In this work, we report the multifunctional character of neodymium-doped LaF₃ core/shell nanoparticles. Because of the spectral overlap of the neodymium emission bands with the transparency windows of human tissues, these nanoparticles emerge as relevant subtissue optical probes. For neodymium contents optimizing the luminescence brightness of Nd³⁺:LaF₃ nanoparticles, subtissue penetration depths of several millimeters have been demonstrated. At the same time, it has been found that the infrared emission bands of Nd³⁺:LaF₃ nanoparticles show a remarkable thermal sensitivity, so that they can be advantageously used as luminescent nanothermometers for subtissue thermal sensing. This possibility has been demonstrated in this work: Nd³⁺:LaF₃ nanoparticles have been used to provide optical control over subtissue temperature in a single-beam plasmonic-mediated heating experiment. In this experiment, gold nanorods are used as nanoheaters while thermal reading is performed by the Nd³⁺:LaF₃ nanoparticles. The possibility of a real single-beam-controlled subtissue hyperthermia process is, therefore, pointed out.

We investigate the potential use of two-photon absorption of Er3+/Yb3+ co-doped NaNbO3 nanocrystals for nanothermometry as well as thermal imaging, based on the thermally coupled green Er3+ emission lines. In fact, thermal sensor in the range of 20-80 degrees C with -0.1 degrees C accuracy using excitation powers readily obtained from commercially available semiconductor laser was achieved. The pump-intensity induced local heating was also investigated upon femtosecond laser excitation and 0.55 K/kW x cm(-2) was achieved. The highly efficient green emission together with two-photon dependence and femtosecond laser excitation should increase the brightness of thermal imaging. Additionally, the high temperature-sensitive fluorescence, when compared to previous literatures, should increase the resolution of nanothermometers.

Intense infrared-to-visible upconversion (UC) emission in Tm 3þ ∕Yb 3þ -codoped sodium niobate (NaNbO 3 ) nanocrystals under resonant excitation at 976 nm is presented. The results showed that by increasing the pump power/intensity, a strong reduction is observed at the 800∕480 nm emitted intensity ratio, characterizing what can be denominated as laser pump power-induced color tunability or luminescent switching. The physical origin is discussed with a focus on tailoring of luminescent switchers to operate at a large pump power range and, indeed, it is intrinsically associated with the competition of the two-and three-photon UC processes and with highly efficient UC emissions in the investigated material. The effect of Yb 3þ -ion concentration along with the theoretical aspects on luminescence switching has been investigated. The results obtained here could be useful in the field of sensors and networks for optical processing and optical communications.