YVO₄ Nanoparticles Doped with Eu³⁺ and Nd³⁺ for Optical Nanothermometry

The ongoing research in biology, medicine, and technology requires accurate measurement and control of temperature at micro and nanoscales. Rare-earth-doped luminescence nanoparticles were found to be one of the most perspective systems for noncontact ratiometric temperature sensing for various applications. Despite plenty of single-doped sensors with thermally coupled levels, the development of a dual-center thermometer with enhanced thermometric performances is still challenging. Here, we demonstrate two approaches to construct ratiometric luminescence YVO4:Eu3+/Nd3+ nanothermometers: co-doping and mixture of single-doped nanoparticles. The rational choice of doping concentration could significantly improve thermometric characteristics. An increase in doping concentration did not affect thermal sensitivity, while temperature resolution was improved. Co-doped and mixed nanoparticles displayed similar thermal sensitivity (∼0.8% K–1), whereas the temperature resolution of mixed sensors (0.4–1.0 K) was found to be several times better compared to the co-doped ones (1.1–3.0 K). The obtained results provide a strategy for developing promising dual-center luminescence thermometers with submicron spatial and subdegree thermal resolution.