Controlling the exciton energy of zinc oxide (ZnO) quantum dots by changing the confinement conditions

• Ability to control the particle size of ZnO with two different synthesis routes.
• Assignment of intrinsic defect centers in ZnO by EPR and PL spectroscopy.
• Exciton energy calculations by Brus theory.
• Observation of the quantum confinement effect during in situ precipitation reaction.

ZnO nanoparticles were synthesized by solid state and hydrolysis methods based on the conventional precipitation. In situ growth of ZnO nanoparticles were monitored by photoluminescence spectroscopy (PL). By the help of electron paramagnetic resonance (EPR) technique, detailed analysis of intrinsic defect structure of ZnO was given with respect to mean particle size. In nanoscale concentration of surface defects enormously increased and core defects reduced. In addition, blue-shift was observed in PL spectra at near-band-edge UV region due to e–h recombination. Calculation of band gap energies by the aid of Brus equation revealed consistent results with the experimental observations.

Monitoring quantum size effects by EPR spectra. With the aid of different chemical routes (SS, HydNa, HydLi) EPR spectra show drastic changes from bulk to nano-size samples.Figure optionsDownload as PowerPoint slide