Ultrasensitive optical thermometer based on abnormal thermal quenching Stark transitions operating beyond 1500 nm

Guotao Xiang, Menglin Yang, Qing Xia, Sha Jiang, Yongjie Wang, Xianju Zhou, Li Li, Li Ma, Xiaojun Wang, Jiahua Zhang

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Light with wavelength longer than 1500 nm has great potential to afford deep bio-tissue penetration due to its extremely weak photon scattering and undetectable autofluorescence in vivo. Here, in order to satisfy the requirements for thermometry during the tumor hyperthermia process, an ultrasensitive optical thermometer operating beyond 1500 nm is developed by employing the thermally coupled Stark sublevels of Er3+: 4I13/2 → 4I15/2 transition based on fluorescence intensity ratio (FIR) technology in Yb3+ and Er3+ codoped BaY2O4. Compared with the typical upconversion (UC) material β-NaYF4: Yb3+/Er3+ and Y2O3: Yb3+/Er3+, BaY2O4: Yb3+/Er3+ shows more intense red Er3+: 4F9/2 → 4I15/2 transition and 1.5 μm near-infrared (NIR) Er3+: 4I13/2 → 4I15/2 transition induced by its larger phonon energy and higher quenching concentration of Er3+. An equivalent four-level model is proposed to investigate the temperature characteristics of the NIR emission, from which four Stark transitions are separated from the raw spectra, named α, β, γ, and δ respectively. Then, the NIR thermal sensing performance have been developed by utilizing the FIR of Iβ to Iα and Iγ to Iα. More importantly, an ultra-high sensitivity for optical thermometry has been obtained through the combination of transition β and γ, especially in the physiological temperature region. Furthermore, the detection depth of NIR light in bio-tissues is assessed by an ex vivo test, demonstrating that the maximal detection depth of NIR emission can reach to 8 mm without any influence on optical thermometry. These findings indicate that Yb3+ and Er3+ codoped BaY2O4 is a remarkable contender for optical thermometry in deep tissue with ultra-high sensitivity.

Original languageEnglish
Pages (from-to)5784-5793
Number of pages10
JournalJournal of the American Ceramic Society
Volume104
Issue number11
DOIs
StatePublished - Nov 2021

Scopus Subject Areas

  • Ceramics and Composites
  • Materials Chemistry

Keywords

  • 1.5 μm emission
  • energy transfer
  • Stark sublevel
  • temperature sensing
  • upconversion

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