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Dynamics and stability of divacancy defects in graphene

Physical Review B 2011年第7期84卷 075445-075445页

作者： Youngkuk Kim Jisoon Ihm Euijoon Yoon Gun-Do Lee Department of Physics and Astronomy Seoul National University Seoul 151-747 Republic of Korea Department of Materials Science and Engineering Seoul National University Seoul 151-742 Republic of Korea Department of Nano Science and Technology Graduate School of Convergence Science and Technology Seoul National University Suwon 433-270 Republic of Korea Department of Materials Science and Engineering WCU Hybrid Materials Program Seoul National University Seoul 151-742 Republic of Korea Energy Semiconductor Research Center Advanced Institutes of Convergence Technology Seoul National University Suwon 443-270 Korea

A divacancy (DV) is one of the most abundant and most important defects in irradiated graphene, which modifies electronic and chemical properties of graphene. In this paper, we present ab initio calculations to study the dynamics and stability of DVs in graphene. Divacancies in graphene have various reconstructed structures, such as triple pentagon-triple heptagon (555-777) and pentagon-octagon-pentagon (5-8-5) patterns. A direct observation of the structural transformations between these reconstructions was recorded in transmission electron microscope images reported by Girit et al. in science 323, 1705 (2009). We clarify the atomic structures of DVs observed in the experiment and investigate the atomic processes and energetics for the observed dynamical motions in great detail. It is found that a series of Stone–Wales-type transformations are responsible for the migration and structural transformations of DVs and that a pentagon-heptagon-heptagon-pentagon (5-7-7-5) defect appearing as an intermediate structure during the dynamical process plays an important role in the transformations of DVs.

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Encapsulation of Curcumin Loaded Oil Droplets By Cryotropic Gel Formation from O/W Emulsion

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Procedia Food science 2011年 1卷 1973-1979页

作者： Kyuya Nakagawa Nataporn Sowasod Tawatchai Charinpanitkul Apinan Soottitantawat Wiwut Tanthapanichakoon Research Centre for Nano-Micro Science and Engineering University of Hyogo 2167 Shosha Himeji 671-2280 Japan Nanoscience and Technology Program Graduate School Chulalongkorn University Patumwan Bangkok 10330 Thailand Center of Excellence in Particle Technology Chulalongkorn University Patumwan Bangkok 10330 Thailand

Cryogel based encapsulation was attempted to entrap oil phase (containing curcumin) with a ternary system of colloidal chitosan, κ-carrageenan, and carboxy methylcellulose sodium salt (NaCMC). The cryotropic gel formation was investigated by varying the cooling rate during freezing and type of polymer suspension. The microstructure of the resulting curcumin cryogels revealed oil droplets entrapped in the cryogel matrix. The encapsulation yield for two types of suspension was found to vary from 83.89 to 99.37%. Controlled release of the curcumin in an aqueous system could be maintained for 4 days, and the released amount of curcumin was found to vary from 41.1-59.9%. The encapsulation yield as well as the released pattern and amount of curcumin were influenced by the cooling protocol used during freezing. The release patterns were found to be sensitive to the ambient aqueous pH and, interestingly, either a burst release or a first order release was achievable simply by changing the freezing condition. These results suggested that freezing could modify the gel formation of the present cryogel, and the resulting structural modification evidently controlled the oil encapsulation manner. The present ternary system (chitosan, κ- carrageenan, and NaCMC) is an interesting matrix for designing controlled release system in a food system.

关键词： cryogel curcumin chitosan carrageenan carboxymethylcellulose freezing

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Quantum Dots: Ultrasensitive, Biocompatible, Quantum‐Dot‐Embedded Silica nanoparticles for Bioimaging (Adv. Funct. Mater. 9/2012)

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Advanced Functional Materials 2012年第9期22卷

作者： Bong‐Hyun Jun Do Won Hwang Heung Su Jung Jaeho Jang Hyunsoo Kim Homan Kang Taegyu Kang San Kyeong Hyeokjae Lee Dae Hong Jeong Keon Wook Kang Hyewon Youn Dong Soo Lee Yoon‐Sik Lee School of Chemical and Biological Engineering Seoul National University Seoul 151‐747 Korea Department of Nuclear Medicine Seoul National University College of Medicine Seoul 110‐744 Korea Institute of Radiation Medicine Medical Research Center Seoul 110‐744 Korea Nanosquare Inc. ENG BLD39‐122 Seoul National University Seoul 151‐747 Korea WCU Department of Molecular Medicine and Biopharmaceutical Sciences Graduate School of Convergence Science and Technology Seoul National University Seoul 151‐747 Korea Nano Systems Institute and Interdisciplinary Program in Nano‐Science and Technology Seoul National University Seoul 151‐747 Korea Department of Chemistry Education Seoul National University Seoul 151‐747 Korea Cancer Imaging Center Seoul National University Cancer Hospital Cancer Research Institute Seoul National University College of Medicine Seoul 110‐799 Korea

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Continuous surface potential versus voltage equation of intrinsic surrounding-gate MOSFETs and analytic solution from accumulation to strong inversion region

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Journal of Semiconductors 2010年第6期31卷 27-33页

作者：何进郑睿张立宁张健林信南陈文新 Department of Electronics and Computer Engineering Hong Kong University of Science & Technology Micro & Nano Electric Device and Integrated Technology Group Key Laboratory of Integrated MicrosystemsPeking UniversityShenzhen Graduate School Micro & Nano Electric Device and Integrated Technology Group Key Laboratory of Integrated Microsystems Peking UniversityShenzhen Graduate School

A continuous surface potential versus voltage equation is proposed and then its solution is further discussed for a long channel intrinsic surrounding-gate（SRG） MOSFET from the accumulation to strong inversion *** original equation is derived from the exact solution of a simplified Poisson equation and then the empirical correction is performed from the mathematical condition required by the continuity of the solution,which results in a continuous surface potential versus voltage equation,allowing the surface potential and the related derivatives to be described by an analytic solution from the accumulation to strong inversion region and from linear to the saturation region accurately and *** these results,the dependences of surface potential and centric potential characteristics on device geometry are analyzed and the results are also verified with the 3-D numerical simulation from the aspect of accuracy and continuity tests.

关键词： non-classical CMOS surrounding-gate MOSFETs device physics surface potential accuracy continuity issue

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An oxide/silicon core/shell nanowire metal-oxide semiconductor field-effect transistor

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Chinese Physics B 2010年第4期19卷 398-401页

作者：张立宁何进周旺陈林徐艺文 Tera-Scale Research Centre Key Laboratory of Microelectronic Devices and Circuits of Ministry of EducationSchool of Electronics Engineering and Computer SciencePeking University Research Centre of Micro-& Nano-Device and Technology The Key Laboratory of Integrated MicrosystemsPeking University Shenzhen Graduate School

This paper studies an oxide/silicon core/shell nanowire MOSFET （OS-CSNM）. Through three-dimensional device simulations, we have demonstrated that the OS-CSNM has a lower leakage current and higher Ion/Ioff ratio after intro- ducing the oxide core into a traditional nanowire MOSFET （TNM）. The oxide/silicon OS-CSNM structure suppresses threshold voltage roll-off, drain induced barrier lowering and subthreshold swing degradation. Smaller intrinsic device delay is also observed in OS-CSNM in comparison with that of TNM.

关键词： core/shell nanowire nanowire MOSFET

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Front Cover: Catalyst-free growth of InN nanorods by metal-organic chemical vapor deposition (Phys. Status Solidi A 1/2012)

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physica status solidi (a) 2011年第1期209卷

作者： Min Hwa Kim Dae Young Moon Jinsub Park Yasushi Nanishi Gyu-Chul Yi Euijoon Yoon Hybrid Materials Program (WCU) Department of Materials Science and Engineering Seoul National University Seoul 151-744 Korea Department of Electronic Engineering Hanyang University Seoul 133-791 Korea Department of Photonics Ritsumeikan University Shiga 525-8577 Japan National Creative Research Initiative Center for Semiconductor Nanorods Department of Physics and Astronomy Seoul National University Seoul 151-747 Korea Euijoon Yoon Phone: +82 2 880 2651 Fax: +82 2 6008 3712 Department of Nano Science and Technology Graduate School of Convergence Science and Technology Seoul National University Suwon 443-270 Korea Energy Semiconductor Research Center Advanced Institute of Convergence Technology Seoul National University Suwon 443-270 Korea Gyu-Chul Yi Phone: +82 2 880 7169 Fax: +82 2 884 3002

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Hydrogen sensors based on zinc oxide nanoparticles

Hydrogen sensors based on zinc oxide nanoparticles

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IEEE International Conference on nano/Micro Engineered and Molecular Systems

作者： Samerjai, Thanittha Liewhiran, Chaikarn Wisitsoraat, Anurat Phanichphant, Sukon Nanoscience and Nanotechnology Program Graduate School Chiang Mai University Chiang Mai Thailand Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai Thailand National Electronics and Computer Technology Center 112 Pahol Yothin Rd Pathumthani Thailand NANOTEC Center of Excellence Chiang Mai University Chiang Mai Thailand

ISBN: (纸本)9781424465439

Pure ZnO, pure MgO and 5 wt%MgO/ZnO nanocomposites were produced by flame spray pyrolysis (FSP) in a single step using zinc naphthenate and magnesium acetate tetrahydrate as Zn and Mg precursors. The particle properties were analyzed by XRD, BET and TEM analyses. The sensing films were prepared by mixing the nanoparticles into an organic paste composed of ethyl cellulose and terpineol as a vehicle binder and solvent, respectively. The resulting paste was spin-coated on Al2O3 substrates interdigitated Au electrodes. The gas sensing of H2 concentration ranging from 0.5-1 vol% was studied at 300oC in dry air. The 5 wt% MgO/ZnO nanocomposites film showed higher sensitivity. The sensitivity increased and the response time decreased with increasing H2 concentrations. ©2010 IEEE.

关键词： Zinc oxide

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Reconstruction and evaporation at graphene nanoribbon edges

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Physical Review B 2010年第19期81卷 195419-195419页

作者： Gun-Do Lee C. Z. Wang Euijoon Yoon Nong-Moon Hwang K. M. Ho Department of Materials Science and Engineering Seoul National University Seoul 151-742 Korea Ames Laboratory and Department of Physics and Astronomy Iowa State University Ames Iowa 50011 USA Department of Nano Science and Technology Graduate School of Convergence Science and Technology Seoul National University Suwon 433-270 Korea WCU Hybrid Materials Program Department of Materials Science and Engineering Seoul National University Seoul 151-742 Korea National Research Laboratory of Charged Nanoparticles Seoul National University Seoul 151-742 Korea

The reconstruction and evaporation at graphene nanoribbon (GNR) edges are investigated by tight-binding molecular-dynamics simulations and ab initio calculations. It is observed that reconstruction through the formation of pentagon-heptagon pairs can take place quickly along the zigzag edge and it is energetically favorable. At very high temperatures, the armchair edge is found to change into a zigzag edge structure, which further accelerates the evaporation of carbon atoms and leads to the formation of carbon linear chains. The evaporation of carbon atoms from both the zigzag and armchair edges is preceded by the formation of heptagon rings, which serve as a gateway for carbon atoms to escape. In the simulation for a GNR armchair-zigzag-armchair junction, carbon atoms are evaporated row by row from the outermost row of the zigzag edge while the armchair edge remains nearly intact. These results can be applied to nanoelectronic devices fabrication through the temperature-controlled edge structure of GNR.

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Single-wall carbon nanotube modified glassy carbon electrode for electroanalytical determination of dopamine

Single-wall carbon nanotube modified glassy carbon electrode...

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IEEE International Conference on nano/Micro Engineered and Molecular Systems

作者： Chuekachang, Sopis Kruefu, Viruntachar Chaiyasit, Suwan Phanichphant, Sukon Department of Chemistry Faculty of Science Chiang Mai University Chiang Mai Thailand Nanosciences and Nanotechnology Program Graduate School Chiang Mai University Chiang Mai Thailand Department of Chemistry Faculty of Science King Mongkut's Institute of Technology Ladkrabang Chalongkrung Ladkrabang Bangkok Thailand NANOTEC Center of Excellence Chiang Mai University Chiang Mai 50200 Thailand

ISBN: (纸本)9781424465439

In this research, a glassy carbon electrode modified with single-wall carbon nanotubes for electrochemical determination of dopamine was studied by cyclicvoltammetry (CV) and differential pulse voltammetry (DPV). The oxidation and reduction potentials of dopamine using voltammetric technique were measured. The SWCNTs/GC 10 μL was used to test the linearity of anodic oxidation of dopamine by DPV. The peak current increased linearly with concentration of dopamine in the range of 2.5-25 ppm (R2=0.9766).For the life time of the SWCNTs/GC, the cut-off criterion of the DPV was detected in the reduction of current by 50 %. The lifetime of the SWCNTsmodified depended on the oxidation of dopamine because of fouling of the electrode surface due to the adsorption of oxidation products. 34 repetition cycles was obtained. The detection limit of the dopamine as obtained from the oxidation current in DPV was 0.021 ppm (S/N=3) with minimum current for the detection of dopamine of 0.033 μA. The reproducibility of electrocatalytical studies was better within 90% (10% RSD). The relative standard deviation (RSD) of 8.42% for 100 ppm dopamine (n=20) showed excellent reproducibility. Drug samples obtained from Radvitee hospital were tested as the mentioned procedure. The percentage recovery of dopamine in drug samples was 120. ©2010 IEEE.

关键词： Anodic oxidation

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Thin‐Film Formation of Imidazolium‐Based Conjugated Polydiacetylenes and Their Application for Sensing Anionic Surfactants†

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Angewandte Chemie 2010年第8期122卷

作者： Xiaoqiang Chen Sunwoo Kang Min Jung Kim Joohee Kim Youn Sang Kim Heejin Kim Bo Chi Sung‐Jin Kim Jin Yong Lee Juyoung Yoon Department of Chemistry and Nano Science Ewha Womans University Seoul 120‐750 (Korea) Fax: (+82) 2‐3277‐3419 Department of Chemistry Sungkyunkwan University Suwon 440‐746 (Korea) Fax: (+82) 31‐290‐7075 Department of Nano Science and Technology Graduate School of Convergence Science and Technology Seoul National University Seoul 443‐72 (Korea) Department of Bioinspired Science Ewha Womans University Seoul 120‐750 (Korea)

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