Single Molecule Lifetime Studies of Small Clusters of Semiconductor Nanocrystals

Enhanced fluorescence intermittency has been reported in single molecule fluorescence experiments on small clusters of semiconductor nanocrystals$^{1}$, and single Mn$^{2+}$ doped semiconductor nanocrystals$^{2}$. This behavior is attributed to electronic coupling between nanocrystals in the clusters. We report here on further studies of small clusters of semiconductor nanocrystals utilizing single molecule time-correlated single photon counting, which provides insight into the nature of the coupling. According to this analysis, clusters typically blink on a microsecond to millisecond time scale; whereas, isolated nanocrystals blink on much longer millisecond to second time scale. 1. Yu, M. and A. Van Orden, \textit{Enhanced Fluorescence Intermittency of CdSe-ZnS Quantum-Dot Clusters.} Physical Review Letters, 2006. \textbf{97}(23): p. 237402-4 2. Yanpeng Zhang, C.G., Javed Muhammad, David Battaglia, Xiaogang Peng and Min Xiao, \textit{Enhanced Fluorescence Intermittency in Mn-Doped Single ZnSe Quantum Dots.} Journal of Physical Chemistry C, 2008. \textbf{112}(51): p. 20200-20205