Multicolor emission tuning of ZnS@SiO₂-Eu³⁺ composite as potential application in light-emitting devices

In this report, we present luminescent properties of a composite based on zinc sulfide quantum dots (ZnS QDs) in a SiO₂ matrix, doped with different concentrations of Eu³⁺ ions and with different thermal treatments in order to obtain white light and a tunable emitting phosphor. Various complementary techniques have extensively studied the evolution of effects of thermal treatment and Eu³⁺ doping on the crystallinity and emission properties. Transmission electron microscopy certifies the formation of undoped ZnS powder of particles with sizes of approximately 4.6 nm, combined with XRD, shows the amorphous nature of the matrix host as well as the presence of embedded crystalline nanoparticles. The incorporation of the Eu³⁺ dopant does not produce a significant effect in the crystalline structure of the ZnS@SiO₂ composite. Raman spectroscopy results indicate that thermal treatment induced to formation cristobalite-low and Zn₂SiO₄. The photoluminescence measurements indicated that ZnS@SiO₂ nanocomposite exhibit an intense and wide blue emission band centered at around 440 nm under 325 nm excitation, which is modified by the temperature, with the enhancement of the intensity, widening of the band emission, as well as maximum shifting. The calculations of the CIE 1931 chromaticity coordinates show the tuning of the tonality of the emission color from blue to cold white light, these results strengthened the possibility that the prepared samples could be applied as an efficient phosphor in the visible range.