A Theoretical Framework for Ratiometric Single Ion Luminescent Thermometers—Thermodynamic and Kinetic Guidelines for Optimized Performance

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Engineering of Mixed Eu 3+ /Tb 3+ Metal‐Organic Frameworks Luminescent Thermometers with Tunable Sensitivity

Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4fn energy levels is an emerging technique for non-invasive remote temperature sensing with high spatial and temporal resolution. Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzmann’s law. Despite its simplicity, Boltzmann thermometry with two excited levels allows precise temperature sensing, but only within a limited temperature range. While low temperatures slow down the nonradiative transitions required to generate a measurable population in the higher excitation level, temperatures that are too high favour equalized populations of the two excited levels, at the expense of low relative thermal sensitivity. In this work, we extend the concept of Boltzmann thermometry to more than two excited levels and provide quantitative guidelines that link the choice of energy gaps between multiple excited states to the performance in different temperature windows. By this approach, it is possible to retain the high relative sensitivity and precision of the temperature measurement over a wide temperature range within the same system. We demonstrate this concept using YAl3(BO3)4 (YAB):Pr3+, Gd3+ with an excited 6PJ crystal field and spin-orbit split levels of Gd3+ in the UV range to avoid a thermal black body background even at the highest temperatures. This phosphor is easily excitable with inexpensive and powerful blue LEDs at 450 nm. Zero-background luminescence thermometry is realized by using blue-to-UV energy transfer upconversion with the Pr3+−Gd3+ couple upon excitation in the visible range. This method allows us to cover a temperature window between 30 and 800 K.

One ion to catch them all: Targeted high-precision Boltzmann thermometry over a wide temperature range with Gd3.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adpr.202000211

mOptical Sensing for the Internet of Things: A Smartphone-Controlled Platform for Temperature Monitoring

Polymer optical fibers (POFs) have been utilized in several applications since the late 1950s. Adding photoluminescence (PL) to the fiber considerably widens the optical functionality of POFs and opens new application fields. In recent years, the availability of laboratory-scale production methods with industrialization potential has triggered a surge of new studies and developments in the promising area of PL-POFs. These applications, profiting from the addition of PL to fibers, are identified in this review as: light harvesting, sensing, color illumination, anti-counterfeiting, and random lasing. Progress in these fields is foreseen to generate a need for larger quantities of fibers, therefore large-scale manufacturing and processing methods are becoming more relevant. This review thus provides an overview of the most important developments in this emerging area, together with a description of the key parameters describing PL-POF performance and efficiency.

Recent advances in photoluminescent polymer optical fibers

Flexible coatings with dual capabilities for remote real-time temperature sensing and photothermal conversion have a huge potential in the field of advanced thermal actuated optoelectronic applicat...

High-Quantum-Yield Upconverting Er3+/Yb3+-Organic–Inorganic Hybrid Dual Coatings for Real-Time Temperature Sensing and Photothermal Conversion

This paper reports on the preparation of Er3+/Yb3+/Tm3+, Er3+/Yb3+/Nd3+, and Er3+/Tm3+/Nd3+ triply doped and Er3+-doped SiO2-Ta2O5 glass ceramic nanocomposites and active planar waveguides by the sol–gel process using the dip-coating technique as deposition method. The investigation of their structural, morphological, and luminescent properties using XRD, AFM, and photoluminescence analysis, are reported here. The XRD results showed the presence of L-Ta2O5 nanocrystals dispersed in the SiO2-based amorphous host for all the nanocomposites and films. The rare earth ion (RE3+) doping concentration affected both the crystallinity, and the crystallite sizes of the Ta2O5 dispersed into SiO2-Ta2O5 nanocomposites and waveguides. AFM characterization revealed crack free and smooth surface roughness and differences in viscoelasticity on the Er3+-doped SiO2-Ta2O5 films surface, which allows the identification of Ta2O5 nanocrystals on the SiO2 amorphous host. The Er3+ doped and triply doped SiO2-Ta2O5 nanocomposites displayed broad- and super broadband NIR emissions with a FWHM up to 173 nm achieved in the telecom wavelengths. The lifetime of the 4I13/2 emitting level of the Er3+-doped SiO2-Ta2O5 waveguides is strongly dependent on Er3+ concentration and an emission quenching was negligible up to 0.81 mol%. The structural and luminescent investigations indicated that RE3+-doped SiO2-Ta2O5 glass ceramics are promising candidates for photonic applications in optical devices operating in wide wavelengths at the telecom bands.

https://www.frontiersin.org/articles/10.3389/fchem.2022.915335/pdf

Leonardo S. Rosa

Papers

High-Quantum-Yield Upconverting Er3+/Yb3+-Organic–Inorganic Hybrid Dual Coatings for Real-Time Temperature Sensing and Photothermal Conversion

Super Broadband at Telecom Wavelengths From RE3+-Doped SiO2-Ta2O5 Glass Ceramics Planar Waveguides