Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems

Abstract

The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. The atoms remain in the cages upon heating to 400 K. The trapping and release of Ar is studied combining surface science methods and density functional theory calculations. While the frameworks stay intact with the inclusion of Ar atoms, the permeability of gasses (for example, CO) through them is significantly affected, making these structures also interesting candidates for tunable atomic and molecular sieves. These findings enable the study of individually confined noble gas atoms using surface science methods, opening up new opportunities for fundamental research.

Ionization‐Facilitated Formation of 2D (Alumino)Silicate–Noble Gas Clathrate Compounds

“…These peaks are assigned to trapped noble gas atoms in the silica bilayer/Ru(0001) system. Consistent with our previous results, while most trapped atoms are located in the cages, there is a small fraction of noble gas atoms located as well at the interface between the silica/Ru(0001) interface. This minority species is evident in the deconvolution of the Ar 2p, Kr 3d, and Xe 3d 5/2 core level spectra shown in Figure S2 (Supporting Information) as a small component on the lower binding energy side.…”

“…Desorption of these trapped noble gas atoms at 300 K is slow for Ar and negligible for Kr and Xe. For example, we showed in recent work that only 25% of trapped Ar atoms desorb in the ultrahigh vacuum (UHV) after 12 h . In the experiments reported here, there is virtually no desorption for trapped Kr and Xe atoms at room temperature.…”

“…However, our instrument has a lower wavelength cutoff at 800 cm −1 , rendering this lower‐frequency mode inaccessible in our experiments. Previous work did not show any visible shift on the 1300 cm −1 mode upon Ar inclusion due to the negligible distortion of the bilayer upon Ar intake . Upon Xe trapping, however, there is an 8 cm −1 redshift in the signature interlayer phonon mode in IRRAS (Figure S7, Supporting Information), which could be explained by the distortion of the bilayer where d (O m –O m ) increases by 0.14 Å and the film thickness ( d z (O t –O b )) increases by 0.01 Å at Θ Xe = 0.5 (Figure S5D, Supporting Information).…”

“…We recently reported that 2D (alumino)silicate films are able to trap single Ar atoms, where both desorption measurements and density functional theory (DFT) calculations point to a high desorption barrier of about 1 eV . However, these results created a big puzzle, namely, if the activation energy barrier for Ar to enter these nanocages is at a similar magnitude (≈1 eV), how did Ar atoms get trapped inside nanocages at room temperature below the atmosphere pressure?…”

Friends or strangers? Attempts at reactivating buyer–supplier relationships

“…The vdW-DF-cx version tends to overestimate the binding energy in some layered systems [12,119,120], but remains accurate on structure [68,121]. It works for both intraand for inter-molecular bonds [9, 11, 13-15, 44, 122-124], for hybrid organic-inorganic perovskites [125], and for analysis and design of porous-materials gas storage [11,45,[126][127][128] and of surface pacification [129]. It also works for studies of the role of polycyclic aromatic hydrocarbons in interstellar H 2 formation [130], of electric-field driven reactions [131], and of mechanochemical cocrystal formation [132].…”