Ensembles Of Y2O2S:Eu3+ widegap semiconductor nano-crystals exhibit ON-OFF fluorescence blinking phenomenon, which mimic II-VI semiconductor quantum-structures. Attempt has been made to explain this phenomenon under the ambit of diffusion controlled electron transfer (DCET) model. Insights derived using opto-impedance technique in conjunction with the DCET model clearly establish the relaxation of surface state(s) through a diffusion process. Ensembles Of Y2O3:Eu3+ nano-crystals, the insulating counterpart investigated for comparison does not show such fluorescence blinking. (c) 2007 Elsevier B.V. All rights reserved.