Dr. Taeghwan Hyeon
University Distinguished Professor, Director of Center for Nanoparticle Research at the Institute for Basic Science,
and Associate Editor of J. Am. Chem. Soc.
School of Chemical and Biological Engineering, Seoul National University, Korea

Part of the Fall 2019 Graduate Seminar Series

Abstract

Chemistry for Nano, and Nano for Medicine & Energy

Taeghwan Hyeon^1,2

¹ Center for Nanoparticle Research, Institute for Basic Science (IBS),
² School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea. thyeon@snu.ac.kr

Over the last 20 years, our laboratory has focused on the designed chemical synthesis, assembly and applications of uniform-sized nanocrystals. Especially, we developed a novel generalized procedure, called as “heat-up process” for the direct synthesis of uniform-sized nanocrystals of many metals, oxides, and chalcogenides.¹ For the last 10 years, our group has been focused on medical applications of various uniform-sized nanoparticles. We reported that uniform 2 nm iron oxide nanoclusters can be successfully used as T1 MRI contrast agent for high-resolution MR angiography of monkeys.² We reported the first successful demonstration of high-resolution in vivo 3-photon imaging using biocompatible and bright Mn²⁺/ZnS nanocrystals.³

I will present recent advances on the fabrication of stretchable electronic & optoelectronic devices integrated with various functional nanomaterials and their applications to wearable & implantable healthcare devices. We reported graphene-hybrid electrochemical devices integrated with thermo-responsive micro-needles for the sweat-based diabetes monitoring and feedback therapy.⁴ We introduced electromechanical cardioplasty using an epicardial mesh made of electrically conductive and elastic Ag nanowire-rubber composite material to resemble the innate cardiac tissue and confer cardiac conduction system function.⁵ We report a highly sensitive and selective K⁺ nanosensor that can quantitatively monitor extracellular K⁺ concentration changes in the brains of freely moving mice experiencing epileptic seizures.⁶

Recently we have focused on the architecture engineering of nanomaterials for their applications to lithium ion battery, fuel cell electrocatalysts, solar cells, and thermoelectrics. We reported the first demonstration of galvanic replacement reactions in metal oxide nanocrystals, and were able to synthesize hollow nanocrystals of various multimetallic oxides including Mn₃O₄/γ-Fe₂O₃.⁷ We report a simple synthetic method of carbon-based hybrid cellular nanosheets loaded with SnO₂ nanoparticles.⁸ We designed hollow anatase TiO₂ nanostructures composed of interconnected ~5 nm-sized nanocrystals, which can individually reach the theoretical lithium storage limit and maintain a stable capacity during prolonged cycling.⁹ We present a synthesis of highly durable and active electrocatalysts based on ordered fct-PtFe nanoparticles and FeP nanoparticles coated with N-doped carbon shell.¹⁰ The effect of porous structures on the electrocatalytic activity of N-doped carbon is studied by using electrochemical analysis techniques, and the results are applied to synthesize highly active and stable Fe-N-C catalyst for oxygen reduction reaction (ORR).¹¹ We report on the design and synthesis of highly active TiO₂ photocatalysts incorporated with site-specific single copper atoms (Cu/TiO₂) that exhibit reversible & cooperative photoactivation process, and enhancement of photocatalytic hydrogen generation activity.¹² We synthesized multigrain nanocrystals consisting of Co₃O₄ nanocube cores and Mn₃O₄ shells. At the sharp edges of the Co₃O₄ nanocubes, we observed that tilt boundaries of the Mn₃O₄ grains exist in the form of disclinations, and we obtained a correlation between the defects and the resulting electrocatalytic behavior for the oxygen reduction reaction.¹³

1. "Ultra-Large Scale Syntheses of Monodisperse Nanocrystals," Nature Mater. 2004, 3, 891.
2. “Iron oxide nanoclusters for T1 MRI of nonhuman primates,” Nature Biomed. Eng. 2017, 1, 637.

3. “High-Resolution Three-Photon Biomedical Imaging using Doped ZnS Nanocrystals,” Nature Mater. 2013, 12, 359.

4. “A graphene-based electrochemical device with thermo-responsive microneedles for diabetes monitoring and therapy,” Nature Nanotech. 2016, 11, 566;“Wearable/disposable sweat-based glucose monitoring device with multi-stage transdermal drug delivery module,” Science Adv. 2017, 3, e1601314.

5. “Electromechanical cardioplasty using a wrapped elasto-conductive epicardial mesh,” Science Transl. Med. 2016, 8, 344ra86; “Highly conductive, stretchable, and biocompatible Ag-Au core-sheath nanowire composite for wearable and implantable bioelectronics,” Nature Nanotech. 2018, 13, 1048.

6. “Signal sorting and amplifying potassium nanosensors for monitoring epilepsy in freely moving mice,” Nature Nanotechnol. 2019, in revision.

7. “Galvanic Replacement Reactions in Metal Oxide Nanocrystals,” Science 2013, 340, 964.

8. “Hybrid Cellular Nanosheets for High-Performance Lithium Ion Battery Anodes,” J. Am. Chem. Soc. 2015, 137, 11954.

9. “Engineering Titanium Dioxide Nanostructures for Enhanced Lithium-Ion Storage,” J. Am. Chem. Soc., 2018, 140, 16676.
10. “Highly durable and active PtFe nanocatalyst for electrochemical oxygen reduction reaction,” J. Am. Chem. Soc. 2015, 137, 15478; “Large-scale Synthesis of Carbon Shell-coated FeP Nanoparticles for Robust Hydrogen Evolution Reaction Electrocatalyst,” J. Am. Chem. Soc. 2017, 139, 6669.
11. “Design Principle of Fe–N–C Electrocatalysts: How to Optimize Multimodal Porous Structures?” J. Am. Chem. Soc. 2019, 141, 2035.

12. “Reversible and cooperative photoactivation of single-atom Cu/TiO2 photocatalysts,” Nature Mater. 2019, 18, 620.

13. “Design and Synthesis of Multigrain Nanocrystals via Geometric Misfit Strain,” Nature 2019, in revision.

Biography

Taeghwan Hyeon received his B. S. (1987) and M. S. (1989) in Chemistry from Seoul National University (SNU), Korea. He obtained his Ph.D. in Chemistry from U. Illinois at Urbana-Champaign (1996), and conducted one-year postdoctoral research at the Catalysis Center of Northwestern University. Since he joined the faculty of the School of Chemical and Biological Engineering of Seoul National University in 1997, he has focused on the synthesis and applications of uniform-sized nanoparticles and related nanostructured materials, and published > 350 papers in prominent international journals (> 50,000 citations and h-index of > 120). He is a SNU Distinguished Professor. In 2011, he was selected as “Top 100 Chemists” of the decade by UNESCO&IUPAC. For the last > 5 years, he has chosen as “Highly Cited Researcher” in Chemistry and Materials Science areas by Clarivate Analytics. Since 2012, he has been serving as a Director of Center for Nanoparticle Research of Institute for Basic Science (IBS). He is Fellow of Royal Society of Chemistry (RSC) and Materials Research Society (MRS). He received many awards including the Korea S&T Award from the Korean President (2016), Hoam Prize (2012, Samsung Hoam Foundation), POSCO-T. J. Park Award (2008), and the IUVSTA Prize for Technology (International Union for Vacuum Science, Technique and Applications, 2016). Since 2010, he has served as an Associate Editor of Journal of the American Chemical Society. He has been serving as editorial (advisory) board members of ACS Central Science, Advanced Materials, Nano Today, and Small.