Abstract:

Fluorescent anti-counterfeit printing technology is applied in the special fluorescent printing ink used for logos, which in conjunction with additional light excitation to expose the encrypted information play an anti-counterfeiting role. Fluorescent anti-counterfeiting is mostly used in film or solid state; therefore, it is necessary for fluorescent ink to have strong luminescent properties in both states. Aggregation-induced emission (AIE) molecules are a class of molecules that emit weak or even no light in a single molecule state and exhibit strong luminescence in an aggregated state. As a typical AIE molecule with simple synthesis and high fluorescence intensity, the salicylaldehyde Schiff base molecule has a stimulus-responsive fluorescence mechanism. Its different fluorescence characteristics in acid-base environments make this kind of molecule outstanding in the field of anti-counterfeit printing. In this study, the salicylaldehyde Schiff base AIE molecule was prepared by a one-step nucleophilic addition reaction of salicylaldehyde and amine, and its application in anti-counterfeit printing was further demonstrated. Through the characterization of the molecule in different environments, the role of its AIE characteristics and stimulus response fluorescence mechanism in anti-counterfeit printing applications was elucidated. The experimental raw materials are easy to obtain, safe, low cost, and the required instruments are routine, which meets the requirements of laboratory teaching. Through this experimental training, students not only master the preparation method of Schiff base compounds, but also learn the application of stimulus response fluorescence of salicylaldehyde Schiff base molecules in anti-counterfeit printing. The combination of classroom teaching and extended reading, enables students to further understand the characteristics of anti-counterfeit printing products and design concepts.

Key words: Aggregation-induced emission, Anti-counterfeiting printing, Schiff base, Fluorescent molecule, Comprehensive experiment