Highly stable colloidal ZnO nanocrystals by MgO passivation

The surface of ZnO nanocrystals was engineered by the creation of an MgO shell layer that prevents the particle aggregation and improves the luminescent properties. The ZnO core with a diameter of ∼3.0 nm and ∼0.3 nm thick MgO-passivated ZnO nanocrystals were prepared at 0 deg. C using the reaction between Zn(CH3COO)2, Mg(CH3COO)2 and NaOH dissolved in ethanol medium. While unpassivated or organically capped ZnO nanocrystals are lacking in a colloidal stability against ageing, MgO-passivated ones show a remarkable colloidal stability, demonstrating that the surface passivation of ZnO nanocrystals by an MgO shell is effective. Luminescent efficiencies of green emission of ZnO/MgO nanocrystals versus bare ZnO counterparts are compared, and combined EDS/XPS and Raman spectroscopic data are further provided to verify the core/shell structure of ZnO/MgO nanocrystals.