Nanoclusters, nanoparticles, and surfaces: Bridging the gap between homogeneous and heterogeneous catalysis.

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Gold nanoparticles date from Roman times, when mixing gold salts and molten glass gave bright red glasses by the unintentional formation of nanoparticles. These procedures were used for centuries, such that all stained-glass windows contain metallic nanoparticles. Despite the high level of sophistication in modern nanomaterials synthesis, these materials are still mixtures, with structures characterized by size distributions not precise chemical formulae. Since the properties of nanomaterials are fundamentally related to size, controlling and predicting these properties will always be guess work until precision synthesis methods are developed. Metal nanoclusters are an important advance towards the goal of precision synthesis, but they are still prepared using a black box approach that makes control and prediction of structure problematic. The ubiquity of size-focusing processes that etch cluster mixtures to enable the isolation of one product illustrates a lack of control of synthetic parameters. We will approach this challenging problem through the use of well-defined metal precursors with robust, easily tunable ligands. These ligands, (N-heterocyclic carbenes: NHCs), form exceptionally strong bonds to transition elements, and, in the last 6 yrs, we have shown that they also form highly robust monolayers on planar gold surfaces. Here we explore their applicability on nanoparticles and clusters. Our goal is to design novel, logical routes to nanomaterials through the use of stable, well-defined organometallic precursors, and stoichiometric reducing agents. We will use the NHC to tune the redox potential of the starting material, and to affect the electronics of the resulting cluster. We will move away from gold, developing routes to nanoclusters and nanoparticles from non-noble metals (Cu, Pd, Ru, Fe) addressing reactions of significant importance such as CH activation, CO2 reduction and alkane metathesis. The impact will be significant since nanomaterials provide an important bridge between well understood molecular catalysts and less understood but industrially relevant heterogeneous catalysts. Structure/activity relationships obtained from nanomaterial catalysis will enable improvements in existing processes and the development of new ones such as alkane metathesis, which can convert plastic waste into valuable chemicals. This work is highly collaborative, providing exceptional learning opportunities for  graduate students and PDFs. We strive to understand the techniques employed by collaborators, which translates to students learning materials characterization techniques along with materials/organometallic synthesis. We currently have internal experts in X-ray photoelectron spectroscopy, electrochemistry, synthesis and nanocluster purification/crystallization. I strongly believe in research exchanges for PhD students, which may revolve around learning new techniques, and will provide these opportunities for my students.