Controlling Reactivity in Metal/Metal Oxide Nanoparticles

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Nanoparticles (NPs)-clusters of atoms no larger than 100 nm in any dimension-are critical materials for a variety of high-stake applications that will address global challenges in healthcare (regenerative medicine and cancer therapy), nformation technologies (data storage), catalysis, and environmental remediation (contaminant/bacteria removal). Whilst significant progress in these areas has been made, key challenges remain. In medical applications such as hyperthermia and drug delivery, high-magnetic-moment NP cores are prone to oxidative degradation, which reduces their effectiveness. Similarly, catalytic NPs used in motor vehicle exhaust systems undergo rapid on-stream deactivation which is estimated to consume more than 50 times more platinum than necessary. Reactivity is clearly at the heart of these issues and a better atomic-scale understanding of how NPs react in different gaseous and aqueous environments, particularly with regard to nanoscale oxidation, is required (see, for example, Pratt, Kröger et al., Nature Materials, 2014). This project aims to provide this understanding by combining a new, unique nanoparticle growth facility with state-of-the-art characterisation techniques. Specifically, the balance between grain-boundary and interstitial diffusion during oxidation and how this can be tailored by engineering NP size, shape, coating material and strain will be investigated. More insight on these mechanisms will benefit the above NP applications with potential for significant scientific and commercial impact. Initially, NPs will be synthesised using a new gas-aggregation cluster source which affords very careful control of NP properties such as size, size distribution, core and shell composition, and geometry. The project will then involve the use of a variety of cutting-edge characterisation techniques to monitor reactivity: aberration-corrected and in situ fluid cell electron microscopy will provide high resolution images of isolated and in-solution particles so that we can monitor changes in NP structure; a unique ultrahigh vacuum (UHV) surface analysis facility will be used to probe the electronic and magnetic properties of native, core-shell and functionalized NPs; theoretical input on magnetic properties and the role of grain boundaries/defects will also be considered.