Noble Gas Trapping in Silica Nanocages

The separation and purification of noble gases is challenging due to their chemical inertness, requiring energy-intensive and expensive processes. A promising alternative involves capturing noble gases within metal-supported nanocages through physical confinement and electronic interactions, which has been achieved previously under low-pressure conditions at room temperature [1]. In this mechanism, xenon can enter the nanocages when ionized. Species are then neutralized via electron donation from the metal substrate; it is energetically unfavorable for neutral xenon to escape the nanocage, and the xenon becomes trapped. This study explores the impact of various metal supports on the longevity of xenon trapping in silica nanocages. Using a Langmuir–Blodgett trough, we deposited near monolayer films of nanocages onto single crystals of Ag(111), Au(111), and Ru(0001). The samples were then calcined to remove organic ligands and reduced to ensure a metallic support. Samples were exposed to a xenon plasma to load the nanocages and X-ray photoelectron spectroscopy (XPS) was subsequently employed to quantify xenon capture. Results showed that all three metal substrates facilitated xenon trapping, retaining 30-40% of trapped xenon even after 12 hours. A exponential Retention was greatest for Ag(111) substrates, while initial loading was greatest for Au(111). These findings highlight the potential of metal substrates to be customized for enhanced noble gas trapping, offering a more energy-efficient and cost-effective alternative to conventional separation techniques.

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