Commun., 2021, 12(1), 699

Abstract:

Creating a security label that carries entirely distinct information in reflective and fluorescent states would enhance anti-counterfeiting levels to deter counterfeits ranging from currencies to pharmaceuticals, but has proven extremely challenging. Efforts to tune the reflection color of luminescent materials by modifying inherent chemical structures remain outweighed by substantial trade-offs in fluorescence properties, and vice versa, which destroys the information integrity of labels in either reflection or fluorescent color. Here, a strategy is reported to design geminate labels by programming fluorescent cholesteric liquid crystal microdroplets (two-tone inks), where the luminescent material is ‘coated’ with the structural color from helical superstructures. These structurally defined microdroplets fabricated by a capillary microfluidic technique contribute to different but intact messages of both reflective and fluorescent patterns in the geminate labels. Such two-tone inks have enormous potential to provide a platform for encryption and protection of valuable authentic information in anti-counterfeiting technology.

Fulltext Link: https://www.nature.com/articles/s41467-021-20908-y

The research team first synthesized a cyano-substituted oligo(p-phenylene vinylene) derivative DC5, which is similar to the liquid crystal structure and has high quantum efficiency, as a fluorescent molecule. Through doping DC5 in the cholesteric liquid crystal E7 and changing the content of chiral dopant to adjust the pitch, fluorescent cholesteric liquid crystal microdroplets with different structural colors can be obtained by capillary microfluidic technique. Combining the "two-color" microdroplets with adjustable structural color and stable fluorescence properties and the "monochrome" microdroplets with structural colors can create a security label that carries entirely distinct information in reflective and fluorescent states, which realizes the concept of information encryption.