Room temperature crystallization of highly luminescent lanthanide-doped CaF2 in nanosized droplets: first example of the synthesis of metal halogenide in miniemulsion with effective doping and size control

In this paper, we report the first successful preparation of calcium fluoride by miniemulsion. Calcium fluoride is a widely investigated material known to be an excellent host for luminescent lanthanide ions; herein we report an easy and reproducible way to achieve the controlled doping of CaF2 nanostructures (Ca : Ln = 50 : 1, with Ln = Sm-III, Gd-III and Tb-III) at room temperature, through the miniemulsion approach. The materials are thoroughly characterized from a structural, morphological and functional point of view, by the combined use of several techniques, i.e. X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Scanning and Transmission Electron Microscopy (SEM and TEM respectively) and photoluminescence (PL) spectroscopy. In addition, to get further insight into the local structure around the dopants, Extended X-ray Absorption Fine Structure (EXAFS) experiments are performed.