Designable luminescence with quantum dot-silver plasmon coupler.

We explore a strongly interacting QDs/Ag plasmonic coupling structure that enables multiple approaches to manipulate light emission from QDs. Group II-VI semiconductor QDs with unique surface states (SSs) impressively modify the plasmonic character of the contiguous Ag nanostructures whereby the localized plasmons (LPs) in the Ag nanostructures can effectively extract the non-radiative SSs of the QDs to radiatively emit via SS-LP resonance. The SS-LP coupling is demonstrated to be readily tunable through surface-state engineering both during QD synthesis and in the post-synthesis stage. The combination of surface-state engineering and band-tailoring engineering allows us to precisely control the luminescence color of the QDs and enables the realization of white-light emission with single-size QDs. Being a versatile metal, the Ag in our optical device functions in multiple ways: as a support for the LPs, for optical reflection, and for electrical conduction. Two application examples of the QDs/Ag plasmon coupler for optical devices are given, an Ag microcavity + plasmon-coupling structure and a new QD light-emitting diode. The new QDs/Ag plasmon coupler opens exciting possibilities in developing novel light sources and biomarker detectors.