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Highly Stable Red-Emissive Ratiometric Probe for Monitoring beta-Galactosidase Activity Using Fluorescence Microscopy and Flow Cytometry by Lee, Hyo Won;Juvekar, Vinayak;Lee, Dong Joon;Kim, Sun Mi;Kim, Hwan Myung; Analytical Chemistry, 2021 https://doi.org/10.1021/acs.analchem.1c03453 Abstract β-Galactosidase (β-gal), well known as a useful reporter enzyme, is a potent biomarker for various diseases such as colorectal and ovarian cancers. We have developed a highly stable red-emissive ratiometric fluorescent probe (CCGal1) for quantitatively monitoring the β-gal enzyme activity in live cells and tissues. This ratiometric probe showed a fast emission color change (620–662 nm) in response to β-gal selectively, which was accompanied by high enzyme reaction efficacy, cell-staining ability, and outstanding stability with minimized cytotoxicity. Confocal fluorescence microscopy ratiometric images, combined with fluorescence-activated cell sorting flow cytometry, demonstrated that CCGal1 could provide useful information for the diagnosis, prognosis, and treatment of β-gal enzyme activity-related diseases such as colorectal and ovarian cancers. Further, it may yield meaningful strategies for designing and modifying multifunctional bioprobes with different biomedical applications.
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6
- 작성자박은영
- 작성일2022-01-20
- 845
- 동영상동영상
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Light intensity dependence of organic solar cell operation and dominance switching between Shockley-Read-Hall and bimolecular recombination losses by Ryu, Shinyoung;Ha, Na Young;Ahn, Y. H.;Park, Ji-Yong;Lee, Soonil Scientific Reports, 2021 https://doi.org/10.1038/s41598-021-96222-w Abstract IWe investigated the variation of current density–voltage (J–V) characteristics of an organic solar cell (OSC) in the dark and at 9 different light intensities ranging from 0.01 to 1 sun of the AM1.5G spectrum. All three conventional parameters, short-circuit currents (Jsc), open-circuit voltage (Voc), and Fill factor (FF), representing OSC performance evolved systematically in response to light intensity increase. Unlike Jsc that showed quasi-linear monotonic increase, Voc and FF showed distinctive non-monotonic variations. To elucidate the origin of such variations, we performed extensive simulation studies including Shockley–Read–Hall (SRH) recombination losses. Simulation results were sensitive to defect densities, and simultaneous agreement to 10 measured J–V curves was possible only with the defect density of 5×1012 cm−3. Based on analyses of simulation results, we were able to separate current losses into SRH- and bimolecular-recombination components and, moreover, identify that the competition between SRH- and bimolecular-loss currents were responsible for the aforementioned variations in Jsc, Voc, and FF. In particular, we verified that apparent demarcation in Voc, and FF variations, which seemed to appear at different light intensities, originated from the same mechanism of dominance switching between recombination losses.
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4
- 작성자박은영
- 작성일2022-01-20
- 747
- 동영상동영상
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2
- 작성자박은영
- 작성일2022-01-20
- 723
- 동영상동영상
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A Novel Carbon-Assisted Chemical Vapor Deposition Growth of Large-Area Uniform Monolayer MoS2 and WS2 by Bae, Jeonghwan;Yoo, Youngdong Nanomaterials, 2021 https://doi.org/10.3390/nano11092423 Abstract Monolayer MoS2 can be used for various applications such as flexible optoelectronics and electronics due to its exceptional optical and electronic properties. For these applications, large-area synthesis of high-quality monolayer MoS2 is highly desirable. However, the conventional chemical vapor deposition (CVD) method using MoO3 and S powder has shown limitations in synthesizing high-quality monolayer MoS2 over a large area on a substrate. In this study, we present a novel carbon cloth-assisted CVD method for large-area uniform synthesis of high-quality monolayer MoS2. While the conventional CVD method produces thick MoS2 films in the center of the substrate and forms MoS2 monolayers at the edge of the thick MoS2 films, our carbon cloth-assisted CVD method uniformly grows high-quality monolayer MoS2 in the center of the substrate. The as-synthesized monolayer MoS2 was characterized in detail by Raman/photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy. We reveal the growth process of monolayer MoS2 initiated from MoS2 seeds by synthesizing monolayer MoS2 with varying reaction times. In addition, we show that the CVD method employing carbon powder also produces uniform monolayer MoS2 without forming thick MoS2 films in the center of the substrate. This confirms that the large-area growth of monolayer MoS2 using the carbon cloth-assisted CVD method is mainly due to reducing properties of the carbon material, rather than the effect of covering the carbon cloth. Furthermore, we demonstrate that our carbon cloth-assisted CVD method is generally applicable to large-area uniform synthesis of other monolayer transition metal dichalcogenides, including monolayer WS2. Keywords: carbon-assisted CVD; growth mechanism; monolayer; MoS2; WS2
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0
- 작성자박은영
- 작성일2022-01-20
- 722
- 동영상동영상
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High-Speed Imaging of Second-Harmonic Generation in MoS2 Bilayer under Femtosecond Laser Ablation by Kim, Young Chul;Yoo, Hoseong;Nguyen, Van Tu;Lee, Soonil;Park, Ji-Yong;Ahn, Yeong Hwan Nanomaterials, 2021 https://doi.org/10.3390/nano11071786 Abstract We report an in situ characterization of transition-metal dichalcogenide (TMD) monolayers and twisted bilayers using a high-speed second-harmonic generation (SHG) imaging technique. High-frequency laser modulation and galvano scanning in the SHG imaging enabled a rapid identification of the crystallinity in the TMD, including the orientation and homogeneity with a speed of 1 frame/s. For a twisted bilayer MoS2, we studied the SHG peak intensity and angles as a function of the twist angle under a strong interlayer coupling. In addition, rapid SHG imaging can be used to visualize laser-induced ablation of monolayer and bilayer MoS2 in situ under illumination by a strong femtosecond laser. Importantly, we observed a characteristic threshold behavior; the ablation process occurred for a very short time duration once the preheating condition was reached. We investigated the laser thinning of the bilayer MoS2 with different twist angles. When the twist angle was 0°, the SHG decreased by approximately one-fourth of the initial intensity when one layer was removed. Conversely, when the twist angle was approximately 60° (the SHG intensity was suppressed), the SHG increased abruptly close to that of the nearby monolayer when one layer was removed. Precise layer-by-layer control was possible because of the unique threshold behavior of the laser-induced ablation. Keywords: second-harmonic generation; transition-metal dichalcogenides; twisted bilayer; laser ablation
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-2
- 작성자박은영
- 작성일2022-01-20
- 705
- 동영상동영상
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Nondestructive Tomographic Imaging of Rust with Rapid THz Time-Domain Spectroscopy by Kim, Hwan Sik;Baik, Seung Yeob;Lee, Joong Wook;Kim, Jangsun;Ahn, Yeong Hwan Applied Sciences-Basel, 2021 https://doi.org/10.3390/app112210594 Abstract In this study, we developed a rapid nondestructive tool for testing rust spread in a metal covered by a paint layer by using a THz time-domain spectroscopy system at a speed of 100 Hz/pixel. Time-of-flight imaging helps identify rust formation by exclusively obtaining the reflection from the steel below the paint surface. The use of frequency-selective imaging allows us to manipulate the contrast in rust imaging. Higher contrast is generally obtained when monitoring using the higher frequency component. In addition, we monitored the spread of rust in a steel plate under the influence of two different chemical solutions: NaCl and acid. We found that in the early stages, the decrease in THz reflection was governed by the high-frequency components due to the formation of lepidocrocite, whereas the low-frequency component develops as the proportion of hematite increases with time. Keywords: terahertz imaging; nondestructive testing; rust
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-4
- 작성자박은영
- 작성일2022-01-20
- 610
- 동영상동영상
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Low Dark Current and Performance Enhanced Perovskite Photodetector by Graphene Oxide as an Interfacial Layer by Ali Hassan;Muhammad Azam;Yeong Hwan Ahn;Muhammad Zubair;Yu Cao;Abbas Ahmad Khan Nanomaterials, 2021 https://doi.org/10.3390/nano12020190 Abstract Organic-inorganic hybrid perovskite photodetectors are gaining much interest recently for their high performance in photodetection, due to excellent light absorption, low cost, and ease of fabrication. Lower defect density and large grain size are always favorable for efficient and stable devices. Herein, we applied the interface engineering technique for hybrid trilayer (TiO2/graphene oxide/perovskite) photodetector to attain better crystallinity and defect passivation. The graphene oxide (GO) sandwich layer has been introduced in the perovskite photodetector for improved crystallization, better charge extraction, low dark current, and enhanced carrier lifetime. Moreover, the trilayer photodetector exhibits improved device performance with a high on/off ratio of 1.3 × 104, high responsivity of 3.38 AW−1, and low dark current of 1.55 × 10−11 A. The insertion of the GO layer also suppressed the perovskite degradation process and consequently improved the device stability. The current study focuses on the significance of interface engineering to boost device performance by improving interfacial defect passivation and better carrier transport. Keywords: photodetector; perovskite; graphene oxide; low dark current; defect passivation
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-6
- 작성자박은영
- 작성일2022-01-20
- 622
- 동영상동영상
[논문] 이효원 - Highly Stable Red-Emissive Ratiometric Probe for Monitoring β‑Galactosidase Activity Using Fluorescence Micro 위치 확인