Nonplasmonic Metal Particles as Excitation Energy Transfer Acceptors: an Unexpected Efficiency Revealed by Quantum Mechanics

We present a time-dependent density functional theory investigation of the excitation energy transfer (EET) between a typical chromophore (perylene diimide) and a small metal cluster (Au-20). Two different physical descriptions are tested for the metal: the real (nonplasmonic) cluster and a hypothetical nanoparticle characterized by a bulk gold dielectric response (which thus sustains surface plasmons). By comparing the results obtained for the same EET process with the two types of metal particles, we show that, surprisingly, nonplasmonic small metal clusters can be as intrinsically effective as plasmonic particles in EET, a finding that is also relevant for applications in several field ranging from analytical chemistry to nanoscience.