Scientists report the world’s first X-ray of a single atom

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When you shine X-rays (the color blue) at an iron atom (a red ball in the center of the molecule), the electrons of the core level are excited. The X-ray-excited electrons are then passed to the detector tip (gray) through overlapping atomic/molecular orbitals, which provide elemental and chemical information to the iron atom. Credit: Saw-Wai Hla

A team of scientists from Ohio University, Argonne National Laboratory, University of Illinois-Chicago, and others, led by Ohio University physics professor and Argonne National Laboratory scientist Saw Wai Hla, has taken the world’s first X-ray signal (or signature) from just one atom. This pioneering achievement could revolutionize the way scientists discover materials.

Since its discovery by Roentgen in 1895, X-rays have been used everywhere, from medical checks to security checks at airports. Even Curiosity, NASA’s Mars rover, is equipped with an X-ray machine to examine the material composition of rocks on Mars. An important use of X-rays in science is to determine the type of material in a sample. Over the years, the amount of material in the sample required for X-ray detection has been greatly reduced thanks to the development of synchrotron X-ray sources and new instruments. To date, the smallest amount an individual can x-ray is in an autogram, about 10,000 atoms or more. This is because the X-ray signal produced by the atom is too weak to be used by conventional X-ray detectors to detect it. According to Hla, it’s a longtime dream of scientists to X-ray a single atom, which is now being realized by the research team he leads.

“Atoms can be routinely imaged with scanning probe microscopes, but without X-rays, one can’t tell what they’re made of. We can now detect exactly what type of atom a particular atom is, one atom at a time, and we can measure it,” explained Hla, who is also director of the Institute for Phenomenology. Nanoparticles and Quantum at Ohio University “his chemical state.” “Once we can do that, we can track the material down to the limit of just one atom. This will have a huge impact on environmental and medical sciences and may even find a cure that could have a huge impact on the human race. This discovery will change the world.”

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Their paper published in the scientific journal nature on May 31, 2023, and adorning the cover of the science magazine print edition on June 1, 2023, detailing How Hala and many other physicists and chemists, including Ph.D. Students at OHIO, used a purpose-built synchrotron X-ray instrument at the XTIP beamline of the Advanced Photon Source and Nanomaterials Center at Argonne National Laboratory.

To illustrate, the team chose an iron atom and a terbium atom, both of which were inserted into two molecular hosts. To detect the X-ray signal of a single atom, the research team supplemented conventional X-ray detectors with a specialized detector made of a sharp metal tip that was placed very close to the sample to collect the X-ray-excited electrons — a technique known as synchrotron X-ray tunneling microscopy, or SX-STM. . X-ray spectroscopy in the SX-STM is powered by the photoabsorption of core-level electrons, which form fingerprints and are effective in directly identifying the elemental type of materials.

According to Hla, spectra are like fingerprints, each one unique and able to detect exactly what it is.

“The technique used, and the concept demonstrated in this study, opened up new horizons in X-ray science and nanoscale studies,” said Tololop Michael Ajayi, the paper’s first author who did the work as part of his PhD thesis. thesis. What’s more, the use of X-rays to detect and characterize individual atoms could revolutionize research and generate new technologies in areas such as quantitative information and trace element detection in environmental and medical research, to name a few. This achievement also opens the way for advanced materials science devices. .”

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(Left) Image of a ring-shaped supermolecule where only one iron atom is present in the entire ring. (Right) X-ray signature of only one iron atom. Credit: Saw-Wai Hla

Over the past 12 years, Hla has been involved in developing the SX-STM instrument and its measurement methods together with Volker Rose, Scientist at Advanced Photon Source at Argonne National Laboratory.

“I have been able to successfully supervise four OHIO graduate students for PhD theses related to the development of the SX-STM method over the course of 12 years. We have come a long way to achieve single-atom X-ray detection,” Hala said.

Hla’s study focuses on nano and quantum sciences with a particular focus on understanding the chemical and physical properties of materials at the most fundamental level – on the basis of the individual atom. In addition to achieving the X-ray signature of a single atom, the team’s main goal was to use this technique to probe the environmental impact on a single rare earth atom.

“We also discovered the chemical states of individual atoms,” Hla explained. “By comparing the chemical states of an iron atom and a terbium atom within their respective molecular hosts, we find that the terbium atom, a rare earth metal, is fairly isolated and does not change its chemical state while the iron atom interacts strongly with atoms in its surroundings.”

Many rare earth materials are used in everyday devices, such as cell phones, computers, and televisions, to name a few, and are extremely important in the creation and development of technology. With this discovery, scientists can now determine not only the type of element but its chemical state as well, which will allow them to better manipulate the atoms within different material hosts to meet the ever-changing needs in various fields. Moreover, they have also developed a new method called “X-ray excitation resonance tunneling, or X-ERT” that allows them to detect how the orbitals of a single molecule on the surface of a material are oriented using synchrotron X-rays.

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“This achievement links synchrotron X-rays with the quantum tunneling process to detect the X-ray signature of a single atom and opens many exciting research directions including the search for the quantum and spin (magnetic) properties of a single atom using only synchrotron X-rays,” Hla said.

In addition to Ajayi, many other graduate students from OHIO including current Ph.D. students Sineth Premarathna in Physics and Xinyue Cheng in Chemistry, as well as Ph.D. Physics alumni Sanjoy Sarkar, Chauz Wang, Kyaw Zhen Lat, Thomas Rojas, and Ann T. Ngo, who is currently an associate professor of chemical engineering at the University of Illinois-Chicago, participated in this research. Roenigk College of Arts and Sciences Chair and Professor of Chemistry Eric Masson designed and synthesized the rare earth molecule used in this study.

Going forward, Hla and his research team will continue to use X-rays to discover the properties of just one atom and find ways to revolutionize their applications for use in critical materials research collection and more.

more information:
Saw-Wai Hla, characterization of only one atom using synchrotron X-rays, nature (2023). DOI: 10.1038/s41586-023-06011-w.

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