The study of optical properties of ZnS, ZnS:Co2+ nanoparticlesC. Vatankhah, M. H. Yuosefi, A. A. Khosravi and M. SavarianEur. Phys. J. Appl. Phys., 48 2 (2009) 20601DOI: https://doi.org/10.1051/epjap/2009157