LAMA-produced metal-on-oxide nanoparticles and films
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The capability for the Laser Ablation of Microparticle (LAMA) process for producing unique nanostructured particles and films are studied. The processing parameters are adjusted to create nanostructures that have potential for producing superior properties in two distinct technologically important areas – olefin gas separations and plasmonic films. Two extremes in film nanostructure are targeted; 1) Highly porous metallic films for olefin separation and 2) Dense films for plasmonic optical films. For olefin separations, weak chemisorption of ethylene has been shown to be an important characteristic in the use of metals for the separation of ethylene from ethane. Previously, density functional theory (DFT) has been used to predict the binding energies of various metals and alloys, with Ag having the lowest chemisorption energy amongst the metals and alloys studied. Here non-equilibrium Au/Cu alloys are produced using LAMA and investigated by a combination of DFT calculations and experimental measurements. It is inferred from experiments that the binding energy between a Au/Cu alloy and ethylene is lower than to either of the pure metals Au or Cu, and DFT calculations confirm this results from Au segregation to the particle surface. Implications of this work suggest that it may be possible to further tune the binding energy with ethylene by compositional and morphological control of films produced from Au-surface segregated alloys. LAMA-produced metal-on-oxide nanoparticles (NP) are investigated to determine whether the thermal stability of LAMA-produced nanoparticles can be improved without impacting their chemical reactivity. Investigations before and after heating using the transmission electron microscope show that Ag-on-TiO2 nanostructures exhibit excellent resistance to coarsening at elevated temperatures and that there is no change to the binding energy of the ethylene to Ag. For plasmonic film applications, SiO2 and metal-in-SiO2 films were produced using LAMA and studied. Although dense SiO2 films were not produced, it was demonstrated that it was possible to measure the plasmonic absorption peaks of metal NPs embedded in SiO2 films. This opens up a new possibility for the investigation of the plasmonic properties of non-equilibrium metal NPs.