It is essential to simultaneously boost the luminescence intensity and thermometric sensitivity of up-converted optical thermometers towards potential biomedical sensing applications. Herein, the effects of local site symmetry on the up-conversion (UC) emission and thermal sensing ability in trigonal-phased La₂O₃:Er³⁺/Yb³⁺ nanospheres were qualitatively explored using cubic-phased Lu₂O₃ and Y₂O₃ with a similar shape and phonon energy as contrasts. Under 980 nm light excitation, much stronger UC emissions were detected in La₂O₃ samples than that in cubic Lu₂O₃ and Y₂O₃ samples, and the possible mechanisms were elaborately proposed using Eu³⁺ as a luminescent probe. Thermo-responsive emission intensity from ²H_11/2/⁴S_3/2 levels was monitored to evaluate the absolute sensitivity of three samples, which strongly depends on the dopant-induced local site symmetric distortions according to the Judd–Ofelt theory. The potentiality of La₂O₃:Er³⁺/Yb³⁺ for sub-tissue thermometry was also validated by ex vivo experiments. Results open a promising avenue for realizing highly sensitive thermometry with a large signal-to-noise ratio in sub-tissues via finely tailoring the local site symmetry.

中文翻译：

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局部对称畸变促进了氧化镧纳米球中的光子上转换和温度灵敏度†

对于潜在的生物医学传感应用，同时提高上转换光学温度计的发光强度和测温灵敏度至关重要。在此，定性地研究了立方相的Lu ₂ O ₃和Al ₂ O ₃：三角形相变的La ₂ O ₃：Er ³⁺ / Yb ³⁺纳米球中局部位点对称性对上转换（UC）发射和热传感能力的影响。相比之下，Y ₂ O ₃具有相似的形状和声子能量。在980 nm的光激发下，La ₂ O ₃样品中检测到的UC排放量比立方Lu ₂中的检测到的强得多。用Eu ³⁺作为发光探针详细地提出了O ₃和Y ₂ O ₃样品，并提出了可能的机理。监测了² H _11/2 / ⁴ S _3/2水平的热响应发射强度，以评估三个样品的绝对灵敏度，这在很大程度上取决于根据Judd-Ofelt理论的掺杂剂引起的局部对称对称畸变。La ₂ O ₃：Er ³⁺ / Yb ³⁺用于亚组织体温计的潜力也通过离体验证实验。结果为通过精细定制局部对称性在亚组织中实现具有大信噪比的高灵敏度测温开辟了一条有希望的途径。