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Fluorescence Modulation in UiO-66-NH2 via Photooxidation and Selective Reduction

2025-08-31T15:00:00Z

Title: Fluorescence Modulation in UiO-66-NH2 via Photooxidation and Selective Reduction Author(s): Ahn, Yongdeok; Park, Minsoo; Son, Younghu; Cho, Juhyeong; Park, Min Jeong; Seo, Daeha; Yoon, Minyoung Abstract: Metal-organic frameworks with emissive ligands offer tunable photophysical properties that are sensitive to their coordination environment and structural configuration. In this study, we demonstrate that the fluorescence of UiO-66-NH2 can be modulated through photo-oxidation-induced quenching and subsequent solvent-mediated recovery. Upon visible-light irradiation, reactive oxygen species induce two distinct oxidation pathways: irreversible oxidation of the ligand and reversible oxidation of the metal-oxo cluster. These redox events lead to partial disruption of the coordination environment and result in fluorescence loss. Reduction using mild alcohols selectively removes adsorbed oxidative species from Zr6O4(OH)4, leading to partial recovery of fluorescence and porosity. The extent of fluorescence restoration correlates with both the reducing strength and molecular size of the alcohol, reflecting its ability to penetrate internal pores and access to redox-active sites. Notably, some alcohol-treated samples exhibited nitrogen uptake beyond that of pristine UiO-66-NH2, suggesting redux-induced structural reorganization and defect-assisted pore expansion. These results establish a structure-function relationship in MOFs governed by localized redox chemistry, providing a platform for designing reconfigurable optical materials with switchable photophysical and porous characteristics.

Incomplete chirality of exceptional points in asymmetric optical microcavity

2025-09-30T15:00:00Z

Title: Incomplete chirality of exceptional points in asymmetric optical microcavity Author(s): Kim, Hyundong; Eom, Youngmin; Lee, Hoyeon; Cho, Yanni; Lee, Seungwoo; Gwak, Sunjae; Yu, Hyeon-Hye; Yi, Chang-Hwan; Kim, Chil-Min Abstract: A chiral exceptional point (EP) in an optical microcavity emerges from the coalescence of even and odd modes with identical azimuthal modal numbers under asymmetric perturbation. While the chirality of such EPs is well understood in circular disks with asymmetrically positioned Rayleigh scatterers, it becomes more intricate in asymmetric microcavities, where the contributing modes can exhibit nontrivial wave morphology according to chaotic deformation. To explore this, we consider a stand-alone microcavity composed of one half ellipse and two quarter ellipses, for which EPs exhibit incomplete chirality. Our analysis reveals that this incomplete chirality originates from prior mode coupling. After the prior mode coupling, only the quasinormal modes within each superposed mode pair that have identical azimuthal modal numbers but opposite parities contribute to the chirality at EPs. Consequently, the chirality of the EP modes remains incomplete, depending on the relative weight of the original mode pair. Finally, we analyze the formation of EPs and their chiral properties in a generic asymmetric microcavity, providing insights into the underlying mechanisms of incomplete chirality.

체성분 분석을 위한 초음파 영상 시스템 및 초음파 영상 시스템의 동작 방법

Title: 체성분 분석을 위한 초음파 영상 시스템 및 초음파 영상 시스템의 동작 방법 Author(s): 유천열; 이문환; 황재윤 Abstract: 대상체에 대한 복수의 위치에서 대상체로 초음파 신호를 송신하고 그로부터 반사된 신호를 수신 가능한 스캔 장치를 이용하여, 대상체의 3차원 초음파 영상을 용이하게 생성하는 체성분 분석을 위한 초음파 영상 시스템 및 초음파 영상 시스템의 동작 방법이 개시된다. 초음파 영상 시스템은 대상체를 삽입 가능한 스캔 장치와, 상기 스캔 장치의 일부에 연결된 초음파 탐촉자와, 상기 초음파 탐촉자로 하여금 상기 스캔 장치에 대하여 복수의 위치에서 상기 대상체로 송신 초음파 신호를 발생시키고, 상기 대상체로부터 반사된 반사 초음파 신호를 수신하도록 제어하는 제어부와, 상기 스캔 장치에 대한 복수의 위치에서 각각 수신된 상기 반사 초음파 신호에 기초하여 복수의 2D 초음파 영상을 생성하고, 상기 복수의 2D 초음파 영상에 기초하여 3D 초음파 영상을 생성하는 영상 처리부를 포함할 수 있다.

Signatures of Kramers-Weyl fermions in the charge density wave material (TaSe4)2I

2025-09-30T15:00:00Z

Title: Signatures of Kramers-Weyl fermions in the charge density wave material (TaSe4)2I Author(s): Kim, Soyeun; McKay, Robert C.; Bielinski, Nina G.; Park, Junehu; Zhao, Chengxi; Lin, Meng Kai; Hlevyack, Joseph Andrew; Guo, Xuefei; Mo, Sung Kwan; Abbamonte, Peter M.; Chiang, Taichang; Schleife, André; Shoemaker, Daniel P.; Bradlyn, Barry; Mahmood, Fahad Abstract: The quasi-one-dimensional charge density wave (CDW) material (TaSe4)2I has been recently predicted to host Kramers-Weyl (KW) fermions which should exist in the vicinity of high symmetry points in the Brillouin zone in chiral materials with strong spin-orbit coupling. However, direct spectroscopic evidence of KW fermions is limited. Here we use helicity-dependent laser-based angle-resolved photoemission spectroscopy (ARPES) in conjunction with tight-binding and first-principles calculations to identify KW fermions in (TaSe4)2I. We find that topological and symmetry considerations place distinct constraints on the (pseudo-) spin texture and the observed spectra around a KW node. Our findings highlight the unique topological nature of (TaSe4)2I and provide a pathway for identifying KW fermions in other chiral materials.