Plasmonic effect of nanoshelled nanocavity on encapsulated emitter's spontaneous emission

The plasmonic enhancement of nanoshelled nanocavity (a silica core coated by Ag or Au shell) on the spontaneous emission of an encapsulated emitter (a molecule or quantum dot) is studied systematically by analyzing the excitation rate and the apparent quantum yield together. By averaging all possible locations and orientations of the emitter, the average enhancement factor (AEF) of the emitter randomly located in the core is calculated. Our results show that the AEF is weaker than that of the emitter located at the core center. In addition, Ag nanoshell (NS) is a narrowband enhancer. As the thickness of the shell becomes thinner, the surface plasmon resonance of NS is red-shifted and the peak of AEF increases. The specificity of Ag NS for enhancing a specific spontaneous emission is higher than Au NS. In addition, Ag NS with a smaller core has a larger AEF, while Au NS has an optimal radius of core (30 nm) to obtain the maximum AEF. Moreover, the AEF is reduced, as the Stokes shift increases. (C) 2011 Elsevier Ltd. All rights reserved.