Good quality highly mono-dispersed nanoparticles of II–VI binary chalcogenides ME (M = Zn or Cd, E = S or Se) have been prepared in a ‘one-pot’ synthesis by the thermolysis in tri-n-octylphosphine oxide (TOPO, e.g. at 200 °C for 45 min, ca. 50 Å ± 2.5 Å diameter) of the corresponding bis[methyl(n-hexyl)di-thio or -seleno]carbamato {M[E2CNMe(C6H13)]2, E = S or Se} complexes; the CdS, CdSe and ZnSe particles have been characterized by electronic spectroscopy, photoluminiscence, X-ray diffraction and electron microscopy (SAED, SEM and TEM).