Effect of Surface Passivation on the Electrogenerated Chemiluminescence of CdSe/ZnSe Nanocrystals

The electrogenerated chemiluminescence (ECL) spectrum of CdSe/ZnSe nanocrystals (NCs) dispersed in a CH2Cl2 solution containing 0.1 M TBAP was obtained by stepping the potential between +2.3 and −2.3 V. Unlike the spectra from the ECL of Si or CdSe NCs, where the emission occurs in a single peak that is significantly red-shifted from the photoluminescence (PL) peak (attributed to emission from surface states), ECL from CdSe/ZnSe produced a spectrum containing two peaks: a sharp peak whose position was almost identical to that in the PL spectrum and another broader peak with a red shift of ∼200 nm compared to that in the PL. This suggests emission from both surface states on the NCs and from the bulk in NCs where the surface states have been passivated.