Electrochromic triphenylamine-based cobalt(ii) complex nanosheets

Two bottom-up Co(ii) complex nanosheets Co-S1 and Co-S2 were prepared by coordination of trifunctional terpyridine-based triphenylamine derivatives (L1 and L2) and a cobalt(ii) ion, in order to demonstrate the structural flexibility and functional tunability of these nanosheets over the top-down type. A liquid-liquid interface-assisted synthesis was employed, which is a facile method to generate multi-layer nanosheets. The nanosheets formed were characterized, revealing the proposed sheet morphology and uniform composition. They have large size domains and good mechanical strength. Besides, both Co-S1 and Co-S2 show reversible electrochromism. The color of Co-S1 was switched from red to green while that of Co-S2 was changed from light red to orange when a positive voltage was applied. An electrochromic device was also fabricated with Co-S1, indicating the promising application of these kinds of structurally tunable, easy-processable and stable nanosheets as low-cost and solid-state electrochromic materials.