Recently, Prof. Wei Huang from Institute of Flexible Electronics (Frontiers Science Center for Flexible Electronics) of Northwestern Polytechnical University and Prof. QiangZhao from Institute of Advanced Materials of Nanjing University of Posts and Telecommunications have proposedanovel strategy toachievedynamicregulation ofphotochromicbehaviorthrough different counterions. The related results under the title “On-demand regulation of photochromic behavior through various counterions for high-level security printing” were published online on April 17 in the top international academic journal – ScienceAdvances.

   Materials exhibiting reversible changes in optical properties upon light irradiation have shown great potential in diverse optoelectronic areas. In particular, the modulation of photochromic behavior on demand for such materials is of fundamental importance, but it remains a formidable challenge. Here, thepaper reported a facile and effective strategy to engineer controllable photochromic properties by varying the counterions in a series of zinc complexes consisting of a spirolactam-based photochromic ligand. Colorability and coloration rate can be finely tuned by conveniently changing their counterions. Through utilization of the reversible feature of the metal-ligand coordination bond between zincions and the spirolactam-based ligand, dynamic manipulation of photochromic behavior was achieved. Furthermore, thepaper demonstrated the practical applications of the tunable photochromic properties for these complexes by creating photochromic films and developing multilevel security printing. These findings show opportunities for the development of smart materials with dynamically controllable responsive behavior in advanced optoelectronic applications.