The aqueous dispersion of ZnO quantum dots (QDs) with strong blue emission (quantum yield of 76%) was synthesized through a simple solution route. The water stability of such QDs is provided by the hydroxyl groups on their surface, and the strong blue emission is suggested to arise from the formation of surface ZnO/oleic acid complexes. Under irradiation, these complexes are thought to absorb the excitation light with 3.54 eV and then generate the blue emission with 2.82 eV.

ZnS/ZnO heteronanostructures were prepared to serve as the photoanode of the dye-sensitized solar cells. Two nanostructures, namely, ZnS/ZnO coaxial nanowires and ZnS/ZnO hierarchical nanowires (ZnS nanoparticles on ZnO nanowires), were successfully synthesized by chemical bath deposition and chemical etching processes, respectively. For both of the nanostructures, the ZnS coating can enhance photocurrent and conversion efficiency compared with the bare ZnO nanowires. We propose that ZnS layers in the two nanostructures take effect in different ways in that the ZnS compact layer in the coaxial structure retards the back transfer of electrons to the dye and electrolyte, while the coarse surface of ZnS nanoparticles in the hierarchical nanowires significantly enhances the adsorption of dye molecules. Hence, the ideal photoanode structure for high power-conversion efficiency should have both the compact shell layer and the high surface roughness.

Preparation and photoluminescence (PL) properties of zinc oxide (ZnO) nanoparticles embedded in a lipophilic polymethyl methacrylate (PMMA) matrix are reported in detail with an unbalanced sol-gel route. A high-resolution transmission electron microscope (HRTEM) indicates that ZnO particles are highly crystallized, with a size of 5-6 nm and hexagonal wurtzite structure. During the sol-gel reaction, partial ester groups of R-COOCH 3 in PMMA are hydrolyzed to form carboxylic ion groups, which chemisorb on the surface of ZnO nanoparticles to eliminate the defects; thus ZnO nanoparticles in the PMMA matrix exhibit complete ultraviolet (UV) emissions, while emissions in the visible region are fully quenched.

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