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Name (Title):
Renzhi Ma (MANA Scientist), Takayoshi Sasaki (MANA Principal
Investigator)
Affiliation:
International Center for Materials Nanoarchitectonics (MANA), NIMS
Address:
1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
Email: MA.Renzhi@nims.go.jp
Home Page: www.nims.go.jp/softionics
Presentation Title:
ATopochemical Approach to Transition-metal Layered Double Hydroxide (LDH) Nanosheets
Abstract:
A topochemical synthetic approach to transition-metal constituting layered double hydroxide
(LDH) is described. Uniformly micrometer-sized hexagonal platelets of brucite-type Co(OH)2
and Co2/3Fe1/3(OH)2 were first prepared by a homogeneous precipitation of an aqueous solution
containing divalent cobalt and/or ferrous ions through hydrolysis of hexamethylenetetramine
(HMT). Subsequent oxidative intercalation processes employing halogens as oxidizing agents
transformed them into hydrotalcite-type Co 2+ -Co 3+ and Co 2+ −Fe 3+ LDHs, in which the oxidization
of a portion of divalent transition-metal cations into trivalent state induced positive charges to the
octahedral hydroxyl layers while halide anions were intercalated into the interlayer gallery to
balance the extra charge. Due to the topotactic nature of the transformation, resultant Co 2+ -Co 3+
and Co 2+ −Fe 3+ LDHs inherited high crystallinity as well as hexagonal platelet morphology from
their brucite-type precursors. The topotactic feature was verified by abundant microscopic and
spectroscopic characterizations. After a normal ion-exchange process, LDHs intercalating
perchlorate anions were exfoliated in formamide into unilamellar nanosheets of
[Co 2+
2/3Co 3+
48
1/3(OH)2] 1/3+ and [Co 2+
2/3Fe 3+
1/3(OH)2] 1/3+ . These positively charged transition-metal
hydroxide nanosheets are ideal building blocks for ultrathin films/coatings, nanocomposites and
electromagnetic devices.
Fig. 1 Schematic illustration of topochemical synthesis and exfoliation of transition-metal LDHs.
Poster Session PM-6
References:
[1] R. Ma, Z. Liu, K. Takada, N. Iyi, Y. Bando, T. Sasaki, J. Am. Chem. Soc. 129 (2007) 5257.
[2] R. Ma, K. Takada, K. Fukuda, N. Iyi, Y. Bando, T. Sasaki, Angew. Chem. Intl. Ed. 47 (2008)
86.