It can be seen that these
nanoparticles exhibit two distinct photoluminescence bands, one
with the peak position at 500 nm and the other with the peak
position at 580 nm. The photoluminescence band with the peak at
500 nm gets converted to another band with the peak at 580 nm
upon increase in the excitation wavelength from 380 nm to
480 nm under identical conditions. This clearly indicates that
with decrease in the excitation photon energy the red shifted
photoluminescence band dominates. The present observation
could not be correlated to the size distribution of the CdSe
nanoparticles, as the size of the primary nanoparticles was about
3 nm without much variation. It is to be mentioned here that, this
observation is quite different from the earlier study reported by
Chandrasekharan and Kamat