Reversible Switching of the Magnetic Orientation of Titanate Nanosheets by Photochemical Reduction and Autoxidation

Xiang Wang; Xiaoyu Li; Satoshi Aya; Fumito Araoka; Yasuhiro Ishida; Akiko Kikkawa; Markus Kriener; Yasujiro Taguchi; Yasuo Ebina; Takayoshi Sasaki; Shogo Koshiya; Koji Kimoto; Takuzo Aida

doi:10.1021/jacs.8b09625

Reversible Switching of the Magnetic Orientation of Titanate Nanosheets by Photochemical Reduction and Autoxidation

J Am Chem Soc. 2018 Dec 5;140(48):16396-16401. doi: 10.1021/jacs.8b09625. Epub 2018 Nov 21.

Authors

Xiang Wang^{1

2}, Xiaoyu Li³, Satoshi Aya², Fumito Araoka², Yasuhiro Ishida², Akiko Kikkawa², Markus Kriener², Yasujiro Taguchi², Yasuo Ebina⁴, Takayoshi Sasaki⁴, Shogo Koshiya⁴, Koji Kimoto⁴, Takuzo Aida^{1

2}

Affiliations

¹ Department of Chemistry and Biotechnology, School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan.
² RIKEN Center for Emergent Matter Science , 2-1 Hirosawa , Wako , Saitama 351-0198 , Japan.
³ School of Material Science and Technology , Beijing Institute of Technology , Beijing 100081 , China.
⁴ National Institute for Materials Science, International Center for Materials Nanoarchitectonics , 1-1 Namiki , Tsukuba , Ibaraki 305-0044 , Japan.

PMID: 30444605
DOI: 10.1021/jacs.8b09625

Abstract

Optical properties of aqueous colloidal dispersions of 2D electrolytes, if their aspect ratios are extra-large, can be determined by their orientation preferences. Recently, we reported that a colloidal dispersion of diamagnetic titanate(IV) nanosheets (Ti^IVNSs), when placed in a magnetic field, is highly anisotropic because Ti^IVNS anomalously orients its 2D plane orthogonal to the magnetic flux lines due to its large anisotropic magnetic susceptibility. Herein, we report a serendipitous finding that Ti^IVNSs can be in situ photochemically reduced into a paramagnetic species (Ti^IV/IIINSs), so that their preference of magnetic orientation changes from orthogonal to parallel. This transition distinctly alters the structural anisotropy and therefore optical appearance of the colloidal dispersion in a magnetic field. We also found that Ti^IV/IIINSs is autoxidized back to Ti^IVNSs under non-deaerated conditions. By using an elaborate setup, the dispersion of Ti^IVNSs serves as an optical switch remotely operable by magnet and light.