Elongated Lifetime and Enhanced Flux of Hot Electrons on a Perovskite Plasmonic Nanodiode

Park, Yujin,Choi, Jungkweon,Lee, Changhwan,Cho, An-Na,Cho, Dae Won,Park, Nam-Gyu,Ihee, Hyotcherl,Park, Jeong Young American Chemical Society 2019 NANO LETTERS Vol.19 No.8

<P>A fundamental understanding of hot electron transport is critical for developing efficient hot-carrier-based solar cells. There have been significant efforts to enhance hot electron flux, and it has been found that a key factor affecting the hot electron flux is the lifetime of the hot electrons. Here, we report a combined study of hot electron flux and the lifetime of hot carriers using a perovskite-modified plasmonic nanodiode. We found that perovskite deposition on a plasmonic nanodiode can considerably improve hot electron generation induced by photon absorption. The perovskite plasmonic nanodiode consists of MAPbI<SUB>3</SUB> layers covering a plasmonic-Au/TiO<SUB>2</SUB> Schottky junction that is composed of randomly connected Au nanoislands deposited on a TiO<SUB>2</SUB> layer. The measured incident photon-to-electron conversion efficiency and the short-circuit photocurrent show a significantly improved solar-to-electrical conversion performance of this nanodiode. Such an improvement is ascribed to the improved hot electron flux in MAPbI<SUB>3</SUB> caused by effective light absorption from near-field enhancement of plasmonic Au and the efficient capture of hot electrons from Au nanoislands via the formation of a three-dimensional Schottky interface. The relation between the lifetime and flux of hot electrons was confirmed by femtosecond transient absorption spectroscopy that showed considerably longer hot electron lifetimes in MAPbI<SUB>3</SUB> combined with the plasmonic Au structure. These findings can provide a fundamental understanding of hot electron generation and transport in perovskite, which can provide helpful guidance to designing efficient hot carrier photovoltaics.</P> [FIG OMISSION]</BR>

Evaluation of fouling in nanofiltration for desalination using a resistance-in-series model and optical coherence tomography

Park, Jongkwan,Lee, Sungyun,You, Jeongyeop,Park, Sanghun,Ahn, Yujin,Jung, Woonggyu,Cho, Kyung Hwa Elsevier 2018 The Science of the total environment Vol.642 No.-

<P><B>Abstract</B></P> <P>Resistance-in-series models have been applied to investigate fouling behavior. However, it is difficult to model the influence of morphology on fouling behavior because resistance is indirectly calculated from the water flux and transmembrane pressure. In this study, optical coherence tomography (OCT) was applied to evaluate the resistance of the fouling layer based on fouling morphology. Sodium alginate, humic acid, and bovine serum albumin (BSA) with high salts concentrations (conductivity: 23 mS/cm) were used as model foulants. At the same total fouling resistance, BSA showed the highest cake layer thickness (BSA (114.5 μm) > humic acid (53.5 μm) > sodium alginate (20.0 μm)). However, a different order was found for the cake layer resistance (BSA > sodium alginate > humic acid). This indicates that fouling thickness is not correlated with cake layer resistance. According to the Carman–Kozeny equation, fouling layer porosity decreased in the following order: humic acid (0.30) > BSA (0.21) > sodium alginate (0.20). In addition, we provided a specific value that was calculated using the ratio between the fouling thickness and cake layer resistance. The results show that alginic acid induced a stronger cake layer resistance, despite its thin fouling layer, whereas BSA showed a relatively low potential for inducing cake layer resistance. The results obtained in this study could be used for estimating and predicting fouling behavior.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Property of fouling layer was investigated by the membrane resistance value and fouling thickness. </LI> <LI> Humic acid, sodium alginate, and BSA fouling layers in brackish water were visualized via OCT. </LI> <LI> Gel/cake layer and adsorbed/pore blocking fouling types were distinguished by 2D OCT images. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Evaluating the effects of organic matter bioavailability on nanofiltration membrane using real-time monitoring

Park, Sanghun,You, Jeongyeop,Ahn, Yujin,Jung, Woonggyu,Kim, Jihye,Lee, Sungyun,Park, Jongkwan,Cho, Kyung Hwa Elsevier 2018 Journal of membrane science Vol.548 No.-

<P><B>Abstract</B></P> <P>We studied the influence of bioavailability of organic matter on membrane fouling layer development by comparing the filtration performance of two feed waters (wetland water and graywater). Dissolved organic carbon (DOC) concentration, size exclusion chromatography (SEC), and fluorescence excitation-emission matrix (FEEM) were used to characterize the bioavailability of organic matter in these water samples during the nanofiltration process. The wetland sample contained a high proportion of humic acid- and fulvic acid-like matter with low bioavailability, whereas the graywater sample comprised substantial amounts of aromatic proteins and microbial byproduct-like matter with high bioavailability. In addition, the molecular size distribution revealed that the wetland sample contained a large portion of recalcitrant organic matter, whereas the graywater sample contained easily bioavailable organic matter. After the filtration experiment, the DOC of the wetland sample decreased to 4.8mgC/L, whereas the graywater sample resulted in a lower DOC concentration of 3.4mgC/L. Optical coherence tomography (OCT) illustrated real-time variations in the fouling layer morphology, providing both 2D and 3D images. In addition, confocal laser scanning microscopy (CLSM) quantified the bacterial volume in the fouling layer. The wetland sample yielded a bacterial volume of 11.8µm<SUP>3</SUP>/μm<SUP>2</SUP> from a total fouling volume of 103µm<SUP>3</SUP>/μm<SUP>2</SUP>, whereas the graywater sample yielded a bacterial volume of 53.2µm<SUP>3</SUP>/μm<SUP>2</SUP> from a total fouling layer volume of 134µm<SUP>3</SUP>/μm<SUP>2</SUP>. Fitting of the two-phase Monod model to the fouling layer growth on the membrane resulted in lower-yield coefficients (i.e., the volumes produced per unit amount of substrate, <SUB> Y xs </SUB> ) of 7.46 and 27.95µm<SUP>3</SUP>/μm<SUP>2</SUP> in wetland water and higher-yield coefficients of 13.17 and 47.53µm<SUP>3</SUP>/μm<SUP>2</SUP> in the graywater at first and second phase, respectively. This study addresses the quantitative evaluation of the organic matter bioavailability in terms of membrane fouling using OCT images and a two-phase Monod model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The difference of bioavailability of DOM influenced the amount of fouling layer growth. </LI> <LI> In situ OCT monitoring provided 2D and 3D morphology of the fouling layer and quantified the volume. </LI> <LI> Two-phase Monod model evaluated the influence of bioavailability of DOM on fouling layer growth. </LI> </UL> </P>

PCR amplification and cell-free expression of single-molecule DNA in water-in-oil emulsion droplets

Park YUJIN,Kim DONG-MYUNG 한국생물공학회 2016 한국생물공학회 학술대회 Vol.2016 No.4

Microwave-assisted Synthesis of Fluorescent Polymer Dots from Hyperbranched Polyethylenimine and Glycerol

Park, Jongyeap,Kwon, Binhee,Jeong, Woojun,Chae, Ari,Choi, Yujin,Park, Sung Young,In, Insik Chemical Society of Japan 2017 Chemistry letters Vol.46 No.10

Exploring Online Learning Profiles of In-service Teachers in a Professional Development Course

( Yujin Park ),( Jihyun Sung ),( Young Hoan Cho ) 한국교육공학회 2017 Educational Technology International Vol.18 No.2

This study aimed to explore online learning profiles of in-service teachers in South Korea, focusing on video lecture and discussion activities. A total of 269 teachers took an online professional development course for 14 days, using an online learning platform from which web log data were collected. The data showed the frequency of participation and the initial participation time, which was closely related to procrastinating behaviors. A cluster analysis revealed three online learning profiles of in-service teachers: procrastinating (n=42), passive interaction (n=136), and active learning (n=91) clusters. The active learning cluster showed high-level participation in both video lecture and discussion activities from the beginning of the online course, whereas the procrastinating cluster was seldom engaged in learning activities for the first half of the learning period. The passive interaction cluster was actively engaged in watching video lectures from the beginning of the online course but passively participated in discussion activities. As a result, the active learning cluster outperformed the passive interaction cluster in learning achievements. The findings were discussed in regard to how to improve online learning environments through considering online learning profiles of in-service teachers.

Utilization of turanose as a quality improver in gluten-free extruded rice noodles

Yujin Park,Sang-Ho Yoo,Sung Won Park,Suyong Lee 한국산업식품공학회 2017 학술대회 및 심포지엄 Vol.2017 No.11

Gluten-free industry has experienced consistent growth with increasing the number of individuals with celiac disease. Among gluten-free products, the popularity of rice noodles has been worldwide increasing over the recent years. However, rice noodles have several processing limitations such as high cooking turbidity and long cooking time. Therefore, various ingredients have been incorporated into the formulation of rice noodles in order to improve their quality attributes. In this study, turanose which is known to be a new sugar alternative with low sweetness was applied to rice noodles and their effects were characterized in terms of thermal, rheological, and textural properties. Gluten-free rice noodles were prepared with different levels of turanose (0.5, 1.0, 1.5%, w/w) by using a twin-screw extruder. Rice flour with turanose had higher gelatinization temperature and also showed higher enthalpy values after storage at 4°C. The use of turanose also increased the pasting and mixing parameters of rice flour. In addition, the application of turanose to rice noodles affected their qualities such as texture and cooking loss. Thus, this study demonstrated that turanose could positively contribute to enhancing the qualities of gluten-free rice noodles as a new additive.

Characterization of the life cycle carbon footprint of the automobile industry in the Republic of Korea by environmentally extended input-output model

Yujin Park,Agusta Samodra Putra,Hung-Suck Park,Junbeum Kim 대한환경공학회 2024 Environmental Engineering Research Vol.29 No.5

The automobile industry is a major economic driver in Republic of Korea (Korea). However, little is known about its climate change contribution. This study estimates the direct and indirect greenhouse gases (GHG) emissions of the Korean automobile industry for the first time, by using a 2017 environmentally extended input-output (EEIO) model integrated by energy balance, GHG inventory and input-output table of 2017. The results show that the final demand of Korean automobile industry led to 8.4% of national GHG emissions in 2017, mostly because of indirect emissions embodied in the supply chain. The study also found that the Scope 1, Scope 2 and Scope 3 emissions on average accounted for 3.0%, 2.9%, and 94.7%, respectively. This highlights the contribution of the upstream supply chain such as primary metals (40.9%) and electricity (32.5%) when assessing the GHG emissions. Finally, the study underscores that carbon taxes could have a significant impact on the competitiveness of automobile export. Overall, this study provides valuable insights on countermeasures by identifying the GHG emissions characteristics of the automobile industry. The results of the study could be used to develop policies and strategies to reduce the GHG emissions and promote sustainable practices in the Korean automobile industry.

Association between Type and Intensity of Physical Activity and Depression

Yujin Chang,Kye-Yeung Park,Hwan-Sik Hwang,Hoon-Ki Park 대한가정의학회 2022 Korean Journal of Family Medicine Vol.43 No.4

Background: Although numerous studies have indicated that lower levels of physical activity correlate with a high-er risk of depression, an association between the type of physical activity and depression has not been identified in Korea. This study aimed to examine whether the type and intensity of physical activity are associated with depres-sion in Korean adults.Methods: This cross-sectional study used data from the Korea National Health and Nutrition Examination Survey (KNHANES). A total of 11,679 individuals were analyzed using multiple logistic regression analyses to identify any association between the type of physical activity and depressive disorders in the sample subjects.Results: Measured weekly in units of energy expenditure, known as metabolic equivalents (METs), the amount of work-related physical activity was higher in individuals with depression according to the Patient Health Question-naire-9 than the participants without depression (386.7 vs. 206.7 MET-min/wk, P=0.01). Those diagnosed with de-pression tended to engage in less recreational activity per week (143.7 vs. 316.3 MET-min/wk, P<0.001) than those without depression. After controlling for covariates, the risk of depression among all participants was 1.012 times higher with a 100-unit increase in total work-related activity measured in METs (95% confidence interval [CI], 1.006–1.017; P<0.001) and 0.962 times lower with a 100-unit increase in total leisure activity measured in METs (95% CI, 0.937–0.987; P=0.003).Conclusion: Different types of physical activity were shown to be differently associated with depressive disorders in Korean adults. This study might guide in reducing work-related physical activity and increasing leisure activity to prevent the occurrence of depression.

The role of platelet to lymphocyte ratio and neutrophil to lymphocyte ratio in ulcerative colitis

( Yujin Jeong ),( Seong Ran Jeon ),( Hyun Gun Kim ),( Jung Rock Moon ),( Tae Hee Lee ),( Jae Young Jang ),( Jun-hyung Cho ),( Jun Seok Park ),( Heesu Park ),( Ki-hun Lee ),( Jin-oh Kim ),( Joon Seong 대한장연구학회 2021 Intestinal Research Vol.19 No.1

Background/Aims: Neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) can serve as biomarkers for diagnosing and assessing disease activity in ulcerative colitis (UC). We investigated their clinical significance in UC. Methods: We analyzed 48 patients with UC who underwent measurement of fecal calprotectin (FC) and endoscopy and 96 age- and sex-matched healthy controls. NLR and PLR were compared between the patients and healthy controls. The endoscopic activity was divided into 2 groups: group 1 (mild to moderate inflammation) and group 2 (severe inflammation) according to the Mayo endoscopic subscore in UC. Results: To diagnose UC, the optimal cutoff of NLR and PLR was 2.26 (sensitivity 54.2%; specificity 90.6%; positive likelihood ratio 5.778, 95% confidence interval [CI] 2.944-11.339; area under the curve [AUC] 0.774, 95% CI, 0.690-0.859) and 179.8 (sensitivity 35.4%; specificity 90.6%; positive likelihood ratio 3.778, 95% CI 1.821-7.838; AUC 0.654, 95% CI 0.556-0.753), respectively. The optimal cutoff to differentiate group 1 and group 2 was 3.44, 175.9, and 453 μg/g for NLR, PLR, and FC, respectively (sensitivity, 63.6% vs. 90.9% vs. 81.8%; specificity, 81.1% vs. 78.4% vs. 73.0%; positive likelihood ratio, 3.364 vs. 4.205 vs. 3.027; AUC, 0.714 vs. 0.897 vs. 0.813). PLR had the highest AUC and positive likelihood ratio. Conclusions: NLR and PLR help differentiate patients with UC from healthy controls. NLR, PLR, and FC indicate endoscopic activity and may reflect intestinal mucosal conditions. (Intest Res 2021;19:62-70)