Abstract:  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 We demonstrated that ceria nanoparticles and ceria–zirconia nanoparticles can work as therapeutic antioxidants to treat various nasty diseases including ischemic stroke, Alzheimer’s disease, sepsis, and Parkinson’s disease.⁴ We developed a click reaction-assisted immune cell targeting (CRAIT) strategy to deliver drug-loaded nanoparticles deep into tumor interiors, reducing tumor burden in an aggressive 4T1 breast cancer model without any systemic toxicity.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 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.^7.

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-Fe2O3.⁸ We report a simple synthetic method of carbon-based hybrid cellular nanosheets loaded with SnO2 nanoparticles.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

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 3-Photon Biomedical Imaging using Doped ZnS Nanocrystals,” Nature Mater. 2013, 12, 359.    
4. “Ceria Nanoparticles that can Protect against Ischemic Stroke,” Angew. Chem. Int. Ed. 2012, 51, 11039; “Mitochondria-Targeting Ceria Nanoparticles as Antioxidants for Alzheimer's Disease,” ACS Nano, 2016, 10, 2860; “Ceria–Zirconia Nanoparticles as Enhanced Multi-Antioxidant for Sepsis Treatment,” Angew. Chem. Int. Ed. 2017, 56, 11399; “Ceria nanoparticle systems for selective scavenging of mitochondrial, intracellular, and extracellular reactive oxygen species in Parkinson’s disease,” Angew. Chem. Int. Ed. 2018, 57, 9408; “Magnetite/Ceria Nanoparticle Assemblies for Extracorporeal Cleansing of Amyloid-β in Alzheimer’s Disease,” Adv. Mater. 2018, 30, 1807965.         
5. “Deep tumor penetration of drug-loaded nanoparticles by click reaction-assisted immune cell targeting strategy,” JACS 2019, ASAP.    
6. “Signal sorting and amplifying potassium nanosensors for monitoring epilepsy in freely moving mice,” Nature Nanotechnol. 2019, in 2nd revision.    
7. “Highly conductive, stretchable, and biocompatible Ag-Au core-sheath nanowire composite for wearable and implantable bioelectronics,” Nature Nanotech. 2018, 13, 1048; “Electromechanical cardioplasty using a wrapped elasto-conductive epicardial mesh,” Science Transl. Med. 2016, 8, 344ra86.    
8. “Galvanic Replacement Reactions in Metal Oxide Nanocrystals,” Science 2013, 340, 964.     
9. “Hybrid Cellular Nanosheets for High-Performance Lithium Ion Battery Anodes,” J. Am. Chem. Soc. 2015, 137, 11954.    
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?” JACS 2019, 141, 2035.    
12. “Reversible and cooperative photoactivation of single-atom Cu/TiO2 photocatalysts,” Nature Mater. 2019, 18, 620.