Yongsoo Yang

Nanomaterials with core-shell architectures are prominent examples of strain-engineered materials. The lattice mismatch between the core and shell materials can cause strong interface strain, which affects the surface structures. Therefore, surface functional properties such as catalytic activities can be designed by fine-tuning the misfit strain at the interface. To precisely control the core-shell effect, it is essential to understand how the surface and interface strains are related at the at

Functional properties of nanomaterials strongly depend on their surface atomic structures, but they often become largely different from their bulk structures, exhibiting surface reconstructions and relaxations. However, most of the surface characterization methods are either limited to 2D measurements or not reaching to true 3D atomic-scale resolution, and single-atom level determination of the 3D surface atomic structure for general 3D nanomaterials still remains elusive. Here we demonstrate th

Controlling the electrochemical CO 2 reduction process for multicarbon production is challenging. Ethanol is typically produced with lower selectivity compared to ethylene. In addition, ill-defined catalytic active sites and elusive mechanisms of C–C coupling further hinder the enhancement of ethanol generation. Here, we carefully regulated the quantity of the Cu atoms and deposited them onto a Ag inverse-opal structure (AgIOs) using the pulse-electrodeposition method. Subnanometer Cu clusters d

We determined a full 3D atomic structure of a dumbbell-shaped Pt nanoparticle formed by a coalescence of two nanoclusters using deep learning assisted atomic electron tomography. Formation of a double twin boundary was clearly observed at the interface, while substantial anisotropy and disorder were also found throughout the nanodumbbell. This suggests that the diffusion of interfacial atoms mainly governed the coalescence process, but other dynamic processes such as surface restructuring and pl

We report on the role of oxygen octahedral tilting in the monoclinic-to-tetragonal phase transition in ultra-thin BiFeO3 films grown on (001) SrTiO3 substrates. Reciprocal space maps clearly show the disappearance of the integer-order Bragg peak splitting associated with the monoclinic phase when the film thickness decreases below 20 unit cells. This monoclinic-to-tetragonal transition is accompanied by the evolution of the half-order diffraction peaks, which reflects untilting of the oxygen oct

Abstract In the early 2000s, low dimensional ferroelectric systems were predicted to have topologically nontrivial polar structures, such as vortices or skyrmions, depending on mechanical or electrical boundary conditions. A few variants of these structures have been experimentally observed in thin film model systems, where they are engineered by balancing electrostatic charge and elastic distortion energies. However, the measurement and classification of topological textures for general ferroel

Pt-based electrocatalysts are the primary choice for fuel cells due to their superior oxygen reduction reaction (ORR) activity. To enhance ORR performance and durability, extensive studies have investigated transition metal alloying, doping, and shape control to optimize the three key governing factors for ORR: geometry, local chemistry, and strain of their surface and subsurface. However, systematic optimization remains incomplete, as it requires an atomic-scale understanding of these factors a

Two structural phase transitions are investigated in highly strained BiFeO3 thin films as a function of film thickness and temperature via synchrotron x-ray diffraction. Both transition temperatures (upon heating: monoclinic MC to monoclinic MA to tetragonal) decrease as the film becomes thinner. A film-substrate interface layer, evidenced by half-order peaks, contributes to this behavior, but at larger thicknesses (above a few nanometers), the temperature dependence results from electrostatic c

High Resolution Image Download MS PowerPoint Slide Obtaining the heterogeneous conformation of small proteins is important for understanding their biological role, but it is still challenging. Here, we developed a multi-tilt nanoparticle-aided cryo-electron microscopy sampling (MT-NACS) technique that enables the observation of heterogeneous conformations of small proteins and applied it to calmodulin. By imaging the proteins labeled by two gold nanoparticles at multiple tilt angles and analyzin

Abstract Controlling the non‐stoichiometry is an effective way to tune physicochemical properties of functional oxides and explore novel physical phenomena in complex oxides. Therefore, quantitative control of oxygen non‐stoichiometry in perovskite oxides plays an important role in understanding the mechanism of topotactic phase transition and improving the applicability of electrochemical devices. Here, an electrochemical titration cell is fabricated to control the oxygen non‐stoichiometry of a

Accurate determination of three-dimensional (3D) atomic structures is crucial for understanding and controlling the properties of nanomaterials. Atomic electron tomography (AET) offers non-destructive atomic imaging with picometer-level precision, enabling the resolution of defects, interfaces, and strain fields in 3D, as well as the observation of dynamic structural evolution. However, reconstruction artifacts arising from geometric limitations and electron dose constraints can hinder reliable

Battery life and capacity are paramount factors in determining the efficacy of a battery [1]. Lithium nickel cobalt manganese oxide (NCM) has emerged as a highly promising cathode material, renowned for its extended battery life and improved capacity [2-3]. Despite the significance of structural degradation as a governing factor of battery life and capacity, the precise mechanism remains largely elusive, although several degradation mechanisms have been suggested [4-5]. In this research, we simu

Measuring the conformational distribution of small proteins is essential to understanding their role in biological systems. Multi-Tilt Nanoparticle-aided cryo-electron microscopy sampling (MT-NACS) was devised to measure the three-dimensional interparticle distance distribution (P(d)) of two gold nanoparticles (AuNPs) labeled on a protein by taking cryogenic electron microscopy (cryo-EM) images at multiple-tilt angles. However, tracking the same particles in a pseudo-tomographic manner during th