Atomic-Scale Time-Resolved Imaging of Krypton Dimers, Chains and Transition to a One-Dimensional Gas.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38251654.
- Also identified by DOI 10.1021/acsnano.3c07853 and PMC identifier 10832048.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Single-atom dynamics of noble-gas elements have been investigated using time-resolved transmission electron microscopy (TEM), with direct observation providing for a deeper understanding of chemical bonding, reactivity, and states of matter at the nanoscale. We report on a nanoscale system consisting of endohedral fullerenes encapsulated within single-walled carbon nanotubes ((Kr@C<sub>60</sub>)@SWCNT), capable of the delivery and release of krypton atoms on-demand, via coalescence of host fullerene cages under the action of the electron beam (<i>in situ</i>) or heat (<i>ex situ</i>). The state and dynamics of Kr atoms were investigated by energy dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS). Kr atom positions were measured precisely using aberration-corrected high-resolution TEM (AC-HRTEM), aberration-corrected scanning TEM (AC-STEM), and single-atom spectroscopic imaging (STEM-EELS). The electron beam drove the formation of 2Kr@C<sub>120</sub> capsules, in which van der Waals Kr<sub>2</sub> and transient covalent [Kr<sub>2</sub>]<sup>+</sup> bonding states were identified. Thermal coalescence led to the formation of longer coalesced nested nanotubes containing more loosely bound Kr<sub><i>n</i></sub> chains (<i>n</i> = 3-6). In some instances, delocalization of Kr atomic positions was confirmed by STEM analysis as the transition to a one-dimensional (1D) gas, as Kr atoms were constrained to only one degree of translational freedom within long, well-annealed, nested nanotubes. Such nested nanotube structures were investigated by Raman spectroscopy. This material represents a highly compressed and dimensionally constrained 1D gas stable under ambient conditions. Direct atomic-scale imaging has revealed elusive bonding states and a previously unseen 1D gaseous state of matter of this noble gas element, demonstrating TEM to be a powerful tool in the discovery of chemistry at the single-atom level.