Dual Europium Luminescence Centers in Colloidal Ga2O3 Nanocrystals: Controlled in Situ Reduction of Eu(III) and Stabilization of Eu(II),Chemistry of Materials

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Dual Europium Luminescence Centers in Colloidal Ga2O3 Nanocrystals: Controlled in Situ Reduction of Eu(III) and Stabilization of Eu(II)
Chemistry of Materials ( IF 7.2 ) Pub Date : 2015-08-21 00:00:00 , DOI: 10.1021/acs.chemmater.5b02383
Arunasish Layek ₁ , Baran Yildirim ₁ , Vahid Ghodsi ₁ , Lisa N. Hutfluss ₁ , Manu Hegde ₁ , Ting Wang ₁ , Pavle V. Radovanovic ₁

Affiliation

Introducing multiple luminescent centers into colloidal nanocrystals is an attractive way to impart new optical properties into this class of materials. Doping disparate ions into specific nanocrystals is often challenging, due to the preferential incorporation of one type of dopant. Here, we demonstrate the coexistence of europium dopants as divalent and trivalent ions in colloidal Ga₂O₃ nanocrystals, achieved by controlled in situ reduction of Eu³⁺ to Eu²⁺. The two dopant species exhibit distinctly different steady-state and time-resolved photoluminescence, and their ratio can be modified via doping concentration, reaction temperature, or thermal treatment of as-synthesized NCs. The Eu²⁺ ions are proposed to be stabilized internally owing to the attractive interaction with oxygen vacancies, while Eu³⁺ dopants partly reside in the nanocrystal surface region. The relationship between the electronic structure of the native defects and the dopant centers is discussed in the context of the overall emission properties. The exposure of these samples to X-ray radiation leads to the reduction of Eu³⁺ to Eu²⁺, demonstrating an alternative way of manipulating the oxidation state and suggesting the potential application of this material as an X-ray storage phosphor. The coexistence of Eu²⁺ and Eu³⁺ and the ability to control their relative fraction over the full oxidation state range in group III oxide nanocrystals allow for the design and preparation of new photonic and light emitting materials.

中文翻译：

Ga ₂ O ₃胶态纳米晶体中的双发光中心：Eu（III）的原位还原控制和Eu（II）的稳定化

在胶体纳米晶体中引入多个发光中心是将新的光学性质赋予此类材料的一种有吸引力的方法。由于优先掺入一种类型的掺杂剂，因此将不同的离子掺杂到特定的纳米晶体中通常很困难。在这里，我们证明了controlled掺杂物在胶态Ga ₂ O ₃纳米晶体中以二价和三价离子的形式共存，这是通过将原位Eu ³⁺还原为Eu ^{2+来实现的}。两种掺杂物表现出明显不同的稳态和时间分辨光致发光，可通过掺杂浓度，反应温度或合成的NC进行热处理来改变它们的比率。2 ²⁺由于与氧空位的吸引相互作用，建议离子内部稳定，而Eu ³⁺掺杂剂部分存在于纳米晶体表面区域。在整体发射特性的背景下，讨论了自然缺陷的电子结构与掺杂中心之间的关系。这些样品暴露于X射线辐射会导致Eu ³⁺还原为Eu ²⁺，这表明了控制氧化态的另一种方法，并暗示了这种材料作为X射线存储磷光体的潜在应用。Eu ²⁺和Eu ³⁺的共存并且能够在III族氧化物纳米晶体的整个氧化态范围内控制其相对分数的能力允许设计和制备新的光子和发光材料。

更新日期：2015-08-21

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