Photoluminescence from nanosize gold clusters

We have observed visible light emission from nanosize gold clusters. Liquid chromatographic analysis of the metal clusters shows that relatively intense photoluminescence occurs only when the size of the metal nanocluster is sufficiently small (<5 nm). The emission is strongly Stokes shifted and is assigned to radiative recombination of Fermi level electrons and sp- or d-band holes. The electron and/or hole states are perturbed by surface states, as indicated by the dependence of the emission spectrum on the nature of the cluster surface. Finally, we found that large, nonemitting gold clusters can also be made luminescent by partial dissolution using KCN. (C) 1998 American Institute of Physics. [S0021-9606(98)00819-8].