홍성철 교수

Two-dimensional (2D) materials and their heterostructures are promising for next-generation optoelectronics, spintronics, valleytronics, and electronics. Despite recent progress in various growth studies of 2D materials, mechanical exfoliation of flakes is still the most common method to obtain high-quality 2D materials because precisely controlling material growth and synthesizing a single domain during the growth process of 2D materials, for the desired shape and quality, is challenging. Here,

Understanding the atomic-scale mechanisms that govern the structure of interfaces is critical across materials systems but particularly so for two-dimensional (2D) moiré materials. Here, we image, atom-by-atom, the thermally induced structural evolution of twisted bilayer transition metal dichalcogenides using in situ transmission electron microscopy. We observe low-temperature, local conversion of moiré superlattice into nanoscale aligned domains. Unexpectedly, this process occurs by nucleating

changed from n-type to ambipolar, along with an enhanced hole transport, which also support dedoping of annealed TMDs. This work provides an innovative approach to elevate the optical grade of monolayer TMDs, enabling the fabrication of high-performance optoelectronic devices.

We study emission patterns in periodic nano-hole arrays perforated in a metal film. In the nearfield region, higher order multiple components of diffraction interfere with each other to generate complicated spatial patterns. These patterns simplify to a sinusoidal one in the intermediate region and become either homogeneous or sinusoidal in the far-field region, depending on whether the excitation wavelength is larger or smaller than the lattice constant. For an incident wavelength much smaller

Abstract Silicon‐based anodes offer exceptional energy density but are limited by severe volume changes and poor electrical conductivity, hindering their commercial integration. Herein, a silicon/carbon composite is designed for seamless incorporation into conventional graphite anodes, addressing the industry's focus on boosting practical energy density. This composite is obtained by simple, scalable vibratory milling of industrial waste silicon with functionally distinct carbon materials, meeti

High Resolution Image Download MS PowerPoint Slide Rhombohedrally stacked transition metal dichalcogenides (3R-TMDs) exhibit robust ferroelectricity enabled by in-plane interlayer sliding, positioning them as promising candidates for atomically thin nonvolatile memory devices. However, controlling the distribution of ferroelectric domains, which is governed by domain wall (DW) dynamics, remains a major challenge due to various imperfections that arise during the formation of stacked bilayer stru

In eukaryotes, small RNAs play important roles in both gene regulation and resistance to viral infection. Argonaute proteins have been identified as a key component of the effector complexes of various RNA-silencing pathways, but the mechanistic roles of Argonaute proteins in these pathways are not clearly understood. To address this question, we performed single- molecule fluorescence experiments using an RNA-induced silencing complex (core-RISC) composed of a small RNA and human Argonaute 2. W

Prokaryotic Argonaute facilitates the target recognition process by the guide strand via a still unknown mechanism. Using single-molecule fluorescence resonance energy transfer and systematic mutagenesis of Thermus thermophilus Argonaute and guide-target base pairing, we study the kinetic roles of various structural features of guide strand in the prokaryotic Argonaute. We reveal that the 5′-end anchoring of the guide strand, and the sequence complementarity in the seed- and mid-regions greatly

Twisted transition metal dichalcogenide (TMD) bilayers have garnered significant attention due to the emergence of unconventional quantum phenomena, such as sliding ferroelectricity in multidomain TMD bilayers with domain walls (DWs). Thus, understanding their atomic reconstruction is essential for elucidating the origin of such properties. While atomic reconstruction has been observed in twisted bilayers with small lattice mismatch, large-mismatch systems have generally been thought to retain i

Riboswitches regulate gene expression by coupling ligand binding to a structural transition of the riboswitch, but the coupling mechanism is still controversial. We addressed this issue by characterizing both the ligand-free state of the Escherichia coli thiamine pyrophosphate (TPP) riboswitch aptamer and its structural transition upon ligand binding using single-molecule fluorescence resonance energy transfer (FRET). Our results reveal that the apo-aptamer dynamically samples a partially closed

Fluorescence resonance energy transfer (FRET) between organic fluorophores is conventionally used to monitor binding/dissociation and conformational change of macromolecules. Here we use FRET between a cyanine dye and single transition metal ions (tmFRET) to monitor the binding/dissociation of transition metal ions to a synthetic polypeptide, and show that different transition metal ion species can be clearly distinguished based on their binding lifetimes and FRET efficiencies. Furthermore, we d