PNNL

Abstract

The combination of long term aging studies and molecular dynamics (MD) simulations has been successfully used to explain the time dependent, hierarchical assembly of ceria nanoparticles (CNPs). When the CNPs were aged in as-synthesized condition at room temperature, in water, it was observed that the individual 3-5 nm CNPs result in octahedral super-structures through a fractal assembly. This hierarchical, fractal selfassembly was observed despite the absence of any surfactant, use of room temperature and atmospheric pressure. High resolution transmission electron microscopy (HRTEM), and fast Fourier transform (FFT) analysis have been used to explore the assembly of the individual nanoparticles into fractal superoctahedra. Both experimental and theoretical analysis showed that the initial octahedral and truncated octahedral seeds symmetrically assemble and result in the superoctahedra with intermediate transformation steps.