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1,263 results on '"Jeong, Kwang"'

21. Chiroptical Smart Paints: Polymerization of Helical Structures in Cholesteric Liquid Crystal Films

Author

Ko, Hyeyoon, Kim, Minwook, Wi, Youngjae, Rim, Minwoo, Lim, Seok-In, Koo, Jahyeon, Kang, Dong-Gue, and Jeong, Kwang-Un

Abstract

Using polymerizable cholesteric liquid crystal (CLC) paints, we prepare circularly polarized freestanding films that enable students to acquire a basic understanding of circular polarization and molecular chirality. The polymerized helical structures of CLC films can exhibit brilliant structural colors by selective reflection of visible light corresponding to their helical pitch. For the fabrication of freestanding and circularly polarizing films of various colors and shapes, students control helical pitch with the amount of chiral dopants and stabilize them by photopolymerization. On the basis of an understanding of the circularly polarized reflection of CLC paints, students can encode secret letters that are visible only with a specific circular polarizer.

Published
2021
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28. Polarization‐Dependent and Color‐Tunable Electrochromic Smart Windows: Uniaxially Oriented and Polymer‐Stabilized Viologen‐Based Liquid Crystal Networks.

Author

Pham, Huan Huu, Rim, Minwoo, Wi, Youngjae, Ko, Hyeyoon, Yu, Dongmin, Hyeong, Jaeseok, Tran, Duy Thanh, Ha, Minjeong, Na, Seok‐In, and Jeong, Kwang‐Un

Subjects
PHASE transitions, ELECTROCHROMIC windows, CHEMICAL stability, COATING processes, LIQUID crystals
Abstract

Viologen‐based reactive mesogen (VRM) is newly designed and synthesized for the development of polarization‐dependent, color‐tunable, and transparent electrochromic (EC) smart windows. By controlling electric field, the color of VRM can be intentionally tuned due to the formation of dication (D state), cation‐radical (C state), and neutral state (N state). Based on the deep understanding of phase transition of VRM, a uniaxially oriented VRM hierarchical nanostructure is successfully constructed on the macroscopic area by simple coating and self‐assembly processes. The subsequent photopolymerization significantly improves thermal, mechanical, and chemical stabilities of the VRM thin film. In addition to the control of color, the transmittance of uniaxially oriented VRM‐based EC smart window can be precisely tuned by rotating a linear polarizer. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Novel non-plasmonic nanolasers empowered by topology and interference effects

Author

Hwang Min-Soo, Kim Ha-Reem, Jeong Kwang-Yong, Park Hong-Gyu, and Kivshar Yuri

Subjects
bound states in the continuum, mie resonances, nanolaser, spaser, topological photonics, Physics, QC1-999
Abstract

Historically, nanophotonics deals with a control of light at the nanoscale being closely connected with the rapid advances in plasmonics – the physics of surface plasmon polaritons supported by metal–dielectric interfaces. Properly engineered nanostructures allow the subwavelength propagation of light and its strong confinement in nanowaveguides and nanocavities, making possible the field enhancement and lasing. Spaser was suggested as a special type of nanolaser with a very small footprint that can be modulated quickly thus becoming a good candidate for on-chip optical data processing. However, recent developments in the physics of high-index dielectric nanoparticles and resonant dielectric metasurfaces allowed to advance the field of nanophotonics and introduce novel nonplasmonic nanostructures and nanolasers empowered by topology and interference effects. Here we present first some examples of experimentally realized spasers, and then discuss the recent developments in the cutting-edge high-index dielectric nanostructures employed for nonplasmonic nanolasers based on Mie resonances, anapole states, bound states in the continuum, and the physics of topological phases.

Published
2021
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38. Rational Design of Dendritic Phase‐Pure Tin Antimonide Intermetallic Film‐Based Negatrodes for Commercially‐Viable Flexible Sodium‐Ion Pouch Cell Battery.

Author

Jena, Sambedan, Sathishkumar, Lakshmanan, Tran, Duy Thanh, Jeong, Kwang‐Un, Kim, Nam Hoon, and Lee, Joong Hee

Subjects
SODIUM ions, MANUFACTURING cells, TIN, AQUEOUS electrolytes, PRUSSIAN blue, ELECTRIC batteries, FOAM
Abstract

Exploiting the ability to directly deposit larger‐sized, flexible, alloying‐type sodium‐ion battery electrodes without the need of additional inactive components and processing steps is a strategic way to achieve higher gravimetric capacities which will be suitable for commercial‐level sodium‐ion (SIB) pouch cell manufacturing. In this regard, a simple, template‐free electroplating protocol is reported for designing phase‐pure tin antimonide (TA)‐based negatrode. An optimum control over the potentiostatic electroplating parameters allows the preferential formation of dendritic nanostructures over an electroplated foam‐based current collector. The prepared negatrode and Mn‐based Prussian blue analog positrode in full coin cell format deliver an average nominal working voltage of 3.0 V with a discharge energy density of 342 Wh kg−1. In single‐layer full pouch cell format, an 8.01 mAh capacity (89.89 mAh g−1, 593.3 µAh cm−2) is achieved at an undeformed state and 97.12% capacity is retained at 180° bend condition. In multi‐layer full pouch cell format, a 35.86 mAh capacity (80.58 mAh g−1, 531.2 µAh cm−2) is achieved with 62.77% capacity retention after 200 cycles (0.125 C). The results of this work showcase how a simple, template free, aqueous electrolyte based electroplating protocol can be developed for the direct fabrication of large‐sized, flexible, alloying‐type negatrodes for commercial SIB pouch cells. [ABSTRACT FROM AUTHOR]

Published
2024
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