The effects of Mg addition on the emission of green photons from ZnO nanoparticles were studied. Energy dispersive x-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) data demonstrated that ZnO nanoparticles with surface segregation of MgO (ZnO:MgO) were precipitated from colloidal reactions between Zn(2+),Mg(2+) and OH(-) ions suspended in ethanol. The photoluminescence emission spectra showed stronger green emission from suspended ZnO:MgO versus ZnO nanoparticles. ZnO:MgO also exhibited a stable green emission colour, which was slightly red-shifted from 495 to 520 nm with 168 days of ageing. It was postulated that the presence of MgO on the surface of ZnO prevented both the aggregation of ZnO nanoparticles via electrostatic stabilization of the suspension, and the formation of non-radiative recombination states on the surface, resulting in more intense, stable photoemission from ZnO. The red shift of the green emission from suspended ZnO nanoparticles with extended ageing was attributed to filling of radiative surface trap states in the bandgap.

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ZnO nanoparticles embedded into SiO(2) by an ex situ method were shown to result in stable green emission with a peak at 510 nm compared to the normal peak at 495 nm from micron-sized ZnO powders. Green emission from ZnO nanoparticles was completely suppressed when they were embedded in SiO2 doped with Eu3+. Instead, the f-f emissions from Eu3+ were enhanced 5-10 times by energy transfer from the embedded ZnO nanoparticles to Eu3+. The Eu3+ luminescence increased as the Eu3+ concentration increased from 1 vs 5 mole % (for 10 mole % ZnO). In addition, the intensity increased as the embedded ZnO nanoparticles concentration increased up to 10 mole % (for 5 mole % Eu3+). The effects of phonon mediated energy transfer, quenching by activator interactions between Eu3+ ions, and energy back-transfer from Eu3+ ions to ZnO nanoparticles were discussed.

Degradation of ZnS and Y2O2S cathodoluminescent (CL) phosphors has been studied at 1–4 keV using Auger electron spectroscopy simultaneous with CL. The data are consistent with an electron stimulated surface chemical reaction (ESSCR) which led to destruction of ZnS and formation of a surface nonluminescent ZnO layer as well as injection of oxygen point defects into the near-surface region. In the case of Y2O2S:Eu, the electron beam stimulated removal of S and formation of Y2O3:Eu in the presence of 1×10−6 Torr of oxygen. A model is presented which predicts that degradation by the ESSCR should increase with pressure in the vacuum, depend exponentially on electron dose, increase as the primary beam energy was reduced below 4 keV, and depend upon the type of gas present in the vacuum. These trends were demonstrated from the experimental data.