Temperature-induced phase transition in LiYO2:Sm3+ for ultrasensitive thermometry in the physiological temperature range

Ratiometric luminescent thermometry is favored for its unique advantages and significant potential applications, particularly in the biomedical field. That has driven growing interest in the development of novel luminescent materials with ultra-high sensitivity in the physiological temperature range. Our study focuses on materials that exhibit temperature-induced phase transition within the physiological temperature range, thus facilitating the development of highly sensitive luminescent thermometers. Through a series of experimental explorations, we have discovered that LiYO 2 :1%Sm 3+ undergoes a phase transition from a monoclinic structure to a tetragonal structure within the temperature range of 320–330 K. Subsequently, a luminescent thermometer based on LiYO 2 :Sm 3+ phosphor was designed, capitalizing on the contrasting thermal response of the emissions associated with monoclinic and tetragonal structures, achieving ultra-high sensitivity of 17.51% K −1 at 322 K, making it suitable for the application in the biomedical field. Especially, the optimal temperature range for LiYO 2 : Sm 3+ thermometer aligns well with mitochondrial temperature, presenting potential applications in cancer diagnosis and photothermal therapy.