Dual-Branched Dense Hexagonal Fe(II)-Based Coordination Nanosheets with Red-to-Colorless Electrochromism and Durable Device Fabrication

Sanjoy Mondal, Yoshikazu Ninomiya, Takefumi Yoshida, Taizo Mori, Manas Kumar Bera, Katsuhiko Ariga, Masayoshi Higuchi

Research output: Contribution to journalArticle

Abstract

Highly dense hexagonal Fe(II)-based coordination nanosheets (CONASHs) were designed by dual-branching, at the metal-coordination moieties and the tritopic ligands, which successfully obtained a liquid/liquid interface by the complexation of Fe(II) ions and the tritopic bidentate ligands. The 1:1 complexation was confirmed by titration. The obtained Fe(II)-based nanosheets were fully characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). A monolayer of the sheets was obtained, employing the Langmuir-Blodgett (LB) method, and the determined thickness was a2.5 nm. The polymer nanosheets exhibited red-to-colorless electrochromism because the electrochemical redox transformation between Fe(II) and Fe (III) ions controlled the appearance/disappearance of the metal (ion)-to-ligand charge-transfer (MLCT) absorption. The poor Ï-conjugation in the tritopic ligands contributed to the highly colorless electrochromic state. A solid-state device, with the robust polymer film, exhibited excellent electrochromic (EC) properties, with high optical contrast (Î"T > 65%) and high durability after repeated color changes for >15â»000 cycles, upon applying low-operating voltages (+1.5/0 V).

Original languageEnglish
Pages (from-to)31896-31903
Number of pages8
JournalACS Applied Materials and Interfaces
Volume12
Issue number28
DOIs
Publication statusPublished - 2020 Jul 15

Keywords

  • cyclic stability
  • electrochromism
  • liquid/liquid interfacial technique
  • redox nanosheet
  • transparent

ASJC Scopus subject areas

  • Materials Science(all)

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