The spectroscopic properties of different infrared-emitting neodymium-doped nanoparticles (LaF3:Nd3+, SrF2:Nd3+, NaGdF4: Nd3+, NaYF4: Nd3+, KYF4: Nd3+, GdVO4: Nd3+, and Nd:YAG) have been systematically analyzed. A comparison of the spectral shapes of both emission and absorption spectra is presented, from which the relevant role played by the host matrix is evidenced. The lack of a “universal” optimum system for infrared bioimaging is discussed, as the specific bioimaging application and the experimental setup for infrared imaging determine the neodymium-doped nanoparticle to be preferentially used in each case.

We report on Ytterbium and Neodymium codoped LaF₃ core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd³⁺ → Yb³⁺ energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated.

The current status of the use of core–shell rare-earth-doped nanoparticles in biomedical applications is reviewed highlighting the most relevant advances.