Longevity of Xenon Trapping in Metal-Supported Nanocages

Noble gases have many useful applications, ranging from anesthetics to nuclear waste detection, but their purification is currently very energy-intensive, requiring extremely low temperatures. Recent studies have successfully physically trapped xenon (Xe) in metal-supported nanostructures between 400 and 600 K [1]. We investigated the longevity of trapped Xe in silicate nanocages deposited on Ru(0001), Ag(111), and Au(111). DodecaPhenyl Polyhedral Oligomeric Silsesquioxane (DP-POSS) was deposited on the metal substrates with a Langmuir-Blodgett trough; then the samples were calcined (to burn the organic ligands) and reduced (to remove the metal oxide) to prepare for trapping. Xe was trapped in the cages by exposure to a low-temperature Xe plasma. To measure trapped Xe, we used continuous X-ray photoelectron spectroscopy (XPS) while the sample was in ultra-high vacuum. We found that Xe is lost over time in all three samples, with Xe at interstitial sites being lost first due to being in a more unstable state than the Xe physically confined in nanocages. Our work suggests that nanocages deposited on Ru(0001), Ag(111), and Au(111) could serve as noble gas traps with significant retention times.

[1] Xu et al., “Xenon Trapping in Metal-Supported Silica Nanocages,” Small (2021)