New synthetic entry to the family of molecular nanoparticles of cerium dioxide

Charlotte S. Bailey, Lucasz Wojtas, George Christou

University of Florida, University of South Florida

Cerium dioxide (CeO2 or ceria) nanoparticles (CNPs) are versatile materials which are employed or investigated for a range of applications, including their use in energy applications, industrial catalysis and, more recently, biomedical applications. The activity of CNPs depends on their size, shape, exposed surface facets, Ce3+ concentration, etc. However, these factors cannot be easily controlled using traditional nanoparticle syntheses, which suffer from poor control over size and shape. In addition, traditional nanoparticles cannot be structurally analyzed to atomic resolution. As a result, many questions regarding the effect of the nanoparticle morphology and surface composition on the activity of the particle remain unanswered. In an effort to improve our knowledge of this important material, our group has synthesized several cerium-oxo clusters with nanometer dimensions up to 2.4 nm which possess the same features as the bulk ceria lattice. We term these clusters ‘molecular nanoparticles’ owing to their molecular nature, size, and strong resemblance to the bulk material [1-3]. The molecular approach allows for true monodispersity, solubility and crystallinity. The latter enables the clusters to be structurally analyzed by X-ray crystallography to evaluate their core structure and surface features to atomic resolution. By making small changes to the established synthetic procedures, new members of the family can be isolated. In this presentation, we introduce synthetic methodologies to new cerium-oxo clusters that resemble a piece of the (111) surface of bulk ceria. The syntheses, crystal structures and catalytic activity towards radical scavenging will be discussed. We will also discuss the relevance of our new clusters to our established family of molecular nanoparticles.