In(OH)3 and In2O3 Micro/Nanostructures: Controllable NaOAc-Assisted Microemulsion Synthesis and Raman Properties

In(OH)3 micro/nanostructures, including nanorods, nanoellipses, microspheres, and microbricks, were successfully synthesized using a CH3COONa(NaOAc)-assisted method involving a cetyltrimethylammonium bromide (CTAB)/water/cyclohexane/n-pentanol microemulsion process. It was found that the experimental parameters, such as the molar ratio (w) between water and CTAB, reaction temperature, chelating ligand CH3COONa, and the concentration of reactants, played important roles in the morphological control of In(OH)3 structures. An oriented attachment or coalescence-based “self-assembly” mechanism was used to explain the morphology evolution from nanorods to nanoellipses, then to microspheres. When the In(OH)3 micro/nanostructures were calcined at 500 °C in air, the resulting In2O3 crystals succeeded to similar morphologies and sizes as the corresponding In(OH)3 precursors. Raman vibrational dynamics modes of the In2O3 structures were analyzed in detail, where these Raman peaks exhibit shape- and size-dependent Raman properties.