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Chang I.,Seoul National University | Lee M.H.,University of California at Merced | Lee J.-H.,Seoul National University | Kim Y.-S.,Seoul National University | And 2 more authors.
International Journal of Precision Engineering and Manufacturing | Year: 2013

The paper examines a fabrication method of flexible fuel cells (FCs), and its feasibility through a set of electrical measurements both in the as-prepared and the bended condition. The flexible FC consists of three parts: membrane electrode assembly (MEA), anode and cathode endplates with current collectors. The endplate material for anode and cathode used in this study is Polydimethylsiloxane (PDMS), and metallic films are sputtered on a patterned PDMS to use the resulting structure as current collector. The power density of bended cell with the curvature of ~1.8 m-1 decreased by ~30% compared to the as-prepared (non-bended) cell. © 2013 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg. Source

Chung D.Y.,Korea Basic Science Institute | Chung D.Y.,Seoul National University | Park S.-K.,Korea Advanced Institute of Science and Technology | Chung Y.-H.,Korea Institute of Science and Technology | And 11 more authors.
Nanoscale | Year: 2014

Edge-exposed MoS2 nano-assembled structures are designed for high hydrogen evolution reaction activity and long term stability. The number of sulfur edge sites of nano-assembled spheres and sheets is confirmed by Raman spectroscopy and EXAFS analysis. By controlling the MoS2 morphology with the formation of nano-assembled spheres with the assembly of small-size fragments of MoS2, the resulting assembled spheres have high electrocatalytic HER activity and high thermodynamic stability. © 2014 The Royal Society of Chemistry. Source

Lee E.,Korea Advanced Institute of Science and Technology | Ko J.,Korea Advanced Institute of Science and Technology | Lim K.-H.,Korea Advanced Institute of Science and Technology | Kim K.,Korea Advanced Institute of Science and Technology | And 4 more authors.
Advanced Functional Materials | Year: 2014

Solution-processed oxide semiconductors (OSs) used as channel layer have been presented as a solution to the demand for flexible, cheap, and transparent thin-film transistors (TFTs). In order to produce high-performance and long-sustainable portable devices with the solution-processed OS TFTs, the low-operational voltage driving current is a key issue. Experimentally, increasing the gate-insulator capacitances by high-k dielectrics in the OS TFTs has significantly improved the field-effect mobility of the OS TFTs. But, methodical examinations of how the field-effect mobility depends on gate capacitance have not been presented yet. Here, a systematic analysis of the field-effect mobility on the gate capacitances in the solution-processed OS TFTs is presented, where the multiple-trapping-and-release and hopping percolation mechanism are used to describe the electrical conductivity of the nanocrystalline and amorphous OSs, respectively. An intuitive single-piece expression showing how the field-effect mobility depends on gate capacitance is developed based on the aforementioned mechanisms. The field-effect mobility, depending on the gate capacitances, of the fabricated ZnO and ZnSnO TFTs clearly follows the theoretical prediction. In addition, the way in which the gate insulator properties (e.g., gate capacitance or dielectric constant) affect the field-effect mobility maximum in the nanocrystalline ZnO and amorphous ZnSnO TFTs are investigated. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Kim B.,Seoul National University | Fujioka S.,RIKEN | Kwon M.,Seoul National University | Jeon J.,Seoul National University | And 2 more authors.
Plant Cell Reports | Year: 2013

Key message: Arabidopsis gulliver3 - D/dwarf4 - D displays growth-promoting phenotypes due to activation tagging of a key brassinosteroid biosynthetic gene DWARF4. In gul3-D/dwf4-D, the Jasmonate and Salicylate signaling pathways were relatively activated and suppressed, respectively. Energy allocation between growth and defense is elegantly balanced to achieve optimal development in plants. Brassinosteroids (BRs), steroidal hormones essential for plant growth, are regulated by other plant hormones, including auxin and jasmonates (JA); auxin stimulates the expression of a key brassinosteroid (BR) biosynthetic gene, DWARF4 (DWF4), whereas JA represses it. To better understand the interaction mechanisms between growth and defense, we isolated a fast-growing mutant, gulliver3-D (gul3-D), that resulted from the activation tagging of DWF4, and examined the response of this mutant to defense signals, including JA, Pseudomonas syringae pv. tomato (Pst DC3000) infection, and wounding. The degree of root growth inhibition following MeJA treatment was significantly decreased in gul3-1D/dwf4-5D relative to the wild type, suggesting that JA signaling is partially desensitized in gul3-1D. Quantitative RT-PCR analysis of the genes involved in JA and salicylic acid (SA) responses, including MYC2, PDF1.2, CORI3, PR1, and PR2, revealed that JA signaling was preferentially activated in gul3-1D, whereas SA signaling was suppressed. As a result, gul3-1D was more susceptible to a biotrophic pathogen, Pst DC3000. Based on our results, we propose a model in which BR and JA cooperate to balance energy allocation between growth and defense responses. In ambient conditions, BRs promote plant growth; however, when stresses trigger JA signaling, JA compromises BR signaling by downregulating DWF4 expression. © 2013 Springer-Verlag Berlin Heidelberg. Source

Kim K.,Korea Advanced Institute of Science and Technology | Lee E.,Korea Advanced Institute of Science and Technology | Kim J.,Korea Advanced Institute of Science and Technology | Park S.Y.,Korea Advanced Institute of Science and Technology | And 4 more authors.
Journal of Materials Chemistry C | Year: 2013

Flexible and transparent thin film transistors (FTTFTs) can lead to next generation displays that involve large area, future-oriented flexible and transparent displays. In order to achieve stable FTTFTs, solution processes of organic and inorganic compounds have received significant attention. Above all, transparent oxide semiconductors such as ZnO have been studied to enhance flexibility with high electrical performance by integration with organic dielectrics. However, interfacial traps between inorganic and organic compounds are derived by interface dipole, which induce a considerable flat band shift. Herein, we have developed a self-assembled inorganic layer (SAIL) via the photo-induced transformation of a mono-poly(dimethylsiloxane) (PDMS) layer as interface engineering. Especially, the shifting of flat band voltage (V FB) was effectively suppressed by the SAIL process, which was analyzed with a single-piece analytical model for ZnO TFTs. In addition, flexible ZnO/SAIL/polymer dielectric TFTs with low process temperature as high as 200 °C exhibited a good field-effect mobility μ = 0.28 cm2 V-1 s-1, more than 106 on-off current ratio and excellent device operational stability and flexibility. © 2013 The Royal Society of Chemistry. Source

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