A yellow-emitting phosphor, ${\mathrm{La}}_{1-x}{\mathrm{Ce}}_x^{3+}{\mathrm{Sr}}_2\mathrm{Al}{\mathrm{O}}_5$ , is reported that displays a peak in the excitation at $450\mathrm{nm}$ and a peak in the emission at $556\mathrm{nm}$ . When this phosphor is pumped by a blue InGaN light-emitting diode $({\lambda }_{\max }=450\mathrm{nm})$ we obtain white light with color rendering index $\left(R_a\right)$ between 81 and 85 and color temperatures between 4200 and $5500\mathrm{K}$ , suggesting that this material is competitive as a blue-pumped yellow phosphors.

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.