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Metal Ions Induce Growth and Magnetism Alternation of α-Fe2O3 Crystals Bound by High-Index Facets

Authors

  • Rongmei Liu,

    1. State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (P.R. China)
    2. Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (P.R. China)
    3. College of Biological and Chemical Engineering, Anhui Polytechnic University, Wuhu Anhui 241000 (P.R. China)
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  • Yuanwen Jiang,

    1. State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (P.R. China)
    2. Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (P.R. China)
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  • Hao Fan,

    1. State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (P.R. China)
    2. Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (P.R. China)
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  • Prof. Qingyi Lu,

    Corresponding author
    1. State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (P.R. China)
    • State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (P.R. China)
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  • Wei Du,

    1. State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (P.R. China)
    2. Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (P.R. China)
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  • Prof. Feng Gao

    Corresponding author
    1. Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (P.R. China)
    • Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (P.R. China)
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Abstract

In this study, quasi-cubic and hexagonal bipyramid α-Fe2O3 polyhedrons with high-index facets exposed were controllably synthesized by applying metal ions Zn2+ or Cu2+ as structure-directing agents. The growth of the α-Fe2O3 nanostructures with high-index facets were induced by metal ions without the addition of any other surfactants. The quasi-cubic form controlled by Zn2+ looks like a cube but has an angle of approximately 86° bound by (012), (10-2), and (1-12) facets, whereas the hexagonal bipyramid form controlled by Cu2+ has a sixfold axis bound by {012} facets. Magnetic measurements confirm that these two kinds of nanocrystals display shape- and surface-dependent magnetic behaviors. The hexagonal bipyramid iron oxide nanocrystals show a lower Morin transition temperature of 240 K and might be spin-canted ferromagnetically controlled at room temperature, and the ferromagnetism disappears at low temperature. The quasi-cubic nanocrystals have a splitting between FC curve and ZFC curve from the highest experimental temperature and no Morin transformation occurs; this indicates that they would be defect ferromagnetically controlled at low temperature. The reported metal-ion-directing technique could provide a universal method for shape- and surface-controlled synthesis of nanocrystals with high-index facets exposed.

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