Fluorescence spectroscopy of single lead sulfide quantum dots.

We report the observation of fluorescence from single PbS quantum dots (QDs) using confocal microscopy in an inert atmosphere. Single PbS QDs exhibit a narrowing of the fluorescence line width (relative to the ensemble) and fluorescence intermittency ("blinking"), consistent with the properties of other single QDs. However, single-particle line widths averaged 100 meV, indicating a significant homogeneous component to the ensemble line width. In addition, the duration of an on/off blinking event has a probability density that decays according to an inverse power law, indicating a broad distribution of kinetic rates to multiple on/off states.