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  1. Article: High turbidity water treatment by ceramic microfiltration membrane: Fouling identification and process optimization

    Park, Won-il / Jeong, Sanghyun / Im, Sung-Ju / Jang, Am

    Environmental technology & innovation. 2020 Feb., v. 17

    2020  

    Abstract: Ceramic membranes have been introduced in various fields; however, research on ceramic membranes in high-turbidity environments has been rarely performed. In this study, the fouling characteristics of a ceramic microfiltration membrane in a high- ... ...

    Abstract Ceramic membranes have been introduced in various fields; however, research on ceramic membranes in high-turbidity environments has been rarely performed. In this study, the fouling characteristics of a ceramic microfiltration membrane in a high-turbidity environment were examined. First, the factors affecting the ceramic-membrane fouling were investigated through filtration tests in various feed-water conditions. Next, as a pretreatment to the membrane process, three types of coagulant were compared, and the optimum coagulant and coagulation concentration were selected. Finally, the ceramic and polymeric membranes’ treating of high-turbidity water was compared, with and without coagulation. The results indicated that the turbidity was the major influential factor of irreversible fouling on the ceramic membrane. When the turbidity increased, irreversible fouling occurred rapidly, which may be caused by small particulates entering the membrane, and resulting in standard pore blocking. Therefore, the coagulation experiment was conducted using feed water with high turbidity, which causes the most irreversible fouling. As a result, poly-aluminum chloride was selected as the optimum coagulant. In the comparison between the ceramic and polymer membranes, there was no significant difference in removal efficiency; however, the ceramic membrane had a better water flux and lower membrane-fouling potential. Moreover, the efficiency increased when a coagulation process was used as the pretreatment. Thus, ceramic membranes are more efficient for treating high turbidity water.
    Keywords artificial membranes ; ceramics ; chlorides ; coagulants ; coagulation ; fouling ; microfiltration ; particulates ; polymers ; turbidity ; water treatment
    Language English
    Dates of publication 2020-02
    Publishing place Elsevier B.V.
    Document type Article
    ISSN 2352-1864
    DOI 10.1016/j.eti.2019.100578
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  2. Article ; Online: MoS

    Chang, Won Jun / Jang, Suhee / Kim, Minjoo / Kim, Yelim / Jeong, Dae Yeop / Kim, Beomju / Kim, Jin Myung / Nam, SungWoo / Park, Won Il

    Small (Weinheim an der Bergstrasse, Germany)

    2023  Volume 19, Issue 18, Page(s) e2207020

    Abstract: Abundant Li resources in the ocean are promising alternatives to refining ore, whose supplies are limited by the total amount and geopolitical imbalance of reserves in Earth's crust. Despite advances in ... ...

    Abstract Abundant Li resources in the ocean are promising alternatives to refining ore, whose supplies are limited by the total amount and geopolitical imbalance of reserves in Earth's crust. Despite advances in Li
    Language English
    Publishing date 2023-01-15
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2168935-0
    ISSN 1613-6829 ; 1613-6810
    ISSN (online) 1613-6829
    ISSN 1613-6810
    DOI 10.1002/smll.202207020
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  3. Article ; Online: Direct nanofluidic channels via hardening and wrinkling of thin polymer films.

    Lee, Jae Hyung / Chang, Won Jun / Choi, Won Young / Park, Jeong-Min / Jang, Jae-Il / Park, Won Il

    Nanoscale

    2020  Volume 12, Issue 32, Page(s) 16895–16900

    Abstract: In this study, we propose a rational route to create wrinkling patterns with individually controllable location and direction in thin polymer films. Optical and atomic force microscopy analysis confirmed the formation of straight wrinkles with a typical ... ...

    Abstract In this study, we propose a rational route to create wrinkling patterns with individually controllable location and direction in thin polymer films. Optical and atomic force microscopy analysis confirmed the formation of straight wrinkles with a typical width of 1.51 to 1.55 μm and a height of 60 to 65 nm. Confocal fluorescence microscopy revealed that each wrinkle produces a continuous hollow channel that interconnects neighboring holes in the polymer film, demonstrating potential applications as nanoscale fluidic channel and reactor. Moreover, we propose a mechanism that considers the elastic deformation energy and interface energies as crucial parameters that govern the mechanical instabilities, which provides scaling relationships between the height, width, and thickness of the wrinkles. This offers additional opportunities for control over the size and aspect ratio of the wrinkles and channels.
    Language English
    Publishing date 2020-08-07
    Publishing country England
    Document type Journal Article
    ZDB-ID 2515664-0
    ISSN 2040-3372 ; 2040-3364
    ISSN (online) 2040-3372
    ISSN 2040-3364
    DOI 10.1039/d0nr04032k
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Defect-Mediated Molecular Interaction and Charge Transfer in Graphene Mesh–Glucose Sensors

    Kwon, Sun Sang / Choi Jonghyun / Nam SungWoo / Park Won Il / Shin Jae Hyeok

    ACS Applied Materials & Interfaces. 2017 Apr. 26, v. 9, no. 16

    2017  

    Abstract: We report the role of defects in enzymatic graphene field-effect transistor sensors by introducing engineered defects in graphene channels. Compared with conventional graphene sensors (Gr sensors), graphene mesh sensors (GM sensors), with an array of ... ...

    Abstract We report the role of defects in enzymatic graphene field-effect transistor sensors by introducing engineered defects in graphene channels. Compared with conventional graphene sensors (Gr sensors), graphene mesh sensors (GM sensors), with an array of circular holes, initially exhibited a higher irreversible response to glucose, involving strong chemisorption to edge defects. However, after immobilization of glucose oxidase, the irreversibility of the responses was substantially diminished, without any reduction in the sensitivity of the GM sensors (i.e., −0.53 mV/mM for the GM sensor vs −0.37 mV/mM for Gr sensor). Furthermore, multiple cycle operation led to rapid sensing and improved the reversibility of GM sensors. In addition, control tests with sensors containing a linker showed that sensitivity was increased in Gr sensors but decreased in GM sensors. Our findings indicate that edge defects can be used to replace linkers for immobilization of glucose oxidase and improve charge transfer across glucose oxidase–graphene interfaces.
    Keywords glucose ; glucose oxidase ; graphene
    Language English
    Dates of publication 2017-0426
    Size p. 14216-14221.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1944-8252
    DOI 10.1021%2Facsami.7b00848
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  5. Article: Synthesis of hierarchical porous TiNb2O7 nanotubes with controllable porosity and their application in high power Li-ion batteries

    Park, Hyunjung / Shin, Dong Hyeok / Song, Taeseup / Park, Won Il / Paik, Ungyu

    Journal of materials chemistry A. 2017 Apr. 11, v. 5, no. 15

    2017  

    Abstract: Porous transition metal oxides are widely used in energy storage applications owing to their unique physicochemical properties. However, the development of simple synthetic routes using cheap precursors without sacrificial templates still remains ... ...

    Abstract Porous transition metal oxides are widely used in energy storage applications owing to their unique physicochemical properties. However, the development of simple synthetic routes using cheap precursors without sacrificial templates still remains challenging. Herein we report a synthesis of hierarchical porous TiNb2O7 nanotubes via dual nozzle electrospinning as a high power anode material for LIBs. The porosity and dimensions of the nanotubes were controlled by varying the molar concentration ratio of Ti/Nb metal precursors to acetic acid and adjusting the degree of formation of Ti/Nb hydroxides in electrospun fibers. The TiNb2O7 nanotubes have a diameter of ∼300 nm with tunable wall thickness and a surface area in the range of 52–151 m2 g−1. Moreover, the nanotubes have a hierarchical porous structure consisting of micropores below 2 nm and mesopores in the range of 5–60 nm in their walls that are connected to the macroscale inner hole with a diameter of 150 nm. The unique structure of the nanotubes enables a high discharge capacity of ∼294 mA h g−1, a stable cycle performance of 86% capacity retention over 700 cycles, and a superior rate capability of ∼230 mA h g−1 at high 50C, which is the highest retention ever reported to the best of our knowledge. Our strategy demonstrates a facile synthesis of hierarchical porous TiNb2O7 nanotubes without templates and their potential as a high power anode material for LIBs.
    Keywords acetic acid ; anodes ; energy ; hydroxides ; lithium batteries ; micropores ; nanotubes ; oxides ; physicochemical properties ; porosity ; surface area
    Language English
    Dates of publication 2017-0411
    Size p. 6958-6965.
    Publishing place The Royal Society of Chemistry
    Document type Article
    ZDB-ID 2702232-8
    ISSN 2050-7496 ; 2050-7488
    ISSN (online) 2050-7496
    ISSN 2050-7488
    DOI 10.1039/c7ta00597k
    Database NAL-Catalogue (AGRICOLA)

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  6. Article: Chemical and biological sensors based on defect-engineered graphene mesh field-effect transistors.

    Cho, Seunghee H / Kwon, Sun Sang / Yi, Jaeseok / Park, Won Il

    Nano convergence

    2016  Volume 3, Issue 1, Page(s) 14

    Abstract: Graphene has been intensively studied for applications to high-performance sensors, but the sensing characteristics of graphene devices have varied from case to case, and the sensing mechanism has not been satisfactorily determined thus far. In this ... ...

    Abstract Graphene has been intensively studied for applications to high-performance sensors, but the sensing characteristics of graphene devices have varied from case to case, and the sensing mechanism has not been satisfactorily determined thus far. In this review, we describe recent progress in engineering of the defects in graphene grown by a silica-assisted chemical vapor deposition technique and elucidate the effect of the defects upon the electrical response of graphene sensors. This review provides guidelines for engineering and/or passivating defects to improve sensor performance and reliability.
    Language English
    Publishing date 2016-07-11
    Publishing country England
    Document type Journal Article ; Review
    ZDB-ID 2760386-6
    ISSN 2196-5404
    ISSN 2196-5404
    DOI 10.1186/s40580-016-0075-9
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  7. Article ; Online: Defect-Mediated Molecular Interaction and Charge Transfer in Graphene Mesh-Glucose Sensors.

    Kwon, Sun Sang / Shin, Jae Hyeok / Choi, Jonghyun / Nam, SungWoo / Park, Won Il

    ACS applied materials & interfaces

    2017  Volume 9, Issue 16, Page(s) 14216–14221

    Abstract: We report the role of defects in enzymatic graphene field-effect transistor sensors by introducing engineered defects in graphene channels. Compared with conventional graphene sensors (Gr sensors), graphene mesh sensors (GM sensors), with an array of ... ...

    Abstract We report the role of defects in enzymatic graphene field-effect transistor sensors by introducing engineered defects in graphene channels. Compared with conventional graphene sensors (Gr sensors), graphene mesh sensors (GM sensors), with an array of circular holes, initially exhibited a higher irreversible response to glucose, involving strong chemisorption to edge defects. However, after immobilization of glucose oxidase, the irreversibility of the responses was substantially diminished, without any reduction in the sensitivity of the GM sensors (i.e., -0.53 mV/mM for the GM sensor vs -0.37 mV/mM for Gr sensor). Furthermore, multiple cycle operation led to rapid sensing and improved the reversibility of GM sensors. In addition, control tests with sensors containing a linker showed that sensitivity was increased in Gr sensors but decreased in GM sensors. Our findings indicate that edge defects can be used to replace linkers for immobilization of glucose oxidase and improve charge transfer across glucose oxidase-graphene interfaces.
    Language English
    Publishing date 2017-04-26
    Publishing country United States
    Document type Journal Article
    ISSN 1944-8252
    ISSN (online) 1944-8252
    DOI 10.1021/acsami.7b00848
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  8. Article: Direct Observation of Carboxymethyl Cellulose and Styrene–Butadiene Rubber Binder Distribution in Practical Graphite Anodes for Li-Ion Batteries

    Chang, Won Jun / Lee, Gyu Hyeon / Cheon, Yeong Jun / Kim, Jin Tae / Lee, Sang Il / Kim, Jaehyuk / Kim, Myungseop / Park, Won Il / Lee, Yun Jung

    ACS applied materials & interfaces. 2019 Oct. 15, v. 11, no. 44

    2019  

    Abstract: Despite the important role of carboxymethyl cellulose (CMC) and styrene–butadiene rubber (SBR) binders in graphite electrodes for Li-ion batteries, the direct analysis of these binders remains challenging, particularly at very low concentrations as in ... ...

    Abstract Despite the important role of carboxymethyl cellulose (CMC) and styrene–butadiene rubber (SBR) binders in graphite electrodes for Li-ion batteries, the direct analysis of these binders remains challenging, particularly at very low concentrations as in practical graphite anodes. In this paper, we report the systematic investigation of the physiochemical behavior of the CMC and SBR binders and direct observations of their distributions in practical graphite electrodes. The key to this unprecedented capability is combining the advantages of several analytic techniques, including laser-ablation laser-induced break-down spectroscopy, time of flight secondary ion mass spectrometry, and a surface and interfacial cutting analysis system. By correlating the vertical distribution with the adsorption behaviors of the CMC, our study reveals that the CMC migration toward the surface during the drying process depends on the degree of cross-linked binder-graphite network generation, which is determined by the surface property of graphite and CMC materials. The suggested analytical techniques enable the independent tracing of CMC and SBR, disclosing the different vertical distribution of SBR from that of the CMC binder in our practical graphite anodes. This achievement provides additional opportunity to analyze the correlation between the binder distribution and mechanical properties of the electrodes.
    Keywords adsorption ; anodes ; carbon electrodes ; carboxymethylcellulose ; crosslinking ; cutting ; drying ; graphene ; lithium batteries ; mass spectrometry ; mechanical properties ; rubber ; spatial distribution
    Language English
    Dates of publication 2019-1015
    Size p. 41330-41337.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1944-8252
    DOI 10.1021/acsami.9b13803
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  9. Article: Vertically aligned ZnO nanorods and graphene hybrid architectures for high-sensitive flexible gas sensors

    Yi, Jaeseok / Lee, Jung Min / Park, Won Il

    Sensors & Actuators: B. Chemical. 2011 July 5, v. 155, no. 1

    2011  

    Abstract: We present the fabrication and characterization of new type of flexible gas sensors, composed mainly of a bottom ZnO conductive layer on metal foil, vertically aligned ZnO nanorod channel, and graphene-based top conductive electrode. Multiple cycling ... ...

    Abstract We present the fabrication and characterization of new type of flexible gas sensors, composed mainly of a bottom ZnO conductive layer on metal foil, vertically aligned ZnO nanorod channel, and graphene-based top conductive electrode. Multiple cycling tests demonstrated the ZnO nanorods (NRs) and graphene (Gr) hybrid architectures accommodated the flexural deformation without mechanical or electrical failure for bending radius below 0.8cm under the repeated bending and releasing up to 100 times. In addition, the hybrid architectures fabricated on glass substrate showed good optical transmittance larger than ∼70% for visible light, indicating potential application in transparent devices. Furthermore, our gas sensors demonstrated the ppm level detection of ethanol gas vapor with the sensitivity (resistance in air/resistance in target gas) as high as ∼9 for 10ppm ethanol.
    Keywords air ; deformation ; electrodes ; ethanol ; foil ; glass ; graphene ; nanorods ; transmittance ; vapors ; zinc oxide
    Language English
    Dates of publication 2011-0705
    Size p. 264-269.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 1021505-0
    ISSN 0925-4005
    ISSN 0925-4005
    DOI 10.1016/j.snb.2010.12.033
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  10. Article: Fast synthesis of large-scale single-crystal graphene with well-defined edges upon sodium chloride addition

    Kim, Su Han / Jiang, Jie / Jang, Suhee / Lee, Jae Hyung / Yang, Dong Won / Chang, Won Jun / Shin, Jae Hyeok / Oh, Nuri / Kim, Jaeyong / Pachter, Ruth / Park, Won Il

    Carbon. 2020 Mar., v. 158

    2020  

    Abstract: There have been many efforts to grow high-quality, single-crystalline graphene on a cheap substrate, such as a metal foil. However, control of nucleation and growth of individual flakes, as well as their seamless stitching, remains elusive. Here we ... ...

    Abstract There have been many efforts to grow high-quality, single-crystalline graphene on a cheap substrate, such as a metal foil. However, control of nucleation and growth of individual flakes, as well as their seamless stitching, remains elusive. Here we demonstrate a new strategy to fast and facile synthesis of large scale single-crystal graphene on copper foil. Polycrystalline Cu foils were first converted to single-crystal Cu foils through high-temperature annealing processes. Then, a sodium chloride (NaCl) additive was introduced during chemical vapor deposition growth of graphene on the Cu foils. Investigation of early stage growth in this process suggests that the NaCl additive enhances nucleation events and depresses dendritic growth, producing high-density graphene flakes (GFs) with crystallographically well-defined edges: (i) rectangular-shaped GFs on Cu(100) and (ii) hexagonal-shaped GFs on Cu(111). Density functional theory calculations show that NaCl can assist in the elimination of remnant oxygen atoms on the Cu surface and promote epitaxial interactions between Cu and graphene. This behavior was further exploited to achieve large-scale single-crystal graphene through epitaxial, seamless stitching of hexagonal GFs within 90 s.
    Keywords annealing ; copper ; density functional theory ; foil ; graphene ; oxygen ; sodium chloride ; vapors
    Language English
    Dates of publication 2020-03
    Size p. 904-911.
    Publishing place Elsevier Ltd
    Document type Article
    ISSN 0008-6223
    DOI 10.1016/j.carbon.2019.11.080
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