Superacid-Catalyzed Preparation of Highly Dispersible Zirconium Oxide and Titanium Oxide Nanoparticles Without Hydrocarbon Units

Abstract

Highly dispersible, hydrocarbon-free zirconium oxide and titanium oxide nanoparticles (ZrO2–NTf2– NP and TiO2–NTf2–NP) were successfully prepared via the simple sol–gel reactions of zirconium tetra-n-butoxide and titanium tetra-n-butoxide, respectively, using a water/methanol mixed solution of the bis(trifluoromethanesulfonyl)imide superacid. ZrO2–NTf2–NP could be dispersed in acetone, ethanol, methanol, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and water, whereas TiO2–NTf2–NP could be dispersed in acetone, DMF, DMSO, and water. The number-average particle sizes of ZrO2–NTf2–NP and TiO2–NTf2–NP were determined to be 3.6±0.6 nm and 5.8±1.1 nm; these values were obtained by dynamic light-scattering measurements of the acetone dispersions (1.0 w/v%). Highly dispersible ZrO2 nanoparticles could be prepared using other acid catalysts containing trifluoromethyl groups, such as trifluoromethanesulfonic acid and trifluoroacetic acid. In contrast, dispersible TiO2 nanoparticles could not be prepared using these acid catalysts.