Synthesis of nearly monodispersed metal oxide nanoparticles in water

We report a generalized aqueous route for the synthesis of a variety of nearly monodisperse nanostructured metal oxides with controllable sizes and shapes using aqueous metal ammonium carbonate solution as a precursor and decanoic acid under reflux as well as hydrothermal conditions. The procedure is based on direct formation of metal oxide through hydrolysis followed by dehydration of a metal ammonium carbonate complex in basic medium, in situ dissolution and surface modification of an oxide nanoparticle by decanoic acid through the formation of ammonium salt of decanoic acid. All the synthesized metal oxide nanostructures were characterized by transmission electron microscopy, powder X-ray diffraction and IR spectroscopy. The characterization result shows that all the particles are monodispersed in size and shape, and highly crystalline in nature. A probable formation mechanism is proposed to explain the formation of the size and shape selective CeO2.