Cd1-yMnyS nanoparticles:: absorption and photoluminescence properties

In this paper we demonstrate that the use of colloidal assemblies permits to control independently the size and composition of Cd1-yMnyS nanosized particles. As expected, for a given composition, the increase in the band-edge energy with decreasing the particle size is observed and attributed to a quantum size effect. For a similar average particle size, the band gap does not vary linearly when manganese concentration increases. The minimum is more pronounced and its depth increases with decreasing the particle size. This is attributed to a quantum size effect and due to strong interactions between manganese ions and the conduction and valence bands electrons. For similar size of nanocrystals, the photoluminescence due to isolated Mn2+ ions in Cd1-yMnyS nanoclusters is observed when the particles are aged and the CdS trap emission is observed immediately after the synthesis. The most important parameter in order to observe the Mn2+ ions luminescence is the aging time of the particles and not a quantum size effect as claimed previously. (C) 1998 Elsevier Science B.V. All rights reserved.