title: Tens of micron-sized unilamellar nanosheets of Y/Eu layered rare-earth hydroxide: efficient exfoliation via fast anion exchange and their self-assembly into oriented oxide film with enhanced photoluminescence.
abstract: Layered rare-earth hydroxide (LRH) crystals of (Y0.95Eu0.05)2(OH)5NO3·nH2O with a lateral size of ∼ 300μm and a thickness of ∼ 9μm have been synthesized via a hydrothermal reaction of mixed nitrate solutions in the presence of mineralizer NH4NO3at 200 °C for 24 h. LRH exhibits the ability to undergo intercalation and anion exchange with DS-(C12H25OSO3-) via hydrothermal treatment. Compared with traditional anion exchange at room temperature, hydrothermal processing not only shortens the anion exchange time from 720 to 24 h but also increases the basal spacing. The arrangements of DS-in the interlayer of LRH are significantly affected by the DS-concentration and reaction temperature, and the basal spacing of the LRH-DS sample in the crystal edge is assumed to be larger than that in the crystal center. A higher DS-concentration and reaction temperature both induce more intercalation of DS-anions into the interlayer gallery, thus yielding a larger basal spacing. Unilamellar nanosheets with a lateral size of ≽60μm and a thickness of ∼ 1.6 nm can be obtained by delaminating LRH-DS in formamide. The resultant unilamellar nanosheets are single crystalline. Transparent (Y0.95Eu0.05)2O3phosphor films with a uniform [111] orientation and a layer thickness of ∼ 90 nm were constructed with the nanosheets as building blocks via spin-coating, followed by proper annealing. The oriented oxide film exhibits a strong red emission at 614 nm (the5D0-7F2transition of Eu3+), whose intensity is ∼ 2 times that of the powder form owing to the significant exposure of the (222) facets.
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110819, People's Republic of China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110819, People's Republic of China; Advanced Materials Processing Unit, National Institute for Materials Science, Sengen 1-2-1, Tsukuba, Ibaraki, 305-0047, Japan.
authors.forename: Ji-Guang
authors.initials: JG
authors.lastname: Li
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110819, People's Republic of China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110819, People's Republic of China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Sun
authors.affiliation: Institute of Materials Physics and Chemistry, School of Sciences, Northeastern University, Shenyang, Liaoning, 110819, People's Republic of China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Qi
authors.affiliation: School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning, 110819, People's Republic of China.
authors.forename: Miaoyong
authors.initials: M
authors.lastname: Zhu
authors.affiliation: Advanced Materials Processing Unit, National Institute for Materials Science, Sengen 1-2-1, Tsukuba, Ibaraki, 305-0047, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Sakka
keywords: anion exchange; exfoliation; layered rare earth hydroxide; oriented fluorescent film; unilamellar nanosheet