Semiconductor molecular clusters: Studies with NMR spectroscopy.

Three sizes of CdSe molecular clusters have been studied by sup (77) Se and sup (111) Cd nuclear magnetic resonance (NMR) spectroscopy. The semiconductor clusters are synthesised via arrested precipitation in a structured medium and can be isolated as a molecular solid after modification of the surface with covalently attached organic ligands. Sup (77) Se and sup (111) Cd spectra of these particles consist of broad lines due to a distribution of chemical shifts. While the component of the lineshape always corresponds to the bulk cubic material, increasing proportions appear shifted upfield as a function of decreasing particle diameter. These results are interpreted in terms of a size dependence on both the electronic structure of the particle and the chemical environments of the nuclear spins.