Multi-stimulus-responsive coating based on fluorescent waterborne polyurethane electrochemical construction for multilevel information encryption

Currently, with the rapidly evolving technology landscape, there is growing demand for advanced secure information encryption and anti-counterfeiting technologies. Multi-stimulus-response materials have gained significant attention due to their promising application potential. In this study, 2,7-dichlorofluorescein (DCF) was anchored onto waterborne polyurethane chains to synthesize a fluorescent waterborne polyurethane (FWPU) with multi-stimulus response properties. The demulsification-induced fast solidification (DIFS) method developed by our group combined with the electrochemical approach was used to prepare an in situ information-encrypted coating on a metal surface. A triple-locked information-encrypted system based on anodic metal selection and pH-regulated fluorescence intensity was successfully designed and prepared. The anodic metal ions were automatically introduced in the process of preparing the FWPU coating, and the fluorescence intensity of FWPU was reduced or quenched by heavy metal anodes. Concurrently, the introduced DCF group in FWPU underwent structural change from a lactone ring to a quinone structure at higher pH levels, leading to a shift in fluorescence intensity. The pH response of FWPU coating and the change in fluorescence intensity with pH and anode metal were investigated by UV–vis and fluorescence spectra analysis. This innovative approach achieved multiple-stimulus response, enabling both encryption and decryption of information from one-dimensional to three-dimensional modes. The findings in this study may broaden the applications of information encryption, anti-counterfeiting, and fluorescent probes.