Synthesis and organic modification of CoAl₂O₄ nanocrystals under supercritical water conditions

The synthesis and in situ organic surface modification of cobalt aluminate nanoparticles were carried out to change the hydrophilic surface of pigment nanoparticles to hydrophobic by using organic reagents such as R-COOH and R-NH₂ along with the respective metal hydroxide as starting materials at supercritical temperature, under 30-40 MPa pressure at a rapid reaction rate. The organic ligand capping could effectively inhibit the particle growth and also control the size of the nanocrystals. The resultant nanoparticles are dispersed in a binary solvent system, where organic modified particles are dispersed well in an upper organic solvent medium.