title: Synthesis, anion exchange, and delamination of Co-Al layered double hydroxide: assembly of the exfoliated nanosheet/polyanion composite films and magneto-optical studies.
abstract: This paper describes a systematic study on the synthesis, anion exchange, and delamination of Co-Al layered double hydroxide (LDH), with the aim of achieving fabrication and clarifying the properties of LDH nanosheet/polyanion composite films. Co-Al-CO3 LDH hexagonal platelets of 4 mum in lateral size were synthesized by the urea method under optimized reaction conditions. The as-prepared CO3(2-)-LDH was converted to Cl- -LDH by treating with a NaCl-HCl mixed solution, retaining its high crystallinity and hexagonal platelike morphology. LDHs intercalated with a variety of anions (such as NO3-, ClO4-, acetate, lactate, dodecyl sulfate, and oleate) were further prepared from Cl- -LDH via an anion-exchange process employing corresponding salts. Exchanged products in various anion forms were found to show different delamination behaviors in formamide. Among them, best results were observed for NO3- -LDH in terms of the exfoliating degree and the quality of the exfoliated nanosheets. The delamination gave a pink transparent suspension containing well-defined nanosheets with lateral sizes of up to 2 microm. The resulting nanosheets were assembled layer-by-layer with an anionic polymer, poly(sodium styrene 4-sulfonate) (PSS), onto quartz glass substrates to produce composite films. Magnetic circular dichroism (MCD) measurements revealed that the assembled multilayer films exhibited an interesting magneto-optical response.
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Zhaoping
authors.initials: Z
authors.lastname: Liu
authors.forename: Renzhi
authors.initials: R
authors.lastname: Ma
authors.forename: Minoru
authors.initials: M
authors.lastname: Osada
authors.forename: Nobuo
authors.initials: N
authors.lastname: Iyi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ebina
authors.forename: Kazunori
authors.initials: K
authors.lastname: Takada
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Sasaki