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Co-deposits of Pt and Bi on Au disk toward formic acid oxidation
Hyein Lee,Young Jun Kim,Sungmin Hong,Youngku Sohn,Choong Kyun Rhee 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
This study presents a simple way to prepare electrocatalysts toward formic acid oxidation (FAO) using co-deposition of Pt and Bi on Au. The previous deposition procedure using irreversible adsorption was two sequential deposition steps of Pt and Bi on Au. In this work, one step to co-deposit Pt and Bi simultaneously was investigated. The amount of Pt and Bi was controlled by repeating the co-deposition cycle. The FAO catalytic activity of Pt-Bi/Au (~14 mA/cm<sup>2</sup>) was higher than Bi/Pt/Au (~6 mA/cm<sup>2</sup>). Thus co-deposition of Pt and Bi was effective in preparation of catalysts for FAO.
Lee Byungkwan,PHAM MINH DUY,CUI MEIYAN,Lee Hyein,Hwang Hyunseung,Jang Inbae,전창후 한국원예학회 2022 Horticulture, Environment, and Biotechnology Vol.63 No.6
The eff ects of light intensity and photoperiod, and their combination as daily light integrals (DLI) on the growth and physi- ological traits of Panax ginseng seedlings were investigated to establish a light environment for seedling production. Strati- fi ed seeds of Panax ginseng ‘Chunpoong’ were sown. The seedlings were cultivated for 20 weeks using warm-white LEDs with DLI from 1.44 to 10.94 mol m −2 d −1, which are combinations of three light intensities (50, 120, and 190 μmol m −2 s−1) and three photoperiods (8, 12, and 16 h d −1) in a plant factory with artifi cial lighting (PFAL). As the DLI increased, the shoot length and leaf area were exponentially reduced after shoot development at both nine and 20 weeks of treatments. At nine weeks of treatment, the greater light intensity and longer photoperiod treatments, where the shoot established fastest, the photosynthetic products were translocated to the roots fi rst and the dry weight distribution in the root increased as DLI increased. In the high light intensity and long photoperiod treatments, SPAD value, maximum (F v/Fm), and minimum (F v/ Fo) quantum effi ciency tended to decrease, and the photosynthetic traits were negatively aff ected over time with leaf senes- cence. The root growth rate in high light intensity with long photoperiod treatments seemed to lag behind that in low light intensity with short photoperiod treatments. As a result, this study found that a light intensity of 50 μmol m −2 s−1 with a 12 h d −1 photoperiod (DLI of 2.16 mol m −2 d −1) was a suitable light environment for both shoot and root growth of ginseng seedlings. Further, the shoot establishment should be considered to design a light environment for ginseng seedling produc- tion in a PFAL.
Lee, Hyein,Kim, Young Jun,Sohn, Youngku,Rhee, Choong Kyun The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.3
This work presents a contrasting behavior of formic acid oxidation (FAO) on the Pt and Bi deposits on different Pt substrates. Using irreversible adsorption method, Bi and Pt were sequentially deposited on Pt electrodes of nanoparticle (Pt NP) and disk (Pt disk). The deposited layers of Bi and Pt on the Pt substrates were characterized with X-ray photoelectron spectroscopy, transmission microscopy and scanning tunneling microscopy. The electrochemical behaviors and FAO enhancements of Pt NP and Pt disk with deposited Bi only (i.e., Bi/Pt NP and Bi/Pt disk), were similar to each other. However, additional deposition of Pt on Bi/Pt NP and Bi/Pt disk (i.e., Pt/Bi/Pt NP and Pt/Bi/Pt disk) changed the electrochemical behavior and FAO activity in different ways depending on the shapes of the Pt substrates. With Pt/Bi/Pt NP, the hydrogen adsorption was suppressed and the surface oxidation of Pt was enhanced; while with Pt/Bi/Pt disk, the opposite behavior was observed. This difference was interpreted as a stronger interaction between the deposited Bi and Pt on Pt NP than that on Pt disk. The FAO performance on Pt/Bi/Pt NP is much better than that on Pt/Bi/Pt disk, most likely due to the difference in the interaction between the deposited Pt and Bi depending on the shapes of Pt substrates. In designing FAO electrochemical catalysts using Pt and Bi, the shape of a Pt substrate was concluded to be critically considered.
Hyein Lee,Seon Woo Park,Minh Duy Pham,Hyunseung Hwang,Changhoo Chun 한국원예학회 2020 Horticulture, Environment, and Biotechnology Vol.61 No.6
The application of plant factory with artifi cial lighting (PFAL) for producing strawberry transplants (S-PFAL) was recentlyintroduced due to the capacity for high quality and year-round transplant production. To achieve greater effi ciency with thissystem, it is essential to select lighting sources that have a suitable spectrum for runner plant propagation. This study wasconducted to investigate the eff ects of the light spectrum of white light-emitting diodes (LEDs), which have a diff erent correlatedcolor temperature compared with that of white fl uorescent lamps, on the growth of strawberry ( Fragaria × ananassaDuch. cv. Maehyang) propagules and runner plants in a PFAL. Uniform propagules with one fi xed runner each were placedinto a PFAL for transplant production and were grown under either warm-white LEDs (WWL), mint-white LEDs (MWL),or cool-white fl uorescent lamps (CWF) for 21 days. The propagules in the MWL treatment group had the greatest numberof leaves, leaf area, top/root dry weight ratio and number of newly formed runners per propagule among the treatments. Thedry weight of the newly formed runners of each propagule was also greatest after MWL treatment, whereas it was lowestafter CWF treatment. However, there was no signifi cant diff erence in the growth parameters of the runner plants amongthe three treatments. The photosynthetic photon effi cacy of WWL and MWL was 5.40 μmol s − 1 W − 1 , which was 62.6%higher than that of CWF (3.38 μmol s − 1 W − 1 ). The dry weight effi cacies of the MWL, WWL, and CWF treatments were23.5, 22.1, and 10.0 g kWh − 1 , respectively. These results indicate that MWL with high photosynthetic photon effi cacy canhave positive eff ects on the runner formation and growth of strawberry propagules and can replace cool-white fl uorescentlamps in an S-PFAL.
( Hyein Kim ),( Seul Ki Kim ),( Chang-woo Choo ),( Jung Ryeol Lee ),( Byung Chul Jee ),( Won Don Lee ),( Seok Hyun Kim ) 대한산부인과학회 2018 대한산부인과학회 학술대회 Vol.104 No.-
Objective: To investigate the recognition and knowledge about oocyte freezing for social or medical reasons among unmarried women of reproductive age in Korea. Methods: This was a survey study performed at a single center between December 2016 and May 2018. Women of reproductive age (20-45 years) who had no partner at the time of recruitment were included. The 30-item questionnaire consisted of following parts: (1) demographics; (2) awareness of pregnancy and childbirth; (3) recognition about oocyte freezing and factors that affect a woman's decision-making in the utilization of fertility preservation; and (4) knowledge about oocyte freezing. Results: 86 women received an electrical survey and 15 were excluded as they were incomplete. Mean age was 37.0 years. Over half of the women (73%) responded they decided to undergo oocyte freezing for their fertility preservation. Most frequently reported reason for the decision was to maintain their fertility in the future when they attempt pregnancy (70.6%). Most of the respondents (61.8%) expressed positive intent for oocyte donation. In the evaluation of background knowledge about fertility, most respondents got only 1 question correct out of the 6. Most respondents thought that costs for the procedure should be covered by medical insurance or social security system. They expected proper medical advice about fertility preservation when they met health care providers. Conclusion: Interest in the preservation of freezing eggs has increased and the number of procedures is increasing in Korea, but it has not been universal yet. Reinforcement in governmental and institutional support is essential to meet the demand of women who want to preserve their fertility. This could be one of the solutions to the low fertility crisis in Korea.
Electron transport mechanism of bathocuproine exciton blocking layer in organic photovoltaics
Lee, Jeihyun,Park, Soohyung,Lee, Younjoo,Kim, Hyein,Shin, Dongguen,Jeong, Junkyeong,Jeong, Kwangho,Cho, Sang Wan,Lee, Hyunbok,Yi, Yeonjin The Royal Society of Chemistry 2016 Physical chemistry chemical physics Vol.18 No.7
<P>Efficient exciton management is a key issue to improve the power conversion efficiency of organic photovoltaics (OPVs). It is well known that the insertion of an exciton blocking layer (ExBL) having a large band gap promotes the efficient dissociation of photogenerated excitons at the donor-acceptor interface. However, the large band gap induces an energy barrier which disrupts the charge transport. Therefore, building an adequate strategy based on the knowledge of the true charge transport mechanism is necessary. In this study, the true electron transport mechanism of a bathocuproine (BCP) ExBL in OPVs is comprehensively investigated by in situ ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy, density functional theory calculation, and impedance spectroscopy. The chemical interaction between deposited Al and BCP induces new states within the band gap of BCP, so that electrons can transport through these new energy levels. Localized trap states are also formed upon the Al-BCP interaction. The activation energy of these traps is estimated with temperature-dependent conductance measurements to be 0.20 eV. The Al-BCP interaction induces both transport and trap levels in the energy gap of BCP and their interplay results in the electron transport observed.</P>