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 degrees C for 45 min, ca. 50 Angstrom +/- 2.5 A diameter) of the corresponding bis[methyl(n-hexyl)di-thio or -seleno]carbamato {M[E2CN-Me(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).