Critical work of adhesion for economical patterning of silver nanowire-based transparent electrodes

Ko, Dongwook,Gu, Bongjun,Kang, Seok Ju,Jo, Sungjin,Hyun, Dong Choon,Kim, Chang Su,Kim, Jongbok The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.24

<P>The lithographic process for flexible transparent electrodes is essential for constructing wearable optoelectronic devices with a well-defined active area. Although photolithography is a well-established patterning process, and can generate small features, it involves toxic materials and high processing cost. Herein, we introduce a novel lithographic process for both silver nanowire (AgNW)-embedded and AgNW-exposed flexible transparent electrodes. We selectively control the adhesion between AgNWs and the substrate <I>via</I> a local surface treatment with ultraviolet/ozone (UV/ozone), oxygen plasma, and atmosphere plasma. Since strong adhesion leads to retention of AgNWs on the substrate during embedding of AgNWs in a UV-curable polymer, selective control of adhesion induces selective embedding of AgNWs, generating AgNW-embedded and AgNW-exposed transparent electrodes with desirable patterns. Additionally, this process is versatile enough to be applicable to various substrates including poly(methyl methacrylate) (PMMA)-coated surfaces, poly(ethylene terephthalate) (PET) films, and acrylic substrates, and various AgNWs with different surface energies. The critical work of adhesion to successfully pattern AgNW-based transparent electrodes is experimentally obtained. Conclusively, we demonstrate that patterning of AgNW-based electrodes by controlling the work of adhesion is economical and eco-friendly, and can be successfully applied for designing various optoelectronic devices such as organic photovoltaic cells and liquid crystal cells.</P>

Decoupling the contributions to the enhancement of electrical conductivity in transparent silver nanowire/zinc oxide composite electrodes

Ko, Dongwook,Gu, Bongjun,Cheon, Jimin,Roh, Jae-Seung,Kim, Chang Su,Jo, Sungjin,Hyun, Dong Choon,Kim, Jongbok Elsevier 2019 Materials chemistry and physics Vol.223 No.-

<P><B>Abstract</B></P> <P>Electrical properties of silver nanowire (AgNW)-based transparent electrodes have been improved without transmittance loss by forming a composite with zinc oxide (ZnO). Here, we identified the dominant effect responsible for the improvement of electrical conductivity of the transparent AgNW:ZnO composite electrodes by fabricating the AgNW:ZnO composite electrodes with different architectures and theoretically calculating the overall resistance of their equivalent circuits. Specifically, when we compared the overall resistances of the AgNW:ZnO electrodes with various architectures by experiment, the electrode with only the electrical bridge effect showed the lowest electrical resistance. In addition, while the theoretical overall resistances were comparable on changing the interconnect resistances between the silver nanowires in the equivalent circuits of all architectures, they decreased dramatically with the decreasing ZnO bridging resistance. Thus, it was concluded that the electrical bridge effect is more important than the capillary force effect which decreases the interconnect resistance between the silver nanowires for the enhancement of the electrical properties of AgNW:ZnO composite electrodes. It was also found that the AgNW:ZnO electrodes with only the electrical bridge effect showed better device performances when applied to optoelectronic devices such as organic photovoltaics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We find the dominant mechanism for conductivity improvement of the AgNW electrodes. </LI> <LI> This provides the basis for enhancing the electrical properties of AgNW electrodes. </LI> <LI> That is possible to construct electric device with better device performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Comparison of field- and satellite-based vegetation cover estimation methods

Ko, Dongwook W.,Kim, Dasom,Narantsetseg, Amartuvshin,Kang, Sinkyu The Ecological Society of Korea 2017 Journal of Ecology and Environment Vol.41 No.2

Background: Monitoring terrestrial vegetation cover condition is important to evaluate its current condition and to identify potential vulnerabilities. Due to simplicity and low cost, point intercept method has been widely used in evaluating grassland surface and quantifying cover conditions. Field-based digital photography method is gaining popularity for the purpose of cover estimate, as it can reduce field time and enable additional analysis in the future. However, the caveats and uncertainty among field-based vegetation cover estimation methods is not well known, especially across a wide range of cover conditions. We compared cover estimates from point intercept and digital photography methods with varying sampling intensities (25, 49, and 100 points within an image), across 61 transects in typical steppe, forest steppe, and desert steppe in central Mongolia. We classified three photosynthetic groups of cover important to grassland ecosystem functioning: photosynthetic vegetation, non-photosynthetic vegetation, and bare soil. We also acquired normalized difference vegetation index from satellite image comparison with the field-based cover. Results: Photosynthetic vegetation estimates by point intercept method were correlated with normalized difference vegetation index, with improvement when non-photosynthetic vegetation was combined. For digital photography method, photosynthetic and non-photosynthetic vegetation estimates showed no correlation with normalized difference vegetation index, but combining of both showed moderate and significant correlation, which slightly increased with greater sampling intensity. Conclusions: Results imply that varying greenness is playing an important role in classification accuracy confusion. We suggest adopting measures to reduce observer bias and better distinguishing greenness levels in combination with multispectral indices to improve estimates on dry matter.

Effect of sol-gel ZnO layer position on electrical conductivity improvement in AgNW-based transparent electrode

Dongwook Ko,Bongjun Gu,Moonsoo Chae,Jongbok Kim 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

행위자 기반 모형을 활용한 아프리카돼지열병 확산 분석

고찬우(Ko, Chanwoo),조원희(Cho, Wonhee),황병묵(Hwang, Byungmook),고동욱(Ko, Dongwook W.),강완모(Kang, Wanmo) 한국지적정보학회 2021 한국지적정보학회지 Vol.23 No.2

아프리카돼지열병(ASF)은 전 세계적으로 유행하는 야생동물 질병으로 야생멧돼지(Sus scrofa)와 집돼지(Sus scrofa domesticus)에게 전파되며, 축산 농가에 큰 피해를 일으키고 있다. 2019년 9월 경기도 파주시 연다산동 축산 농가에서 국내 아프리카돼지열병이 최초 보고된 이후, 동년 10월 야생멧돼지 감염개체가 최초로 확인되었다. ASF는 비감염체가 감염개체 또는 감염사체와의 접촉을 통해 확산되며, 야생멧돼지의 이동경로 추적과 확산 통제를 위해 많은 노력이 필요한 시점이다. 효과적인 확산방지를 위해서는 야생멧돼지의 이동에 대한 이해가 매우 중요하지만, 기존의 연구는 대부분 종분포 모형과 같은 서식지 선호도 기반 중심으로 수행되어 실제로 확산을 일으키는 야생멧돼지 개체 간의 접촉이나 이동특성 고려가 미비한 실정이다. 이에 본 연구에서는 야생멧돼지의 이동, 수명, 번식 등 생태적 특성과 포획된 감염 및 비감염 야생멧돼지의 위치정보를 활용하여 야생멧돼지의 ASF 확산을 모의하는 행위자 기반 모형(Agent-based model)을 개발하고 적용성을 평가하였다. 환경부의 전국자연환경조사자료를 활용하여 3,000여 개의 비감염 야생멧돼지 출현자료를 확인하였다. 감염 야생멧돼지는 주로 DMZ 인근지역에서 확인되었고, 모형에는 600여 개의 출현자료가 활용되었다. 모형에서 야생멧돼지는 서식지 선호와 개체군 간 경쟁에 따라 이동이 결정되며, 하루 최대 1㎞를 이동할 수 있다. 이를 활용하여 1년간 모의한 결과 ASF는 강원도 춘천시 서부경계와 경기도 가평군 일대, 춘천시 동부경계와 백두대간으로 우회하여 남쪽으로 확산하는 경향을 보였다. 특히, 백두대간은 야생멧돼지의 서식지 선호도가 높고 개체수가 많은 곳으로 ASF 감염개체가 활발히 이동하며 확산을 일으키는 주요한 경로로 나타났다. 이를 기반으로 ASF 위험지도를 제작하였으며, 산림지 비율이 높은 강원도 일대와 경기도 북부 및 동부지역도 감염확산 위험성이 클 것으로 판단된다. 본 연구결과는 ASF 확산방지를 위한 모니터링의 효율성 증대와 방제전략 마련에 기여할 수 있을 것으로 기대된다. African swine fever (ASF) is a highly contagious and deadly viral disease for both domestic pigs and wild boars. ASF has caused major damage to the pig farming industry globally since it left its native range. Since ASF was first reported in South Korea in 2019, a massive effort has been directed to prevent further spread. While some studies indicate that wild boars significantly contribute to the spread of the disease, it is very difficult to track or control their movement. For effective control of the spread, it is crucial to improve our understanding of the characteristics of their movement and events that may trigger contagion. To overcome the limits of the previous studies that mostly focused on habitat suitability modeling (HSM), we propose a hybrid model that incorporates both HSM and agent-based modeling (ABM) approach. The model is based on the species ecological characteristics, habitat preference, and locations of confirmed infections to evaluate the potential movement and contagion process of ASF, to suggest hotspots for effective control, and to map high-risk areas for ASF spread. We used approximately 3,000 presence locations to estimate its habitat suitability in relation to environmental variables (topography, seasonal vegetation quality, road, and human population density), and approximately 600 locations of infected individuals were derived from confirmed ASF cases. ABM was developed from a NetLogo platform, and the model algorithm was based on the habitat suitability and species characteristics (density, range, lifespan, ASF mortality, and reproduction) of the wild boar. The model was validated and then simulated for 1 year on a daily timestep with 10 replicates. The model results showed two potential major corridors for south-bound ASF spread from the DMZ area: 1) western boundary of Chuncheon and Gapyeong, and 2) eastern boundary of Chuncheon and Baekdu Daegan mountain range. In particular, the Baekdu Daegan mountain range can be considered a hotspot for the spread due to its high habitat preference and large wild boar population. We suggest that our modeling approach can be a useful tool for effective monitoring and mitigation for ASF spread.

Synthesis of BaMgAl10O17:Eu2+ blue phosphor by electro-spray aerosol flame deposition.

Ko, Sangwon,Shin, Dongwook American Scientific Publishers 2009 Journal of nanoscience and nanotechnology Vol.9 No.2

<P>Spherical and nano-sized BaMgAl10O17:Eu2+ (BAM) phosphor particles for plasma display panel (PDP) application were synthesized by Aerosol Flame Deposition (AFD) and subsequent heat treatment at 1250 degrees C for 4 h under reducing atmosphere. The effects of various atomization methods, precursor solution and various deposition position along flame axis were investigated in order to control the morphology and size of the phosphor. Characteristics of BAM phosphor were investigated for products prepared under various condition and they were compared with those of the commercial BAM. It was found that electro-spray gas-assisted atomization produce the most fine particle, while the optimum particle size for real application in phosphor devices (200-400 nm) was produced by the gas-blast atomizer.</P>

Identifying Type of Refined Petroleum Products in Environmental Media: Thin-Layer Chromatography (TLC) as a Quick Methodology

Ko, Myoung-Soo,Kwon, Dongwook,Yang, Jung-Seok,Kwon, Man Jae,Lee, Seung-Woo,Lee, Seunghak Springer-Verlag 2014 Water, Air and Soil Pollution Vol.225 No.10

A Case of Cyclosporine Treatment in Cat with Allergic Dermatitis, Nonresponsive to Prednisolone Treatment

Dongwook Ryu,Jooyeon Kang,Minho Ko,Hyunkee Cho,Jeong Hee Han,Jin-Young Chung 한국임상수의학회 2016 한국임상수의학회지 Vol.33 No.6

A 2-year-old spayed female Persian cat presented to Kangwon National University Veterinary MedicalTeaching Hospital with pruritus and erythema on the tips of both ears, around the eyes, and in the caudal abdomen. This patient had previously been prescribed prednisolone, but did not respond positively to the treatment. A skinscreening test revealed that there were no fleas or fungi, and that only cocci were present. Blood testing revealedno remarkable findings. The patient was prescribed antibiotics (amoxicillin-clavulanic acid 25 mg/kg for 2 weeks) withno prednisolone. After 2 weeks, clinical signs were alleviated and the skin screening test showed no signs of cocci. However, clinical signs recurred even with the prescription of antibiotics. Four weeks after the steroid-free interval,Malassezia spp. hypersensitivity was detected upon a serum allergy test, and pathological analysis confirmed eosinophilicand mastocytic superficial dermatitis in the caudal abdomen. Based on these results, we suspected allergic dermatitisand prescribed 7 mg/kg cyclosporine A once a day. After 3 weeks, clinical signs were resolved. Seven weeks afterthe first trial with cyclosporine A, we reduced the cyclosporine A dose to 7 mg/kg every other day. The patient’ssymptoms have since been well controlled for 6 months. This study suggests that cyclosporine A can be a good choicefor treating cats with suspected allergic dermatitis that has not responded positively to steroid treatment.

주성분 회귀분석을 활용한 유량 자료에 대한 기후변화 및 인위적 인자의 영향 평가

김동욱(Dongwook, Kim),고민수(Min Soo, Ko),무하마드 제한제이브(Muhammad Jehanzaib),김태웅(Tae-Woong, Kim) 대한토목학회 2020 대한토목학회 학술대회 Vol.2020 No.10

Identification of refined petroleum products in contaminated soils using an identification index for GC chromatograms.

Kwon, Dongwook,Ko, Myoung-Soo,Yang, Jung-Seok,Kwon, Man Jae,Lee, Seung-Woo,Lee, Seunghak Ecomed 2015 Environmental Science and Pollution Research Vol.22 No.16

<P>Hydrocarbons found in the environment are typically characterized by gas chromatography (GC). The shape of the GC chromatogram has been used to identify the source of petroleum contamination. However, the conventional practice of simply comparing the peak patterns of source products to those of environmental samples is dependent on the subjective decisions of individual analysts. We have developed and verified a quantitative analytical method for interpreting GC chromatograms to distinguish refined petroleum products in contaminated soils. We found that chromatograms for gasoline, kerosene, and diesel could be divided into three ranges with boundaries at C6, C8, C16, and C26. In addition, the relative peak area (RPAGC) of each range, a dimensionless ratio of the peak area within each range to that of the total range (C6-C26), had a unique value for each petroleum product. An identification index for GC chromatograms (IDGC), defined as the ratio of RPAGC of C8-C16 to that of C16-C26, was able to identify diesel and kerosene sources in samples extracted from artificially contaminated soils even after weathering. Thus, the IDGC can be used to effectively distinguish between refined petroleum products in contaminated soils.</P>