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Flexible and disposable paper-based gas sensor using reduced graphene oxide/chitosan composite

journal of Materials Science & Technology 2022年第6期101卷 165-172页

作者： Hyunjun park Woong Kim Sang Won Lee joohyung park Gyudo Lee Dae Sung Yoon Wonseok Lee jinsung park Department of Control and Instrumentation Engineering Korea UniversitySejong 30019Republic of Korea School of Biomedical Engineering Korea UniversitySeoul 02841Republic of Korea Department of Biotechnology and Bioinformatics Korea UniversitySejong 30019Republic of Korea Department of Electrical Engineering Korea National University of TransportationChungju 27469Republic of Korea

Nitrogen dioxide(NO_(2))is a representative toxicant in air pollution that mostly arises from the exhaust gas released by *** is related to various respiratory diseases such as pneumonia and sudden infant death ***,because the toxicity of nitrogen dioxide is high in overpopulated areas(i.e.,a capital or metropolis),the development of simple,practical,and facile sensors is highly *** work presents a flexible and disposable paper-based NO_(2)sensor based on a reduced graphene oxide/chitosan(r GO/CS)*** synthesized r GO/CS composite can be easily flexed and deformed into various shapes,which are attributed to chitosan molecules that function as a dispersion and reduction agent and support *** addition,this composite can be attached to paper owing to its adhesive property;hence it can be utilized in versatile applications in a disposable *** analyzing the conductive change of the r GO/CS composite when it reacts with NO_(2),we can detect nitrogen dioxide in a concentration range of 0–100 ppm with a detection limit of 1 ***,we performed NO_(2)detection in the exhaust gas released by automobiles using the r GO/CS composite for practical *** results indicated that the r GO/CS composite has the potential to be used in feasible gas sensing as a facile and disposable sensor under various conditions.

关键词： Reduced graphene oxide Chitosan Composite material Nitrogen dioxide Paper-based gas sensor Flexible and disposable sensor

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An in-situ Raman spectroscopic study on potential-pO^(2-) phase diagram of lanthanum in LiCl-KCl eutectic melt

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journal of Rare Earths 2020年第7期38卷 793-800,I0004页

作者： Seung park jong-IL Yun Department of Nuclear and Quantum Engineering.KAIST Yuseong-guDaejeon 34141Republic of Korea

The oxidative reaction between lanthanum trichloride and oxide ion was studied in the molten LiCl-KCl eutectic at 773 K by in-situ Raman spectroscopy using an yttria-stabilized zirconia electrode in conjunction with electrochemical *** formation of lanthanum oxychloride,LaOCl(s),was confirmed by studying the vibrational properties of crystalline LaOCl and X-ray diffraction *** solubility product of LaOCl in the LiCl-KCl molten eutectic at 773 K is found to be pKsp(LaOCl)=7.569±0.100,by combining the results of Raman spectroscopy and potentiometric titration with the addition of barium *** use of Raman spectroscopic quantitation of dissolved lanthanum ions in the system allows faster and more accurate determination of the stable phase of lanthanum as well as the solubility product of LaOCl compared with that measured by potentiometric titration *** on experimentally obtained pKsp and standard equilibrium potentials,the potentialpO2- phase diagram of lanthanum in the molten LiCl-KCl eutectic was reported.

关键词： Lanthanum Solubility product E-pO2-diagram Raman spectroscopy Chloride molten salt Rare earths

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Quantitative phase imaging of erythrocytes under microfluidic constriction in a high refractive index medium reveals water content changes

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Microsystems & Nanoengineering 2019年第1期5卷 50-58页

作者： Han Sang park Will j.Eldridge Wen-Hsuan Yang Michael Crose Silvia Ceballos john D.Roback jen-Tsan Ashley Chi Adam Wax Department of Biomedical Engineering Duke UniversityDurhamNC 27708USA Department of Molecular Genetics and Microbiology Duke UniversityDurhamNC 27708USA Duke Center for Genomic and Computational Biology Duke UniversityDurhamNC 27708USA Department of Biochemistry Duke UniversityDurhamNC 27708USA Department of Pathology and Laboratory Medicine Emory University School of MedicineAtlantaGA 30322USA

Changes in the deformability of red blood cells can reveal a range of *** example,cells which have been stored for transfusion are known to exhibit progressively impaired ***,this aspect of red blood cells has been characterized previously using a range of *** this paper,we show a novel approach for examining the biophysical response of the cells with quantitative phase ***,optical volume changes are observed as the cells transit restrictive channels of a microfluidic chip in a high refractive index *** optical volume changes indicate an increase of cell’s internal density,ostensibly due to water ***,we characterize these changes over time for red blood cells from two *** storage day 29,a significant decrease in the magnitude of optical volume change in response to mechanical stress was *** exchange of water with the environment due to mechanical stress is seen to modulate with storage time,suggesting a potential means for studying cell storage.

关键词： impaired fluid transfusion

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Electrochemically Deposited CZTSSe Thin Films for Monolithic Perovskite Tandem Solar Cells with Efficiencies Over 17%

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Energy & Environmental Materials 2024年第1期7卷 147-152页

作者： Sun Kyung Hwang Ik jae park Se Won Seo jae Hyun park So jeong park jin Young Kim Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Korea Department of Applied Physics Sookmyung Women's UniversitySeoul 04310Korea Research Institute of Advanced Materials and Systems Sookmyung Women's UniversitySeoul 04310Korea Research Institute of Advanced Materials(RIAM) Seoul National UniversitySeoul 08826Korea

In spite of the high potential economic feasibility of the tandem solar cells consisting of the halide perovskite and the kesterite Cu2ZnSn(S,Se)4(CZTSSe),they have rarely been demonstrated due to the difficulty in implementing solution-processed perovskite top cell on the rough surface of the bottom ***,we firstly demonstrate an efficient monolithic two-terminal perovskite/CZTSSe tandem solar cell by significantly reducing the surface roughness of the electrochemically deposited CZTSSe bottom *** surface roughness(R_(rms))of the CZTSSe thin film could be reduced from 424 to 86 nm by using the potentiostatic mode rather than using the conventional galvanostatic mode,which can be further reduced to 22 nm after the subsequent ion-milling *** perovskite top cell with a bandgap of 1.65 eV could be prepared using a solution process on the flattened CZTSSe bottom cell,resulting in the efficient perovskite/CZTSSe tandem solar *** the current matching between two subcells involving the thickness control of the perovskite layer,the best performing tandem device exhibited a high conversion efficiency of 17.5%without the hysteresis effect.

关键词： CZTSSe monolithic tandem solar cells perovskite solution process surface roughness control

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Highly efficient reduction of aqueous Cr(VI) with novel ZnO/SnS nanocomposites through the piezoelectric effect

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journal of Environmental Sciences 2022年第8期34卷 57-66页

作者： Hao Sun Soo-jin park Department of Chemistry and Chemical Engineering Inha UniversityIncheon 22212South Korea

In this work, novel ZnO/SnS nanocomposites were successfully synthesized via a hydrothermal approach, which is developed for piezoelectric catalytic reduction of hexavalent chromium(Cr(VI)) in an aqueous solution. The constructed ZnO/SnS nanocomposites exhibited higher catalytic efficiency for Cr(VI) reduction under a mechanical force(e.g., ultrasonic vibration) compared to pristine ZnO and SnS. In particular, the ZnO/SnS(with 30 wt.% of SnS) heterojunctions revealed an optimal degradation activity among all the prepared samples, which completely removed the Cr(VI)(20 mg/L) solution within 35 min. Moreover, the piezoelectric catalytic activity of ZnO/SnS remained stable after four consecutive cycling experiments. The results of the morphology observations indicated that the SnS nanoparticles adhere to the surface of the ZnO nanorods. The improved piezoelectric catalytic performance of the ZnO/SnS heterojunctions can be attributed to the formation of an intimate interfacial between ZnO and SnS, which effectively inhibits the electron-hole recombination and speeds up the rate of charge transfer. The study reveals a new design of ZnO/SnS heterojunctions as a high-performance and eco-friendly piezoelectric catalyst and provides a promising strategy for addressing environmental problems and energy crises.

关键词： Cr(VI)reduction ZnO/SnS Piezoelectric effect

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Anti-neuro-inflammatory effects of Nardostachys chinensis in lipopolysaccharide-and lipoteichoic acid-stimulated microglial cells

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Chinese journal of Natural Medicines 2016年第5期14卷 343-353页

作者： Sun Young park Young Hun Kim Geuntae park Bio-IT Fusion Technology Research Institute Pusan National University Department of Nanomaterials Engineering Pusan National University

Excessive microglial cell activation is related to the progression of chronic neuro-inflammatory disorders. Heme oxygenase-1(HO-1) expression mediated by the NFE2-related factor(Nrf-2) pathway is a key regulator of neuro-inflammation. Nardostachys chinensis is used as an anti-malarial, anti-nociceptive, and neurotrophic treatment in traditional Asian medicines. In the present study, we examined the effects of an ethyl acetate extract of N. chinensis(EN) on the anti-neuro-inflammatory effects mediated by HO-1 up-regulation in Salmonella lipopolysaccharide(LPS)- or Staphylococcus aureus lipoteichoic acid(LTA)-stimulated BV2 microglial cells. Our results indicated that EN suppressed pro-inflammatory cytokine production and induced HO-1 transcription and translation through Nrf-2/antioxidant response element(ARE) signaling. EN markedly inhibited LPS- and LTA-induced activation of nuclear factor-kappa B(NF-?B) as well as phosphorylation of mitogen-activated protein kinases(MAPKs) and signal transducer and activator of transcription(STAT). Furthermore, EN protected hippocampal HT22 cells from indirect neuronal toxicity mediated by LPS- and LTA-treated microglial cells. These results suggested that EN impairs LPS- and LTA-induced neuro-inflammatory responses in microglial cells and confers protection against indirect neuronal damage to HT22 cells. In conclusion, our findings indicate that EN could be used as a natural anti-neuro-inflammatory and neuroprotective agent.

关键词： Nardostachys chinensis Anti-inflammation Lipopolysaccharide Lipoteichoic acid Heme oxygenase-1

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Review of bio-optical imaging systems with a high space-bandwidth product

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Advanced Photonics 2021年第4期3卷 1-18页

作者： jongchan park David j.Brady Guoan Zheng Lei Tian Liang Gao University of California Department of BioengineeringLos AngelesCaliforniaUnited States University of Arizona James C.Wyant College of Optical SciencesTucsonArizonaUnited States University of Connecticut Department of Biomedical EngineeringStorrsConnecticutUnited States University of Connecticut Department of Electrical and Computer EngineeringStorrsConnecticutUnited States Boston University Department of Electrical and Computer EngineeringBostonMassachusettsUnited States

Optical imaging has served as a primary method to collect information about biosystems across scales—from functionalities of tissues to morphological structures of cells and even at biomolecular ***,to adequately characterize a complex biosystem,an imaging system with a number of resolvable points,referred to as a space-bandwidth product(SBP),in excess of one billion is typically *** a gigapixel-scale far exceeds the capacity of current optical imagers,compromises must be made to obtain either a low spatial resolution or a narrow field-of-view(FOV).The problem originates from constituent refractive optics—the larger the aperture,the more challenging the correction of lens ***,it is impractical for a conventional optical imaging system to achieve an SBP over hundreds of *** address this unmet need,a variety of high-SBP imagers have emerged over the past decade,enabling an unprecedented resolution and FOV beyond the limit of conventional *** provide a comprehensive survey of high-SBP imaging techniques,exploring their underlying principles and applications in bioimaging.

关键词： space-bandwidth product bioimaging gigapixel imaging high resolution wide field of view

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Extended X-ray absorption fine structure (EXAFS) of FAPbI_(3) for understanding local structure-stability relation in perovskite solar cells

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journal of Energy Chemistry 2022年第4期31卷 549-554页

作者： Dong-Ho Kang Yong-jun park Yun-Sung jeon Nam-Gyu park School of Chemical Engineering and Center for Antibonding Regulated Crystals Sungkyunkwan UniversitySuwon 16419Korea

Perovskite solar cells (PSCs) employing formamidinium lead iodide (FAPbI_(3)) have shown high ***,operational stability has been issued due to phase instability of α phase FAPbI_(3) at ambient *** precursors in the perovskite precursor solution has been proposed to improve not only power conversion efficiency (PCE) but also device ***,there is a controversial issue on the beneficial effect on PCE and/or stability between excess FAI and excess PbI_(2).We report here extended X-ray absorption fine structure (EXAFS) of FAPbI_(3) to study local structural change and explain the effect of excess precursors on photovoltaic performance and *** films prepared from the precursor solution with excess PbI_(2)shows better stability than those from the one with excess FAI,despite similar PCE.A rapid phase transition from α phase to non-perovskite δ phase is observed from the perovskite film formed by excess ***,the (Pb-I) bond distance evaluated by the Pb L_(III)-edge EXAFS study is increased by excess FAI,which is responsible for the phase transition and poor device *** work can provide important insight into local structure-stability relation in the FAPbI_(3)-based PSCs.

关键词： Extended X-ray absorption fine structure EXAFS Excess precursor Local structure Stability Perovskite solar cells

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Amine functionalization on thermal and mechanical behaviors of graphite nanofibers-loaded epoxy composites

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journal of Materials Science & Technology 2023年第20期151卷 80-88页

作者： Seong-Hwang Kim Sang-jin park Seul-Yi Lee Soo-jin park Department of Chemistry Inha University100 InharoIncheon 22212the Republic of Korea

With the growing demand for faster and more powerful computing,effective heat dissipation is essential to ensure the longevity,reliability,and high performance of electronic *** the field of modern electronic packaging materials,there is a great need for graphitic material-loaded polymeric composites(GPCs)with excellent thermal ***,the enhancement efficiency of GPCs is hindered by the agglomeration of fillers and the interfacial thermal resistance caused by the lack of continuous thermally conductive pathways between the filler and *** the interfaces between filler and matrix is of great importance in optimizing the performances of ***,we fabricated graphite nanofibers(GNF)-loaded nanocomposites using acid-functionalized GNF(AGNF)and acidtetraethylenepentamine-functionalized(TGNF)as a filler and epoxy resin as a matrix with different GNF loading contents to explore the interfacial properties of the *** optimal GNF loading for AGNF was 0.5 wt.%,while the TGNF showed 0.75 wt.%.The highest thermal conductivity(0.51 W m^(−1) K^(−1))and fracture toughness(25.8 MPa m^(1/2))values were found in the TGNF-loaded nanocomposites with a fraction of 0.75 wt.%,representing enhancements of∼145%and∼400%,respectively,compared to those of neat *** experimental data presented herein demonstrate that the interfacial properties play a significant role in enhancing the thermal and mechanical performances of the *** present approach is expected to serve as a valuable tool in the design of conductive polymeric nanocomposites for further practical applications,such as thermal interface materials and packaging of high-power electric devices.

关键词： Graphite nanofiber Nanocomposites Interfacial interaction Thermal conductivity Fracture resistance

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journal of Materials Science & Technology 2021年第26期85卷 95-105页

作者： Nana Kwabena Adomako Giseung Shin Nokeun park Kyoungtae park jeoung Han Kim Department of Materials Science and Engineering Hanbat National UniversityYuseong-guDaejeon34158Republic of Korea Department of Materials Science and Engineering Pusan National UniversityGeumjeong-guBusan46241Republic of Korea School of Materials Science and Engineering Yeungnam University280 Daehak-roGyeongbuk38541Republic of Korea Rare Metal R&D Group Korea Institute of Industrial TechnologyIncheon21999Republic of Korea

High entropy alloys(HEAs)have superior mechanical properties that have enabled them to be used as structural materials in nuclear and aerospace *** a dissimilar joint design is required for these applications,we created a dissimilar joint between CoCrFeMnNi-HEA and duplex stainless steel(DSS)through laser beam welding;a technique capable of producing a sound joint between the two *** structure examination using SEM/EBSD/XRD analysis revealed that the weld metal(WM)exhibits an FCC phase regardless of the postweld heat treatment(PWHT)temperature(800 and 1000℃)without forming detrimental intermetallic compounds or *** heat-affected zone of the CoCrFeMnNi-HEA showed CrMn oxide inclusions while that of the DSS showed no ***,a lower hardness was recorded by the WM compared to the base metal after *** PWHT,the hardness of the WM,CoCrFeMnNi-HEA,and DSS decreased with an increase in the PWHT ***,the decrease in the hardness of the HEA was more significant than in the WM and *** cause for this reduction in hardness was attributed to recrystallization and grain *** addition,a strength of 584 MPa with low ductility was recorded after *** obtained strength was lower than that of the BMs,but comparable to that of the welded *** application of PWHT resulted in over a 20%increment in ductility,with only a marginal reduction in *** defo rmation mechanism in the as-weld joint was mainly dominated by dislocation while that for the PWHT joint was *** propose laser beam offset welding as a technique to improve the mechanical properties of the dissimilar joint,which will be the subject of future studies.

关键词： High entropy alloys Welding Duplex stainless steel Post-weld heat treatment

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