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The Reactivity of Pure and Alloy Organic-Modified Metal Nanoparticles
University of Louisville The goal of our research is to understand and control the reactivity of organic-modified Pd and Pd-containing alloy nanoparticles as a function of metal composition, atomic arrangement, and organic composition. Preliminary data shows vastly different reactivities between H2 gas and Pd and PdAg alloy nanoparticles synthesized by different methods and functionalized with different monolayers (alkanethiols or alkylamines). We found that an Ag/Pd core/shell arrangement for alloys and mixed monolayers of alkanethiols and alkylamines in a specific ratio is optimal for high reactivity while providing nanoparticle stability. We propose to extend our work by 1) better characterizing the AgPd alloy nanoparticles with high resolution electron microscopy to correlate the reactivity with the atomic arrangement and composition, 2) fully exploring the effect of mixed monolayers of alkanethiols and alkylamines on the stability and reactivity of Pd and AgPd alloy nanoparticles, 3) examining the effect of other organic monolayers on the reactivity of metal nanoparticles (i.e. compare disordered, branched monolayers with those that are ordered and crystalline), and 4) exploring the use of these organic-modified Pd-containing nanoparticle in the catalysis of organic reactions, such as hydrogenations. The nanoparticles are very stable and their size and composition are easily controlled synthetically. In addition, they can serve as a homogeneous catalyst in solution or heterogeneous catalyst by attachment to a high surface area solid support. Despite these desireable attributes, these materials have not found widespread use as catalysts because their surfaces are coated with organic ligands, making them generally inaccessible for reactivity. Based on our preliminary data, we believe we can find conditions where the organic monolayer imparts stability to the nanoparticles, but allows a high level of reactivity. This would provide the best of both worlds and could lead to many important applications for these fascinating materials in both catalysis and sensing.
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