NMR Study of Semiconductor Molecular Clusters

Three sizes of CdSe molecular clusters were studied by ${}_{}{}^{77}{}_{}{}^{}\mathrm{Se}$ NMR spectroscopy. The clusters are synthesized via arrested precipitation in a structured medium and are isolated as a molecular solid after modification of their surfaces with covalently attached organic ligands. While one component of the broad ${}_{}{}^{77}{}_{}{}^{}\mathrm{Se}$ NMR line shape corresponds to the bulk material, increasing proportions appear at shifts upfield as a function of decreasing particle size. The line positions and distribution of chemical shifts can be related to a size dependence of the electronic structure and the local chemical environments.