Sensitivity Modulation of Upconverting Thermometry through Engineering Phonon Energy of a Matrix

Abstract

Investigation of the unclear influential factors to thermal sensing capability is the only way to achieve highly sensitive thermometry, which is greatly needed to meet the growing demand for potential sensing applications. Here, the effect from the phonon energy of a matrix on the sensitivity of upconversion (UC) microthermometers is elaborately discussed using a controllable method. Uniform truncated octahedral YF:Er/Yb microcrystals were prepared by a hydrothermal approach, and phase transformation from YF to YOF and YO with nearly unchanged morphology and size was successfully realized by controlling the annealing temperature. The phonon energies of blank matrixes were determined by FT-IR spectra and Raman scattering. Upon 980 nm excitation, phonon energy-dependent UC emitting color was finely tuned from green to yellow for three samples, and the mechanisms were proposed. Thermal sensing behaviors based on the TCLs (H/S) were evaluated, and the sensitivities gradually grew with the increase in the matrix's phonon energy. According to chemical bond theory and first-principle calculations, the most intrinsic factors associated with thermometric ability were qualitatively demonstrated through analyzing the inner relation between the phonon energy and bond covalency. The exciting results provide guiding insights into employing appropriate host materials with desired thermometric ability while offering the possibility of highly accurate measurement of temperature.

NUV light induced visible emission in Er3+‐activated NaSrLa(MoO4)O3 phosphors for green LEDs and thermometer

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Structural and luminescence properties of silica powders and transparent glass‐ceramics containing LaF3:Eu3+ nanocrystals

“…Hence, much research attention has been paid to the synthesis of RE 3+ ‐doped AF 3 nanocrystalline fluoride systems: LaF 3 , GdF 3 , and YF 3 . Fluorides provide some distinct advantages owing to their low‐phonon crystal lattices (LaF 3 : ~350 cm −1 , GdF 3 : ~350 cm −1 , YF 3 : ~360 cm −1 ) . In this case, fluorides display low probabilities for multiphonon relaxation process of RE 3+ dopants resulting in their efficient and long‐lived photoluminescence .…”

Reversible luminescence modulation and temperature‐sensing properties of Pr3+/Yb3+ codoped K0.5Na0.5NbO3 ceramics

“…Particularly, the optical temperature sensors based on the thermally coupled levels of the RE ions have been realized through the fluorescence intensity radio (FIR) technique . Generally, the energy gap between two adjacent thermally coupled levels should be in the range of 200‐2000 cm −1 . So far, a few RE ions such as Ho 3+ ( 5 F 1 / 5 G 6 and 5 F 2,3 / 3 K 8 ), Tm 3+ ( 3 F 2,3 and 3 H 4 ), Er 3+ ( 2 H 11/2 and 4 S 3/2 ) and Pr 3+ ( 3 P 0 and 3 P 1 ) have been confirmed to have a pair of thermally coupled levels .…”