Upconverting nanoparticles as primary thermometers and power sensors
Joana Costa Martins, Artiom Skripka, Carlos D. S. Brites, Antonio Benayas, Rute A. S. Ferreira, Fiorenzo Vetrone, Luís D. Carlos
Abstract
Luminescence thermometry is a spectroscopic technique for remote temperature detection based on the thermal dependence of the luminescence of phosphors, presenting numerous applications ranging from biosciences to engineering. In this work, we use the Er 3+ emission of the NaGdF 4 /NaGdF 4 :Yb 3+ ,Er 3+ /NaGdF 4 upconverting nanoparticles upon 980 nm laser excitation to determine simultaneously the absolute temperature and the excitation power density. The Er 3+ 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 emission bands, which are commonly used for thermometric purposes, overlap with the 2 H 9/2 → 4 I 13/2 emission band, which can lead to erroneous temperature readout. Applying the concept of luminescent primary thermometry to resolve the overlapping Er 3+ transitions, a dual nanosensor synchronously measuring the temperature and the delivered laser pump power is successfully realized holding promising applications in laser-supported thermal therapies.