• Title, Summary, Keyword: Surface potential

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Surface Potential Change Depending on Molecular Orientation of Hexadecanethiol Self-Assembled Monolayers on Au(111)

  • Ito, Eisuke;Arai, Takayuki;Hara, Masahiko;Noh, Jaegeun
    • Bulletin of the Korean Chemical Society
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    • v.30 no.6
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    • pp.1309-1312
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    • 2009
  • Surface potential and growth processes of hexadecanethiol (HDT) self-assembled monolayers (SAMs) on Au(111) surfaces were examined by Kelvin probe method and scanning tunneling microscopy. It was found that surface potential strongly depends on surface structure of HDT SAMs. The surface potential shift for the striped phase of HDT SAMs chemisorbed on Au(111) surface was +0.45 eV, which was nearly the same as that of the flat-lying hexadecane layer physisorbed on Au(111) surface. This result indicates that the interfacial dipole layer induced by adsorption of alkyl chains is a main contributor to the surface potential change. In the densely-packed HDT monolayer, further change of the surface potential was observed, suggesting that the dipole moment of the alkanethiol molecules is an origin of the surface potential change. These results indicate that the work function of a metal electrode can be modified by controlling the molecular orientation of an adsorbed molecule.

Probing of Surface Potential Using Atomic Force Microscopy

  • Kwon, Owoong;Kim, Yunseok
    • Applied Microscopy
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    • v.44 no.3
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    • pp.100-104
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    • 2014
  • As decreasing device size, probing of nanoscale surface properties becomes more significant. In particular, nanoscale probing of surface potential has paid much attention for understanding various surface phenomena. In this article, we review different atomic force microscopy techniques, including electrostatic force microscopy and Kelvin probe force microscopy, for measuring surface potential at the nanoscale. The review could provide fundamental information on the probing method of surface potential using atomic force microscopy.

A Cohesive Surface Separation Potential

  • Lee, Youngseog;Kim, Kwang-Soo
    • Journal of Mechanical Science and Technology
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    • v.16 no.11
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    • pp.1435-1439
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    • 2002
  • This paper presents a form of the cohesive surface separation potential, which can produce potential curves by varying a single dimensionless parameter. Results show that a partial modification of Xu and Needleman's (1994) cohesive surface separation potential makes it possible to present the other potential corves as a special case as long as the normal separation is concerned. The proposed potential may describe interfacial debonding-crack initiation and growth-character of materials and, through numerical simulation, provide an insight for the effect of different cohesive surface separation potentials on the interfacial debonding.

Measurements and methods for analyzing zeta potential of the external surface of hollow fiber membranes (중공사막 외부표면의 제타전위 측정방법 고찰)

  • Lee, Taeseop;Lee, Sangyoup;Lee, Joohee;Hong, Seungkwan
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.3
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    • pp.353-362
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    • 2009
  • A new method and equipment for measuring the zeta potential of the external surface of hollow fiber (HF) membranes is reported. An existing commercial streaming potential analyzer in conjunction with home-made test cells was used to determine the electrokinetic surface characteristics of various HF membranes. It was shown that measurements of the external surface of HF membrane using the home-made test cells designed in this study were easy and reliable. The zeta potential values were quite accurate and reproducible. By varying the physical shape of the test cells to adjust hydrodynamics inside the test cells, several upgrade versions of home-made test cells were obtained. It was shown that the zeta potential of the external surface of HF membranes was most influenced by membrane materials as well as the way of surface modification. However, the overall surface charge of tested HF membranes were much less than that of commercial polyamide thin-film-composite (TFC) reverse osmosis (RO) membranes due to the lack of surface functional groups. For the HF membranes with the same material, the effect of pore size on the zeta potential was not significant, implying the potential of accurate zeta potential measurements for various HF membranes. The results obtained in this study are expected to be useful for better understating of electrokinetic surface characteristics of the external surface of HF membranes.

Activity Coefficients and Coulombic Correction Factor for Surface Complexation Modeling

  • Rhee, In-Hyoung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.3 no.2
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    • pp.146-155
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    • 2002
  • Surface complexation models employ mass law equations to describe the reaction of surface functional groups with ions in the solution and also Gouy-Chapman theory to consider the electrostatic effects in the surface reactions. In current surface complexation models, however, the coulombic factors used are not wholly consistent with the Gouy-Chapman model of the surface. This study was to provide the derivation of the coulombic term usually employed and then a revised coulombic term completely consistent with Gouy-Chapman Theory. The electrical potential energy. zF${\psi}$, in current surface complexation models is not consistent with the Gouy-Chapman theory with the potential gradient close to the charged surface but with the Donnan model with the uniform potential. Even though the new coulombic factor yielded lower surface potential, it provided worse fits for acid-base titration data of the goethite suspensions.

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Analysis of the Ground Surface Potential Rise using a Hemisphere-Shaped Test Model (반구형 실험모델을 이용한 대지표면 전위상승의 분석)

  • Yoo, Jae-Duk;Cho, Yong-Seung;Lee, Bok-Hee
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.12
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    • pp.208-213
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    • 2010
  • This paper deal with an analysis of the ground surface potential profiles using a hemispherical scaled-model. Because it is very difficult to draw valid conclusions concerning a general grounding problem from actual field data, scale model tests can be used to determine the ground surface potential profile around the grounding electrodes according to the configuration of grounding electrodes. In this work, a hemispherical vessel with a diameter of 1,100 [mm] was employed to simulate uniform soil and CDEGS program was employed to compare the measured and simulated results. As a result, the ground surface potential around the grounding electrode was significantly raised and the ground surface potential at the just upper point of ground electrode particularly was higher than other points. The ground surface potential of counterpoise was higher than other grounding electrodes such as mesh and grounding rods and the ground surface potential strongly depends on the frequency responses of grounding electrodes. Also the results measured with the small-sized model were in reasonably agreement with the data obtained from simulation.

Zeta-potential Measurement on Glass Surface by Measuring Electro-osmotic Velocity inside a Micro-channel (마이크로 채널 내부 전기삼투 유속 측정을 통한 유리표면의 Zeta-potential 측정)

  • Han, Su-Dong;Lee, Sang-Joon
    • 한국가시화정보학회:학술대회논문집
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    • pp.80-84
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    • 2005
  • Many important properties in colloidal systems are usually determined by surface charge ($\zeta$-potential) of the contacted solid surface. In this study, $\zeta$-potential of glass $\mu$-channel was evaluated from the electro-osmotic velocity distribution. The electro-osmotic velocity inside a glass $\mu$-channel was measured using a micro-PIV velocity field measurement technique. This evaluation method is more simple and easy to approach, compared with the traditional streaming potential technique. The $\zeta$-potential in the glass $\mu$-channel was measured for two different mole NaCl solutions. The effect of an anion surfactant, sodium dodecyl sulphate (SDS), on the electro-osmotic velocity and $\zeta$-potential in the glass surface was also studied. In the range of $0\∼6$mM, the surfactant SDS was added to NaCl solution in four different mole concentrations. As a result, the addition of SDS increases $\zeta$-potential in the surface of the glass $\mu$-channel. The measured $\zeta$-potential was found to vary from-260 to-70mV. When negatively charged particles were used, the flow direction was opposite compared with that of neutral particles. The $\zeta$-potential has a positive sign for the negative particles.

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Motion Planning for Mobile Robots Using a Spline Surface

  • Kato, Kiyotaka;Tanaka, Jyunichi;Tokunaga, Hironori
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1054-1059
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    • 2005
  • The artificial potential method uses a potential field to guide a robot from a start to a goal configuration respectively. The potential field consists of attractive potential used to pull a robot toward a goal and repulsive potential to keep it away from obstacles. However, there are two problems concerning local minimum and computational cost to be resolved in conventional artificial potential methods. This study proposes a method utilizing a spline surface that interpolates arbitrary boundaries and a domain reduction method that reduces the unnecessary area. The proposed spline surface interpolates arbitrary shaped boundaries and is used as an artificial potential to guide a robot for global motion planning of a mobile robot. A reduced domain process reduces the unnecessary domain. We apply a distance-weighted function as such a function, which blends distances from each boundary with a reduction in computational time compared with other analytical methods. As a result, this paper shows that an arbitrary boundary spline surface provides global planning and a domain reduction method reduces local minimum with quick operation.

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Ground Surface Potential Distribution near Ground Rod Associated with Soil Structures (대지구조에 따른 접지봉 주번의 대지표면전위분포)

  • Lee, Bok-Hee;Jung, Hyun-Uk;Baek, Young-Hwan
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.21 no.1
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    • pp.142-147
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    • 2007
  • This paper presents the distributions of ground surface potential rises as functions of soil structure and buried depth of ground rod. To propose fundamental data relevant to the reduction of electric shock of human beings due to ground surface rise, the ground surface potential rises near the ground rod were computed and measured. Ground surface potential rises near ground rod strongly depend on the soil structure, and an increase of the buried depth of ground rod results in a decrease of the ground surface potentials. The maximum ground surface potential appeared at the just above point of ground rod. Also, the measured results were in reasonably agreement with the data computered by grounding analysis program.

Potential Energy Surface from Spectroscopic Data in the Photodissociation of Polyatomic Molecules

  • Kim, Hwa Jung;Kim, Yeong Sik
    • Bulletin of the Korean Chemical Society
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    • v.22 no.5
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    • pp.455-462
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    • 2001
  • The time-dependent tracking inversion method is studied to extract the potential energy surface of the electronic excited state in the photodissociation of triatomic molecules. Based on the relay of the regularized inversion procedure and time-dependent wave packet propagation, the algorithm extracts the underlying potential energy surface piece by piece by tracking the time-dependent data, which can be synthesized from Raman excitation profiles. We have demonstrated the algorithm to extract the potential energy surface of electronic excited state for NO2 molecule where the wave packet split on a saddle-shaped surface. Finally, we describe the merits of the time-dependent tracking inversion method compared with the time-independent inversion method and discussed several extensions of the algorithm.

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