Environment-mediated structure, surface redox activity and reactivity of ceria nanoparticles

    Authors

    T. X. T. Sayle; M. Molinari; S. Das; U. M. Bhatta; G. Mobus; S. C. Parker; S. Seal;D. C. Sayle

    Comments

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    Abbreviated Journal Title

    Nanoscale

    Keywords

    OXIDE NANOPARTICLES; OXYGEN; SIMULATION; ADSORPTION; BOUNDARIES; RESOLUTION; STABILITY; OXIDATION; DYNAMICS; BEHAVIOR; Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials; Science, Multidisciplinary; Physics, Applied

    Abstract

    Nanomaterials, with potential application as bio-medicinal agents, exploit the chemical properties of a solid, with the ability to be transported (like a molecule) to a variety of bodily compartments. However, the chemical environment can change significantly the structure and hence properties of a nanomaterial. Accordingly, its surface reactivity is critically dependent upon the nature of the (biological) environment in which it resides. Here, we use Molecular Dynamics (MD) simulation, Density Functional Theory (DFT) and aberration corrected TEM to predict and rationalise differences in structure and hence surface reactivity of ceria nanoparticles in different environments. In particular we calculate reactivity 'fingerprints' for unreduced and reduced ceria nanoparticles immersed in water and in vacuum. Our simulations predict higher activities of ceria nanoparticles, towards oxygen release, when immersed in water because the water quenches the coordinative unsaturation of surface ions. Conversely, in vacuum, surface ions relax into the body of the nanoparticle to relieve coordinative unsaturation, which increases the energy barriers associated with oxygen release. Our simulations also reveal that reduced ceria nanoparticles are more active towards surface oxygen release compared to unreduced nanoceria. In parallel, experiment is used to explore the activities of ceria nanoparticles that have suffered a change in environment. In particular, we compare the ability of ceria nanoparticles, in an aqueous environment, to scavenge superoxide radicals compared to the same batch of nanoparticles, which have first been dried and then rehydrated. The latter show a distinct reduction in activity, which we correlate to a change in the redox chemistry associated with moving between different environments. The reactivity of ceria nanoparticles is therefore not only environment dependent, but is also influenced by the transport pathway or history required to reach the particular environment in which its reactivity is to be exploited.

    Journal Title

    Nanoscale

    Volume

    5

    Issue/Number

    13

    Publication Date

    1-1-2013

    Document Type

    Article

    Language

    English

    First Page

    6063

    Last Page

    6073

    WOS Identifier

    WOS:000320398300051

    ISSN

    2040-3364

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