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

Abstract

Synthesis of lanthanide-doped fluoride SrF2:3Dy and SrF2:3Dy@CaF2 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 (SrF2:3Dy) is found to increase when core is covered by shell (CaF2). 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 SrF2:3Dy is found to be highly enhanced when SrF2:3Dy is covered by CaF2 due to the decrease of cross relaxation amongst the Dy3+-Dy3+ ions. Such type of enhancement of luminescence in homonanostructure SrF2:3Dy@CaF2 (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 SrF2:3Dy, SrF2:3Dy@CaF2 (1:0.05), SrF2:3Dy@CaF2 (1:1) and SrF2:3Dy@CaF2 (1:2) are 5475, 5476, 5384 and 5525 K, respectively, which lie in the cold white region.Graphical abstractWhite light emitting homonanostructure material SrF2:3Dy@CaF2(core@shell).

Extending the luminescence properties of zinc gallogermanate via co-doping with cost-effective metals ions (Cr3+/Mg2+, Cr3+/Ca2+, and Cr3+/Sr2+)

“…The observed morphology and particle size are in a good agreement with previously reported studies [27,28]. The broad and shallow absorption band observed around 300-3600 cm − 1 in Cr-ZGGO sample could be assigned to the stretching vibration of O-H bonds in the absorbed water molecules [29]. The incorporation of Mg 2+ and Sr 2+ ions shifts this band to lower wave numbers, while the Ca 2+ addition diminishes this absorption peak.…”

Persistent Spectral Hole-Burning and Zeeman Effect of X-ray-Induced Sm2+ in CaF2:Sm3+ Nanocrystals

“…This is most likely due to effects by charge compensation as Sm 3+ substitutes for Ca 2+ disrupting the lattice ( O h symmetry with 8-fold (bcc) coordination). The excess positive charge may be compensated by interstitial F – and/or O 2– on fluoride lattice sites which may increase the lattice parameter. , Note that the effective ionic radius, r (coordination number of 8), of Sm 3+ is 1.08 Å, which is comparable with the one of Ca 2+ (1.12 Å) . From Table 1 it follows that the goodness of fit G = R wp / R exp was <1.3 for all refinements, indicating very good refinements …”