PEG aggregation templated porous ZnO nanostructure: room temperature solution synthesis, pore formation mechanism, and their photoluminescence properties

Porous ZnO micro/nanostructures were prepared using a simple PEG assistant solution synthetic method at room temperature. The concentration of the zinc ions has a great influence on the morphology and chemical composition of the final products. The presence of hydrophobic groups of PEG resulted in the existence of microheterogeneities and the PEG aggregations in the mixed solution, which act as a soft template and play key roles in the formation of the porous structure of ZnO. High reaction temperature resulted in the decreased hydrogen bonding between the PEG and water molecules, and the increased hydrophobic interactions between the PEG chains as well as the increased pore size of final ZnO products. The influence of PEG molecular weight on the pore structure was also investigated. Photoluminescence studies show that the porous ZnO micro/nanostructures exhibited ultraviolet emission peak located at 385 nm and broad visible green emission peak centered at 525 nm with a shoulder at the yellow region. The origin and the intensity of the photoluminescence visible emissions was attributed to the structure defects, which was investigated by X-ray photoelectron spectroscopy.