Enhancement of luminescence in white emitting strontium fluoride core @ calcium fluoride shell nanoparticles

Abstract

Synthesis of lanthanide-doped fluoride SrF 2 :3Dy and SrF 2 :3Dy@CaF 2 nanoparticles with different ratios of core to shell (1:0.5, 1:1 and 1:2) has been carried out by employing ethylene glycol route. X-ray diffraction (XRD) patterns reveal that the structure of the prepared nanoparticles was of cubical shape, which is also evident in TEM images. The size of the nanoparticles for core (SrF 2 :3Dy) is found to increase when core is covered by shell (CaF 2). It is also evident from Fourier transform infrared spectroscopy (FTIR) that ethylene glycol successfully controls the growth and acts as a shape modifier by regulating growth rate. In the photoluminescence investigation, emission spectra of SrF 2 :3Dy is found to be highly enhanced when SrF 2 :3Dy is covered by CaF 2 due to the decrease of cross relaxation amongst the Dy 3+ -Dy 3+ ions. Such type of enhancement of luminescence in homonanostructure SrF 2 :3Dy@CaF 2 (core@shell) has not been studied so far, to the best of the authors’ knowledge. This luminescent material exhibits prominently white light emitting properties as shown by the Commission Internationale d’Eclairage (CIE) chromaticity diagram. The calculated correlate colour temperature (CCT) values for SrF 2 :3Dy, SrF 2 :3Dy@CaF 2 (1:0.05), SrF 2 :3Dy@CaF 2 (1:1) and SrF 2 :3Dy@CaF 2 (1:2) are 5475, 5476, 5384 and 5525 K, respectively, which lie in the cold white region. [Figure not available: see fulltext.]