Towards the realization of luminescence from visible emitting trivalent lanthanides (Sm, Eu, Tb, Dy) in polar zinc sulfide nanoparticles: evaluation of in vitro cytotoxicity

This work reports on the realization of luminescence from four visible emitting trivalent lanthanide (Ln) cations [samarium (Sm), europium (Eu), terbium (Tb) and dysprosium (Dy)] in polar zinc sulfide nanoparticles, Zn(Ln)S. Among the Zn(Ln)S nanoparticles studied, noticeable lanthanide cation centered luminescence has only been realized from the Zn(Tb)S and Zn(Eu)S nanoparticles in water, whereas no such effect has been observed in the corresponding Sm and Dy containing nanoparticles. In all the nanoparticles with characteristic lanthanide luminescence, the nanoparticles were found to be acting as an optical antenna and protector matrix, in order to realize luminescence from the respective lanthanide cations. The results have been rationalized with the lanthanide cations acting as charge (hole and/or electron) traps in the semiconductor nanoparticle matrix along with associated environmental effects. A comparison of the corresponding hydrophobic Zn(Tb)S nanoparticles reveal significant differences in photophysical properties. Finally, the hydrophilic Zn(Tb)S nanoparticles have been examined for in vitro cytotoxicity and the results indicate potential anti-cancer therapy for human mammary adenocarcinoma cells (MDA-MB-231) with the capability of cellular imaging.