Formation of spherical, rod- And branch-shaped colloidal In₂O₃ Nanocrystals through Simple Thermolysis of an Oleate Precursor

Synthesis of colloidal indium(III) oxide (In₂O₃) nanocrystals (NCs) by a simple non-injection method, using indium(III) oleate as an indium and oxygen source, was studied under conditions of various precursor concentrations, reaction temperatures and times. In the case of using a solution with a low precursor concentration, spherical In₂O₃ NCs that exhibited high crystallinity were successfully obtained. Their size was easily controllable in the range of 4 to 6nm in diameter by changing the reaction temperature and time. Because the growth of the spherical NCs was developed by the precipitation of new In₂O₃ components from solution and not by Ostwald ripening, the obtained NCs exhibited a narrow size distribution and were almost monodispersed. In contrast to the case of using a solution with a low precursor concentration, rod- and triple-fork-shaped NCs were obtained in the case of using a solution with a high precursor concentration. Formation of the rod- and triple-forkshaped NCs was attributed to the high growth rate after the nucleation because of the high initial precursor concentration.