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Size-dependent microstructure and europium site preference influence fluorescent properties of Eu-doped Ca10(PO4)6(OH)2 nanocrystal |
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| Authors: | Mei Long Wei Li Haiyan Zhao Huixin Li Lingdong Sun Zhenggui Wei |
| Affiliation: | a College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China b Department of Biology, College of Life Sciences, Suzhou University, Suzhou 215006, PR China c State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory on Rare Earth Materials and Bioinorganic Chemistry, Peking University, Beijing 100871, PR China |
| Abstract: | In this study, Eu3+-doped nanocrystalline Ca10(PO4)6(OH)2 (Ca10−xEux(PO4)6(OH)2) with different particle sizes have been prepared by the thermal decomposition of precursors. Size-dependent microstructure could be observed in nanocrystalline Ca10−xEux(PO4)6(OH)2. The lattices of Ca10−xEux(PO4)6(OH)2 nanocrystals were more distorted in comparison with the bulk, and the smaller the particle size, the more distorted the lattices. Room temperature photoluminescence showed europium site preference was also size-dependent, with the majority of Eu3+ ions occupying Ca(II) sites in the bulk, but more and more Eu3+ ions occupying Ca(I) sites in Ca10−xEux(PO4)6(OH)2 with decreasing particle size. Fluorescent properties of Ca10−xEux(PO4)6(OH)2 were considered to be influenced by both microstructure and site preference of Eu3+ ions. An abnormal strong intensity of 5D0-7F0 transition was observed in bulk and larger Ca10−xEux(PO4)6(OH)2 nanocrystals, but the relative intensities of 5D0-7F0 transition to 5D0-7F1,2,3,4 transition of Eu3+ became weaker as the particle sizes decreased. As the particle sizes became smaller, the ratios of the red emission transition (5D0-7F2) to the orange emission transition (5D0-7F1) (R/O values) first increased by comparing the bulk sample with 96 nm sample, and then decreased by comparing 96 nm sample to 57 nm sample. The quenching concentrations of Ca10−xEux(PO4)6(OH)2 samples increased with decreasing particle size. Possible mechanisms responsible for these phenomena were proposed. Since nanosized Ca10−xEux(PO4)6(OH)2 showed higher fluorescent intensities, higher R/O values and higher quenching concentrations, this material is considered to be a promising phosphor. |
| Keywords: | Nanostructures Eu ions Hydroxyapatite Fluorescence |
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