Mechanochromic luminescent material with high quantum yield for multi-mode anti-counterfeiting applications

The multi-mode anti-counterfeiting materials, constructed by mechanochromic luminescent materials with high quantum yield, can effectively prevent illegal counterfeiting, but their design and construction still present significant challenges. Herein, a twisting D-A-D conjugated molecule, FBtF, is obtained with a special hybridized local and charge transfer excited state, and shows approximately 100 % photoluminescence quantum yield in the coating film. The self-assembled FBtF microplates exhibit bathochromic-shifted emission from green to orange, accompanied by the photoluminescence quantum yield increase from 47.8 % to 89.0 % upon grinding, which is the highest in reported MCL materials, to the best of our knowledge. In contrast, a D-π-D type molecule (FBenF) and a D-D'-D molecule (FAnF) maintain the blue-emission after grinding. Through mechanistic investigation, the force-induced molecular conformational planarization and the breakage of the intermolecular charge transfer collaboratively lead to the emission-color change and photoluminescence quantum yield increase. The FBtF microplates are designed as ink for anti-counterfeiting applications based on multi-mode output signals, including the UV light-excited image and the grinding-induced emission color change together with the photoluminescence quantum yield increase. The written tags exhibit high stability in various harsh environments, and demonstrate superior anti-counterfeiting performance in practical applications, such as medicine anti-counterfeiting.