Multimode high-sensitivity optical YVO4:Ln3+ nanothermometers (Ln3+ = Eu3+, Dy3+, Sm3+) using charge transfer band features.

Accurate thermal sensing with good spatial resolution is currently required in a variety of scientific and technological areas. Luminescence nanothermometry has shown competitive superiority in contactless temperature sensing, especially at the nanoscale. To broaden the use of such thermometers, development of a novel sensor type with high sensitivity and resolution is highly demanded. Herein, we report single-phase Ln3+-doped YVO4 nanophosphors synthesized using a modified Pechini method as multimode optical thermometers for wide-range temperature probing (299-466 K). The observed temperature-induced red shift of the charge transfer band was utilized to provide thermal sensing. Temperature sensing was based on the luminescence intensity ratio using emission intensities obtained upon charge transfer and direct lanthanide excitation, the spectral position of the charge transfer band and its bandwidth. The suggested probing strategies provided a high relative thermal sensitivity (up to 3.09% K-1) and a precise temperature resolution (up to 0.1 K). The obtained results can be useful for the design of novel contactless luminescence thermometers.

Bifunctional heater-thermometer Nd3+-doped nanoparticles with multiple temperature sensing parameters.

Achieving a combination of real-time diagnosis and therapy in a single platform with sensitive thermometry and efficient heat production is a crucial step towards controllable photothermal therapy. Here, Nd3+-doped Y2O3 nanoparticles prepared using the combined Pechini-foaming technique operating in the first and second biological windows were demonstrated as thermal sensors within the wide temperature range of 123-873 K, and as heaters with a temperature increase of 100 K. Thermal sensing was performed based on various approaches: luminescence intensity ratio (electronic levels; Stark sublevels), spectral line position and line bandwidth were used as temperature-dependent parameters. The applicability of these sensing parameters, along with relative thermal sensitivity and temperature resolution, are discussed and compared. The influence of Nd3+-doping concentration on thermometer and heater efficiency was also investigated.