Highly-sensitive Eu³⁺ ratiometric thermometers based on excited state absorption with predictable calibration

Abstract

Temperature measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnology. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu(3+) ion. The thermometer is based on the simple Eu(3+) energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K(-1). The thermometric parameter is defined as the ratio between the emission intensities of the (5)D0 → (7)F4 transition when the (5)D0 emitting level is excited through the (7)F2 (physiological range) or (7)F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu(3+) were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biological transparent window. A novel and of paramount importance aspect is that the calibration factor can be calculated from the Eu(3+) emission spectrum avoiding the need for new calibration procedures whenever the thermometer operates in different media.

Lanthanide‐Based Thermometers: At the Cutting‐Edge of Luminescence Thermometry

“…Examples of primary luminescent thermometers are, however, very scarce. Up to now, the reported examples are based on CdSe(ZnS) QDs, Si NPs functionalized with 1‐dodecene, Y 2 O 3 :Eu 3+ microparticles and nanoparticles, and SrF 2 :Yb 3+ /Er 3+ UCNPs . This last work, discussed in detail in Section , is based on the Boltzmann law as the equation of state and is a major breakthrough on the subject.…”

Making Nd3+ a Sensitive Luminescent Thermometer for Physiological Temperatures—An Account of Pitfalls in Boltzmann Thermometry

“…Among the various temperature-dependent optical parameters that can be used for temperature calibration, the luminescence intensity ratio (LIR) of two emissive transitions from thermally coupled excited states has emerged as an especially robust and yet easily measurable representative to extract information about the local temperature of a medium in contact with luminescent nanocrystals. Also, other methodological approaches such as lifetime thermometry [15][16][17][18][19][20][21], or the concept of excited state absorption (ESA) [22][23][24] have been developed for that purpose while organic framework-based thermometers increasingly attract attention [25,26].…”

Multiscale and luminescent, hollow microspheres for gas phase thermometry

“…A theoretical calculation of the intensity ratio based on the spectra 36 is not possible as the ratio varies significantly with changes in the optical arrangement, as shown earlier 37 .…”

“…6 are based on a calculation following equation (1) from ref. 36 , with Δ being the temperature-dependent ratio and T the temperature.

Figure 6Temperatures derived by thermometry compared to thermocouple measurement. Emission intensity ratios measured with the filter set shown in the inset of Fig.

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