Fabrication of ultrafine cerium oxide nanoparticles as an aqueous colloidal solution with single-molecular dispersant via shear agitation reactor or one-pot hydrolysis

Abstract

Herein, ultrafine CeO2 nanoparticles are synthesized using monomolecular amino acids as dispersants. Monomolecular amino acids are suitable dispersants for the dispersion of nanoparticles with a diameter of 1 nm. Batch-type room-temperature hydrolysis (RTH) synthetic method, which takes advantage of the low decomposition pH of Ce (IV) nitrate, and a shear agitation (SA) reactor, which is highly versatile for multicomponent systems of colloidal synthesis, are used. After adding glycine, ultrafine CeO2 colloids of sizes 1.1 and 1.2 nm are obtained via the batch-type RTH synthesis method and SA reactor, respectively. The smallest CeO2 colloid size is 0.7 nm, which earned at the close concentration of the saturation of glycine using the batch-type RTH method. Because RTH can slowly hydrolyze Ce (IV) nitrate over several hours, we were able to observe the initial stage of nucleation (0.7 nm), which passes instantaneously in the SA reactor. Furthermore, glycine was found to be particularly effective in stabilizing the surface of cerium oxide due to its high adsorption capacity. Therefore, cerium oxide, which is amorphous in the synthesis stage, remained amorphous up to 100 °C due to glycine adsorption, neutralized the colloidal dispersion to form precipitates, and crystallized at room temperature after glycine was removed by washing treatment, resulting in a fluorite structure with a crystallite diameter of 1.5 nm. This crystallite diameter is maintained after heat treatment at 200 °C for 30 min.