Crystal growth control of rod-shaped ε-Fe2O3 nanocrystals

Hiroko Tokoro; Junpei Fukui; Koki Watanabe; Marie Yoshikiyo; Asuka Namai; Shin-Ichi Ohkoshi

doi:10.1039/d0ra07256g

Crystal growth control of rod-shaped ε-Fe₂O₃ nanocrystals

RSC Adv. 2020 Oct 29;10(65):39611-39616. doi: 10.1039/d0ra07256g. eCollection 2020 Oct 27.

Authors

Hiroko Tokoro^{1

2}, Junpei Fukui¹, Koki Watanabe¹, Marie Yoshikiyo², Asuka Namai², Shin-Ichi Ohkoshi²

Affiliations

¹ Department of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba 1-1-1 Tennodai, Tsukuba Ibaraki 305-8573 Japan tokoro@ims.tsukuba.ac.jp.
² Department of Chemistry, School of Science, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan ohkoshi@chem.s.u-tokyo.ac.jp.

Abstract

Herein we report crystal growth control of rod-shaped ε-Fe₂O₃ nanocrystals by developing a synthesis based on the sol-gel technique using β-FeO(OH) as a seed in the presence of a barium cation. ε-Fe₂O₃ nanocrystals are obtained over a wide calcination temperature range between 800 °C and 1000 °C. A low calcination temperature (800 °C) provides an almost cubic rectangular-shaped ε-Fe₂O₃ nanocrystal with an aspect ratio of 1.4, whereas a high calcination temperature (1000 °C) provides an elongated rod-shaped ε-Fe₂O₃ nanocrystal with an aspect ratio of 3.3. Such systematic anisotropic growth of ε-Fe₂O₃ is achieved due to the wide calcination temperature in the presence of barium cations. The surface energy and the anisotropic adsorption of barium on the surface of ε-Fe₂O₃ can explain the anisotropic crystal growth of rod-shaped ε-Fe₂O₃ along the crystallographic a-axis. The present work may provide important knowledge about how to control the anisotropic crystal shape of nanomaterials.