Ceria nanoparticles: Size, size distribution, and shape

Nanocrystalline ceria particles have been prepared by mixing aqueous solutions of cerium nitrate and hexamethylenetetramine at room temperature. The smallest size of nanoparticles synthesized is 2 nm. For each batch prepared, a narrow size distribution is found with a standard deviation less than ±15%. A transmission electron microscopy (TEM) investigation shows that these particles are single crystals having either an octahedral shape with eight {111} surfaces, or with an additional {200} surface-truncated octahedral shape. In-situ ultraviolet-visible light absorption has been performed to measure the absorption edge and to monitor the growth of nanoparticles. The results from light absorption correlate well with those of the TEM images, providing an in-situ method to measure the particle size during synthesis.