https://scholar.dgist.ac.kr/handle/20.500.11750/171 2026-10-28T18:20:29Z https://scholar.dgist.ac.kr/handle/20.500.11750/60988 Title: Composition-driven anion vacancy control in I–III–VI CuIn(S1−xSex)2 quantum dots for efficient photoelectrochemical hydrogen production Author(s): Kim, Kiwook; Kim, Hwapyong; Ha, Seung Beom; Chung, Wookjin; Lee, Hyo Cheol; Park, Soo Ik; Kim, Minseo; Li, Shi; Lee, Kyunghoon; Lee, Gyudong; Lee, Orim; Ji, Seunghyun; Ma, Hyeonjong; Lim, Sung Jun; Choi, Hongsoo; Ko, Seo-Jin; Kim, In Young; Kim, Jae-Yup; In, Su-Il; Yang, Jiwoong Abstract: Heavy-metal-free I–III–VI quantum dots (QDs) are promising candidates for solar energy conversion owing to their strong light absorption, broadly tunable bandgap spanning the full solar spectrum, and environmentally benign composition. However, precise control over their composition and defect states remains challenging due to their complex multinary synthesis chemistry, which critically governs their optoelectronic properties. Here, we demonstrate composition-driven control of anion vacancies in p -type CuIn(S1− x Se x )2 QDs and elucidate their impact on photoelectrochemical (PEC) hydrogen production. Systematic variation of the chalcogenide S/Se ratio enables modulation of anion vacancy concentrations without altering QD size or Cu/In stoichiometry. Notably, CuIn(S0.5Se0.5)2 QDs exhibit the lowest density of anion vacancies, attributed to enhanced anion coordination and reduced lattice distortion. These structural improvements result in increased hole concentration and extended carrier lifetimes. As a result, when integrated into TiO2-based photoanodes, these QDs deliver a high photocurrent density of 15.1 mA cm−2 at 0.6 VRHE for PEC hydrogen generation, exceeding the performance of most previously reported heavy-metal-free QD-based systems. This work provides fundamental mechanistic insights into the role of anion vacancies in I–III–VI QDs and offers a promising strategy for advancing their PEC performance. © 2025 The Authors. 2026-08-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60953 Title: Facile synthesis of large-Stokes-shift giant CdHgSe/CdHgSeS near-infrared quantum dots via chlorine-mediated Ostwald ripening Author(s): Lee, Gyudong; Park, Sanghwang; Seo, Jongcheol; Lee, Wonseok; Arogundade, Opeyemi H.; Smith, Andrew M.; Choi, Jongmin; Choi, Hongsoo; Lim, Sung Jun Abstract: Giant core/shell quantum dots (GQDs) offer advantages for optoelectronics, including suppressed blinking and reduced Auger recombination, yet thick-shell growth often requires laborious successive ion layer adsorption and reaction (SILAR) cycles. Here we demonstrate a chlorine-mediated controlled Ostwald ripening strategy that transforms NIR-emitting CdHgSe/CdS core/shell seed QDs into giant CdHgSe/CdHgSeS core/gradient-shell QDs in a single post-synthetic step. Seed QDs are prepared by growing a thin (similar to 1.6-monolayer) CdS shell on CdHgSe alloy cores. Injection of CHCl3 at 240 degrees C triggers rapid ripening, in which most seeds dissolve while a minor population grows into GQDs. During ripening, the band-edge absorption feature is strongly attenuated and absorption below similar to 610 nm increases markedly, whereas NIR emission remains centered near similar to 900 nm, yielding a large effective Stokes shift that can mitigate reabsorption in luminescent solar concentrators. HAADF-STEM/EDS and XRD support a compositionally graded shell, while mass spectrometry and numerical simulations are consistent with chlorine-modified surface chemistry and altered monomer solubility/surface tension that accelerate ripening. As a proof of concept, embedding the GQDs in PMMA affords a transparent luminescent solar concentrator prototype with retained NIR emission and favorable spectral overlap with silicon photovoltaics. 2026-07-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60897 Title: A Steerable and Expandable Magnetic Aspiration Catheter for Enhanced Aspiration Thrombectomy Author(s): Lee, Hakjoon; Dong, Xiao; Kim, Dong-in; Chowdhury, A. M. Masum Bulbul; Gharamaleki, Nader Latifi; Kim, Jin-young; Youn, Sung Won; Choi, Hongsoo Abstract: Aspiration thrombectomy is widely used when treating acute ischemic stroke. A blood clot is directly suctioned through a catheter connected to a vacuum system. Although an increase in catheter bore size significantly enhances aspiration efficiency, this compromises endovascular navigability during manual manipulation. To minimize this trade-off, this paper presents a novel, magnetic aspiration catheter that enables both active steering and distal-end expansion via externally applied magnetic fields. The catheter incorporates dual-axis magnetization. Axial magnetization facilitates directional steering by aligning the catheter tip with the magnetic field; radial magnetization enables dynamic expansion of the cross-sectional area in response to the field strength, thereby improving clot contact and reducing leakage between the catheter and vessel wall. A magnetic mold-based fabrication method is employed to realize such dual-axis magnetization. The magnetically actuated motions of the catheter are theoretically and experimentally validated. Active steering reduces the navigation time by 67.5% (30.3 vs. 93.1 s) and expansion increases the aspiration force by 430% (27 vs. 143 & micro;N). Catheter efficacy and feasibility in terms of aspiration thrombectomy are demonstrated using 3D vascular phantoms. By enhancing both navigational control and therapeutic performance, this study advances the development of practical robotic systems for rapid and precise stroke treatment. 2026-06-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60879 Title: Magnetic Control of Intravascular Collaborative Robotic (Cobot) Guidewire: Neurovascular Intervention Studies in Phantom and Swine Models Author(s): Kim, Dong-in; Kim, Beomjoo; Lee, Hakjoon; Hwang, Junsun; Jeon, Sungwoong; Kim, Jin-young; Youn, Sung Won; Choi, Hongsoo Abstract: Strokes such as acute ischemic stroke require vascular access for endovascular thrombectomy. To navigate the small and complex cerebral vessels with multiple branches, clinicians use guidewires or catheters with pre-shaped tips. However, complex procedures still face the problem of increased X-ray exposure for both clinicians and patients. Engineering technologies such as robotic guidewires and catheters are being applied to neurovascular procedures to make them faster and more effective. The technology presented in this study involves Collaborative Robotic (Cobot) guidewires that can be steered by magnetic fields to effectively enter the target vessel and navigate complex blood vessels. The Cobot guidewire can be steered according to the direction of the magnetic field because its tip contains a permanent magnet and a magnetic polymer. The magnetic field for steering the Cobot guidewire can be controlled and generated by electromagnetic control systems (ECS). In this study, the performance of neurovascular procedures using the Cobot guidewire and manual guidewire is compared in both phantom and swine models. Based on various parameters, the Cobot guidewire demonstrates superior performance in neurovascular procedures compared to the manual guidewire. Favorable procedure time and navigation efficiency suggest that a magnetically assisted Cobot guidewire is potentially feasible for neurovascular interventions. 2026-06-30T15:00:00Z