https://scholar.dgist.ac.kr/handle/20.500.11750/13619 2026-08-03T10:05:14Z 2026-08-03T10:05:14Z Lee, Daewon Oaks-Leaf, Sam Ma, Hyeonjong He, Jianlong Wang, Zhiqi Shi, Yifeng Ahn, Eonhyoung Bustillo, Karen C. Song, Chengyu Ribet, Stephanie M. Dhall, Rohan Ophus, Colin Asta, Mark Yang, Jiwoong Xia, Younan Limmer, David T. Zheng, Haimei https://scholar.dgist.ac.kr/handle/20.500.11750/60536 2026-07-30T08:40:12Z 2026-04-30T15:00:00Z

Title: Nanocrystal Geometry Governs Phase Transformation Pathways in Palladium Hydride Author(s): Lee, Daewon; Oaks-Leaf, Sam; Ma, Hyeonjong; He, Jianlong; Wang, Zhiqi; Shi, Yifeng; Ahn, Eonhyoung; Bustillo, Karen C.; Song, Chengyu; Ribet, Stephanie M.; Dhall, Rohan; Ophus, Colin; Asta, Mark; Yang, Jiwoong; Xia, Younan; Limmer, David T.; Zheng, Haimei Abstract: Pathways and structural dynamics of phase transformations impact performance of materials in energy and information storage technologies. Palladium hydride (PdHx ) nanocrystals are an ideal model system for studying solute-induced phase transformations, where elastic energy from lattice mismatch between alpha-PdH, and beta-PdH, phases is often considered a key to determining the transformation pathways. alpha/beta-PdHx interfacial elastic energy is affected by the confined geometry of a nanocrystal. However, how nanocrystal geometry influences phase trans-formation pathways is largely unknown. Using in situ liquid phase transmission electron microscopy, we directly visualize hydrogenation in Pd nanocrystals with two geometries, a nanocube and a hexagonal nanoplate. Both follow similar sequences of an initially curved nucleus, interface flattening, and reverse-stage nucleation; however, their evolving alpha/beta-PdHx interfaces exhibit geometry-dependent crystallographic alignments. In nanocubes, (100)-aligned configurations conform to static elastic energy ordering, representing a pathway that maintains a local mechanical equilibrium, whereas nanoplates display both (110) and (211)-aligned interfaces. Theoretical simulations show that geometry determines the accessibility of alternative phase transformation pathways as the system is driven far from equilibrium during hydrogenation. These findings identify geometry as a fundamental parameter for directing phase transformation pathways, offering design principles for accessing atypical configurations and improving properties of intercalation-based devices.

2026-04-30T15:00:00Z Kim, Minseo Li, Shi Lee, Kyunghoon Ahn, Eonhyoung Lee, Soyeon Kim, Kiwook Kim, Hang Yu, Wookyung Choi, Changsoon Lim, Jung Ah Hwang, Jeeseong Kim, Dae-Hyeong Yang, Jiwoong https://scholar.dgist.ac.kr/handle/20.500.11750/60475 2026-07-22T18:01:28Z 2026-02-28T15:00:00Z

Title: Broadband Circularly Polarized Light Detection via Spin-Selective Charge Transport in Quantum Dot Photodiodes Author(s): Kim, Minseo; Li, Shi; Lee, Kyunghoon; Ahn, Eonhyoung; Lee, Soyeon; Kim, Kiwook; Kim, Hang; Yu, Wookyung; Choi, Changsoon; Lim, Jung Ah; Hwang, Jeeseong; Kim, Dae-Hyeong; Yang, Jiwoong Abstract: Circularly polarized light (CPL) detection provides polarization-resolved information, enabling advanced applications in quantum technologies, bioimaging, secure communications, and multi-level optical data processing. However, conventional CPL photodetectors typically rely on intrinsically chiral absorbers, restricting operation to the UV-vis range and hindering extension into the near-infrared (NIR) and shortwave infrared (SWIR), which are critical for deep tissue imaging and low-visibility sensing. Here, we demonstrate broadband CPL detection with quantum dot (QD) photodiodes that exploit the chiral-induced spin selectivity effect in chiral-ZnO charge transport layers. Chiral ligand-functionalized ZnO electron transport layers selectively transmit spin-polarized charge carriers from QDs, enabling CPL-specific photocurrent generation even in spectral regions without intrinsic chiral absorption. Heavy-metal-free Cu-In-Se QD-photodiodes exhibit outstanding specific detectivity (D *) of 1.28 x 1012 Jones without external bias and broadband CPL detection (g Iph: similar to 0.17 at 260 nm and similar to 0.13 at 780 nm), while PbS QD-devices extend CPL detection across 250-1700 nm (UV-Vis-NIR-SWIR) with superior performance (D *: 1.45 x 1012 Jones). The chiral-transport-driven strategy offers fundamental insights into CPL photodetection and establishes a scalable and optically passive platform for broadband polarization-resolved optoelectronics.

2026-02-28T15:00:00Z Kim, Sowon Yu, Youngwoong Choi, Hyunwoo Ham, Gayoung An, Sanghyeok Lee, Soyeon Yang, Jiwoong Chung, Dae-sung Lee, Jihoon Cha, Hyojung https://scholar.dgist.ac.kr/handle/20.500.11750/60006 2026-02-10T18:01:16Z 2025-12-31T15:00:00Z

Title: Synergistic dual-electron acceptors in linear conjugated polymers for boosting photocatalytic hydrogen evolution Author(s): Kim, Sowon; Yu, Youngwoong; Choi, Hyunwoo; Ham, Gayoung; An, Sanghyeok; Lee, Soyeon; Yang, Jiwoong; Chung, Dae-sung; Lee, Jihoon; Cha, Hyojung Abstract: A conjugated polymer photocatalyst containing dual-electron acceptor units, dibenzo[b,d]thiophene sulfone (DBS) and 2,1,3-benzothiadiazole (BT), known as PBT, has been synthesized for its strong electron-withdrawing abilities and structural flexibility. However, the inherent hydrophobicity of PBT leads to significant particle aggregation, hindering colloidal stability and electron transfer to protons. To overcome these limitations, fluorine and ethylene glycol (EG) groups are strategically incorporated into the BT unit to enhance molecular planarity and hydrophilicity, respectively. This molecular engineering effectively suppresses exciton and charge recombination, facilitating efficient charge separation and extraction. Comprehensive spectroscopic analyses—including time-resolved photoluminescence (Tr-PL) and transient absorption spectroscopy (TAS)—reveal that EG-functionalized polymers exhibit prolonged exciton lifetimes and strong photoinduced absorption at early timescales, indicating both suppressed non-radiative recombination and effective charge generation. Importantly, these modifications enable rapid charge separation and transfer with more efficient electron extraction to protons, mitigating charge accumulation within aggregated domains. Among the modified polymers, 4EG-PBTz-F, with di-fluoro substituents and tetra-ethylene glycol groups, achieves the highest hydrogen evolution rates of 15.476 mmol g−1 and 3.095 mmol g−1 h−1 with a 3 wt% Pt co-catalyst. These results highlight the effectiveness of dual-electron acceptor design and interfacial control, offering a multi-faceted design strategy in photocatalytic hydrogen evolution systems.

2025-12-31T15:00:00Z Ma, Hyeonjong Kim, Hyeongseung Yang, Jiwoong https://scholar.dgist.ac.kr/handle/20.500.11750/60005 2026-02-10T18:01:14Z 2025-11-30T15:00:00Z

Title: Graphene-Based Liquid Cell Designs for In Situ Liquid-Phase Transmission Electron Microscopy: Recent Developments and Perspectives Author(s): Ma, Hyeonjong; Kim, Hyeongseung; Yang, Jiwoong Abstract: Recent advances in liquid-phase transmission electron microscopy (TEM) have enabled the direct visualization of reaction pathways of nanomaterials, providing critical insights into diverse nanoscale processes such as crystallization, phase transition, shape transformation, etching, and nanoparticle motions. Among various liquid cells, graphene liquid cells (GLCs) are particularly advantageous due to the intrinsic properties of graphene—high electrical and thermal conductivity, exceptional mechanical flexibility, and radical scavenging effects—which allow atomic-scale spatial resolution and enhanced imaging stability. This review article highlights the recent progress in GLC-based liquid-phase TEM, focusing on the evolution of structural designs, including veil-type, well-type, liquid-flowing-type, and mixing-type GLCs. Each configuration offers unique advantages tailored to observing distinct types of nanoscale dynamic processes. These studies have elucidated both classical reaction pathways and complex, nonclassical mechanisms involving transient intermediates. Overall, this review highlights how developments in GLC designs have significantly advanced the capabilities of in situ liquid-phase TEM, providing unprecedented opportunities to study nanoscale processes at atomic resolution.

2025-11-30T15:00:00Z