Dr. Myoung-hwan Oh: “Generally, when a metal corrodes, rust is formed as a result of the interaction with oxygen. The rust is a metal oxide. Therefore, there has been a preconceived notion that the galvanic replacement reaction, one of the corrosive phenomena of metal, would not occur in metal oxides themselves. However, questioning that preconceived notion and going back to the basics has made possible the remarkable achievement of this study.” As the author of the research paper, “Galvanic Replacement Reactions in Metal Oxide Nanocrystals” published in Science, Dr. Oh of the Center for Nanoparticle Research (led by Director and Professor Taeghwan Hyeon) in IBS, identified the seemingly minute fact that, ‘already rusted metal can rust again,’ which was a critical factor in the success of the Center’s research. Relying on this observation, he turned the standard approach to conducting research upside down. He said, “The existing approach started from metal atoms in the metal nanocrystals. However, we paid attention to metal ions in the metal oxide nanocrystals. We created a nanocage structure by dissolving metal ions in the interior of a nanocube.”

The new methodology is based not on complex theories, but on ‘basic chemistry.’ The research team used the galvanic replacement reaction method to conduct experiments. Examples of this can be found in basic chemistry textbooks.
Though researchers, and even some students, are familiar with the galvanic replacement reaction that occurs between metallic crystals and metal ions, not much research has been conducted on the reaction between ionic crystals, such as metal oxide and metal ions. Dr. Oh thought this observation might be useful in future endeavors.

Dr. Oh: “In contrast to the nanoscience field, a great deal of research has been conducted on the galvanic replacement reaction between ionic crystals and metal ions in the geochemistry field. Thus, I began to wonder whether the same principle can be applied to the nanoscience field.” The methodology applied by Dr. Oh was as simple as the theory. He created an emulsion appropriate for constructing other nanostructures, and then introduced manganese oxide nanocrystals into the emulsion. Injecting an iron(II) solution into the emulsion at an appropriate temperature was enough to not only form a nanocage structure, but also to cap (this refers to the coating of nanocrystals so that they can maintain their stable, crystalline-like state even in nanoscale dimensions) the nanocrystals with surfactants. Another important outcome was the improvement in the functionality of the nanostructure. It became easier to obtain nanomaterials composed of various types of metal oxides via oxidation–reduction reactions that occurred between different metal ions.

In some ways, both the theory and process appear to be simple. But why then, has no application in nanoscience ever been developed that utilizes the method employed by Dr. Oh?

Dr. Oh: “It is hard to verify whether a nanostructure is properly constructed. Moreover, there might be the influence of the previously mentioned preconceived notion. We were able to achieve the desired result in an environment that has been neglected by researchers thus far.”

Under the existing approach, moisture is eliminated as much as possible during the synthesis and growth of nanoparticles. However, the oxidation–reduction reaction employed by Dr. Oh occurs actively in an aqueous solution. Prof. Taeghwan Hyeon encouraged Dr. Oh to explore his idea in depth—even if Dr. Oh’s idea differed from that of mainstream academic trends. He re-emphasized the importance of basic science. “Researchers usually focus on the latest trends when they select research tasks or investigate references,” he said. “Moreover, recently released research papers tend to deal with fully developed ideas. Therefore, when only that such information is used, the research merely provides an improvement of a finished product. I think the key to new ideas is more likely to be found in textbooks and basic theories. This is because the greatest driving force for new research is an accurate forecast and design of experiments based on basic knowledge.”

A common error is to attach undue importance to research results, and instead encouraged the science community not to ignore the basic principles of science. He cited the example of the pioneering researcher Jean-Marie Tarascon, who is leading the lithium-ion battery research field. Dr. Oh said that other scholars have been able to followed his research center’s work because they can theoretically and accurately predict nanostructures with excellent properties, and are capable of quickly synthesizing these structures. Dr. Oh emphasized that, “Basic chemical knowledge is the most important information in predicting a high performance nanostructure. Consequently, basic skills are the factor that put you ahead of others in the field of research.”

Although there are high expectations regarding the utilization of the nanostructures, such as their use in secondary batteries, Dr. Oh said that there is still a long way to go. The path ahead is full of tricky obstacles, ranging from synthesizing nanocrystals and creating efficient structures to increasing the number of times a nanocrystal can be recycled at a practical level. However, he is confident that the IBS Center for Nanoparticle Research will overcome such challenges and succeed in commercializing the results of their research.

Dr. Oh believes basic science research is crucial, and perhaps the most important component in the application of science. “Several research groups at the center of the basic science community have been studying the entire process, from the formation of nanocrystals to their commercialization,” he said. “Once we develop the ability to predict structures by steadily investing in basic chemistry, IBS can become a world-class research institute.”