Energy Gap Linear Superposition of Thermally Coupled Levels toward Enhanced Relative Sensitivity of Ratiometric Thermometry

Abstract

Ratiometric luminescence thermometry (RLT) has attracted considerable attention for its non-invasive, fast response, and strong electromagnetic interference resistance; however, improving relative sensitivity (S R) is of great significance. Herein, we propose a design principle to promote S R by linearly superposing the energy gaps of thermally coupled levels (TCLs) subordinated to luminescence centers. A new fluorescence intensity ratio (FIR′) is derived from multiplying the previous FIRs of multi-pair TCLs. Then, a new S R′ is significantly enhanced and proves to be the sum of the original S R values. The feasibility of this approach is proclaimed by applying to several materials [Na0.5La0.5TiO3:Yb/Nd, Y2O3:Yb/Er, and (LiMg)2Mo3O12:Yb/Er] with improved S R for RLT. Finally, a flexible film is fabricated for temperature measurement of actual scenes and manifests the superiority of the energy gap linear superposition method as ratiometric thermometry.

KYb2F7:Er3+ based nanothermometers: controlled synthesis, enhanced red emission, and improved sensitivities via crystal-site engineering

“…Optical ratiometric temperature sensing has been recently studied for different activators and compositions, which could be found elsewhere. 84,85…”

“…Optical ratiometric temperature sensing has been recently studied for different activators and compositions, which could be found elsewhere. 84,85 To explore the possibility of using KYb 2 F 7 :Er 3+ (2 mol%) and KYb 1.8 M x F 7 :Er 3+ (2 mol%) (M = Ca 2+ , Ti 4+ , Si 4+ , Ge 4+ , Y 3+ , and Nd 3+ ) nanocrystals as optical nanothermometers, we have studied the temperature dependent UC emission spectra of the KYb 2 F 7 :Er 3+ (2 mol%) and KYb 1.8 M x F 7 :Er 3+ (2 mol%) (M = Ca 2+ , Ti 4+ , Si 4+ , Ge 4+ , Y 3+ , and Nd 3+ ) nanocrystals within the temperature range of 77-513 K, as shown in the ESI † (Fig. S4-S10).…”

Luminescence Thermometry Beyond the Biological Realm

“…Stark sublevels of a single band have also been applied for ratiometric thermometry. , Other strategies that have been used to increase temperature sensitivity include applying inert coatings to the UCNPs, engineering the phonon energies of the host matrix, and manipulating the temperature-dependent electron population through the use of an additional excitation laser . An emerging alternative strategy is to increase sensitivity by defining new temperature-dependent metrics, such as the product of the luminescence intensity ratio based on emission from two thermally coupled energy levels and that based on the emission from a single band upon successive excitation of two TCLs or the product of multiple luminescence intensity ratios from different pairs of thermally coupled energy levels . Recent work has also demonstrated how hardware considerations such as sensor noise can ultimately limit the temperature measurement precision. , Multiparametric sensing approaches that combine several temperature-dependent parameters can also be used to improve sensitivity and are discussed in further detail in Section (Advanced Data Analysis and Machine Learning Approaches).…”

Excitation Mechanism Rearrangement in Yb3+-Introduced La2O2S:Er3+/Polyacrylonitrile Photon-Upconverted Nanofibers for Optical Temperature Sensors

“…Yb 3+ is considered a promising sensitizer, as it can efficiently absorb NIR light, not only bringing strong UC emissions but also maintaining the temperature-sensing capability of Er 3+ . − Many research studies established rate equation models to describe the UC mechanism of Er 3+ /Yb 3+ , facilitating further exploration of the essence of optical temperature sensors. − Additionally, the selection of host materials significantly affects the luminescence performance and temperature-sensing capability of fluorescent thermometers. − Sulfur oxides have been extensively investigated as host materials with large band gaps, low phonon energy, and stable thermochemical properties, offering great potential in optical temperature sensing. − However, the limitations of NCs are high molding consumption, constant shape, and challenging recycling. To address these issues, NCs are embedded in polymer fibers, and the composite fibers maintain flexibility while providing superior temperature-sensing capabilities for a variety of complex environments. − …”