Study of the surface modification with oleic acid of nanosized HfO2 synthesized by the polymerized complex derived sol-gel method

The synthesis of nanosized hafnium oxide by the polymerized complex derived sol-gel method is reported. The structural and morphological characterization of the HfO2 was carried out by X-ray diffraction and scanning electron microscopy. The surface of hafnium oxide nanoparticles was modified by capping with oleic acid. The nanoparticle surface area was measured by the gas adsorption technique in order to determine the minimal amount of oleic acid needed to obtain a uniform coverage of the hafnium oxide. The existence of organic layer can be confirmed by Fourier transform spectroscopy, solid state nuclear magnetic resonance spectroscopy, thermal gravimetric analysis and transmission electron microscopy. The FTIR and solid state NMR results reveal that oleic acid is chemisorbed as a carboxylate onto the HfO2 nanoparticle surface and confirm the formation of a monomolecular layer of oleic acid surrounding the HfO2. The cover density of oleic acid on the HfO2 increases with the amount of oleic acid used to modify the nanoparticles and the surface properties of HfO2 nanoparticles modified with oleic acid change from hydrophilic to hydrophobic.

Highlights► Synthesis and characterization of nanosized HfO2 by the polymerized complex derived sol-gel method. ► The HfO2 nanoparticles were coated with oleic acid. ► The minimum concentration of oleic acid necessary to cover HfO2 particles was determined. ► The oleic acid was chemisorbed as a carboxylate onto the HfO2 nanoparticle surface. ► The surface properties of HfO2 modified with oleic acid changed from hydrophilic to hydrophobic.