Kobashi Shunsuke, Okayasu Yoshinori, Matsumoto Kohsuke, Tsutsumi Osamu, Kobayashi Yoichi
Department of Applied Chemistry, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan.
Chemistry. 2025 Jun 26;31(36):e202500952. doi: 10.1002/chem.202500952. Epub 2025 May 27.
Eu(III) complex nanoparticles (NPs) prepared via reprecipitation exhibit characteristic emission in aqueous solutions without amphiphilic substituents, making them promising for bioimaging applications. However, although it is well established that water efficiently quenches emissions of Eu(III) complexes, reported emission quantum yields of water-soluble Eu(III) complex NPs vary significantly among studies, and the factors governing these emission properties have yet to be fully elucidated. In this study, we systematically investigated the emission quenching mechanisms of Eu(III) β-diketonate complex NPs by time-resolved absorption and emission spectroscopies. We found that the primary pathway is the interaction between coordinated and external water molecules, which strongly enhances nonradiative deactivation. Notably, coordinated water facilitates stronger interactions with the surrounding water, further promoting quenching. Additionally, we also found that aggregation causes emission quenching in Eu(III) complexes lacking phenyl groups in the β-diketonate moiety, which have smaller molecular volumes. These findings clarify the origin of luminescence variability in Eu(III) complex NPs and provide a foundation for rational material design to enhance luminescence stability in aqueous environments.
通过复沉淀法制备的铕（III）配合物纳米颗粒（NPs）在没有两亲取代基的水溶液中表现出特征发射，使其在生物成像应用中具有潜力。然而，尽管水能够有效淬灭铕（III）配合物的发射这一点已得到充分证实，但水溶性铕（III）配合物纳米颗粒的报道发射量子产率在不同研究中差异很大，且控制这些发射特性的因素尚未完全阐明。在本研究中，我们通过时间分辨吸收和发射光谱系统地研究了铕（III）β - 二酮配合物纳米颗粒的发射淬灭机制。我们发现主要途径是配位水分子与外部水分子之间的相互作用，这极大地增强了非辐射失活。值得注意的是，配位水促进了与周围水更强的相互作用，进一步促进淬灭。此外，我们还发现聚集会导致β - 二酮部分缺乏苯基且分子体积较小的铕（III）配合物发生发射淬灭。这些发现阐明了铕（III）配合物纳米颗粒发光变异性的起源，并为合理设计材料以增强水性环境中的发光稳定性提供了基础。
