Excellent Upconversion Luminescence Obtained by Er<sup>3+</sup> Self-Sensitization for Temperature Sensing in Deep Tissues and Anticounterfeiting Application
Guotao Xiang, Hongdou Chen, Yuanyuan Yi, Zhiyu Yang, Yongjie Wang, Yao Lu, Xianju Zhou, Li Li, Xiaojun Wang, Jiahua Zhang
Abstract
The development of high-efficiency upconversion (UC) luminescent materials with multifunctional applications, particularly those excited by wavelengths within the second near-infrared (NIR) biological window, holds a paramount scientific significance. Herein, Er 3+ self-sensitization UC performance excited by 1532 nm wavelength is first studied in the CaSc 2 O 4 matrix. Strong green and red UC emission as well as 4 I 11/2 → 4 I 15/2 NIR transition are observed, though multipath optical thermometry with high sensitivity is realized. Moreover, the penetration depth of the 4 I 11/2 → 4 I 15/2 transition in the biological tissues can reach at least 6 mm, benefiting from its ideal excitation and emission wavelengths located in the biological window. Beyond that, CaSc 2 O 4: Er 3+ phosphor displays variable color luminescence under dual-wavelength excitation, including 980 and 1532 nm, which can be used for enhancing the security of anticounterfeiting materials. Our findings suggest that CaSc 2 O 4: Er 3+ phosphor with excellent UC properties is a promising candidate for the application in optical thermometry and anticounterfeiting field.