Dielectric confinement effects on the emission lineshipe of single semiconductor nanocrystals

We have explored the influence of different matrices on the photoluminescence line shape of individual CdSe core shell nanocrystals (NCs) at room temperature using confocal microscopy / spectroscopy. The results obtained corroborate previous observations of a correlation between blinking events and spectral diffusion but in addition, we have found that the extent of spectral diffusion is almost independent of the dielectric environment of the NC, thus suggesting that ionization and charge reorganization events in the matrix are not responsible for the observed continuous spectral shifts. We also observed that the emission line width is correlated with the emission peak position and that the correlation coefficient between these two variables is a function of the dielectric constant of the matrix surrounding the NC. These results are analyzed in terms of dynamic rearrangements of charges trapped at the surface of the nanocrystal.