Prof. Han Sang Woo is currently a professor at the Department of Chemistry at the Korea Advanced Institute of Science and Technology (KAIST), specializing in Physical and Nanochemistry. He and his team, consisting of several students, are focused on creating different shapes of nanoparticles. They have created a variety of shapes – ranging from simple cube shapes, to more complicated star shapes – in order to manipulate the characteristics of a particle. His team discovered that, although the material was an important factor to the characteristics of the nanoparticle, the structure of a nanoparticle can determine how a reaction plays out, making not just the material, but the shape of the particle extremely important as well. We were very fortunate to be able to ask him a few questions about his career choices and fascinating research. If you’d like to find out more about him or his work, use this link to access his profile. The following is an interview with Prof. Han.
Q. Can you describe some of the shapes you made and why you chose those specific shapes?
A. Various shapes such as cubes, octahedrons, and icosahedrons (20 sides) were made initially to get the most surface area out of the material, which was expensive. However, after 15 years of research and development, we realized that the shape and size impacted the chemical properties – the structure changed for each shape, hence the chemical reaction that happened. Therefore, as my team and I change the shape of the nanoparticles, we research which specific shape exhibits certain characteristics that could be useful. As we manipulate the size and shape, new catalytic characteristics emerge.
Q. Are there materials currently in use that you would like to see replaced by the materials in your research? If so, what materials could you replace by eliminating the cons and amplifying the pros?
A. One material is a photocatalyst. Photocatalysts can break down water to make hydrogen, or convert carbon dioxide into more useful elements. However, basic photocatalysts are made of semiconductors, which have a lot of downsides such as their short lifespan and the fact that they can only absorb certain wavelengths of the light spectrum. So, next generation photocatalysts will use materials that amplify light well, such as gold, to extend their lifespan and increase their efficiency.
Q. When you are researching something, what drives you forward?
A. Well, I think I’m really interested in the field. When society needs something and when a limit is reached while studying that subject, being able to overcome that limit and combine unique, unheard of ideas to the results of my trials and wanting a new start is my biggest driving force.
Q. What made you choose chemistry in university? Later on, what made you choose nanomaterials?
A. It was, really, just fun. At school, I found Chemistry the most exciting, and reactions, particles, and the periodic table the most intriguing. I especially enjoy changing and manipulating the size and shape of the nanomaterials.
Q. What are the main difficulties of being a professor/researcher doing this type of research in Korea?
A. Korea’s current rivals in the nanomaterial industry are China and the U.S, and all of the problems are shared internationally. The most prominent weakness of our field is the stability of our products; although the new products are far more superior in terms of activity, this is the main reason why they cannot be put to commercial use. A solution to this problem would be a great leap forward for the field.
Q. What was the most interesting or fun topic that you’ve researched?
A. Some nanocrystals can be made of more than two metals. For example, metal A can be used in the center and metal B in the shell. These nanocrystals are very useful, but due to the differences in the basic characteristics of the metals, creating the right structure is difficult. However, when several requirements are met, reacting the two metals will result in the formation of a crystal with the exact structure, with metal A in the center, and metal B creating a shell. Because this crystal will have the characteristics of both metals, and they complement each other, it is typically used as a catalyst in reactions.
Q. What is your ultimate goal in your field (of Noble Metal Nanocrystals / Designed Assembly of Noble Metal Nanocrystals)?
A. My ultimate goal at the moment is to be able to assemble certain substances that have certain characteristics. When I need a particular material that requires specific characteristics, I want to be able to create a design and then assemble it based on the design, without going through any trial and error.
Interview collaboratively conducted and written by:
Sam Cho (Seoul Foreign High School)
Jacob Kim (Seoul Foreign High School)
Spencer Lee (Seoul Foreign High School)