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( Yo Sep Kim ),( Na Young Park ),( Shin Ho Lee ),( Kwang Sup Youn ),( Joon Heon Hong ),( Chang Su Park ),( Hong Kyoon No ) 한국키틴키토산학회 2015 한국키틴키토산학회지 Vol.20 No.1
The effects of milled chitosan solutions on growth and selected quality of soybean sprouts were evaluated.Chitosan solution (1% in 1% acetic acid) was milled for 0, 0.5, 1 and 2 h, and diluted with distilled water to 0.05% to use as soaking solutions. Soybean seeds were soaked in water (control), 0.05% acetic acid and milled chitosan solutions for 8 h, and then cultivated for 3 days at 25 o C. Results indicated that chitosan treatment increased total weight by 7.8-10.0% and hypocotyl length by 6.2-11.1% compared with the control and that the effectiveness of chitosan treatment was not affected by milling times of chitosan solution. Chitosan treatment, irrespective of milling times, did not affect the quality of soybean sprouts. No significant differences in moisture content, hardness and DPPH radical scavenging activity were observed among six treatment groups. The total free amino acid contents of soybean sprouts treated with 0.5 and 1 h-milled chitosan solutions were comparable to that of the control soybean sprouts.
Novel chemical route for atomic layer deposition of MoS2 thin film on SiO2/Si substrate.
Jin, Zhenyu,Shin, Seokhee,Kwon, Do Hyun,Han, Seung-Joo,Min, Yo-Sep RSC Pub 2014 Nanoscale Vol.6 No.23
<P>Recently MoS2 with a two-dimensional layered structure has attracted great attention as an emerging material for electronics and catalysis applications. Although atomic layer deposition (ALD) is well-known as a special modification of chemical vapor deposition in order to grow a thin film in a manner of layer-by-layer, there is little literature on ALD of MoS2 due to a lack of suitable chemistry. Here we report MoS2 growth by ALD using molybdenum hexacarbonyl and dimethyldisulfide as Mo and S precursors, respectively. MoS2 can be directly grown on a SiO2/Si substrate at 100 C via the novel chemical route. Although the as-grown films are shown to be amorphous in X-ray diffraction analysis, they clearly show characteristic Raman modes (E(1)2g and A1g) of 2H-MoS2 with a trigonal prismatic arrangement of S-Mo-S units. After annealing at 900 C for 5 min under Ar atmosphere, the film is crystallized for MoS2 layers to be aligned with its basal plane parallel to the substrate.</P>
Band structure of amorphous zinc tin oxide thin films deposited by atomic layer deposition
Lee, Sunyoung,Kim, Sungjoon,Shin, Seokhee,Jin, Zhenyu,Min, Yo-Sep Elsevier 2018 Journal of industrial and engineering chemistry Vol.58 No.-
<P><B>Abstract</B></P> <P>Recently, zinc tin oxide (ZTO) has attracted attention as an alternative buffer layer to replace CdS for photovoltaic cells. ZTO thin films were grown by atomic layer deposition from diethylzinc, tetrakis(dimethylamido)tin, and water. Compositional, structural and optical properties were characterized to construct band diagram of the ZTO films depending on Sn content. The ZTO films exhibit optical bandgaps of 2.95–3.07eV which are wider than that of CdS. Furthermore, their work function is also observed to vary in a wide range of 4.32–5.16eV. It is attributed to incorporation of Sn into ZTO which strongly influences formation of oxygen vacancies.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Bose, Ranjith,Balasingam, Suresh Kannan,Shin, Seokhee,Jin, Zhenyu,Kwon, Do Hyun,Jun, Yongseok,Min, Yo-Sep American Chemical Society 2015 Langmuir Vol.31 No.18
<P>Amorphous molybdenum sulfide (MoS<SUB><I>x</I></SUB>) has been identified as an excellent catalyst for the hydrogen evolution reaction (HER). It is still a challenge to prepare amorphous MoS<SUB><I>x</I></SUB> as a more active and stable catalyst for the HER. Here the amorphous MoS<SUB><I>x</I></SUB> catalysts are prepared on carbon fiber paper (CFP) substrates at 200 °C by a simple hydrothermal method using molybdic acid and thioacetamide. Because the CFP is intrinsically hydrophobic due to its graphene-like carbon structure, two kinds of hydrophilic pretreatment methods [plasma pretreatment (PP) and electrochemical pretreatment (EP)] are investigated to convert the hydrophobic surface of the CFP to be hydrophilic prior to the hydrothermal growth of MoS<SUB><I>x</I></SUB>. In the HER catalysis, the MoS<SUB><I>x</I></SUB> catalysts grown on the pretreated CFPs reach a cathodic current density of 10 mA/cm<SUP>2</SUP> at a much lower overpotential of 231 mV on the MoS<SUB><I>x</I></SUB>/EP-CFP and 205 mV on the MoS<SUB><I>x</I></SUB>/PP-CFP, compared to a high overpotential of 290 mV on the MoS<SUB><I>x</I></SUB> of the nonpretreated CFP. Turnover frequency per site is also significantly improved when the MoS<SUB><I>x</I></SUB> are grown on the pretreated CFPs. However, the Tafel slopes of all amorphous MoS<SUB><I>x</I></SUB> catalysts are in the range of 46–50 mV/dec, suggesting the Volmer–Heyrovsky mechanism as a major pathway for the HER. In addition, regardless of the presence or absence of the pretreatment, the hydrothermally grown MoS<SUB><I>x</I></SUB> catalyst on CFP exhibits such excellent stability that the degradation of the cathodic current density is negligible after 1000 cycles in a stability test, possibly due to the relatively high growth temperature.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2015/langd5.2015.31.issue-18/acs.langmuir.5b00205/production/images/medium/la-2015-00205r_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la5b00205'>ACS Electronic Supporting Info</A></P>
반암(맥반석)으로 제조한 다공성 펠렛의 Ag 담지 및 항균 메디아로서의 적용
한요셉,김현중,신영섭,박재구,고재철,Han, Yo-Sep,Kim, Hyun-Jung,Shin, Young-Seop,Park, Jai-Koo,Ko, Jae-Churl 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.1
The porous pellets were prepared from porphyry by slurry foaming method. The effect of sintering temperatures on pore structure of porous porphyry pellets with different extension ratio ($E_R$) was investigated by specific surface area, water absorption and porosity, which changed with sintering temperatures. When the sintering temperatures increased from $975^{\circ}C$ to $1075^{\circ}C$, specific surface area and water absorption of the all samples decreased. In case of the sample with an equal sintering temperature, $E_R=3.0$ pellets had little influence on pore structure compared to the $E_R=2.0$ pellets. As a results, it was shown by SEM that facilitated formation of micro pores at $E_R=2.0$ pellets shrunk increasingly after sintering process. At $E_R=3.0$ and sintering temperature at $1025^{\circ}C$, optimum conditions of the porous porphyry porous pellets was found. Also, Escherichia coli removal efficiency of the silver-containing porphoyry porous pellets was measured for the feasibility as a antibacterial media. The antibacterial activity of prepared silver-containing sample was maintained above 90% for 40 days.
박요셉,신준철,옥철영,박혁로,Park, Yo-Sep,Shin, Joon-Choul,Ock, Cheol-Young,Park, Hyuk-Ro 한국정보처리학회 2011 정보처리학회논문지B Vol.18 No.4
동형이의어는 여러 가지 의미를 가진 단어를 의미한다. 문장의 의미를 이해하기 위해서는 필수적으로 문장에 포함된 동형이의어의 의미를 결정해야 한다. 기존의 단어 의미 중의성 연구들은 공기 빈도를 기반으로 해결하였다. 하지만, 동사의 경우에는 정확도 향상을 위해서 격 정보가 중요하다. 왜냐하면, 동사 동형이의어의 의미는 행위의 주체나 객체에 따라 결정되어서 종속격(목적격, 부사격, 보격) 정보가 필요하며, 동사동형이의어 의미마다 서로 다른 격 정보가 필요하기 때문이다. 본 논문에서는 한국어 격 정보를 적용한 동사 의미 중의성 해소를 제안한다. 격정보는 표준국어대사전에 명시된 조사 정보를 이용하였다. 실험은 고빈도 동형이의어 12개를 대상으로 하였으며, 실험결과 정확도가 기존의 97.3%에서 98.7%로 1.34% 향상되었다. 이는 원래의 오류율을 2.7%에서 1.3%으로 절반정도 줄였다. Homographs can have multiple senses. In order to understand the meaning of a sentence, it is necessary to identify which sense isused for each word in the sentence. Previous researches on this problem heavily relied on the word co-occurrence information. However, we noticed that in case of verbs, information about subordinating cases of verbs can be utilized to further improve the performance of word sense disambiguation. Different senses require different sets of subordinating cases. In this paper, we propose the verb sense disambiguation using subordinating case information. The case information acquire postposition features in Standard Korean Dictionary. Our experiment on 12 high-frequency verb homographs shows that adding case information can improve the performance of word sense disambiguation by 1.34%, from 97.3% to 98.7%. The amount of improvement may seem marginal, we think it is meaningful because the error ratio reduced to less than a half, from 2.7% to 1.3%.
Kim, Sungjoon,Lee, Sunyoung,Ham, So-Yeon,Ko, Dong-Hyun,Shin, Seokhee,Jin, Zhenyu,Min, Yo-Sep Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.469 No.-
<P><B>Abstract</B></P> <P>We present a kinetic model for the reaction of diethylzinc (DEZ) adsorption in atomic layer deposition (ALD) of ZnO from DEZ and water. The proposed model has been verified by comparing kinetic experimental data to the prediction of the model in the temperature range of 60–200 °C. In this model, DEZ molecules are molecularly adsorbed on the hydroxyl-terminated surface in the first elementary reaction. Then the molecularly-adsorbed DEZs either desorb from the surface, or undergo an irreversible ligand exchange reaction and form monoethylzinc (MEZ)-terminated surface by liberating ethane molecules. According to the integrated rate law of the model, as the exposure time of DEZ increases, the growth per cycle ( gpc ) of ALD, i.e., the thickness increment per cycle, rapidly increases and then saturates showing the self-limiting growth behavior. The required DEZ exposure time to reach the saturated gpc value is shortened when the chemical equilibrium between the molecular adsorption and desorption shifts toward the adsorption, as this leads to higher effective rate constant in the overall mechanism of the DEZ adsorption. Although the saturated gpc value is primarily governed by the hydroxyl concentration on the ZnO surface, it is also heavily influenced by the steric hindrance due to the bulkiness of the ethyl ligands. We have determined that the critical temperature at which the steric hindrance disappears is around 150–200 °C, by investigating the variation of the hydroxyl concentration with temperature. At temperatures lower than 150 °C, we have observed that the saturated gpc value is governed by the steric hindrance rather than the hydroxyl concentration. However, the saturated gpc value at 200 °C has been achieved purely by the hydroxyl concentration. In other words, all hydroxyl groups at 200 °C have been consumed and saturated by the MEZ molecules of which the steric hindrance-free concentration has been evaluated to be ∼7.1 /nm<SUP>2</SUP>. In addition, the effective activation energy was estimated to be ∼8.50 kJ/mol by using the effective rate constants of all temperatures investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Governing factors of growth per cycle ( gpc ) were identified depending on growth temperature. </LI> <LI> The saturated gpc values at T < 150 °C are governed by steric hindrance. </LI> <LI> Above 200 °C, the saturated gpc values are decided by surface hydroxyl concentration. </LI> <LI> Effective activation energy of the DEZ adsorption was found to be ∼8.50 kJ/mol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Steric hindrance of diethylzinc adsorption disappears at 150–200 °C.</P> <P>[DISPLAY OMISSION]</P>
Leem, Jina,Park, Inhye,Li, Yinshi,Zhou, Wenhao,Jin, Zhenyu,Shin, Seokhee,Min, Yo-Sep Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.4
Atomic layer deposition (ALD) of $TiO_2$ thin film from $TiCl_4$ and $H_2O$ has been intensively studied since the invention of ALD method to grow thin films via chemical adsorptions of two precursors. However the role of HCl which is a gaseous byproduct in ALD chemistry for $TiO_2$ growth is still intriguing in terms of the growth mechanism. In order to investigate the role of HCl in $TiO_2$ ALD, HCl pulse and its purging steps are inserted in a typical sequence of $TiCl_4$ pulse-purge-$H_2O$ pulse-purge. When they are inserted after the first-half reaction (chemisorption of $TiCl_4$), the grown thickness of $TiO_2$ becomes thinner or thicker at lower or higher growth temperatures than $300^{\circ}C$, respectively. However the insertion after the second-half reaction (chemisorption of $H_2O$) results in severely reduced thicknesses in all growth temperatures. By using the result, we explain the growth mechanism and the role of HCl in $TiO_2$ ALD.