Globular pattern formation of hierarchical ceria nanoarchitecture

Abstract

Dissipative structures often appear as an unstable counterpart of ordered structures owing to fluctuations that do not form a homogeneous phase. Even a multiphase mixture may simultaneously undergo one chemical reaction near equilibrium and another one that is far from equilibrium. Here, we observed in real time crystal seed formation and simultaneous nanocrystal aggregation proceeding from CeIV complexes to CeO2 nanoparticles in an acidic aqueous solution, and investigated the resultant hierarchical nanoarchitecture. The formed particles exhibited two very different size ranges. The hierarchically assembled structures in solutions were CeO2 colloids, viz. primary core clusters (1–3 nm) of crystalline ceria and secondary clusters (20–30 nm) assembled through surface ions. Such self-assembly is widespread in multi-component complex fluids, paradoxically moderating hierarchical reactions. Stability and instability are not only critical but also complementary for co-optimisation around the nearby free energy landscape prior to bifurcation.

Cerium Nanophases from Cerium Ammonium Nitrate

“…These studies showed via SAXS and TEM imaging that initially primary particles form (∼1–3 nm diameter), followed by aggregation of these into larger particles (20–30 nm) . A follow-on study by Aoyagi et al confirmed that precipitated CeO 2 nanoparticles are actually aggregates of smaller particles, which suggests high surface areas and pore volumes could be obtained from this very simple chemistry, where such topologies could promote Ce III accompanied by oxygen vacancies. In other studies, nano-CeO 2 (NC-CeO 2 ) was also formed from CAN by adding base and by hydrothermal or solvothermal treatment respectively of aqueous and organic solutions. , Equivalent to adding base, Pettinger et al found that low concentration of CAN spontaneously forms colloidal NC-CeO 2 at room temperature .…”