A rapid method for the preparation of silica-coated ZrO2 nanoparticles by microwave irradiation

A novel synthesis of silica-coated ZrO2 nanoparticles is reported based on microwave irradiation (MW) method. The synthesis of silica-coated ZrO2 nanoparticles was realized by a rapid uniform hydrolysis and subsequent copolymerization of the precursor tetraethoxysilane (TEOS) on ZrO2 surface. One of the advantages of this MW irradiation method is the very short coating time and uniform heating in comparison to the conventional ones, allowing the synthesis of uniformly coated ZrO2 nanoparticles with silica. The XPS analysis revealed the shifts in binding energies for Zr 3d5/2 and Zr 3d3/2 peaks after coating confirming the formation of silica layer on the surface of ZrO2 nanoparticles. Characteristic silica peaks were observed in the FTIR spectra of coated nanoparticles. The shift in the isoelectric point measured by dynamic light scattering method was indicator of silica coverage of the ZrO2 surface. The coatings formed at 70 °C were thin and uniform and extended up to 2 nm from the ZrO2 surface as confirmed by the HR-TEM images.