Simple hydrothermal synthesis method for tailoring the physicochemical properties of ZnO: morphology, surface area and polarity

A simple urea-assisted hydrothermal synthesis method was used to tailor the physicochemical properties of ZnO materials. The role of Pluronic P123 block copolymer in the crystal growth, morphology and specific surface area of the as-prepared ZnO was studied. When Pluronic P123 is used, well-dispersed hierarchical microspheres, with a flower-like morphology, are obtained, but in its absence large spherical agglomerated clusters are formed. The polarity of the ZnO, measured as the ratio between plane (002) and plane (100), is also significantly higher for the Pluronic P123 sample. The influence of zinc salt precursors was also analysed. The use of zinc nitrate led to the formation of urchin-like ZnO structures, instead of the microflowers that result from zinc acetate salt. Despite having similar surface areas, the polarity of the zinc nitrate sample was much smaller. The decomposition of methylene blue corroborated the higher photocatalytic activity of the ZnO materials with a higher proportion of polar planes (higher polarity). The formation mechanism of the crystals is also suggested based on the observed gradual growth and assembly of the hydrozincite during the initial steps of the synthesis for the samples with and without Pluronic P123.