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.
Phase-change nanodroplets (PCNDs) have been used as controllable theranostic agents in diverse therapeutic and diagnostic scenarios over the years. However, there is still a pressing need to monitor the accurate distribution of non-flowing extravascular PCNDs by clinical ultrasound for further quantitative analysis. Here, we propose a spatiotemporally super-resolved ultrasound monitoring technique based on tuned post-activation dynamics of high-bulk-boiling-point PCNDs with customized perfluorocarbon cores. The underlying idea was to make the stochastic recondensation-induced contrast signal dominate the total post-activation signal, thus obtaining detectable and resolvable recondensation signals at physiological temperature. The recondensation signal was extracted by inter-frame subtraction and then processed by a deep learning-based detection algorithm tailored to the recondensation signal patterns. Experiments in tissue-mimicking phantoms demonstrate that co-restricting the concentration of PCNDs and the focus-wave activation pulse duration could help generate recondensation signals with ideal detectability and sparsity for accurate monitoring. Meanwhile, the quantitative analysis of the super-resolved results shows the spatiotemporal sensitivity of the proposed technique under varying concentrations and activation pulse durations, which was consistent with the patterns drawn from the total post-activation signal and existing theories on post-activation dynamics of PCNDs. This technique may be suitable for in-depth extravascular monitoring and dose analysis for PCNDs-involved therapies.
Flexible temperature sensors are crucial for monitoring physiological parameters in smart human wearable devices, however, there is a challenge to realize reproducible, sensitive, real-time, and in-situ temperature sensing simultaneously. Herein, Er 3+ /Yb 3+ co-doped Li 2 HfO 3 phosphor thermometries have been designed and prepared, which demonstrate bright upconversion luminescence and precise temperature sensing capabilities. The temperature sensing characteristics of thermally coupled energy states in Li 2 HfO 3 :Er 3+ , Yb 3+ are explored based on the fluorescence intensity ratio technique, with a maximum relative sensitivity of 0.875% K −1 and a temperature uncertainty of 0.017 K at 300 K. In addition, flexible composite fluorescent optical fiber temperature sensors have been fabricated, and the fiber with a double-cladding structure is employed to monitor human body temperature and airflow heat with satisfying performances. This work not only provides a promising rare earth phosphor thermometry but also opens a new avenue for the development of flexible optical fiber temperature sensors for health management.
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