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We report on the potential application of NIR–to–NIR Nd3+-doped yttrium vanadate nanoparticles with both emission and excitation operating within biological windows as thermal sensors in 123–873 K temperature range. It was demonstrated that thermal sensing could be based on three temperature dependent luminescence parameters: the luminescence intensity ratio, the spectral line position and the line bandwidth. Advantages and limitations of each sensing parameter as well as thermal sensitivity and thermal uncertainty were calculated and discussed. The influence of Nd3+ doping concentration on the sensitivity of luminescent thermometers was also studied.

Development of new approaches to the noncontact optical thermometry is of great importance for modern science and technology. In the current work, single-phase YVO 4 :Eu 3+ nanoparticles prepared via the modified Pechini technique were studied as luminescence thermometers. Thermal sensing was performed using two different ratiometric approaches: utilizing the luminescence intensity ratio between transitions emitted from two thermally coupled excited levels (emission spectrum) and between transitions originating from different thermally coupled low-lying levels (excitation spectrum). The first technique allows determining temperature within the 298−873 K range, whereas the second one allows determining temperature within 298−473 K. The spectral position of the 5 D 0 (1)− 7 F 1 (2) band was also suggested as a temperaturedependent parameter. Thermometric performance of YVO 4 :Eu 3+ nanophosphors including absolute and relative sensitivities, minimum temperature uncertainty, and repeatability was obtained and discussed.

We report systematic study of Dy3+-doped YVO4 nanophosphors synthesized via modified Pechini technique. Effect of calcination temperature and doping concentration on structure and luminescence has been investigated. XRD and Raman spectroscopy revealed preparation of single phase nanoparticles without any impurities. Synthesized nanopowders consisted of weakly agglomerated nanoparticles with average size about 50 nm. Photoluminescence spectra of YVO4:Dy3+ nanoparticles consisted of the characteristic narrow lines attributed to the intra-configurational 4f-4f transitions dominating by the hypersensitive 4F9/2–6H13/2 transition. The calcination temperature variation did not affect 4F9/2 lifetime, whereas increase of doping concentration resulted in its gradual decline. Potential application of YVO4:Dy3+ 1 at.% and 2 at.% nanopowders as ratiometric luminescence thermometers within 298–673 K temperature range was tested. The main performances of thermometer including absolute and relative thermal sensitivities and temperature uncertainty were calculated. The maximum relative thermal sensitivity was determined to be 1.8% K−1@298 K, whereas the minimum temperature uncertainty was 2 K.

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