Tag Archives: Jong Min Yuk

Harvesting water from air

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You can watch the nano-sized water droplet form in following video,

A September 30, 2024 Northwestern University news release (received via email and on EurekAlert) by Amanda Morris describes a first, Note: Links have been removed,

For the first time ever, researchers have witnessed — in real time and at the molecular-scale — hydrogen and oxygen atoms merge to form tiny, nano-sized bubbles of water.

The event occurred as part of a new Northwestern University study, during which scientists sought to understand how palladium, a rare metallic element, catalyzes the gaseous reaction to generate water. By witnessing the reaction at the nanoscale, the Northwestern team unraveled how the process occurs and even uncovered new strategies to accelerate it.

Because the reaction does not require extreme conditions, the researchers say it could be harnessed as a practical solution for rapidly generating water in arid environments, including on other planets.

The research will be published on Friday (Sept. 27 [2024]) in the Proceedings of the National Academy of Sciences [PNAS].

“By directly visualizing nanoscale water generation, we were able to identify the optimal conditions for rapid water generation under ambient conditions,” said Northwestern’s Vinayak Dravid, senior author of the study. “These findings have significant implications for practical applications, such as enabling rapid water generation in deep space environments using gases and metal catalysts, without requiring extreme reaction conditions. 

“Think of Matt Damon’s character, Mark Watney, in the movie ‘The Martian.’ He burned rocket fuel to extract hydrogen and then added oxygen from his oxygenator. Our process is analogous, except we bypass the need for fire and other extreme conditions. We simply mixed palladium and gases together.”

Dravid is the Abraham Harris Professor of Materials Science and Engineering at Northwestern’s McCormick School of Engineering and founding director of the Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center, where the study was conducted. He also is director of global initiatives at the International Institute for Nanotechnology.

New technology enabled discovery

Since the early 1900s, researchers have known that palladium can act as a catalyst to rapidly generate water. But how, exactly, this reaction occurs has remained a mystery.

“It’s a known phenomenon, but it was never fully understood,” said Yukun Liu, the study’s first author and a Ph.D. candidate in Dravid’s laboratory. “Because you really need to be able to combine the direct visualization of water generation and the structure analysis at the atomic scale in order to figure out what’s happening with the reaction and how to optimize it.”

But viewing the process with atomic precision was simply impossible — until nine months ago. In January 2024, Dravid’s team unveiled a novel method to analyze gas molecules in real time. Dravid and his team developed an ultra-thin glassy membrane that holds gas molecules within honeycomb-shaped nanoreactors, so they can be viewed within high-vacuum transmission electron microscopes.

With the new technique, previously published in Science Advances, researchers can examine samples in atmospheric pressure gas at a resolution of just 0.102 nanometers, compared to a 0.236-nanometer resolution using other state-of-the-art tools. The technique also enabled, for the first time, concurrent spectral and reciprocal information analysis.

“Using the ultrathin membrane, we are getting more information from the sample itself,” said Kunmo Koo, first author of the Science Advances paper and a research associate at the NUANCE Center, where he is mentored by research associate professor Xiaobing Hu. “Otherwise, information from the thick container interferes with the analysis.”

Smallest bubble ever seen

Using the new technology, Dravid, Liu and Koo examined the palladium reaction. First, they saw the hydrogen atoms enter the palladium, expanding its square lattice. But when they saw tiny water bubbles form at the palladium surface, the researchers couldn’t believe their eyes.

“We think it might be the smallest bubble ever formed that has been viewed directly,” Liu said. “It’s not what we were expecting. Luckily, we were recording it, so we could prove to other people that we weren’t crazy.”

“We were skeptical,” Koo added. “We needed to investigate it further to prove that it was actually water that formed.”

The team implemented a technique, called electron energy loss spectroscopy, to analyze the bubbles. By examining the energy loss of scattered electrons, researchers identified oxygen-bonding characteristics unique to water, confirming the bubbles were, indeed, water. The researchers then cross-checked this result by heating the bubble to evaluate the boiling point.

“It’s a nanoscale analog of the Chandrayaan-1 moon rover experiment, which searched for evidence of water in lunar soil,” Koo said. “While surveying the moon, it used spectroscopy to analyze and identify molecules within the atmosphere and on the surface. We took a similar spectroscopic approach to determine if the generated product was, indeed, water.”

Recipe for optimization

After confirming the palladium reaction generated water, the researchers next sought to optimize the process. They added hydrogen and oxygen separately at different times or mixed together to determine which sequence of events generated water at the fastest rate.

Dravid, Liu and Koo discovered that adding hydrogen first, followed by oxygen, led to the fastest reaction rate. Because hydrogen atoms are so small, they can squeeze between palladium’s atoms — causing the metal to expand. After filling the palladium with hydrogen, the researchers added oxygen gas.

“Oxygen atoms are energetically favorable to adsorb onto palladium surfaces, but they are too large to enter the lattice,” Liu said. “When we flowed in oxygen first, its dissociated atoms covered the entire surface of the palladium, so hydrogen could not adsorb onto surface to trigger the reaction. But when we stored hydrogen in the palladium first, and then added oxygen, the reaction started. Hydrogen comes out of the palladium to react with the oxygen, and the palladium shrinks and returns to its initial state.”

Sustainable system for deep space

The Northwestern team imagines that others, in the future, potentially could prepare hydrogen-filled palladium before traveling into space. Then, to generate water for drinking or for watering plants, travelers will only need to add oxygen. Although the study focused on studying bubble generation at nanoscale, larger sheets of palladium would generate much larger quantities of water.

“Palladium might seem expensive, but it’s recyclable,” Liu said. “Our process doesn’t consume it. The only thing consumed is gas, and hydrogen is the most abundant gas in the universe. After the reaction, we can reuse the palladium platform over and over.”

The study, “Unraveling the adsorption-limited hydrogen oxidation reaction at palladium surface via in situ electron microscopy,” was supported by the Air Force Office of Scientific Research (grant number AFOSR FA9550-22-1-0300) and hydrogen-related work by the Center for Hydrogen in Energy and Information Sciences, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science(grant number DE-SC0023450).

Here’s a link to and a citation for the latest paper,

Unraveling the adsorption-limited hydrogen oxidation reaction at palladium surface via in situ electron microscopy by Yukun Liu, Kunmo Koo, Zugang Mao, Xianbiao Fu, Xiaobing Hu, and Vinayak P. Dravid. PNAS September 27, 2024 121 (40) e2408277121 DOI: https://doi.org/10.1073/pnas.2408277121

This paper is behind a paywall.

Here’s a link to and a citation for the earlier work on the technique that made it possible to create the nano-sized water droplets out of thin air,

Ultrathin silicon nitride microchip for in situ/operando microscopy with high spatial resolution and spectral visibility by Kunmo Koo, Zhiwei Li, Yukun Liu, Stephanie M. Ribet, Xianbiao Fu, Ying Jia, Xinqi Chen, Gajendra Shekhawat, Paul J. M. Smeets, Roberto dos Reis, Jungjae Park, Jong Min Yuk, Xiaobing Hu, and Vinayak P. Dravid. Science Advances 17 Jan 2024 Vol 10, Issue 3 DOI: 10.1126/sciadv.adj641

This paper is open access.

SINGLE (3D Structure Identification of Nanoparticles by Graphene Liquid Cell Electron Microscopy) and the 3D structures of two individual platinum nanoparticles in solution

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It seems to me there’s been an explosion of new imaging techniques lately. This one from the Lawrence Berkelely National Laboratory is all about imaging colloidal nanoparticles (nanoparticles in solution), from a July 20, 2015 news item on Azonano,

Just as proteins are one of the basic building blocks of biology, nanoparticles can serve as the basic building blocks for next generation materials. In keeping with this parallel between biology and nanotechnology, a proven technique for determining the three dimensional structures of individual proteins has been adapted to determine the 3D structures of individual nanoparticles in solution.

A multi-institutional team of researchers led by the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), has developed a new technique called “SINGLE” that provides the first atomic-scale images of colloidal nanoparticles. SINGLE, which stands for 3D Structure Identification of Nanoparticles by Graphene Liquid Cell Electron Microscopy, has been used to separately reconstruct the 3D structures of two individual platinum nanoparticles in solution.

A July 16, 2015 Berkeley Lab news release, which originated the news item, reveals more details about the reason for the research and the research itself,

“Understanding structural details of colloidal nanoparticles is required to bridge our knowledge about their synthesis, growth mechanisms, and physical properties to facilitate their application to renewable energy, catalysis and a great many other fields,” says Berkeley Lab director and renowned nanoscience authority Paul Alivisatos, who led this research. “Whereas most structural studies of colloidal nanoparticles are performed in a vacuum after crystal growth is complete, our SINGLE method allows us to determine their 3D structure in a solution, an important step to improving the design of nanoparticles for catalysis and energy research applications.”

Alivisatos, who also holds the Samsung Distinguished Chair in Nanoscience and Nanotechnology at the University of California Berkeley, and directs the Kavli Energy NanoScience Institute at Berkeley (Kavli ENSI), is the corresponding author of a paper detailing this research in the journal Science. The paper is titled “3D Structure of Individual Nanocrystals in Solution by Electron Microscopy.” The lead co-authors are Jungwon Park of Harvard University, Hans Elmlund of Australia’s Monash University, and Peter Ercius of Berkeley Lab. Other co-authors are Jong Min Yuk, David Limmer, Qian Chen, Kwanpyo Kim, Sang Hoon Han, David Weitz and Alex Zettl.

Colloidal nanoparticles are clusters of hundreds to thousands of atoms suspended in a solution whose collective chemical and physical properties are determined by the size and shape of the individual nanoparticles. Imaging techniques that are routinely used to analyze the 3D structure of individual crystals in a material can’t be applied to suspended nanomaterials because individual particles in a solution are not static. The functionality of proteins are also determined by their size and shape, and scientists who wanted to image 3D protein structures faced a similar problem. The protein imaging problem was solved by a technique called “single-particle cryo-electron microscopy,” in which tens of thousands of 2D transmission electron microscope (TEM) images of identical copies of an individual protein or protein complex frozen in random orientations are recorded then computationally combined into high-resolution 3D reconstructions. Alivisatos and his colleagues utilized this concept to create their SINGLE technique.

“In materials science, we cannot assume the nanoparticles in a solution are all identical so we needed to develop a hybrid approach for reconstructing the 3D structures of individual nanoparticles,” says co-lead author of the Science paper Peter Ercius, a staff scientist with the National Center for Electron Microscopy (NCEM) at the Molecular Foundry, a DOE Office of Science User Facility.

“SINGLE represents a combination of three technological advancements from TEM imaging in biological and materials science,” Ercius says. “These three advancements are the development of a graphene liquid cell that allows TEM imaging of nanoparticles rotating freely in solution, direct electron detectors that can produce movies with millisecond frame-to-frame time resolution of the rotating nanocrystals, and a theory for ab initio single particle 3D reconstruction.”

The graphene liquid cell (GLC) that helped make this study possible was also developed at Berkeley Lab under the leadership of Alivisatos and co-author Zettl, a physicist who also holds joint appointments with Berkeley Lab, UC Berkeley and Kavli ENSI. TEM imaging uses a beam of electrons rather than light for illumination and magnification but can only be used in a high vacuum because molecules in the air disrupt the electron beam. Since liquids evaporate in high vacuum, samples in solutions must be hermetically sealed in special solid containers – called cells – with a very thin viewing window before being imaged with TEM. In the past, liquid cells featured silicon-based viewing windows whose thickness limited resolution and perturbed the natural state of the sample materials. The GLC developed at Berkeley lab features a viewing window made from a graphene sheet that is only a single atom thick.

“The GLC provides us with an ultra-thin covering of our nanoparticles while maintaining liquid conditions in the TEM vacuum,” Ercius says. “Since the graphene surface of the GLC is inert, it does not adsorb or otherwise perturb the natural state of our nanoparticles.”

Working at NCEM’s TEAM I, the world’s most powerful electron microscope, Ercius, Alivisatos and their colleagues were able to image in situ the translational and rotational motions of individual nanoparticles of platinum that were less than two nanometers in diameter. Platinum nanoparticles were chosen because of their high electron scattering strength and because their detailed atomic structure is important for catalysis.

“Our earlier GLC studies of platinum nanocrystals showed that they grow by aggregation, resulting in complex structures that are not possible to determine by any previously developed method,” Ercius says. “Since SINGLE derives its 3D structures from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale.”

The next step for SINGLE is to recover a full 3D atomic resolution density map of colloidal nanoparticles using a more advanced camera installed on TEAM I that can provide 400 frames-per-second and better image quality.

“We plan to image defects in nanoparticles made from different materials, core shell particles, and also alloys made of two different atomic species,” Ercius says. [emphasis mine]

“Two different atomic species?”, they really are pushing that biology analogy.

Here’s a link to and a citation for the paper,

3D structure of individual nanocrystals in solution by electron microscopy by Jungwon Park, Hans Elmlund, Peter Ercius, Jong Min Yuk, David T. Limme, Qian Chen, Kwanpyo Kim, Sang Hoon Han, David A. Weitz, A. Zettl, A. Paul Alivisatos. Science 17 July 2015: Vol. 349 no. 6245 pp. 290-295 DOI: 10.1126/science.aab1343

This paper is behind a paywall.