Excitation Energy Dependence of Flourescence Intermittency in Core/Shell CdSe/ZnS Nanocrystals
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2009
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Swarthmore College. Dept. of Physics & Astronomy
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Thesis (B.A.)
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Abstract
We report measurements of the excitation energy dependence of the fluorescence intermittency
of single CdSe/ZnS core/shell nanocrystals (NCs) using two different excitation
energies. The lower excitation wavelength, 532 nm, corresponds to excitation 270 me V
above the band gap. The higher energy, 405 nm, corresponds to excitation 1000 me V
above the band gap. At each excitation energy, 77 individual NCs were measured for 1500
s. The off-time probability density distribution from each individual NC follows a power
law with a distribution of slopes that is insensitive to the difference in excitation energy
studied. The on-time probability density distributions for individual and aggregated data
follow a truncated power law with slope distributions that are also insensitive to the difference
in excitation energy. However, the distribution of truncation times obtained from
the individual NCs at 405 nm excitation is peaked at a shorter value than the distribution
obtained with 532 nm excitation. These results suggest that blinking dynamics change for
excitation far above the 1P3j21Pe state.