The first X-ray SIGNAL (or SIGNATURE) of a single atom has been captured by
a team of researchers from Ohio University, Argonne National Laboratory, the
University of Illinois at Chicago, and other institutions, under the
direction of Saw Wai Hla, professor of physics at Ohio University and
scientist at Argonne National Laboratory. This ground-breaking
accomplishment may completely alter how scientists now identify
materials.
Since Roentgen's 1895 discovery of them, X-rays have been widely employed
for everything from medical exams to airport security checks. Even NASA's
Mars rover Curiosity has an X-ray instrument to look at the materials made
up of the Martian rocks. The classification of the components in a sample is
a crucial use of X-rays in research. With the advent of new equipment and
synchrotron X-ray sources, the amount of materials in a sample needed for
X-ray detection has significantly decreased over time. The lowest amount of
a sample that can now be X-rayed is an attogram, or 10,000 atoms or more.
The reason for this is because an atom's X-ray signal is so faint that it
cannot be picked up by standard X-ray detectors. Hla claims that the
research team he leads is finally achieving the long-held goal of scientists
to X-ray only one atom.
"Scanning probe microscopes can be used to routinely examine atoms, but
without X-rays, it is impossible to determine their composition. One atom at
a time, we can now determine precisely the kind of an atom while also
measuring its chemical state, according to Hla, who is also the head of Ohio
University's Nanoscale and Quantum Phenomena Institute. We will be able to
track the materials all the way down to just one atom once we are able to
accomplish so. This will have a significant influence on environmental and
medical research, and perhaps even lead to the discovery of a treatment that
would benefit all of humanity greatly. This discovery will alter the course
of history.
Their paper describes how Hla and several other physicists and chemists,
including Ph.D. students at OHIO, used a specially made synchrotron X-ray
instrument at the XTIP beamline of Advanced Photon Source and the Center for
Nanoscale Materials at Argonne National Laboratory. Their paper was
published in the scientific journal Nature on May 31, 2023, and it graced
the cover of the print version of the scientific journal on June 1,
2023.
The group decided to use an iron and a terbium atom in their respective
molecular hosts as examples. The research team used a technique known as
synchrotron X-ray scanning tunneling microscopy, or SX-STM, which combines
conventional X-ray detectors with a specialized detector made of a sharp
metal tip placed in close proximity to the sample to collect X-ray excited
electrons, in order to detect the X-ray signal of a single atom. The
photoabsorption of core level electrons, which creates elemental
fingerprints and effectively identifies the elemental type of the materials,
initiates X-ray spectroscopy in SX-STM.
The spectrums are like fingerprints, each one different and able to
identify what it is, claims Hla.
Tolulope Michael Ajayi, the paper's first author and the person who carried
out this research for his doctoral thesis, noted that the approach employed
and the theory established in this study "broke new ground in X-ray science
and nanoscale studies." "More importantly, the ability to identify and
describe individual atoms using X-rays might change science and lead to the
development of new technologies in fields like quantum information and the
identification of trace substances in environmental and medical studies, to
name a few. Additionally, this accomplishment pave the way for more
sophisticated materials science instruments.
In the last 12 years, Hla has worked with Volker Rose, a researcher at the
Advanced Photon Source at Argonne National Laboratory, to create an SX-STM
apparatus and associated measuring techniques.
"Over a 12-year period, I was able to successfully supervise four OHIO
graduate students for their Ph.D. theses on the development of SX-STM
methods. The discovery of a single atom's X-ray signal represents a
significant accomplishment, according to Hla.
With a specific emphasis on comprehending materials' chemical and physical
characteristics at a fundamental level—on an individual atom basis—Hla's
research focuses on nano- and quantum sciences. The team's main objective
was to utilize this technology to look at the impact of the environment on a
single rare-earth atom in addition to achieving the X-ray signature of one
atom.
Hla said, "We have also discovered the chemical states of individual atoms.
"By comparing the chemical states of an iron atom and a terbium atom inside
respective molecular hosts, we find that the iron atom strongly interacts
with its surroundings while the terbium atom, a rare-earth metal, is rather
isolated and does not change its chemical state."
Numerous rare-earth minerals are crucial for developing and expanding
technology and are used in many commonplace gadgets, like televisions,
computers, and mobile phones, to mention a few. With the use of this
finding, scientists are now able to determine not only the kind of element
but also its chemical state, enabling them to better manage the atoms inside
diverse material hosts to satisfy the constantly shifting requirements in a
variety of disciplines. Additionally, scientists have created a brand-new
technique known as "X-ray excited resonance tunneling, or X-ERT," which
enables them to use synchrotron X-rays to determine how a single molecule's
orbitals are oriented on a material surface.
The use of synchrotron X-rays to study the quantum and spin (magnetic)
characteristics of a single atom is one of the interesting new research
areas made possible by this accomplishment, according to Hla.
In addition to Ajayi, several other graduate students from OHIO
participated in this study, including Sanjoy Sarkar, Shaoze Wang, Kyaw Zin
Latt, Tomas Rojas, and Anh T. Ngo, who is currently an Associate Professor
of Chemical Engineering at the University of Illinois-Chicago and is
pursuing her Ph.D. in Physics. Eric Masson, Roenigk Chair and Professor of
Chemistry in the College of Arts and Sciences, created and synthesized the
rare earth molecule employed in this investigation.
In the future, Hla and his research group will keep using X-rays to
identify characteristics of a single atom and explore new ways to
revolutionize their applications for use in obtaining essential data for
materials research and other purposes.
Provided by
Ohio University
