Chiral Luminescent Liquid Crystal with Multi-State-Reversibility: Breakthrough in Advanced Anti-Counterfeiting Materials
Yonghong Shi, Jianlei Han, Xue Jin, Wangen Miao, Yi Zhang, Pengfei Duan
Creating a security material that carries distinct information in reflective color, fluorescence, and chiroptical property will enhance anti-counterfeiting levels to deter counterfeits ranging from currencies to pharmaceuticals, but is proven extremely challenging. In this work, an advanced anti-counterfeiting material, with three-state of each mode reversibly converted into multi-mode materials including reflective color, fluorescence, and circularly polarized luminescence signal, is constructed by loading photofluorochromic spiropyran (SP) and zinc ion (Zn2+) into the chiral liquid crystal. Under UV irradiation, the complexes of SP and Zn2+ will be transformed into merocyanine (MC) and MC-Zn2+, while the energy transfer occurs from MC-Zn2+ to MC. Upon heating, MC is easy to recover to SP, while the MC-Zn2+ remains unchanged. The MC and MC-Zn2+ can be transformed into the SP and Zn2+ under visible light irradiation. The three states of each mode can reversibly convert. Furthermore, the reflective color or fluorescence of each state shows different intensities under left- and right-handed circular polarized filters, enabling easy distinguishing by naked eyes. The advanced anti-counterfeiting method with multi-state of each mode for multi-mode encryption information output will provide a new concept for designing and fabricating multi-mode anti-counterfeiting materials, improving the security level for practical application.
security materials, luminescence,