Multifunctional Janus-like nano-fibrous film enables time resolved anti-counterfeiting encryption and UV monitoring.

In the realm of information security, time-resolved photo-switchable fluorescent materials hold promise for new-generation multi-level information encryption, yet how to develop these materials with high performance remains formidable challenges. In this study, the photochromic-fluorescent [(spirooxazine) SO/Polystyrene (PS)]//[4, 4"-Bis[2-(2-methoxyphenyl)ethenyl]-1,1'-biphenyl (CBS-127)/PS] Janus-like nano-fibre is devised and facilely fabricated via a side-by-side electro-spinning. This unusual Janus-like structure overcomes two fundamental limitations: (1) the adverse effects of competition between the SO and CBS-127 for ultraviolet light absorption on the overall performance of the material, thus achieving superior multifunctionality; (2) the puzzle of molecular isomerization being hindered by molecular stacking in SO solid state. Based on the structural advantages of the Janus-like nano-fibre, the Janus-like nano-fibrous film exhibits long-lasting photochromic properties, blue fluorescence and excellent environmental stability to lay the foundation for long-term cyclic use. Innovatively, by leveraging the multidimensional complementarity of photochromism and fluorescence, we advance four types applications: (1) The integration of external stimulus conditions as inputs with photochromism and fluorescence signals as outputs creates programmable multi-input logic gates, offering enormous potential for anti-counterfeiting encryption applications; (2) A time-resolved multi-level information anti-counterfeiting encryption system is developed; (3) A "Snapchat" concept is proposed to prevent information leakage by UV-triggering damage, just like burn-after-reading; (4) The film can be flexibly employed as anti-counterfeiting labels in daily applications or as wearable devices for monitoring ultraviolet radiation, surpassing the potential of existing time-resolved encryption materials. These new findings significantly deepen the understanding of time-resolved information encryption anti-counterfeiting and advance the development of intelligent optical anti-counterfeiting encryption and wearable materials.