Influence of the Synthesis Conditions on the Morphology and Thermometric Properties of the Lifetime-Based Luminescent Thermometers in YPO4:Yb3+,Nd3+ Nanocrystals

An increase in the accuracy of remote temperature readout using luminescent thermometry is determined, among other things, by the relative sensitivity of the thermometer. Therefore, to increase the sensitivity, intensive work is carried out to optimize the host material composition and select the luminescent ions accordingly. However, the role of nanocrystal morphology in thermometric performance is often neglected. This paper presents a systematic study determining the role of synthesis parameters of the solvothermal method on the morphology of YPO₄:Yb³⁺,Nd³⁺ nanocrystals and their effect on the lifetime of Yb³⁺ ion-based luminescent thermometer performance. It was shown that by changing the RE³⁺:(PO₄)^3- ratio and the concentration of Nd³⁺ ions, the size, shape, and aggregation level of the nanocrystals can be modified changing the thermometric parameters of the luminescent thermometer. The highest relative sensitivity was obtained for the low RE³⁺:(PO₄)^3- ratio and 1% Nd³⁺ ion concentration.