Scientists from the University of Nottingham’s School of Chemistry say they have successfully trapped individual krypton atoms to create the world’s first-ever one-dimensional gas. The atoms of Krypton (Kr), a noble gas, were trapped inside a carbon nanotube using an advanced version of transmission electron microscopy (TEM).
“As far as we know, this is the first time that chains of noble gas atoms have been imaged directly, leading to the creation of a one-dimensional gas in a solid material,” said Professor Paul Brown, director of the Nanoscale and Microscale Research Centre (nmRC), University of Nottingham.
In the future, the team says they are planning to employ electron microscopy to directly image temperature-controlled phase transitions and chemical reactions in these types of one-dimensional systems, which may “unlock the secrets” of such unusual states of matter.
2D Materials, Advanced Spectroscopy Aid Creation of First-Ever One-Dimensional Gas
Prior to this breakthrough, traditional spectroscopy methods could only track the movements of larger groups of atoms. If researchers wanted to understand individual atoms, they had to use mathematics to approximate their movements. The main barriers are the size of individual atoms, which range anywhere from 0.1 to 0.4 nanometers, and their speed. For example, when in a gas phase, individual atoms can zip around at 400 meters per second, which is nearly the speed of sound.
“This makes the direct imaging of atoms in action very difficult,” the researchers explain, “and the creation of continuous visual representations of atoms in real-time remains one of the most significant scientific challenges.”
To break this previously unbreakable barrier, the Nottingham team tapped into the magical properties of 2 Dimensional structures called carbon nanotubes. These unique nanoscale structures are incredibly small, with a diameter half a million times smaller than a human hair.
“Carbon nanotubes enable us to entrap atoms and accurately position and study them at the single-atom level in real-time,” explained Professor Andrei Khlobystov from the university’s School of Chemistry. “For instance, we successfully trapped noble gas krypton (Kr) atoms in this study.”
According to Khlobystov, the team chose krypton because it has a high atomic number. This makes krypton easier to observe with TEM equipment than atoms with a lower atomic number. “This allowed us to track the positions of Kr atoms as moving dots,” the professor adds.
Buckminster Fullerenes to the Rescue
In their published work, which appears in the journal ACS Nano, the team details how they used incredibly small novel structures called Buckminster fullerenes to transport the individual krypton atoms into the carbon nanotubes. This is accomplished by heating them to 1200oC or via the method chosen by the research team, which involves irradiating them with an electron beam.
Once these krypton atoms are freed from their carrier molecules, they can only move in one dimension along the nanotube channel due to their extremely narrow space. As a result, the atoms trapped in the single-file row of constrained krypton atoms cannot pass each other and are forced to slow down “like vehicles in traffic congestion.” This slow march through the carbon nanotubes allowed the team to simultaneously employ scanning TEM (STEM) imaging and electron energy loss spectroscopy (EELS), which revealed the chemical signature of each individual atom of the one-dimensional gas.
“By focusing the electron beam to a diameter much smaller than the atomic size, we are able to scan across the nano test tube and record spectra of individual atoms confined within, even if these atoms are moving,” explained Professor Quentin Ramasse, Director of SuperSTEM, an EPSRC National Research Facility. “This gives us a spectral map of the one-dimensional gas, confirming that the atoms are delocalised and fill all available space, as a normal gas would do.”
Unlocking the Secrets of Unusual States of Matter
Moving forward, the team says they plan to use electron microscopes to directly image chemical reactions in in these one-dimensional gas systems, which may “unlock the secrets of such unusual states of matter.” For example, Brown says that such strongly correlated atomic systems “may exhibit highly unusual heat conductance and diffusion properties.”
For now, the researchers are celebrating their accomplishments and believe their work can have wide-ranging effects on understanding behavior at the atomic scale.
“This is an exciting innovation, as it allows us to see the van der Waals distance between two atoms in real space,” said Professor Ute Kaiser, former head of the Electron Microscopy of Materials Science group, senior professor at the University of Ulm. “It’s a significant development in the field of chemistry and physics that can help us better understand the workings of atoms and molecules.”
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.