Nonaqueous synthesis of nanocrystalline indium oxide and zinc oxide in the oxygen-free solvent acetonitrile

The nonaqueous preparation of nanocrystalline indium and zinc oxide involving the solvothermal reaction of metal acetylacetonates with acetonitrile is presented. The synthesis approach is characterized by a particularly moderate reaction temperature of 100 degrees C and by the use of an oxygen-free solvent. The oxygen for the metal oxide formation is supplied by the acetylacetonate ligand of the precursor molecules. In the case of In2O3, the product consists of crystalline nanoparticles with a spherical morphology and a narrow size distribution in the range of 3-6 nm. According to transmission electron microscopy (TEM), the ZnO nanoparticles are in the size range of 15-85 nm, sometimes with well-faceted hexagonal morphology. Powder X-ray diffraction (XRD) data as well as high-resolution TEM point to mesocrystal formation, i.e., the ZnO nanoparticles are composed of a highly oriented arrangement of smaller nanocrystallites that scatter like a single crystal.