Soft-chemical exfoliation route to layered cobalt oxide monolayers and its application for film deposition and nanoparticle synthesis.
A colloidal suspension of exfoliated, layered cobalt oxide nanosheets has been synthesized through the intercalation of quaternary tetramethylammonium ions into protonated lithium cobalt oxide. According to atomic force microscopy, exfoliated nanosheets of layered cobalt oxide show a plateau-like height profile with nanometer-level height, underscoring the formation of unilamellar 2D nanosheets. The exfoliation of layered cobalt oxide was cross-confirmed by X-ray diffraction, UV/Vis spectroscopy, and transmission electron microscopy. The maintenance of the hexagonal in-plane structure of the cobalt oxide lattice after the exfoliation process was evidenced by selected-area electron diffraction and Co K-edge X-ray absorption near-edge structure analysis. The zeta-potential measurements clearly demonstrated the negative surface charge of cobalt oxide nanosheets. Adopting the nanosheets of layered cobalt oxide as a precursor, we were able to prepare the monodisperse CoO nanocrystals with a particle size of approximately 10 nm as well as the heterolayered film composed of cobalt oxide monolayer and polycation.
Department of Chemistry and Nano Sciences, Ewha Womans University, Seoul 120-750, Korea.
Tae Woo
TW
Kim
Eun-Jin
EJ
Oh
Ah-Young
AY
Jee
Seung Tae
ST
Lim
Dae Hoon
DH
Park
Minyung
M
Lee
Sang-Hoon
SH
Hyun
Jin-Ho
JH
Choy
Seong-Ju
SJ
Hwang