Polarization Resolved Measurements of Individual DNA-Stabilized Silver Clusters

Polarization-resolved excitation and emission measurements on individual 10-15 atom silver clusters formed on DNA are presented. The emission is highly linearly polarized, typically around 90% for all emitters, whereas the polarization dependence of the excitation strongly varies from emitter to emitter. These observations support the hypothesis that the luminescence arises from collective electron oscillations along rod-shaped silver clusters, whereas the excitation process does not necessarily have a strong preferential polarization direction and thus may involve energy and/or charge transfer between the cluster and DNA. In addition to stabilizing the clusters, the DNA also appears to strongly influence the available paths for excitation.