Intense Yellow Emitting Biocompatible CaS:Eu Nanophosphors Synthesized by Wet Chemical Method

Here we report the synthesis of intense yellow emitting CaS:Eu nanoparticles by a low temperature wet chemical coprecipitation method which can be used for various optoelectronic and biological applications. The particles were characterized systematically using techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, photoluminescence (PL) and UV-Vis absorption spectroscopy. XRD analysis revealed that all the samples exhibited a cubic structure with good crystallinity. Formation of nanoparticles having spherical morphology with the diameter in the range 4-8 nm was confirmed by TEM analysis. The PL emission color varied from yellowish white to yellow as the excitation wavelength was increased from 335 to 395 nm. The PL emission peaks are attributed to ⁵D₀- ⁷F_J (J = 0,1,2,3,...) electronic transitions of Eu³⁺ ions incorporated into the CaS host lattice. Fourier transform infrared spectroscopy measurements were taken to elucidate the presence of various bonds in the sample. In vitro cytotoxicity analysis of the samples was also performed using MTT assay on human L929 fibroblasts cell lines in order to assess the biocompatibility of the nanoparticles. This is the first time report of the cytotoxicity studies of highly fluorescent CaS: Eu nanoparticles synthesized by wet chemical method.