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Destruction of crystallographic position symmetry of rare earth-doped NaYF4 disordered crystals
Rare-earth-doped disordered crystals are a large class of luminescence and laser material systems. Their excellent optical properties have broad applications in fields such as lasers, green illumination sources, flat panel displays, and bioprobe, but they have been used as an alternative to disordered distribution of cations. The symmetry of the exact position of the rare earth ions in the lattice has long been highly controversial, mainly because the experimentally observed rare earth ions exhibit far lower spectral symmetry than the single crystal X-ray diffraction determined crystallographic positions. symmetry. Because the luminescence of rare earth ions is closely related to the replaced matrix cations, the luminescence intensity of the rare earth doped disordered luminescent materials depends on the crystal field environment surrounding the rare earth ions. Therefore, the use of rare earth ions such as Eu3+ as a sensitive structural probe It is of great significance to study the breaking mechanism of the symmetry of the needle position.
Under the support of the Ministry of Science and Technology's 863 Program, the National Natural Science Foundation of China, the "100-person Plan" of the Chinese Academy of Sciences and the research and development of scientific equipment, the Chen Xueyuan Research Group of the Key Laboratory of Optoelectronic Materials Chemistry and Physics of the Chinese Academy of Sciences' Institute of Materials Structure explores the structure of rare earth ions Eu3+. Acupuncture, by low-temperature high-resolution fluorescence spectroscopy, reveals the symmetry of the crystallographic position symmetry that is commonly found in rare-earth doped cation disordered crystals. Taking Eu3+ doped cubic phase and hexagonal NaYF4 as an example, it is confirmed that the spectral symmetry of Eu3+ is reduced from the crystallographic site point group Oh in the cubic phase NaYF4 to Cs (or C2), while in the hexagonal phase NaYF4, The crystallographic position point group C3h is reduced to Cs, and the phenomenon of crystallographic position symmetry breaking is further confirmed by crystal field level fitting.
The study also revealed that the rare earth doped disordered crystal material system has a universal crystallographic positional symmetry breaking phenomenon, thus solving a controversy that has long plagued this field, and laid a theoretical and experimental basis for optimizing the luminescence properties of such materials. basis. The relevant research results were published in "German Applied Chemistry" (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201208218).
Previously, the group has made a series of research progress in controllable synthesis, spectroscopy, and biomedical applications of rare earth-doped luminescent materials, such as rare earth doped NaYF4 and KGdF4 nano fluorescent probes, combined with time-resolved detection technology, to achieve Homogeneous TR-FRET Assay for Avidin Proteins (Angew. Chem. Int. Ed., 2011, 50, 6306; J. Am. Chem. Soc., 2012, 134, 1323); Synthesis has good biocompatibility The ultra-small ZrO2:Tb nanocrystals are used for the sensitive detection of avidin proteins and targeted bioimaging of human lung adenocarcinoma cells (J. Am. Chem. Soc., 2012, 134, 15083). In addition, the team was recently invited to publish the Feature Article on rare earth doped nano-fluorescent probes at Nanoscale and was selected as the cover article (Nanoscale, DOI: 10.1039/C2NR33239F).
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