Photoluminescence of CdSe and CdSe/CdO · nH₂O core/shell nanoparticles prepared in aqueous solution

CdSe sols with different colors were prepared by simply mixing CdSO₄ and NaSSeO₃ solutions under [Cd²⁺]/[Se^2-] ratios of 2.0-0.4 at room temperature. The nanoparticles, with average sizes of 1.8-3.6 nm, showed relatively narrow photoemission peaks at 522-556 nm. The strongest photoluminescence with a FWHM of 35 nm was obtained under [Cd²⁺]/[Se^2-] ratio of 1.2. The possible mechanism for achieving the strongest photoluminescence was proposed. Photoluminescence of these particles was greatly increased by surface modification of cadmium (II) hydrous oxide. The photoluminescence of these core-shell particles was kept constant in the pH range of 8.0-10.0, but dramatically decreased with an obvious blue-shifted peak while the pH was lower than 8.0. In addition, the photochemical oxidation of CdSe nanoparticles was markedly inhibited after they were modified with cadmium hydrous oxide.