World’s First X-Ray of a Single Atom
A cross-institutional team of researchers, led by Saw Wai Hla, a Professor of Physics at Ohio University and a scientist at Argonne National Laboratory, has achieved a groundbreaking feat: capturing the world’s first X-ray signal, also known as a signature, of a single atom. This achievement could potentially transform material detection techniques, elevating them to a new level of precision. Considering the atomic structure’s vital role in the properties of all matter, this innovation could dramatically refine our understanding of the materials that compose our world.
Since Wilhelm Roentgen’s discovery of X-rays in 1895, these high-energy photons have found broad utility in various fields ranging from medicine to security to space exploration. For instance, NASA’s Mars rover, Curiosity, employs an X-ray device to scrutinize Martian rock composition. One of the pivotal uses of X-rays in science is material identification within samples.
With technological advancements, such as the development of synchrotron X-rays sources and the introduction of newer instruments, the amount of material needed for X-ray detection has significantly decreased. The smallest detectable quantity to date is approximately 10,000 atoms or more, roughly equal to an attogram. This limit exists because the X-ray signal from a single atom is incredibly faint, too weak to be detected by conventional X-ray detectors. However, this study led by Professor Hla has actualized the longstanding scientific ambition to X-ray a single atom.
Revolutionary Technique: Deciphering The Chemical State of Single Atoms
According to Professor Hla, Director of the Nanoscale and Quantum Phenomena Institute at Ohio University, atoms can be routinely imaged with scanning probe microscopes. However, without X-rays, the composition of these atoms remains unidentified. The team’s innovative method can detect the type of a specific atom one at a time, while simultaneously gauging its chemical state. This breakthrough technique has the potential to transform various fields including environmental studies and medical sciences, by enabling material tracing down to the level of a single atom. The implications of this discovery are far-reaching, possibly even contributing to significant medical advancements and therapeutic breakthroughs.
In their seminal paper published in the renowned scientific journal Nature, the team provides a detailed description of their experiment. Using a specially built synchrotron X-ray instrument at the Advanced Photon Source’s XTIP beamline and the Center for Nanoscale Materials at Argonne National Laboratory, they succeeded in detecting the X-ray signal from single iron and terbium atoms, each situated within respective molecular hosts. This feat was achieved by enhancing conventional X-ray detectors with a specialized detector composed of a sharp metal tip positioned extraordinarily close to the sample, a method known as synchrotron X-ray scanning tunneling microscopy (SX-STM).
Groundbreaking Instrumentation: The Power of Synchrotron X-Ray Scanning Tunneling Microscopy
SX-STM utilizes X-ray spectroscopy, triggered by photoabsorption of core level electrons, serving as elemental fingerprints effective in directly identifying the elemental type of the materials. The spectra obtained from this method are unique to each atom, analogous to fingerprints, allowing scientists to identify the specific atomic composition of the material under investigation.
According to Tolulope Michael Ajayi, the first author of the paper, this innovative technique and the proof-of-concept achieved in this study are groundbreaking. The utilization of X-rays to detect and characterize individual atoms could instigate a revolution in research, leading to the emergence of new technologies in various fields like quantum information, trace element detection in environmental and medical research, and advanced materials science instrumentation.
Future Implications: Advancing Technological and Environmental Research
For over a decade, Professor Hla has been dedicated to developing SX-STM instruments and methodologies, in collaboration with Volker Rose, a scientist at the Advanced Photon Source at Argonne National Laboratory. This diligent work has culminated in the remarkable achievement of detecting an X-ray signature from a single atom.
Moreover, Hla’s study, primarily focused on nano and quantum sciences, emphasizes understanding the chemical and physical properties of materials at the most fundamental level, the individual atom. This research paves the way for more extensive investigations into the environmental effects on single rare-earth atoms. The ability to detect and differentiate the chemical states of individual atoms is a significant advancement in material science, as it offers a new avenue for manipulating atoms within different materials to meet the evolving needs in various fields.
The team has also introduced a novel method, “X-ray excited resonance tunneling or X-ERT”, to determine the orientation of a single molecule’s orbitals on a material surface using synchrotron X-rays. This achievement opens exciting research directions, including investigations into quantum and spin (magnetic) properties of individual atoms using synchrotron X-rays. The involvement of several graduate students and professors indicates a promising future for this field of study, with the potential to impact many areas, including environmental science, materials research, and technological development.
Read Original Article: https://www.nature.com/articles/s41586-023-06011-w