| Budget Amount *help |
¥15,470,000 (Direct Cost: ¥11,900,000、Indirect Cost: ¥3,570,000)
Fiscal Year 2016: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2015: ¥6,370,000 (Direct Cost: ¥4,900,000、Indirect Cost: ¥1,470,000)
Fiscal Year 2014: ¥6,890,000 (Direct Cost: ¥5,300,000、Indirect Cost: ¥1,590,000)
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| Outline of Final Research Achievements |
We have studied formation and stability of core-shell structures in epitaxial Au/Co nanoparticles (NPs) by using atomic-resolution scanning transmission electron microscopy together with electron energy loss spectroscopy and electron tomography. As the particle size reduces, number of NPs having Au-shell increases and their frequency of occurrence reached 65%. Au segregation proceeds during particle growth at 520 K. The core-shell structure formation is size-dependent; the critical diameter dividing the Au-shell and the Co-shell structures is about 11 nm, below which the Au-shell is stable. After annealing at 800 K for 3.6 ks, Au-shell NPs were conserved while the Co-shell NPs changed to two-phase structures with a planar interface separating Au and Co. Surface-segregation-induced phase separation in small NPs will be responsible for the Au-shell formation. Magnetic properties and photocatalytic activity were also evaluated.
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