Xiao Yu, Yang Xun, Zhao Hao-Ran, Wu Dan, Chen Ming-Xing, Zheng Tianxiang, Zhang Rui, Sun Ling-Dong, Yan Chun-Hua
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
College of Science, Nanjing Forestry University, Nanjing, 210037, China.
Light Sci Appl. 2025 May 13;14(1):194. doi: 10.1038/s41377-025-01816-y.
The enduring enigma surrounding the near-infrared (NIR) emission of Mn continues to ignite intense academic discussions. Numerous hypotheses have emerged from extensive research endeavors to explain this phenomenon, such as the formation of Mn-Mn ion pairs, Mn occupying cubically coordinated sites, as well as conjectures positing the involvement of Mn oxidized from Mn or defects. Despite these diverse and valuable insights, none of the hypotheses have yet achieved broad consensus. In this study, we have observed prolonged fluorescence lifetimes (~10 ms) for the NIR emissions of Mn ions, hinting at these ions occupying the high-symmetry octahedral sites inherent to the garnet lattice. This inference is supported by the corroborating results from X-ray absorption fine structure analysis and first-principles calculations. The intense crystal field of octahedral sites, similar to that of AlO, facilitates the splitting of d-d energy levels, thereby inducing a red-shift in the emission spectrum to the NIR region due to the transition T(G) → A(S) of isolated Mn. Our findings not only offer a plausible rationale for the NIR emission exhibited by other Mn-activated garnet phosphors but also pave a definitive route towards understanding the fundamental mechanisms responsible for the NIR emission of Mn ions.
围绕锰（Mn）近红外（NIR）发射的持久谜团持续引发激烈的学术讨论。通过广泛的研究努力，已经出现了许多假设来解释这一现象，例如Mn-Mn离子对的形成、Mn占据立方配位位点，以及推测Mn由Mn或缺陷氧化而参与其中。尽管有这些多样且有价值的见解，但尚无一种假设达成广泛共识。在本研究中，我们观察到Mn离子近红外发射的荧光寿命延长（约10毫秒），这暗示这些离子占据了石榴石晶格固有的高对称八面体位点。这一推断得到了X射线吸收精细结构分析和第一性原理计算的佐证结果的支持。八面体位点的强晶体场，类似于AlO的晶体场，促进了d-d能级的分裂，从而由于孤立Mn的跃迁T(G)→A(S)导致发射光谱红移至近红外区域。我们的发现不仅为其他Mn激活的石榴石荧光粉所表现出的近红外发射提供了合理的解释，也为理解Mn离子近红外发射的基本机制开辟了一条明确的途径。
