Sol-gel synthesis of nanoscaled spinels using propylene oxide as a gelation agent

Spinel nanoparticles of CoAl2O4 (blue), CoCr2O4 (bluish green), ZnFe2O4 (brown) and CuCr2O4 (black) were synthesized by a sol-gel route with propylene oxide as a gelation agent. This method has proven to be an effective route to synthesize mixed oxide nanoparticles, especially for that with one of metal ion having a formal charge of less than +3. Transmission electron micrographs show the small particle size (less than 60 nm) of the four pigments and their narrow particle size distributions.