Reviewed by Lexie CornerMar 5 2025
A research team led by Professor Jungwon Park from the Department of Chemical and Biological Engineering at Seoul National University College of Engineering has developed a novel technique for observing atomic structural changes in nanoparticles in three dimensions. This study, published in Nature Communications, addresses a long-standing issue that previous Nobel laureates were unable to resolve.
Importance of Nanoparticles
Nanoparticles are widely used in the development of functional materials for industries such as energy, environment, and medicine. Due to their small size (1 nm = one-billionth of a meter), they exhibit unique physical and chemical properties. Observing structural changes in nanoparticles is critical because their reactivity varies significantly with size.
Challenges in Current Methods
Current methods for analyzing nanostructures are limited in their capabilities. These methods typically only provide basic structural identification or averaged data from multiple nanoparticles. Additionally, they often focus on fixed nanoparticles in a vacuum, making it difficult to observe three-dimensional atomic structures over time, especially in liquid environments.
Advancements in Microscopy: From Cryo-TEM to Liquid TEM
While the three-dimensional atomic structures of proteins have already been determined using cryo-transmission electron microscopy (cryo-TEM), the challenge of observing nanoparticles in solution remained unsolved. Professor Park’s team built upon this advancement, developing a new method called liquid transmission electron microscopy (liquid TEM) using graphene to visualize nanostructures in solution in three dimensions. Their earlier work on this method, known as Brownian tomography, was featured on the cover of Science in 2020.
Time-Resolved Brownian Tomography
The newly developed time-resolved Brownian tomography technique allows for real-time monitoring of atomic structural changes in individual nanoparticles. This breakthrough method opens up new opportunities for understanding how chemical reactions alter nanoparticles at the atomic level.
Methodology: Observation of Moving Nanoparticles
Using the “graphene liquid cell transmission electron microscopy (Graphene Liquid Cell TEM)” technique, the researchers developed a way to observe freely moving nanoparticles in solution. Nanoparticles undergoing Brownian motion (random movement in a fluid) are captured from various angles over time, and the resulting images are reconstructed into a three-dimensional model.
Comparison to Traditional Methods
This method marks a significant advancement over traditional transmission electron microscopy (TEM), which analyzes fixed nanoparticles in a vacuum. It is also an improvement over spectroscopic techniques that only provide averaged data from multiple nanoparticles. For the first time, this technology enables direct measurement of a single nanoparticle’s three-dimensional atomic structure as it dynamically changes in a liquid environment.
Observations and Results
The team used this technique to observe atomic-level structural changes in platinum (Pt) nanoparticles during the etching (chemical corrosion) process. They could track, in three dimensions, when surface atoms reattached (re-adsorbed), rearranged, or detached (desorbed). Interestingly, the study revealed that a highly disordered phase appeared when the nanocrystals shrank to approximately 1 nm in size, which was unexpected since platinum typically maintains a highly ordered atomic structure.
Implications and Future Research
The study shows that even nanoparticles made from the same elemental material can exhibit distinct structural characteristics compared to their larger counterparts. This research also represents a significant advancement in the observation of atomic structures, surpassing traditional TEM and cryo-TEM. Thanks to this new approach, scientists can now track how the three-dimensional structures of nanomaterials evolve over time in response to various chemical conditions, such as the composition of reactive solutions or applied voltage.
Applications and Impact
The findings offer a more accurate understanding of how structural changes influence the functionality of next-generation nanomaterials, including metals, semiconductors, and oxides. Furthermore, the study, funded by the National Hydrogen Priority Research Center project, successfully detected structural changes in platinum nanoparticles, which are essential catalysts for environmentally friendly hydrogen energy applications. This paves the way for the development of high-performance catalysts in the future.
The development of ‘time-resolved Brownian tomography’ continues the legacy of the 2017 Nobel Prize-winning ‘cryo-TEM’ and our 2020 Science cover-featured ‘liquid TEM’ innovation. This new technique will significantly contribute to unraveling complex reaction mechanisms in hydrogen fuel cells, CO₂ conversion catalysts, lithium-ion batteries, and other advanced energy materials, facilitating the design of superior materials.
Jungwon Park, Professor and Research Lead, College of Engineering, Seoul National University
The Study's Lead Author, Researcher Sungsu Kang, remarked, “Our research directly captured real-time atomic-level structural changes of nanocrystals in liquid environments. This achievement is particularly significant because it successfully visualized surface atomic movements and the emergence of new phases unique to nanomaterials phenomena that were challenging to detect using conventional spectroscopic or electrochemical methods.”
Sungsu Kang is currently a Postdoctoral Researcher at the University of Chicago. He earned his Ph.D. from SNU's School of Chemical and Biological Engineering. He continues to refine the “time-resolved Brownian tomography” method, expanding its application to various nanomaterials and exploring their potential uses in chemical environments.
Journal Reference:
Kang, S., et al. (2025) Time-resolved Brownian tomography of single nanocrystals in liquid during oxidative etching. Nature Communications. doi.org/10.1038/s41467-025-56476-8.