Results from the research conducted by a team led by Argonne National Laboratory scientist Saw Wai Hla on the groundbreaking X-ray achievement were posted in the scientific journal Nature on Wednesday.
The smallest mass an X-ray can typically detect is an attogram, which is about 10,000 atoms, but scientists have long looked for a way to identify smaller masses.
In their paper, Hla and fellow researchers used a purpose-built synchrotron X-ray instrument at the XTIP beamline of Advanced Photon Source and the Center for Nanoscale Materials at the Argonne lab.
"Atoms can be routinely imaged with scanning probe microscopes, but without X-rays, one cannot tell what they are made of," Hla, a physics professor at Ohio University, said in a news release.
"We can now detect exactly the type of a particular atom, one atom-at-a-time, and can simultaneously measure its chemical state.
"Once we are able to do that, we can trace the materials down to the ultimate limit of just one atom. This will have a great impact on environmental and medical sciences and maybe even find a cure that can have a huge impact for humankind. This discovery will transform the world."
As a test, the researchers took an iron atom and a terbium atom, and then inserted both in their respective molecular hosts.
To detect the X-ray signal of one atom, they supplemented conventional detectors in X-rays with a specialized detector made of a sharp metal tip positioned at extreme proximity to the sample to collect X-ray excited electrons, known as synchrotron X-ray scanning tunneling microscopy or SX-STM.
Hla has worked for the past 12 years helping fine-tune SX-STM.
"The technique used, and concept proven in this study, broke new ground in X-ray science and nanoscale studies," said Tolulope Michael Ajayi, the first author of the paper, who is doing the research as part of his doctoral thesis.
"More so, using X-rays to detect and characterize individual atoms could revolutionize research and give birth to new technologies in areas such as quantum information and the detection of trace elements in environmental and medical research, to name a few.
"This achievement also opens the road for advanced materials science instrumentation."
Along with scientists at Ohio University and the Argonne lab, other researchers participating in the study were from the University of Illinois-Chicago.
Atom identification represents a new breakthrough for X-ray use, which has been employed in a wide variety of fields, from medical examinations to security screenings in airports, to examine the composition of rocks remotely on Mars.
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