Emission properties of single CdSe/ZnS quantum dots close to a dielectric interface

We study the effect of a dielectric interface on the emission of individual semiconductor quantum dots (QDs). By means of a simple experimental method, a single nanoparticle can be placed successively close and far from an interface, enabling a direct comparison of its fluorescence properties in both cases. We analyze the modifications of both the radiation pattern and the radiative lifetime of individual QDs by a glass-air interface. We discuss the role of their degenerate two-dimensional dipole in the emission pattern and show how a simple dielectric interface can affect the collection efficiency. Finally, we present a simple method to determine the quantum efficiency of the emitting state at the single molecule level. (c) 2005 Elsevier B.V. All rights reserved.