Deep-Tissue Temperature Sensing Realized in BaY₂O₄:Yb³⁺/Er³⁺ with Ultrahigh Sensitivity and Extremely Intense Red Upconversion Luminescence

Abstract

In this paper, BaY 2 O 4 :Yb 3+ /Er 3+ , a high efficient red upconversion (UC) material, is first utilized as an optical thermometer in the biological window, accomplished through the fluorescence intensity ratio (FIR) of thermally coupled Stark sublevels of 4 F 9/2 (FIR (654/663) ). The maximum absolute sensitivity of FIR (654/663) ) is 0.19% K −1 at 298 K, which is much higher than most previous reports about FIR-based temperature sensors located in the biological windows. More importantly, the groove of FIR (654/663) for thermometry is nicely located in the physiological temperature range, indicating its potential thermometry application value in biomedicine. Furthermore, a simply ex vivo experiment is implemented to evaluate the penetration depth of the red emission in biological tissues, revealing that a detection depth of 6 mm can be achieved without any effect on the FIR values of I 654 to I 663 . Beyond that, the temperature sensing behaviors of the thermally coupled levels 2 H 11/2 and 4 S 3/2 (FIR (523/550) ) are also investigated in detail. In the studied temperature range, the absolute sensitivity of FIR (523/550) monotonously increases with the rising temperature and reaches its maximum value 0.31% K −1 at 573 K. All the results imply that BaY 2 O 4 :Yb 3+ /Er 3+ is a promising candidate for deep-tissue optical thermometry with high sensitivity.

Negative thermal expansion triggered anomalous thermal upconversion luminescence behaviors in Er3+/Yb3+-codoped Y2Mo3O12 microparticles for highly sensitive thermometry

“…6,7 Currently, fluorescence intensity rate (FIR), which makes use of the temperature-dependent emission Intensities of thermally coupled levels (TCLs) of rare-earth ions, has been greatly researched for optical thermometry. 8,9 In terms of the TCLs, their energy band gap (ΔE) should be within a certain range of 200-2000 cm -1 , which is not benefit for achieving high relative sensitivity (i.e., ). 10,11 Thus, a new S ∝ Δ 2 technique, which takes advantages of the temperature-dependent FIR value of two emitting centers, was proposed to circumvent this issue.…”

Ultrasound‐Powered Implants: A Critical Review of Piezoelectric Material Selection and Applications

“…Deep temperature sensing can be used to detect injury [ 241 ] and diagnose infection. [ 242,243 ] UPIs are being developed to replace ingestible temperature sensors with injectable variants that can be localized outside of the gut. For example, Ozilgen and Maharbiz have developed two passive sensors with volumes of 1.45 and 0.118 mm 3 for long‐term monitoring of deep tissue temperature.…”

Multipath optical thermometry realized in CaSc2O4: Yb3+/Er3+ with high sensitivity and superior resolution

“…[18][19][20][21][22][23][24][25] Among these ions, Er 3+ is the most widely used activator for temperature sensing which has been realized in an enormous variety of materials, due to the excellent thermal coupling between the green emitting levels 2 H 11/2 and 4 S 3/2 of Er 3+ as well as their strong UC intensity under the excitation of 980 nm excitation with the sensitization of Yb 3+ . 26,27 Nevertheless, the thermometric sensitivity and resolution as well as the signal to noise ratio (SNR) of Er 3+typed optical thermometer are still need to be improved.…”