A5047848897- Advanced Electron Microscopy Techniques and Applications
- Quantum Dots Synthesis And Properties
- Catalytic Processes in Materials Science
- Engineering Applied Research
- Electron and X-Ray Spectroscopy Techniques
- Fatigue and fracture mechanics
- nanoparticles nucleation surface interactions
- Hydrogen Storage and Materials
- Gold and Silver Nanoparticles Synthesis and Applications
- Catalysis and Oxidation Reactions
- Iron oxide chemistry and applications
- Electrocatalysts for Energy Conversion
- Machine Learning in Materials Science
- Semiconductor materials and devices
- Metal-Organic Frameworks: Synthesis and Applications
- Ammonia Synthesis and Nitrogen Reduction
- Advanced Welding Techniques Analysis
- Aluminum Alloy Microstructure Properties
- Covalent Organic Framework Applications
- Catalysts for Methane Reforming
- Ferroelectric and Negative Capacitance Devices
- 2D Materials and Applications
- Ion-surface interactions and analysis
- Aluminum Alloys Composites Properties
- Force Microscopy Techniques and Applications
Seoul National University
1990-2025
Institute for Basic Science
2020-2025
Lawrence Livermore National Laboratory
2024
University of Chicago
2024
Pusan National University
1994-2013
Watching early stage nucleation In classic theory, a metastable disordered dense liquid or amorphous solid cluster spontaneously and irreversibly transforms into crystalline nucleus. Jeon et al. observed the formation of gold crystals on graphene substrate through reduction precursor using an electron beam. Rather than view, they instead pathway that involves dynamic reversible fluctuations developing nuclei between states. The lifetime in state decreases with increasing size, at...
Recent advances in flexible and stretchable electronics have led to a surge of electronic skin (e-skin)-based health monitoring platforms. Conventional wireless e-skins rely on rigid integrated circuit chips that compromise the overall flexibility consume considerable power. Chip-less based inductor-capacitor resonators are limited mechanical sensors with low sensitivities. We report chip-less e-skin surface acoustic wave made freestanding ultrathin single-crystalline piezoelectric gallium...
InP/ZnSe/ZnS quantum dots (QDs) stand as promising candidates for advancing QD-organic light-emitting diodes (QLED), but low emission efficiency due to their susceptibility oxidation impedes applications. Structural defects play important roles in the degradation of QDs, formation mechanism oxidized QDs has been less investigated. Here, we investigated impact diverse structural on individual and propagation during UV-facilitated using high-resolution (scanning) transmission electron...
Metal nanoclusters (NCs), an important class of nanoparticles (NPs), are extremely small in size and possess quasi-molecular properties. Due to accurate stoichiometry constituent atoms ligands, NCs have strong structure-property relationship. The synthesis is seemingly similar that NPs as both formed by colloidal phase transitions. However, they considerably different because metal-ligand complexes NC synthesis. Reactive ligands can convert metal salts complexes, actual precursors NCs....
Abstract Ice crystals at low temperatures exhibit structural polymorphs including hexagonal ice, cubic or a hetero-crystalline mixture of the two phases. Despite significant implications structure-dependent roles mechanisms behind growths each polymorph have been difficult to access quantitatively. Using in-situ cryo-electron microscopy and computational ice-dynamics simulations, we directly observe crystalline ice growth in an amorphous film nanoscale thickness, which exhibits...
Here, we present the synthesis and characterization of a novel 2D crystalline framework, named C2O, which mainly consists carbon oxygen in 2:1 molar ratio features crown ether holes its skeletal structure. The covalent-frameworked can be synthesized on gram-scale exhibits fine chemical stability various environments, including acid, base, different organic solvents. C2O efficiently activates KI through strong coordination K+ with rigid enhances nucleophilicity I– significantly improves...
Abstract Reducing the size of perovskite crystals to confine excitons and passivating surface defects has fueled a significant advance in luminescence efficiency light-emitting diodes (LEDs). However, persistent gap between optical limit electroluminescence photoluminescence colloidal nanocrystals (PeNCs) suggests that defect passivation alone is not sufficient achieve highly efficient PeNC-LEDs. Here, we present materials approach controlling dynamic nature surface. Our experimental...
Abstract Ordered mesoporous carbon materials offer robust network of organized pores for energy storage and catalysis applications, but suffer from time‐consuming intricate preparations hindering their widespread use. Here we report a new rapid synthetic route N‐doped ordered structure through preferential heating iron oxide nanoparticles by microwaves. A nanoporous covalent organic polymer is first formed in situ covering the hard templates assembled nanoparticles, paving way long‐range...
Abstract Over the last several decades, colloidal nanoparticles have evolved into a prominent class of building blocks for materials design. Important advances include synthesis uniform with tailored compositions and properties, precision construction intricate, higher-level structures from via self-assembly. Grasping modern complexity their superstructures requires fundamental understandings processes nanoparticle growth In situ liquid phase transmission electron microscopy (TEM) has...
Non-metal hexagonal boron nitride (BN) catalysts hold significant promise for the selective oxidation of light alkanes due to their distinctive anti-overoxidation properties. Although reaction-induced BOx species are typically considered active phase, formation within inert BN lattice generally requires harsh activation conditions and high reaction temperatures, which hinder production value-added liquid oxygenates. In this study, we demonstrate that can be efficiently generated on colloids...
Two-dimensional (2D) transition metal dichalcogenide (TMD) layers are unit-cell thick materials with tunable physical properties according to their size, morphology, and chemical composition. Their of lab-scale research industrial-scale applications requires process development for the wafer-scale growth scalable device fabrication. Herein, we report on a new type atmospheric pressure vapor deposition (APCVD) that utilizes colloidal nanoparticles as process-scalable precursors production TMD...
Active sites and catalytic activity of heterogeneous catalysts is determined by their surface atomic structures. However, probing the structure at an resolution difficult, especially for solution ensembles nanocrystals, which consist particles with irregular shapes surfaces. Here, we constructed 3D maps coordination number (CN) generalized CN (CN_) individual atoms sub-3 nm Pt nanocrystals. Our results reveal that synthesized nanocrystals are enclosed islands nonuniform lead to complex...
A general problem when designing functional nanomaterials for energy storage is the lack of control over stability and reactivity metastable phases. Using high-capacity hydrogen candidate LiAlH4 as an exemplar, we demonstrate alternative approach to thermodynamic stabilization metal hydrides by coordination nitrogen binding sites within nanopores N-doped CMK-3 carbon (NCMK-3). The resulting LiAlH4@NCMK-3 material releases H2 at temperatures low 126 °C with full decomposition below 240 °C,...
Abstract In situ structures of Platinum (Pt) nanoparticles (NPs) can be determined with graphene liquid cell transmission electron microscopy. Atomic-scale three-dimensional structural information about their physiochemical properties in solution is critical for understanding chemical function. We here analyze eight atomic-resolution maps small (<3 nm) colloidal Pt NPs. Their are composed an ordered crystalline core surrounded by surface atoms comparatively high mobility. 3D...
Colloidal nanocrystals inherently undergo structural changes during chemical reactions. The robust structure-property relationships, originating from their nanoscale dimensions, underscore the significance of comprehending dynamic behavior in reactive media. Moreover, complexity and heterogeneity inherent atomic structures require tracking transitions individual at three-dimensional (3D) resolution. In this study, we introduce method time-resolved Brownian tomography to investigate temporal...
Transmission electron microscopy (TEM) is a crucial analysis method in materials science and structural biology, as it offers high spatiotemporal resolution for characterization reveals structure-property relationships dynamics at atomic molecular levels. Despite technical advancements EM, the nature of beam makes EM imaging inherently detrimental to even low-dose applications. We introduce SHINE, Self-supervised High-throughput Image denoising Neural network Electron microscopy,...
Ruthenium is one of the most active catalysts for ammonia dehydrogenation and essential use as a hydrogen storage material. The B5 -type site on surface ruthenium expected to exhibit highest catalytic activity dehydrogenation, but number these sites typically low. Here, -site-rich catalyst synthesized by exploiting crystal symmetry hexagonal boron nitride support. In prepared catalyst, nanoparticles are formed epitaxially sheets with planar morphologies, in which predominate along...
Elucidating the water-induced degradation mechanism of quantum-sized semiconductor nanocrystals is an important prerequisite for their practical application because they are vulnerable to moisture compared bulk counterparts. In-situ liquid-phase transmission electron microscopy a desired method studying nanocrystal degradation, and it has recently gained technical advancement. Herein, moisture-induced investigated using graphene double-liquid-layer cells that can control initiation...
Single-phase formation of active metal oxides on supports has been vigorously pursued in many catalytic applications to suppress undesired reactions and determine direct structure-property relationships. However, this is difficult achieve nanoscale range because the effect non-uniform metal-support interfaces becomes dominant overall catalyst growth, leading nucleation various metastable oxides. Herein, we develop a supported single-phase corundum-Rh2 O3 (I) nanocatalyst by utilizing...
Uniformly dispersed palladium species in small-pore zeolite are successfully prepared for catalytic applications, and investigated by advanced microscopic methods.
Abstract Conformational changes in macromolecules significantly affect their functions and assembly into high‐level structures. Despite advances theoretical experimental studies, investigations the intrinsic conformational variations dynamic motions of single remain challenging. Here, liquid‐phase transmission electron microscopy enables real‐time tracking single‐chain polymers. Imaging linear polymers, synthetically dendronized with conjugated aromatic groups, organic solvent confined...
Liquid-phase transmission electron microscopy (TEM) offers a real-time microscopic observation of the nanometer scale for understanding underlying mechanisms growth, etching, and interactions colloidal nanoparticles. Despite such unique capability potential application in diverse fields analytical chemistry, liquid-phase TEM studies rely on information obtained from limited number observed events. In this work, novel liquid cell with large-scale array highly ordered nanochambers is...