Optical Thermometry Using Upconversion Luminescence: A Breakthrough in Temperature Measurement

Friday - February 2 2024, 02:14 UTC - 9 months ago

Optical thermometry using upconversion luminescence offers high sensitivity and swift response times. By measuring the intensity ratio of emitted photons, temperature can be calculated. Researchers at AHUT have found promising results using Yb3+ and Ho3+ co-doped GYTO single crystal, offering potential applications in harsh conditions.

Optical thermometry, the technique of measuring temperature using the emission of light, has always been a field of interest for scientists and researchers. The development of sensitive and fast temperature measurement techniques is crucial for various industrial, medical, and scientific applications. Recently, a groundbreaking breakthrough in optical thermometry has been achieved using upconversion luminescence (UCL) from lanthanides. This technique offers high sensitivity and swift response times, making it a desirable option for accurate temperature measurement.

The principle behind this technique lies in the process of upconversion luminescence, where low-energy photons in the near-infrared (NIR) spectrum are converted into high-energy photons in the visible spectrum through the anti-Stokes mechanism. In simpler terms, the low-energy photons are absorbed by Yb3+ ions, which then transfer the energy to Ho3+ ions. The Ho3+ ions then emit a photon with a wavelength of either 550 or 650 nm, depending on the energy levels of the ions involved. The intensity ratio of these two bands is known as the luminescence intensity ratio (LIR), which is crucial in calculating the temperature.

The optical thermometry technique works by measuring the alternation of LIR with changes in temperature. As the temperature changes, the LIR also changes, thus allowing precise temperature measurement. This technique is especially useful in harsh conditions where traditional contact thermometers cannot be used. For instance, this technique can be employed for temperature measurement in intracellular environments, coalmines, and power stations.

Researchers at Anhui University of Technology (AHUT), China, led by Prof. Shoujun Ding, have made significant progress in this field by exploring single crystals for optical thermometry. Unlike traditional phosphors used in this technique, single crystals offer higher sensitivities due to their low symmetry and strong crystal field. The team selected a single crystal Gd0.74Y0.2TaO4 (GYTO) to hold Yb3+ and Ho3+ ions and found promising results. The maximum sensitivity achieved for this new single crystal was 0.0010 K-1 for luminescence intensity-based thermometry and 0.0037 K-1 for color-based thermometry.

This achievement has opened doors for potential applications of Yb3+ and Ho3+ co-doped GYTO single crystals in optical thermometry. The researchers are optimistic about the potential of this single crystal for use in harsh conditions and believe it can pave the way for advanced temperature measurement techniques in various fields.