High-yield sol-gel synthesis of well-dispersed, colorless ZrO2 nanocrystals

A 93% high-yield synthesis of well-dispersed, colorless zirconium dioxide (ZrO2) nanocrystals is reported. In this synthesis, hydrolysis and condensation reactions of zirconium(IV) tert-butoxide in the presence of oleic acid (100 degrees C) formed ZrO2 precursors. The ZrO2 precursors were made of-Zr-O-Zr-networks surrounded by oleic acid molecules. Annealing (280 degrees C) the precursors dispersed in dioctyl ether caused crystallization of the -Zr-O-Zr-networks, thereby generating 4 nm ZrO2 nanocrystals stabilized with oleic acid. The particles were highly crystalline and tetragonal phase. A dense ZrO2 nanocrystal dispersion in toluene (280 mg/mL) showed a transmittance of about 90% (3 mm optical path length) in the whole visible region.