2004 Fiscal Year Final Research Report Summary
Characterization of hybrid nanoparticle phosphors synthesized in reverse micelle nano-reactors
| Project/Area Number |
14550678
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Composite materials/Physical properties
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| Research Institution | Keio University |
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Principal Investigator |
ISOBE Tetsuhiko Keio University, Faculty of Science and Technology, Associate Professor, 理工学部, 助教授 (30212971)
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| Project Period (FY) |
2002 – 2004
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| Keywords | ZnS:Mn / Reverse micelle / Photoluminescence / Nano-phosphor / Nanocrystal / Silica coating / シリカ被覆 |
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| Research Abstract |
ZnS:Mn^<2+> nanocrystals of 3nm in diameter were coated with silica to form 20±4nm core/shell particles, as observed by transmission electron spectroscopy. For ZnS:Mn^<2+> nanocrystals modified with silica, the intensity of photoluminescence (PL) due to d-d transition of Mn^<2+> increases with increasing the TEOS amount and hence the thickness of silica shell. This is attributed to the passivation of surface defects and quantum confinement effect. On the contrary, the PL intensity of ZnS:Mn^<2+> nanocrystals modified by both lauryl phosphate (HLP) and silica decreases with increasing the TEOS amount. ^<31>P CP/MAS NMR spectroscopy reveals that chemical interaction between phosphate groups and ZnS:Mn^<2+> is interrupted by silica shell. These results suggest that surface modification of HLP around ZnS:Mn^<2+> nanocrystals is more effective than the formation of silica shell from the viewpoint of PL enhancement.
Aging of the of ZnS:Mn^<2+>/SiO_2 core/shell colloidal solution for 14 days increases the PL intensity of the obtained powder sample by a factor of three, as compared with that for 1 day. This is possibly attributed to the better quantum confinement effect and the more homogeneous incorporation of Mn^<2+> to ZnS by aging. The transparency of the ZnS:Mn^<2+>/SiO_2 core/shell nano-phosphor-dispersed sheet was higher than that of ZnS:Mn^<2+> bulk-phosphor- dispersed sheet. This is attributed to the markedly lower Rayleigh scattering of visible light for the former. The Mie scattering occurs for the bulk-phosphor-dispersed sheet because of the micrometer particle size. The PL intensity of the nano-phosphor-dispersed sheet increased with increasing the phosphor's content, while the PL intensity of the bulk-phosphor-dispersed sheet decreased with increasing the phosphor's content. This is also explained by the high transparency and the negligible backscattering loss of the orange emission for the nano-phosphor's sheet.
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Research Products
(6 results)
