Excited State Absorption for Ratiometric Thermal Imaging

Abstract

Luminescence thermometry, an alternative to thermal imaging using the thermovision technique, requires the development of new approaches and a thorough understanding of the physical phenomena involved, in order to improve the temperature readout parameters. A phenomenon that has recently been shown to cause an extremely strong increase in the emission intensity for the temperature elevation is the thermally induced excited state absorption. This work demonstrates that taking advantage of the strong thermal dependence of the thermally induced excited state absorption process, the limitation associated with the two thermally coupled excited levels usually involved in the ratiometric temperature readout can be overcome, improving the thermometric properties of the luminescent thermometer. The same excitation wavelength was used to induce the emission resulting from the thermally induced excited state absorption of the Tb3+ ions and ground-state absorption of the other type of co-dopant ions causing the opposite nature of the thermal dependence of their emission intensities. Moreover, thanks to the strong color changes exhibited by the phosphors, it was possible to demonstrate the applicability of the proposed approach for through-object 2D thermal imaging of a microelectronic printed circuit board covered with a glass plate using an ordinary commercial digital camera, where the thermovision camera fails.

Embedding Red Emitters in the NbO-Type Metal–Organic Frameworks for Highly Sensitive Luminescence Thermometry over Tunable Temperature Range

“…Considerable efforts has been devoted to noncontact thermometers, especially optical temperature sensors, to meet these requirements, and many achievements have been gained. , The ratiometric luminescence thermometry, based on the intensity ratio of two discriminable emissions, is considered one of the most fascinating noncontact and noninvasive techniques. It is independent of the sensor concentration and inhomogeneity, optoelectronic drifts, and excitation power, and has extensive applicability in conditions where conventional approaches are ineffective. , Nowadays, many ratiometric temperature sensors have been developed based on organic fluorescence molecules, polymers, quantum dots, up-conversion nanoparticles, molecular coordination compounds, and lanthanide metal–organic framework (MOFs). − …”

Rationalizing the Thermal Response of Dual‐Center Molecular Thermometers: The Example of an Eu/Tb Coordination Complex

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The main reason behind the impressive blow-up that occurred in the middle of the last decade [2] was the popularization of light-emitting micro and nanomaterials allowing remote temperature sensing detection at scales below 1 micron, where the traditional thermometers (e.g., thermocouples and pyrometers) are generally unsuitable. [3][4][5][6][7] The impact of luminescence thermometry has been felt, therefore, in disparate areas, such as biomedicine [8][9][10] (including in vivo [11,12] and in vitro [13,14] sensing), catalysis, [15,16] microelectronics, [17][18][19] Internet of Things, [20] magnetism, [21][22][23][24] vacuum sensing, [25] and microfluidics. [26] Indeed, thermographic phosphor thermometry was compared with radiation and contact thermometry in an industrial setting and the results proved that the approach is an effective alternative to conventional techniques offering better performance.

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Effect of the nanoparticle size on thermometric properties of a single-band ratiometric luminescent thermometer in NaYF4:Nd3+

“…As shown recently, unique configuration of the energy level diagram of Nd 3+ ions, including energy difference between ground 4 I 9/2 and first excited 4 I 11/2 states of around 2000 cm À1 , and the possibility of the occurrence of cross-relaxation process, makes them perfect candidate for the single band ratiometric (SBR) approach of luminescence thermometry. 9,[27][28][29][30][31][32][33][34] Temperature determination by this method is based on the analysis of the intensity ratio of a single emission band being excited by two wavelengths, where one of them is matched to the conventionally used ground state absorption (GSA) and the other to the excited state absorption (ESA). This approach was developed to overcome the limitations of the conventional dualband ratiometric thermometry, in which the modulation of the emission spectra shape by the dispersive dependence of the extinction of the medium surrounding the phosphor leads to unreliable temperature readout (in the SBR shape of the emission band in modified in the same way regardless of the excitation wavelength used).…”