Luminescent material consisting of nanocrystals comprising a core surrounded by a shell, said core consisting of a nanocrystal of semiconductor of formula AB in which A represents a metal or a metalloid in oxidation state (II) and B represents a chemical element in oxidation state (VI), and said shell consisting of a ZnSe layer whose surface is provided with an organic passivation layer consisting of at least one primary amine combined with at least one phosphine oxide and/or phosphine selenide compound.The invention relates in particular to nanocrystals with a CdSe core, these being covered by a ZnSe shell.The invention furthermore relates to a method of preparing these materials.