Researchers) SENGA Ryosuke, Senior Researcher, Electron Microscopy Group, Nanomaterials Research Institute
- Development of technique to detect trace amounts of isotopic carbon consisting of one to four atoms by transmission electron microscopy
- Observation of the diffusion of the carbon atoms ingraphene for the first time by atomic-level isotope tracking
- Atomic-level isotope analysis will contribute to materials development and drug discovery research, etc.
Image of carbon isotope identification in graphene by electron beam spectroscopy
Isotopes are elements that differ only in weight (number of neutrons) without changing their chemical properties. Due to this property, isotopes are used as tracking markers (isotope labeling) for biological and chemical reactions. Isotopes are also used in a wide range of fields such as environmental surveys and mineral and fossil dating. Existing isotope detection techniques using light and ion beams can measure mass ratios with high accuracy from a sufficient amount of sample. However, analysis of objects such as valuable artworks and microfossils requires high detection sensitivity even from tiny samples. In addition, the spatial resolution of existing isotope detection techniques is limited to several tens to hundreds of nanometers. Thus, isotope measurements at a single atomic or molecular level, which enable us to trace microscopic phenomena such as chemical reactions, atomic diffusion, and material growth processes, remain a major challenge. Therefore, new isotope analysis technique with both high detection sensitivity and spatial resolution has been in demand.
Researchers in AIST developed a technique to detect and trace isotopes on the order of a few atoms by using transmission electron microscopy in collaboration with Osaka University, the Japan Science and Technology Agency, and JEOL Ltd.
The developed technique of electron spectroscopy using a monochromatic electron source enables the isotope detection with a spatial resolution of less than one nanometer by measuring the difference in the vibrational energy of atoms which reflects a weight difference equivalent to a single neutron. The spatial resolution achieved in this study is more than one or two orders of magnitude higher than existing isotope detection techniques. In addition to conventional structural analysis and chemical assignment, this development allows a transmission electron microscope to distinguish isotopes that has never been possible. In the future, it may also be possible to track isotopes at the monoatomic and monomolecular levels. This will reveal where and how chemical and biological reactions occur, contributing to a wide range of fields such as basic research in materials science and biology, and drug discovery research.