Nanosize indium hydroxide by peptization of colloidal precipitates

A new procedure for the preparation of nanosized In(OH)(3) particles in high concentrations without added surfactants is described. The process is based on the peptization of In(OH)3 dispersions consisting of micrometer colloids, which are obtained by the hydrolysis of InCl3 in ethylene glycol to which aqueous sodium hydroxide solutions are added. Depending on conditions, aging such systems at elevated temperatures (150-175 degrees C), yields colloidal particles of different morphologies (platelets, fibers), which are composed of nanometer subunits. The latter are liberated by repeated washing with water or 2-propanol, resulting in uniform spherical particles of similar to 80 nm in diameter. It is suggested that an In-glycolate compound forms at high temperatures, which keeps the nanoparticles together, but it is decomposed on treating with water or 2-propanol, allowing for their release. The original micrometer-size precipitates retain their shape after calcination; hence, In2O3 particles of different morphologies can be obtained.