nl3008727_si_002.mov (2.01 MB)
Dynamic Fluctuations in Ultrasmall Nanocrystals Induce White Light Emission
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posted on 2012-06-13, 00:00 authored by Timothy J. Pennycook, James R. McBride, Sandra
J. Rosenthal, Stephen
J. Pennycook, Sokrates T. PantelidesIndividual ultrasmall CdSe nanocrystals have recently
been found
to emit white light, but the ultimate origin of the phenomenon has
remained elusive. Here we use a combination of state-of-the-art experiment
and theory to show that excitation sets the ultrasmall nanocrystals
into a fluxional state. Their energy gaps vary continuously on a femtosecond
time scale, so that even an individual nanocrystal can emit across
the entire visual range. In addition, we observe the outer layers
of the larger monochromatic emitting nanocrystals to be fluxional.
Such fluxionality should be considered when optimizing nanocrystals
for applications. Thus, small is indeed different, but ultrasmall
is different yet again.