Photoluminescence Properties of ZnWO4:Eu3+ Nanocrystals Prepared by a Hydrothermal Method

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• 作者：Qilin Dai ; Hongwei Song ; Xue Bai ; Guohui Pan ; Shaozhe Lu ; Tie Wang ; Xinguang Ren ; Haifeng Zhao
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：May 31, 2007
• 年：2007
• 卷：111
• 期：21
• 页码：7586 - 7592
• 全文大小：264K
• 年卷期：v.111,no.21(May 31, 2007)
• ISSN：1932-7455

文摘

ZnWO₄:Eu³⁺ nanocrystals were prepared by the hydrothermal method at various temperatures and pH values.Their luminescent properties including excitation and emission processes, luminescent dynamics, and localenvironments surrounding Eu³⁺ ions were systemically studied. The results indicate that the particle size ofthe nanocrystals grows with increasing hydrothermal temperature, while it rarely changes with pH value. Theexcitation bands for Eu³⁺, which are contributed by different components, shift considerably to blue with theincreasing pH value. The relative intensity of blue-green emission bands caused by the tungstate groups canbe greatly modified by changing the pH value, thus the white color phosphors can be obtained. There existtwo symmetry sites for the ⁵D₀-⁷F₂ emissions of Eu³⁺, inner and surface. The former corresponds to lineswith narrower inhomogeneous width and slower decay time, while the latter to the lines with broader widthand faster decay time. The emissions for tungstate groups mainly originate from the charge transfer fromexcited 2p orbits of O^2- to the empty orbits of the central W⁶⁺ ions. On the other hand, the emissions forEu³⁺ ions are contributed by both the charge transfer from O^2- to Eu³⁺ and the energy transfer from W⁶⁺ions to Eu³⁺ ions. A schematic is proposed to explain the photoluminescence processes in the ZnWO₄:Eu³⁺nanocrystals.