One million cyclable blue/colourless electrochromic device using K 2 Zn 3 [Fe(CN) 6 ] 2 nanoparticles synthesized with a micromixer.

Well-defined K 2 Zn 3 [Fe(CN) 6 ] 2 -nanoparticles (NPs) synthesized with a micromixer showed robust redox reaction cyclability. Crystal structure analysis revealed that the robustness results from the maintenance of the original rhombohedral crystal structure in the oxidation state. The blue/colourless electrochromic device with the K 2 Zn 3 [Fe(CN) 6 ] 2 -NPs and Prussian blue NPs showed recyclability over 1 million redox reactions.