Synthesis of fluoride nanoparticles in non-aqueous nanoreactors.: Luminescence study of Eu3+:CaF2

Monodispersed CaF2 and Eu3+:CaF2 nanoparticles were synthesized through an original non-aqueous route involving isopropanol nanoreactors dispersed in a polystyrene / THF solution. Transmission electron microscopy revealed a mean diameter of 15 nm with a small standard deviation of 5 nm, for both, undoped and doped nanoparticles. CaF2 particles exhibit a cubic morphology, while Eu3+:CaF2 particles are rather spherical. Luminescence experiments carried on Ca1-xEuxF2+x (x = 0.1) at room temperature, revealed that europium cations are only located in one type of site in the CaF2 structure, with an environment rather constituted by F- anions than by OH- or O2-, showing the absence of these later in the synthesized nanoparticles. These measurements highlighted also a long mean life-time for the D-5(0) state of trivalent europium (5.6 ms), compared to the ones observed in literature (around 3 ms). By an adequate choice of reagents, this waterless method of preparation could be adapted allowing the synthesis of other water sensitive compounds than fluorides.