Single crystal molybdenum ditelluride electrocatalyst for the H₂ generation

Jinbong SEOK,Jun-Ho LEE,Suyeon CHO,Byungdo JI,Hyo Won KIM,Young-Min KIM,Sang Ho OH,Sung Wng KIM,Young Hee LEE,Young-Woo SON,Heejun YANG 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Synthesis of Centimeter-Scale Monolayer Tungsten Disulfide Film on Gold Foils

Yun, Seok Joon,Chae, Sang Hoon,Kim, Hyun,Park, Jin Cheol,Park, Ji-Hoon,Han, Gang Hee,Lee, Joo Song,Kim, Soo Min,Oh, Hye Min,Seok, Jinbong,Jeong, Mun Seok,Kim, Ki Kang,Lee, Young Hee American Chemical Society 2015 ACS NANO Vol.9 No.5

<P>We report the synthesis of centimeter-scale monolayer WS<SUB>2</SUB> on gold foil by chemical vapor deposition. The limited tungsten and sulfur solubility in gold foil allows monolayer WS<SUB>2</SUB> film growth on gold surface. To ensure the coverage uniformity of monolayer WS<SUB>2</SUB> film, the tungsten source-coated substrate was placed in parallel with Au foil under hydrogen sulfide atmosphere. The high growth temperature near 935 °C helps to increase a domain size up to 420 μm. Gold foil is reused for the repeatable growth after bubbling transfer. The WS<SUB>2</SUB>-based field effect transistor reveals an electron mobility of 20 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP> with high on–off ratio of ∼10<SUP>8</SUP> at room temperature, which is the highest reported value from previous reports of CVD-grown WS<SUB>2</SUB> samples. The on–off ratio of integrated multiple FETs on the large area WS<SUB>2</SUB> film on SiO<SUB>2</SUB> (300 nm)/Si substrate shows within the same order, implying reasonable uniformity of WS<SUB>2</SUB> FET device characteristics over a large area of 3 × 1.5 cm<SUP>2</SUP>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-5/acsnano.5b01529/production/images/medium/nn-2015-01529j_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5b01529'>ACS Electronic Supporting Info</A></P>

Gas adsorbates are Coulomb scatterers, rather than neutral ones, in a monolayer MoS₂ field effect transistor

Ji, Hyunjin,Yi, Hojoon,Seok, Jinbong,Kim, Hyun,Lee, Young Hee,Lim, Seong Chu The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.23

<P>Direct current (DC) and low-frequency (LF) noise analyses of a chemical vapor deposition (CVD)-grown monolayer MoS2 field effect transistor (FET) indicate that time-varying carrier perturbations originate from gas adsorbates. The LF noise analysis supports that the natural desorption of physisorbed gas molecules, water and oxygen, largely reduces the interface trap density (<I>N</I>ST) under vacuum conditions (∼10<SUP>−8</SUP> Torr) for 2 weeks. After a longer period of 8 months under vacuum, the carrier scattering mechanism alters, in particular for the low carrier density (<I>N</I>acc) region. A decrease of both <I>N</I>ST and the scattering parameter <I>α</I>SC with desorption of surface adsorbates from MoS2, explains the enhanced carrier mobility and the early turn-on of the device. The stabilized carrier behavior is verified with <I>γ</I> = 0.5 in the formula <I>α</I>SC ∝ <I>N</I>acc<SUP>−γ</SUP>, as in Si-MOSFETs. Our results support that the gas adsorbates work as charged impurities, rather than neutral ones.</P>

Vanillic acid attenuates obesity <i>via</i> activation of the AMPK pathway and thermogenic factors <i>in vivo</i> and <i>in vitro</i>

Jung, Yunu,Park, Jinbong,Kim, Hye‐,Lin,Sim, Jung‐,Eun,Youn, Dong‐,Hyun,Kang, JongWook,Lim, Seona,Jeong, Mi‐,Young,Yang, Woong Mo,Lee, Seok‐,Geun,Ahn, Kwang Seok,Um, Jae&# Federation of American Societies for Experimental 2018 The FASEB Journal Vol. No.

<P>Energy expenditure is a target gaining recent interest for obesity treatment. The antiobesity effect of vanillic acid (VA), a well-known flavoring agent, was investigated in vivo and in vitro. High-fat diet (HFD)-induced obese mice and genetically obese db/db mice showed significantly decreased body weights after VA administration. Two major adipogenic markers, peroxisome proliferator activated receptor gamma (PPAR gamma) and CCAAT/enhancer-binding protein alpha (C/EBP alpha), were reduced while the key factor of energy metabolism, AMPK alpha, was increased in the white adipose tissue and liver tissue of VA-treated mice. Furthermore, VA inhibited lipid accumulation and reduced hepatotoxic/inflammatory markers in liver tissues of mice and HepG2 hepatocytes. VA treatment also decreased differentiation of 3T3-L1 adipocytes by regulating adipogenic factors including PPAR gamma and C/EBP alpha. AMPK alpha small interfering RNA was used to examine whether AMPK was associated with the actions of VA. In AMPK alpha-nulled 3T3-L1 cells, the inhibitory action of VA on PPAR gamma and C/EBP alpha was attenuated. Furthermore, in brown adipose tissues of mice and primary cultured brown adipocytes, VA increased mitochondria- and thermogenesis-related factors such as uncoupling protein 1 and PPAR gamma-coactivator 1-alpha. Taken together, our results suggest that VA has potential as an AMPK alpha- and thermogenesis-activating antiobesity agent.</P>

β-Lapachone Inhibits Lung Metastasis of Colorectal Cancer by Inducing Apoptosis of CT26 Cells

Kee, Ji-Ye,Han, Yo-Han,Park, Jinbong,Kim, Dae-Seung,Mun, Jeong-Geon,Ahn, Kwang Seok,Kim, Hyun-Jung,Um, Jae-Young,Hong, Seung-Heon SAGE Publications 2017 Integrative cancer therapies Vol.16 No.4

<P><B>Background:</B> β-Lapachone is a quinone-containing compound found in red lapacho (<I>Tabebuia impetiginosa</I>, syn. <I>T avellanedae</I>) trees. Lapacho has been used in traditional medicine by several South and Central American indigenous people to treat various types of cancer. The purpose of this study was to investigate the antimetastatic properties of β-lapachone and the underlying mechanisms using colon cancer cells. <B>Methods:</B> This research used metastatic murine colon cancer cell lines, colon 26 (CT26) and colon 38 (MC38). A WST assay, annexin V assay, cell cycle analysis, wound healing assay, invasion assay, western blot analysis, and real-time reverse transcription–polymerase chain reaction were performed to examine the effects of β-lapachone on metastatic phenotypes and molecular mechanisms. The effect of β-lapachone on lung metastasis was assessed in a mouse experimental metastasis model. <B>Results:</B> We found that the inhibition of proliferation of the colon cancer cell lines by β-lapachone was due to the induction of apoptosis and cell cycle arrest. β-Lapachone induced the apoptosis of CT26 cells through caspase-3, -8, and -9 activation; poly(ADP-ribose) polymerase cleavage; and downregulation of the Bcl-2 family in a dose- and time-dependent manner. In addition, a low concentration of β-lapachone decreased the cell migration and invasion by decreasing the expression of matrix metalloproteinases-2 and -9, and increased the expression of tissue inhibitors of metalloproteinases-1 and -2. Moreover, β-lapachone treatment regulated the expression of epithelial-mesenchymal transition markers such as E- and N-cadherin, vimentin, β-catenin, and Snail in CT26 cells. In the mouse experimental metastasis model, β-lapachone significantly inhibited the lung metastasis of CT26 cells. <B>Conclusions:</B> Our results demonstrated the inhibitory effect of β-lapachone on colorectal lung metastasis. This compound may be useful for developing therapeutic agents to treat metastatic cancer.</P>

<i>Saengmaeksan</i> inhibits inflammatory mediators by suppressing RIP-2/caspase-1 activation

Jeong, Mi-Young,Park, Dae-Hee,Kim, Min-Cheol,Park, Jinbong,Kim, Dae-Seung,Jeon, Yong-Deok,Kim, Su-Jin,Ahn, Kwang Seok,Kim, Sung-Hoon,Lee, Jong-Hyun,Jung, Hyun-Ju,Hong, Seung-Heon,Um, Jae-Young Informa Healthcare USA, Inc. 2013 Immunopharmacology and immunotoxicology Vol.35 No.2

<P><I>Background and objectives</I>: <I>Saengmaeksan</I> (SMS) is a Korean herbal prescription consisting of three different herbal drugs: Liriopis Tuber (tuber of <I>Liriope platyphylla</I>, Liliaceae), Ginseng Radix (root of <I>Panax ginseng</I>) and Schisandrae Fructus (fruit of <I>Schisandra chinensis</I>). SMS is commonly used in Korea to treat various diseases that involve the respiratory and cardiovascular systems. However, to date, the mechanism underlying the anti-inflammatory effects of SMS is not clearly understood. In this study, we attempt to determine the effects of SMS on lipopolysaccharide (LPS)-induced inflammatory responses in mouse peritoneal macrophages.</P><P><I>Methods</I>: Cell viability was measured by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and nitric oxide (NO) levels were measured by using Griess reagent. The tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels secreted by the cells were measured using a modified enzyme-linked immunosorbent assay. Expression of cyclooxygenase (COX)-2 and nuclear factor-kappa B (NF-κB), respectively was investigated using a western blot analysis. A caspase colorimetric assay kit was used to assay enzymatic caspase-1 activity.</P><P><I>Results</I>: The findings of this study showed that SMS reduced TNF-α and IL-6 production induced by LPS. During the inflammatory process, COX-2 and NO levels were increased in mouse peritoneal macrophages, but SMS decreased the enhanced levels of COX-2 and the production of NO. In addition, SMS suppressed the activation of NF-κB and receptor interacting protein-2/caspase-1.</P><P><I>Discussion and conclusion</I>: Our results provide novel insights into the pharmacological actions of SMS, a molecule that can potentially be exploited in the treatment of inflammatory diseases.</P>

Phase patterning for ohmic homojunction contact in MoTe₂

Cho, Suyeon,Kim, Sera,Kim, Jung Ho,Zhao, Jiong,Seok, Jinbong,Keum, Dong Hoon,Baik, Jaeyoon,Choe, Duk-Hyun,Chang, K. J.,Suenaga, Kazu,Kim, Sung Wng,Lee, Young Hee,Yang, Heejun American Association for the Advancement of Scienc 2015 Science Vol.349 No.6248

<P><B>Making better contacts</B></P><P>A key issue in fabricating transistors is making a good electrical contact to the semiconductor gate material. For two-dimensional materials, one route is through a phase transition that converts a hexagonally packed semiconductor phase into a distorted octahedrally packed metallic phase. Cho <I>et al.</I> show that laser heating of molybdenum telluride (MoTe<SUB>2</SUB>) achieves this conversion through the creation of Te vacancies. The phase transition improves charge carrier mobility while maintaining the low resistance necessary for improved transistor function.</P><P><I>Science</I>, this issue p. 625</P><P>Artificial van der Waals heterostructures with two-dimensional (2D) atomic crystals are promising as an active channel or as a buffer contact layer for next-generation devices. However, genuine 2D heterostructure devices remain limited because of impurity-involved transfer process and metastable and inhomogeneous heterostructure formation. We used laser-induced phase patterning, a polymorph engineering, to fabricate an ohmic heterophase homojunction between semiconducting hexagonal (2H) and metallic monoclinic (1T’) molybdenum ditelluride (MoTe<SUB>2</SUB>) that is stable up to 300°C and increases the carrier mobility of the MoTe<SUB>2</SUB> transistor by a factor of about 50, while retaining a high on/off current ratio of 10<SUP>6</SUP>. In situ scanning transmission electron microscopy results combined with theoretical calculations reveal that the Te vacancy triggers the local phase transition in MoTe<SUB>2</SUB>, achieving a true 2D device with an ohmic contact.</P>

Redox-Driven Route for Widening Voltage Window in Asymmetric Supercapacitor

Sahoo, Ramkrishna,Pham, Duy Tho,Lee, Tae Hoon,Luu, Thi Hoai Thuong,Seok, Jinbong,Lee, Young Hee American Chemical Society 2018 ACS NANO Vol.12 No.8

<P>Although aqueous asymmetric supercapacitors are promising technologies because of their high-energy density and enhanced safety, their voltage window is still limited by the narrow stability window of water. Redox reactions at suitable electrodes near the water splitting potential can increase the working potential. Here, we demonstrate a kinetic approach for expanding the voltage window of aqueous asymmetric supercapacitors using <I>in situ</I> activated Mn<SUB>3</SUB>O<SUB>4</SUB> and VO<SUB>2</SUB> electrodes. The underlying mechanism indicates a specific potential of ∼1 V <I>vs</I> Ag/AgCl for the oxidation of Mn<SUP>4+</SUP>-to-Mn<SUP>7+</SUP> at the positive electrode and ∼ -0.8 V <I>vs</I> Ag/AgCl for the reduction of V<SUP>3+</SUP>-to-V<SUP>2+</SUP> at the negative electrode, which limits oxygen and hydrogen evolution reactions, respectively. The as-fabricated aqueous asymmetric supercapacitor exhibited a working voltage of 2.2 V with a high-energy density of 42.7 Wh/kg and a power density of ∼1.1 kW/kg. This mechanism improves the voltage window and energy and power densities.</P> [FIG OMISSION]</BR>

2차원 층상구조 전이금속칼코젠의 반도체-도체 구조상전이 기반 응용 기술

조수연,김세라,석진봉,양희준,Cho, Suyeon,Kim, Sera,Seok, Jinbong,Yang, Heejun 한국진공학회 2016 진공 이야기 Vol.3 No.1

Motivated by two dimensional graphene, layered transition metal dichalcogenides (TMDs) have attracted scientific interests by their diverse electronic, optical and catalytic properties. In particular, group 6 TMDs such as $MoS_2$ and $MoTe_2$ have polymorphs (with metallic octahedral and semiconducting hexagonal phases) which are not present in graphene. Here, we introduce a new concept in 2D materials' studies, structural phase transition, with group 6 TMDs and its current research trend and applications for electric device and electrochemical catalyst.

Korean Red Ginseng improves atopic dermatitis-like skin lesions by suppressing expression of proinflammatory cytokines and chemokines in vivo and in vitro

Ji-Ye Kee,Yong-Deok Jeon,Dae-Seung Kim,Yo-Han Han,Jinbong Park,Dong-Hyun Youn,Su-Jin Kim,Kwang Seok Ahn,Jae-Young Um,Seung-Heon Hong 고려인삼학회 2017 Journal of Ginseng Research Vol.41 No.2

Background: The prevalence of allergic inflammatory diseases such as atopic dermatitis (AD), asthma, and allergic rhinitis worldwide has increased and complete recovery is difficult. Korean Red Ginseng, which is the heat-processed root of Panax ginseng Meyer, is widely and frequently used as a traditional medicine in East Asia. In this study, we investigated whether Korean Red Ginseng water extract (RGE) regulates the expression of proinflammatory cytokines and chemokines via the mitogen-activated protein kinases (MAPKs)/nuclear factor kappa B (NF-kB) pathway in allergic inflammation. Methods: Compound 48/80-induced anaphylactic shock and 1-fluoro-2,4-dinitrobenzene (DNFB)-induced AD-like skin lesion mice models were used to investigate the antiallergic effects of RGE. Human keratinocytes (HaCaT cells) and human mast cells (HMC-1) were also used to clarify the effects of RGE on the expression of proinflammatory cytokines and chemokines. Results: Anaphylactic shock and DNFB-induced AD-like skin lesions were attenuated by RGE administration through reduction of serum immunoglobulin E (IgE) and interleukin (IL)-6 levels in mouse models. RGE also reduced the production of proinflammatory cytokines including IL-1β, IL-6, and IL-8, and expression of chemokines such as IL-8, thymus and activation-regulated chemokine (TARC), and macrophage-derived chemokine (MDC) in HaCaT cells. Additionally, RGE decreased the release of tumor necrosis factor-α (TNF-α), IL-1β, IL-6, and IL-8 as well as expressions of chemokines including macrophage inflammatory protein (MIP)-1α, MIP-1b, regulated on activation, normal T cell expressed and secreted (RANTES), monocyte chemoattractant protein (MCP)-1, and IL-8 in HMC-1 cells. Furthermore, our data demonstrated that these inhibitory effects occurred through blockage of the MAPK and NF-kB pathway. Conclusion: RGE may be a useful therapeutic agent for the treatment of allergic inflammatory diseases such as AD-like dermatitis.