β-CuI nanocrystallites (NCs) are synthesized on the atomically
smooth graphite basal plane surface using
a new hybrid electrochemical/chemical (E/C) method. This method
involves the following steps: (1) electrochemical
deposition of copper NCs onto an electrode surface, (2) electrochemical
oxidation of these copper NCs to yield
Cu2O, and (3) displacement of oxygen in Cu2O by
iodide in an aqueous KI solution. Dispersions of CuI
NCs
having mean diameters ranging from 10 to 180 Å were prepared using the
E/C method. Selected-area electron
diffraction analysis reveals that β-CuI NCs are obtained; these NCs
are epitaxially aligned with the hexagonal
periodicity of the graphite surface, as are the Cu2O
precursor particles. For samples of supported CuI NCs
having
a mean particle height of <25 Å, individual NCs were well-separated
from one another on the graphite surface and
were narrowly dispersed in height. Photoluminescence spectroscopic
analysis showed a strong, room temperature
emission at an energy corresponding to the band gap. As the
crystallite diameter was reduced from 180 Å to 13 Å,
the energy of this emission shifted from the macroscopic value of 2.92
eV to >3.04 eV, in good agreement with the
predictions of the effective mass, strong confinement
model.
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