• Title/Summary/Keyword: Scanning electrochemical microscopy

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Self-Assembled Monolayers of Dioctyl Diselenides on Au(111)

  • Choi, Jung-Seok;Lee, Yoon-Jung;Kang, Hun-Gu;Han, Jin-Wook;Noh, Jae-Geun
    • Bulletin of the Korean Chemical Society
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    • v.29 no.6
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    • pp.1229-1232
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    • 2008
  • The surface structure, electrochemical behavior, and wetting property of self-assembled monolayers (SAMs) formed by dioctyl diselenide (DODSe) on Au(111) were investigated by scanning tunneling microscopy (STM), cyclic voltammetry (CV), and contact angle measurements. In contrast to the formation of well-ordered SAMs by octanethiol on Au(111), the SAMs formed by DODSe have a disordered phase and many unusual vacancy islands (VIs). In addition, the formation of DODSe SAMs is largely influenced by the solution concentration used. DODSe SAMs formed in 5 $\mu$ M and 50 $\mu$ M solutions have two mixed domains consisting of missing-row ordered phases and disordered phases, while DODSe SAMs formed in 1 mM and 5 mM solutions have only disordered phases with an abnormally high VI fraction of 22-24%. We also found that the wetting property and electrochemical behavior of DODSe SAMs on Au(111) are markedly influenced by the formation of ordered SAMs and the density of VIs.

Comparison of Roughnesses of Polycrystalline Gold Electrode Calculated from STM Images, Oxygen Adsorption-Desorption and Adsorption of N-Docosyl-N'-methyl Viologen (STM 이미지와 산소 흡탈착 그리고 N-docosyl-N'-methyl viologen의 흡착으로부터 구한 다결정 금 전극 표면의 거칠기의 비교)

  • Lee Chi-Woo;Jang Jai-Man
    • Journal of the Korean Electrochemical Society
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    • v.3 no.2
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    • pp.104-108
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    • 2000
  • It is very important to know the real roughness of electrode surface in electrochemistry. But it is impossible to know absolute roughness of electrode surface for various reasons. In this work, we compared the roughnesses of polycrystalline gold electrode often used in electrochemistry calculated from the images of scanning tunneling microscopy (STM) and cyclic voltammetry with those of Au (111) and HOPG. The roughness of polycrystalline gold calculated from STM image was $1.1(\pm0.1)$, that from adsorption-desorption of oxygen was $2.4(\pm0.7)$ and that from adsorption of N-docosyl-N'-methyl viologen was $1.6(\pm0.1)$.

Comparative Study of Undoped and Nickel-Doped Molybdenum Oxide Photoanodes for PEC Water Splitting

  • Garcia-Garcia, Matias
    • Journal of Electrochemical Science and Technology
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    • v.13 no.3
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    • pp.377-389
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    • 2022
  • The current global energy supply depends heavily on fossil fuels. This makes technology such as direct water splitting from harvesting solar energy in photoelectrochemical (PEC) systems potentially attractive due to its a promising route for environmentally benign hydrogen production. In this study, undoped and nickel-doped molybdenum oxide photoanodes (called photoanodes S1 and S2 respectively) were synthesized through electrodeposition by applying -1.377 V vs Ag/AgCl (3 M KCl) for 3 hours on an FTO-coated glass substrate immersed in molibdatecitrate aqueous solutions at pH 9. Scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used for microstructural and compositional characterizations of the photoanodes. In addition, the optical and photoelectrochemical characterizations of these photoanodes were performed by UV-Visible spectroscopy, and linear scanning voltammetry (LSV) respectively. The results showed that all the photoanodes produced exhibit conductivity and catalytic properties that make them attractive for water splitting application in a photoelectrochemical cell. In this context, the photoanode S2 exhibited better photocatalytic activity than the photoanode S1. In addition, photoanode S2 had the lowest optical band-gap energy value (2.58 eV), which would allow better utilization of the solar spectrum.

Study on the Fabrication of Ultrathin Punch (초미세 천공 펀치의 성형에 대한 연구)

  • Im, Hyeong-Jun;Im, Yeong-Mo;Kim, Su-Hyeon;Gwak, Yun-Geun
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.12
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    • pp.145-150
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    • 2000
  • Micro punching is one of general methods to fabricate simple holes such as permanent ink-jet printer nozzles. A thin punch, that is need for micro punching, usually has been obtained by mechanical machining. There are some method to obtain a thin punch from a cylindrical rod, e.g., microgrinding and WEDG (Wire Electro-Discharge Grinding). Inefficiently, only one punch can be obtained from these machining methods. In contrast with these methods, many punches can be fabricated simultaneously by electrochemical process. Electrochemical process has usually aimed to obtain very sharp probe for atomic force microscopy (AFM) or scanning tunneling microscopy (STM), and it has not been considered the whole shape of a probe in spite of good merits. In this paper, an ultrathin punch with a tapered shape and a cylindrical tip is newly fabricated by electrochemical process.

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Fundamentals and Applications of Multi-functional NSOM Technology to Characterization of Nano Structured Materials (다기능 NSOM (mf-NSOM) 을 이용한 나노 구조 재료 분석에 관한 원리와 응용)

  • Lee Woo-Jin;Pyun Su-Il;Smyrl W. H.
    • Journal of the Korean Electrochemical Society
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    • v.7 no.2
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    • pp.108-123
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    • 2004
  • Imaging of surfaces and structures by near-field scanning optical microscopy (NSOM) has matured and is routinely used for studies ranging from biology to materials science. Of interest in this review paper is a versatility of modified or multi-functional NSOM (mf-NSOM) to enable high resolution imaging in several modes: (1) Concurrent fluorescence and Topographical Imaging (gases) (2) Microspectroscopy (gases) (3) Concurrent Scanning Electrochemical and Topographical Imaging (SECM) (liquids) (4) Concurrent Photoelectrochemical and Topographical Imaging (PEM) (liquids) The present study will summarize some of the recent advances in mf-NSOM work confirmed and supported by the results from several other imaging techniques of optical, fluorescence, electron and electrochemical microscopy. The studies are directed at providing local information on pitting precursor sites and vulnerable areas on metal and semiconductor surfaces, and at reactive sites on heterogeneous, catalytic substrates, especially on Al 2024 alloy and polycrystalline Ti. In addition, we will introduce some results related to the laser-induced nanometal (Ag) synthesis using mf-NSOM.

Size-Controlled Cu2O Nanocubes by Pulse Electrodeposition

  • Song, You-Jung;Han, Sang-Beom;Lee, Hyun-Hwi;Park, Kyung-Won
    • Journal of the Korean Electrochemical Society
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    • v.13 no.1
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    • pp.40-44
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    • 2010
  • In this work, highly uniform size-controlled $Cu_2O$ nanocubes can be successfully formed by means of pulse electrodeposition. The size distribution, crystal structure, and chemical state of deposited $Cu_2O$ nanocubes are characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The phase transition from $Cu_2O$ to Cu can be controlled by constant current electrodeposition as a function of deposition time. In particular, the size of the $Cu_2O$ nanocubes can be controlled using pulse electrodeposition as a function of applied current density.

Electrochemical Signal Amplification by Redox Cycling in Distance-Controlled Nanogap Devices

  • Park, Dae Keun;Park, Jong Mo;Shin, Jong-Hwan;Yun, Wan Soo
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.269-269
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    • 2013
  • Redox cycling in between the two working electrodes in an electrochemical cell can lead a great signal enhancement. In this work, we report on a systematic examination of current amplification along with the decrease in the gap distance of a nanogap device which was fabricated by the combination of photo and chemical lithography [1]. The gap distance was controlled by the chemical lithographic process of surfacecatalyzed growth of metallic layer on pre-defined electrodes with wider initial gap. Enhancement of the redox current of ferri/ferrocyanide was observed upon gap distance reduction and the current is amplified about a thousand times in this redox system when the gap distance was decreased from 200 nm to 30 nm. The experimental results were discussed on the basis of the cyclic voltammetry (CV), atomic force microscopy (AFM) and scanning electron microscopy (SEM).

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Use of Modern Non­destructive Techniques in High Temperature Degradation of Material and Coatings

  • Lee, C.K.;Sohn, Y.H.
    • International Journal of Korean Welding Society
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    • v.3 no.2
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    • pp.29-39
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    • 2003
  • The durability and reliability of thermal barrier coatings (TBCs) play an important role in the service reliability, availability and maintainability (RAM) of hot­section components in advanced turbine engines for aero and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary non­destructive evaluation (NDE) techniques for quality control and life­remain assessment of TBCs. This paper overviews the governing principles and applications of the luminescence and the impedance examined in the light of residual stress, phase constituents and resistance (or capacitance) in TBC constituents including the thermally grown oxide (TGO) scale. Results from NDE by PSLS and EIS are discussed and related to the microstructural development during high temperature thermal cycling, examined by using a variety of microscopic techniques including focused ion beam (FIB) in­situ lift­out (INLO), transmission and scanning transmission electron microscopy (TEM and STEM).

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Role of chloride ions with Zwitterions and phosphate groups on the improvement of the passive film in alkaline environment (알칼리성 환경에서 부동태 피막 개선에 대한 양쪽성 이온 및 인산염 그룹을 갖는 염화물 이온의 역할)

  • Tran, Duc Thanh;Lee, Han-seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2022.04a
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    • pp.43-44
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    • 2022
  • In this study, the optimum amount of chloride ions is used to collaborate with hybrid corrosion inhibitor for carbon steel rebar treatment in simulated pore concrete (SCP) solution is discovered. The corrosion inhibition performance of hybrid inhibitors is carried on by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PP). The highest corrosion inhibition resistance is found in case of LP-C2 after 240 h exposure. Surface studies including scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to figure out the surface morphology of the steel rebar treated with hybrid inhibitors in order to collaborate well with electrochemical studies. Anodic type inhibition action was confirmed by potentiodynamic polarization study.

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Effect of Hybrid Inhibitor on the Mitigation of Corrosion Initiation in SCP Solution Contaminated 3.5 wt.% NaCl (3.5 wt.% NaCl로 오염된 SCP 용액의 부식 개시 완화에 대한 하이브리드 억제제의 효과)

  • Tran, Duc Thanh;Lee, Han-seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.65-66
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    • 2021
  • In this study, the optimum amount of hybrid inhibitors i.e. L-Arginine (LA) and sodium phosphate tribasic dodecahydrate (SP), applied for carbon steel rebar in simulated pore concrete (SCP) solution contaminated with 3.5 wt.% NaCl, was discovered. The corrosion inhibition performance of hybrid inhibitors was investigated by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization. The highest corrosion inhibition efficiency was found as 99.52% corresponding to 2% LA and 0.25% SP after 210 h exposure. Anodic type inhibition action was confirmed by potentiodynamic polarization study. Surface studies including scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to figure out the surface morphology of the steel rebar treated with hybrid inhibitors in order to collaborate with electrochemical studies.

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