Sinter-Resistant Gold-144 Iron(III) Oxide Core-Shell Structures: Synthesis, Characterization, and Application via Heterogeneous Catalysis

In the realm of catalysis, small nanoparticles have been an area of interest due to their high surface-to-volume ratio. This is even more so with gold nanoparticles in that gold only becomes catalytically active with small particles sizes. Thus, gold clusters are desirable given their uniformity, high surface-to-volume ratio, and high catalytic activity. Given the nature of small gold particles to sinter, it was found to be advantageous to protect the particles using a gold-metal oxide core-shell configuration. Core-shell heterostructures have been utilized as a catalyst that is thermally stable and exhibits a synergistic effect between core and shell, resulting in increased catalytic activity. The research contained in this document discusses the synthetic procedure of a gold-144 cluster using a variation of the Brust-Schiffrin method followed by an iron oxide coating via post-selective oxidative treatment to create a gold-144 iron oxide core-shell structure. Shell thickness is varied depending on the amount of iron precursor used and studied under the particle’s catalytic efficiency with carbon monoxide oxidation. The gold-144 iron oxide particles with Au:Fe mass ratios of 1:2, 1:4, and 1:6 were synthesized and then deposited onto silica via colloidal deposition. Using CO oxidation, each gold-144 iron oxide catalyst loaded onto silica gave varying degrees of full CO conversion depending on the thickness of the iron oxide layer. The 1:4 gold-144 iron oxide catalyst produced the best catalytic activity and was further investigated using 2-propanol conversion as well as thermal treatments using CO oxidation. Under CO oxidation, the 1:4 structure calcined at 300 degrees Celsius presented the best results, and the 1:4 ratio was still active at 100 degrees Celsius after thermal treatments. Under 2-propanol conversions, the data seems to suggest that core-shell structure provides a synergistic effect for acetone production, however, this cannot be concluded until further testing is accomplished.