New Alkaline-based Fluoride Host Materials for Luminescent Transition Metal and Lanthanide Ions

Abstract

The past decades have witnessed an increased interest in luminescent nanomaterials because of their broad application prospects, among which luminescence sensing. From this perspective, luminescent nanomaterials made of wide band-gap inorganic materials doped with lanthanide and transition metal ions offer unique advantages, including high sensitivity and physicochemical stability. The optical properties of these two types of ions differ considerably, making them suitable for different sensing purposes. Lanthanide ions have narrow emission lines whose energy is minimally affected by the host material, while transition metal ions feature broader emission bands whose energy depends on the crystalline environment. A luminescent nanomaterial containing both types of ions would feature novel, exciting optical properties. However, the preparation of such a nanomaterial is not trivial, because of differences in ionic radius and favoured coordination number. Herein, a strategy for achieving these nanomaterials is reported. A synthesis protocol was developed, which affords alkaline-based fluoride nanoparticles that can be doped with lanthanide and transition metal ions. A thorough optimization of the synthesis parameter was performed, varying reaction time, temperature, and concentration of chemical precursors. The obtained oleate-capped nanocrystals are readily dispersible in non-polar solvents and, when doped with Nd(III) and/or Cr(III) show the typical emission of these ions.