Solvothermal synthesis of zinc oxide microspheres

The solvothermal synthesis of ZnO particles from zinc acetylacetonate [Zn(acac)(2)] in the presence of triethanolamine (TEA) and various solvent systems at 170 degrees C is reported. The structural, optical and morphological characteristics of ZnO particles were investigated. It was found that the size and shape of ZnO nanoparticles and the way of their aggregation depend on the mole ratio [TEA]/[Zn(acac)(2)] and the type of alcohol used as a solvent. Doubling the molar ratio of TEA to Zn(acac)(2) in the presence of ethanol favoured the formation of huge spherical aggregates (>3 mu m) assembled from fine and uniform ZnO nanoparticles (similar to 20 nm). The results of present investigation show a strong impact of surface interactions between the formed ZnO nanoparticles and the molecules of solvent and TEA on the way of growth and aggregation, which enables the control of their morphological properties. The results show that TEA serves as a link between primary ZnO nanoparticles to form spherical aggregates with a controllable diameter. The results of X-ray diffraction size-strain analysis indicate the presence of size anisotropy with bigger crystallites in the direction of the c-ax of the zincite lattice compared with the direction perpendicular to the c-ax. The red shift of the absorption edge and reduced band gap energies are clearly visible with the increased sample microsphere size. (C) 2015 Elsevier B.V. All rights reserved.