Lanthanide-Doped Bismuth-Based Fluoride Nanocrystalline Particles: Formation, Spectroscopic Investigation, and Chemical Stability

Bismuth-based fluoride nanocrystalline particles have recently attracted much attention as hosts for luminescent ions such as lanthanides (Ln) being proposed for lighting devices and biological applications. However, a comprehensive investigation on the chemical properties of this family of materials, the growth of the nanoparticles, and information about the chemical and thermal stabilities are critical to assess the real potential of nanosystems. In this view, a combined experimental and theoretical approach is employed to investigate the crystalline and electronic structure of BiF3 and NaBiF4. A detailed spectroscopic investigation allows us to measure the exciton peaks of these fluoride compounds for the first time and to design the vacuum referred binding energy level diagram of the lanthanide-doped fluorides with respect to the valence and conduction bands of the hosts in comparison with conventional fluorides. In addition, temperature and water effects on the chemical stability of NaBiF4 were addressed, evidencing detrimental limitations and envisaging possible solutions in view of biological applications.