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 InCl 3 in ethylene glycol to which aqueous sodium hydroxide solutions are added. Depending on conditions, aging such systems at elevated temperatures (150−175 °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 ∼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, In 2 O 3 particles of different morphologies can be obtained.