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Atomic force microscopy (AFM) can image the surfaces of flat materials, irrespective of their conductivity. The sample is usually imaged in air, but can be in liquid environments and under vacuum, as described in other chapters (Chaps. 6, and 55). AFM has also been applied to the electrode/electrolyte interfaces, since its invention.

The electrochemical properties of chemically modified electrodes have long been a significant focus of research. Although the electronic states are directly related to the electrochemical properties, there have been only limited systematic efforts to reveal the electronic structures of adsorbed redox molecules with respect to the local environment of the redox center. In this study, density functional theory (DFT) calculations were performed for ferrocene-terminated self-assembled monolayers with different electron-donating abilities, which can be regarded as the simplest class of chemically modified electrodes. We revealed that the local electrostatic potentials, which are changed by the electron donating/withdrawing functional groups at the ferrocene moiety and the dipole field of coadsorbed inert molecules, practically determine the density of states derived from the highest occupied molecular orbital (HOMO) and its vicinities (HOMO−1 and HOMO−2) with respect to the electrode Fermi level. Therefore, to design new, sophisticated electrodes with chemical modification, one should consider not only the electronic properties of the constituent molecules, but also the local electrostatic potentials formed by these molecules and coadsorbed inert molecules.

Boron-doped diamond (BDD) has attracted much attention as a promising electrode material especially for electrochemical sensing systems, because it has excellent properties such as a wide potential window and low background current. It is known that the electrochemical properties of BDD electrodes are very sensitive to the surface termination such as to whether it is hydrogen- or oxygen-terminated. Pretreating BDD electrodes by cathodic reduction (CR) to hydrogenate the surface has been widely used to achieve high sensitivity. However, little is known about the effects of the CR treatment conditions on surface hydrogenation. In this Article, we report on a systematic study of CR treatments that can achieve effective surface hydrogenation. As a result, we found that the surface hydrogenation could be improved by applying a more negative potential in a lower pH solution. This is because hydrogen atoms generated from protons in the CR treatment contribute to the surface hydrogenation. After CR treatments, BDD surface could be hydrogenated not completely but sufficiently to achieve high sensitivity for electrochemical sensing. In addition, we confirmed that hydrogenation with high repeatability could be achieved.

A combined electrochemical and in situ frequency modulation atomic force microscopy (FM-AFM) study of phenalenyl derivatives, tetra tert-butyl derivatives of s-indacenodiphenalene (TTB-IDPL), adsorbed on a highly oriented pyrolytic graphite (HOPG) electrode was investigated. The cyclic voltammetry (CV) showed stable and adsorption-type redox peaks from TTB-IDPL at the double-layer region of the HOPG basal plane, but the peak became much more intense by adding the anodic potential. In situ FM-AFM images of the molecular film revealed the casted molecules formed aggregated islands on the HOPG surface at cathodic potentials. When anodic potentials were applied, the height of aggregates increased and finally became mobile on the surface. By stepping back to the cathodic potentials, the aggregates dispersed as isolated molecules that were invisible by AFM measurements. This morphology change resulted in the increase of the CV peak originated from TTB-IDPL. Reversible dispersion–aggregation processes depending on the electrode potential were imaged by FM-AFM. The size of aggregates at each potential indicates that the origin of the dispersion of aggregates could be the change of the interfacial free energy, which is dependent on the electrode potential. These AFM results aid in the correlation of the structure of the adsorbate layers with their electrochemical response.

Local analyses of ionic liquid/solid electrode interfaces at a controlled electrode potential are of fundamental importance to understanding the origin and properties of the electric double layer at the interfaces, which is necessary for their application to electrochemical devices. This account summarizes our recent achievements of such analyses by using the novel analytical tools of electrochemical frequency modulation AFM (EC-FM-AFM) and electrochemical photoemission spectroscopy (EC-PES). Rather stable stepped structures composed of layers of ion pairs and softer solvation layers outside of the imaged layer were clearly visualized by FM-AFM depending on the substrates. An extremely extended diffusion layer was directly observed by EC-PES during the electrodeposition of metal ion solutes.

The relationship between the oxidation potential determined by electrochemical measurements and the ionization energies measured by gas-phase ultraviolet photoelectron spectroscopy (UPS) has long been a focus of research of various groups. The focus of this study is to reveal such a correlation for redox molecules, which are chemically attached to metal electrodes. X-ray photoelectron spectroscopy, UPS, and cyclic voltammetry were performed for three types of ferrocene-terminated self-assembled monolayers possessing different electron-donating abilities. The results of these experiments indicate a linear relation with a slope of ∼0.7 between the UPS-derived energy of the highest occupied molecular orbital (HOMO) and the electrochemical oxidation potential. This indicates that the HOMO energy can be used to determine the oxidation potential of chemically modified electrodes.

Central to electrochemistry is the electric double layer (EDL) at the electrode-electrolyte interface where important interfacial phenomena including adsorption and charge transfer occur.1 Understanding the nature of the electric double layer regarding the electronic and structural characteristics has implications relating to bio(chemical) sensors, micro-mechanical actuators and energy storage/conversion devices. Amongst model systems, ferrocene-terminated alkanethiol self-assembled monolayers (Fc SAM) on Au are an attractive model electrochemical interface due to their practical applicability and versatility with structural modifications.2 Within the Fc SAM, a change in the ferrocene/ferrocenium (Fc/Fc+) redox state leads to notable changes to the interfacial structure with respect to the EDL, interactions with the electrolyte, and work function. While existing studies exist on probing the redox-induced Fc SAM structural changes using techniques such as surface plasmon resonance (SPR), Raman, IR and quartz crystal microbalance (EQCM),2 experimental efforts aimed at probing the changes in electronic structure are still limited. Here, we employ X-ray and ultraviolet photoelectron spectroscopy combined with an electrochemical cell (EC-XPS/UPS) which allows us to electrochemically control the Fc SAM redox state and spectroscopically probe the redox-induced electronic and structural changes.3 To perform our experiments, electrochemical (EC) measurements are performed in a separate EC chamber in Ar atmosphere followed by evacuation and then transfer to the XPS/UPS analysis chamber.4 The EC chamber contains a retractable PTFE (polytetrafluorethylene) cell where electrochemical measurements are performed under Ar atmosphere. The cell utilizes a hanging meniscus setup connected via PFA (perfluoroalkoxy alkane) tubing to a syringe containing the electrolyte. This controlled setup permits us to reliably probe the oxidized Fc+ moieties and prevent its decomposition upon exposure to the ambient. Using this approach, following EC and electrode immersion, we can probe changes to the ferrocene/ferrocenium (Fc/Fc+) redox center (Fe oxidation state), deduce the occurrence of ion-pairing, changes in molecular orientation and monolayer thickness (Figure 1). Oxidation to Fc+ is corroborated by UPS, which shows that a shift of the highest occupied molecular orbital (HOMO) towards higher binding energy along with an increase in work function. The reversibility of our observations is confirmed by reproducibly switching between the Fc/Fc+ states. More broadly, our approach is potentially applicable to a variety of electrochemically active systems to assist in the elucidation of redox-related structure-function relationships. Specific details will be provided during the presentation. Figure 1. (a) Schematic and photographs of hanging meniscus inside the EC chamber during EC measurements and following removal from the electrolyte. (b) Molecular structure of Fc SAM used in study and cyclic voltammagram performed in 0.1 M NaClO4. (c) Corresponding XPS Fe 2p, Cl 2p and O 1s spectra of the pristine, oxidized Fc+ and neutral Fc states. Kolb, D. M. Angew. Chem. Int. Ed. 2001, 40, 1162. K. Uosaki, Electrochemistry 1999, 12, 1105. R. A. Wong, Y. Yokota, M. Wakisaka, J. Inukai, Y. Kim, J. Am. Chem Soc. 2018, 140, 13672. M. Wakisaka, S. Mitsui, Y. Hirose, K. Kawashima, H. Uchida, M. Watanabe, J. Phys. Chem. B 2006 , 46, 23489. Figure 1

The phenalenyl derivative molecules, diphenyl derivatives of 1,2-bis-(phenalen-1-ylidene) ethene (Ph2-BPLE) and tetra t-butyl derivatives of s-indacenodiphenalene (TTB-IDPL), casted on a highly oriented pyrolytic graphite (HOPG) electrode, were characterized by using cyclic voltammetry (CV) in aqueous electrolyte solution. Stable and adsorption type redox peaks at the double-layer region of a HOPG basal plane electrode revealed that the redox peaks originated from the molecules. It was found that the peak area of the CV curve, the amount of redox-active adsorbates, apparently increased after anodic potential scans up to +1.4 V vs. RHE without any additional redox-active molecules in the liquid phase. Quantitative analyses indicated that it was due to potential-induced dispersion of the phenalenyl derivative molecules on the electrode, and effective electron transfer occurred only from the molecule directly attached to the electrode surface.

The effect of anions on the redox behavior and structure of 11-ferrocenyl-1-undecanethiol (FcC11) monolayers (SAM) on Au(1 1 1) single crystal and Au(1 1 1-25 nm) thin film electrodes was investigated in 0.1 M solutions of HPF6, HClO4, HBF4, HNO3, and H2SO4 by cyclic voltammetry (CV) and in situ surface-enhanced infrared reflection-absorption spectroscopy (SEIRAS). We demonstrate that the FcC11 redox peaks shift toward positive potentials and broaden with increasing hydrophilicity of the anions. In situ surface-enhanced IR-spectroscopy (SEIRAS) provided direct access for the incorporation of anions into the oxidized adlayer. The coadsorption of anions is accompanied by the penetration of water molecules. The latter effect is particularly pronounced in aqueous HNO3 and H2SO4 electrolytes. The adlayer permeability increases with increasing hydrophilicity of the anions. We also found that even the neutral (reduced) FcC11 SAM is permeable for water molecules. Based on the property of interfacial water to reorient upon charge inversion, we propose a spectroscopic approach for estimating the potential of zero total charge of the FcC11-modified Au(1 1 1) electrodes in aqueous electrolytes.

In the shipbuilding industry, welding efficiency without deteriorating weld quality has been desired to, as a consequence of the recent increase in the amount of shipbuilding and the size of ship hulls. Especially, an innovation in the welding efficiency and weld quality in horizontal fillet welding is a more important issue, because the amount of horizontal fillet welding work generally accounts for 70 percent or higher of the total welding work for ship hulls. One of high-speed horizontal fillet welding processes known as “Twin Tandem One Pool process” has been used in actual fabrication. However, the maximum welding speed of the twin tandem one pool process is approximately 1.5 m/min. In order to increase welding speed and welding quality of the twin tandem one pool process, the authors have employed an additional filler wire positioned between the two wires of the twin tandem one pool process. The additional wire carries DC-EN currents, opposite to DC-EP currents for the main welding wires, thereby reducing arc interference and arc blow at high currents. With this new technique, the authors have improved the stability of the weld pool formation at high currents. Consequently, horizontal fillet welding at a speed of 2.0 m/min on primer-coated steel plates has been achieved with excellent bead appearance, shape, and porosity resistance. Recently, this new process has just been installed in actual shipbuilding and it is confirmed that it truly contributes to improve welding efficiency and minimize repair time.

The formation of ion pairs between oxidized ferrocene-terminated self-assembled monolayers (SAMs) and counteranions was investigated using atomic force microscopy under independent controls of the tip and sample potentials in a 0.05 M HClO4 solution. The stability of the system was characterized by retraction force curves, where the adhesion force between the tip and the sample both covered by SAMs can be reversibly tuned by adjusting the applied potentials as a function of the oxidation states of ferrocene moieties. The net repulsive force, which corresponds to a residual surface charge uncompensated with the counteranions, was not observed on the approach curves between two oxidized ferrocene-terminated SAMs, in contrast to the case of positively charged amino-terminated SAMs. When the concentration of the electrolyte solution was decreased to 0.005 M, the net repulsive force was observed. We revealed that the ion-pair layer of oxidized ferrocene moieties and the electrolyte anions possesses net surface...

It was revealed that electrostatic forces between electrodes under the applied bias are almost completely suppressed by an electrochemical potential control. The force operating between n-decanethiol self-assembled monolayers (SAMs) on gold was examined by atomic force microscopy in liquid n-dodecane and in an aqueous solution of HClO4. In inert n-dodecane, the bias voltage was simply applied between the tip and the sample, and the force curve exhibited a long-range attractive force in accordance with the simple capacitance model. Meanwhile under the independent control of the tip and sample potentials in HClO4, the force curve did not depend on the applied potentials due to the small double-layer capacitance. [DOI: 10.1380/ejssnt.2009.731]

Electroactive ferrocenylundecanethiol islands embedded in an n-decanethiol SAM matrix were studied under potential control using in situ scanning tunneling microscopy (STM). Contrary to previous reports, the positive charges on ferrocene moieties are not a prerequisite to enhancing the current through ferrocenylundecanethiol on gold. Rather, conduction paths are opened at determined potentials for both neutral and monocationic ferrocene moieties. In addition, although stable and reproducible images were obtained under potential control, conventional STM measurements under N2 atmosphere were sometimes unstable and irreversibly changed the sample, indicating that current measurements of ferrocenylundecanethiol are much easier under an electrochemical environment.

Electrochemical frequency-modulation atomic force microscopy (EC-FM-AFM) was adopted to analyze the electrified interface between an iodine modified Au(111) and a perchloric acid solution. Atomic resolution imaging of the electrode was strongly dependent on the electrode potential within the electrochemical window: each iodine atom was imaged in the cathodic range of the electrode potential, but not in the more anodic range where the tip is retracted by approximately 0.1 nm compared to the cathodic case for the same imaging parameters. The frequency shift versus tip-to-sample distance curves obtained in the electric double layer region on the iodine adlayer indicated that the water structuring became weaker at the anodic potential, where the atomic resolution images could not be obtained, and immediately recovered at the original cathodic potential. The reversible hydration structures were consistent with the reversible topographic images and the cyclic voltammetry results. These results indicate that perchlorate anions concentrated at the anodic potential affect the interface hydration without any irreversible changes to the interface under these conditions.

Electroactive tetrathiafulvalene (TTF)-containing alkanethiol self-assembled monolayers (SAMs) were designed and synthesized to elucidate the relationship between electrochemical responses and film structures. Two TTF derivative molecules having one alkanethiol chain (1) and two alkanethiol chains (2) were utilized to modulate the molecular packing arrangements in the SAMs, and the formation and structure of the SAMs were characterized by surface plasmon resonance spectroscopy (SPR). SPR measurements in various contacting media demonstrated loose packing of SAM 1 and close packing of SAM 2 due to the different space fillings of the molecules. Two successive one-electron redox waves were observed for both SAMs by cyclic voltammetry. The peak widths of the redox waves were strongly dependent on the oxidation states of the TTF moieties, the packing arrangement of the SAMs, and the contacting medium. We found that TTF-based SAMs exhibited collective electrochemical responses induced by dynamic structural changes, depending on the degree of freedom for the component molecules in the SAMs. These results imply that the molecular design, taking into account the electrochemical responses, extends the available range of molecular-based functionalities in TTF-based SAMs.

Stable sliding contact is the most important factor for stable arc discharge of solid wire. If the contact tube wore seriously, arc discharge would become unstable and wire position would be shifted. Ordinary non-Cu-coated solid wire has much wear of contact tube about ten times comparing to Cu-coated solid wire. The mechanism of contact tube wear is not only friction at high temperature but also molten bridge formed between contact tube and wire surface. Some complex of superfine particles decreases the amount of contact tube wear. For example, the mixture of graphite and magnetite reduces the amount of contact tube wear by 80%. These particles form interface layer on inner surface of contact tube, and the layer prevents the transfer of molten Cu to wire surface. The interface layer mainly consists of FeO and complex oxides.

There are numerous studies1–12 concerning the melting rate of welding wire and various investigations have been carried out on welding current, welding current waveform, wire extension, polarity, chemical composition, wire diameter, arc length, shielding gas composition and melting rate. Joule heating of bulk wire has been a large contributory factor to the melting rate of solid wire for carbon steel (hereafter referred to as either wire or solid wire) and Joule heating is a crucial factor in aspects of melting stability. However, there are few case studies concerning the detailed measurement of Joule heating at the contacts between the contact tube and wire and the calculation of melting rate.

Electroactive tetrathiafulvalene thiol islands embedded in an n-alkanethiol SAM matrix were studied under potential control using in situ scanning tunneling microscopy. Unlike previously studied stochastic switching, the apparent height of the island could be intentionally controlled in the present system by choosing the appropriate potential and the island size. The dependence of the height change on the potential and the size is explained as structural change of the island induced by the charging effect of the electroactive moiety.

Self-assembled monolayer (SAM) systems of alkanethiol and TTF-substituted alkanethiol molecules on Au substrate and metal nanoparticles are investigated. TTF-substituted alkanethiol molecules form charge transfer complex SAM with TCNQ molecules, where charge transfer (CT) rate becomes similar to that in bulk TTF.TCNQ crystal. TTF-substituted alkanethiol SAMs with long alkyl chains shows Coulomb-blockade-type electron transport owing to the resistance of the long alkyl chain bridge. In Pt nanoparticles with alkanethiol SAMs on their surface, CT takes place from core Pt nanoparticle to surface SAMs, producing an electron deficient state in Pt core nanoparticle. Pd nanoparticles with SAMs of mixtures of alkanethiol and TTF-substituted alkanethiol molecules take a large reduction of the Pauli paramagnetic susceptibility, which is brought about by CT.

The structural properties of ionic liquid/rubrene single-crystal interfaces were investigated using frequency modulation atomic force microscopy. The spontaneous dissolution of rubrene molecules into the ionic liquid was triggered by surface defects such as rubrene oxide defects, and the dissolution rate strongly depended on the initial conditions of the rubrene surface. Dissolution of the second rubrene layer was slower due to the lower defect density, leading to the formation of a clean interface irrespective of the initial conditions. Molecular-resolution images were easily obtained at the interface, and their corrugation patterns changed with the applied force. Force curve measurements revealed that a few solvation layers of ionic liquid molecules formed at the interface, and the force needed to penetrate the solvation layers was an order of magnitude smaller than typical ionic liquid/inorganic solid interfaces. These specific properties are discussed with respect to electric double-layer transistors based on the ionic liquid/rubrene single-crystal interface.

In this chapter, applications of frequency modulation AFM (FM-AFM) to electrochemical issues, especially potential-dependent interface structures of adsorbates and electrolyte solutions, are described. One of the difference between electrochemical FM-AFM (EC-FM-AFM) and FM-AFM in liquids is that the sample potential with respect to the potential of the bulk electrolyte solution is controlled by a potentiostat used for general electrochemical measurements. Measurement principles and major parts of the EC-FM-AFM apparatus are similar to the FM-AFM in liquids, thus authors refer the reader to Chaps. 19, 20 in this book (Vol. 3) and Chaps. 15, 16 and 18 in Vol. 2 for some details.

Potential-dependent solvation structures of aqueous electrolyte–graphite interfaces were studied using electrochemical frequency modulation atomic force microscopy. Oscillatory modulations on the force curves reversibly changed with the applied potential on the graphite electrode, and also strongly depended on the anion species in electrolyte solutions.

Local analyses of ionic liquid/solid electrode interfaces at a controlled electrode potential are of fundamental importance to understanding the origin and properties of the electric double layer at the interfaces, which is necessary for their application to electrochemical devices. This account summarizes our recent achievements of such analyses by using the novel analytical tools of electrochemical frequency modulation AFM (EC-FM-AFM) and electrochemical photoemission spectroscopy (EC-PES). Rather stable stepped structures composed of layers of ion pairs and softer solvation layers outside of the imaged layer were clearly visualized by FM-AFM depending on the substrates. An extremely extended diffusion layer was directly observed by EC-PES during the electrodeposition of metal ion solutes.

本文は, 杭基礎の弾性解析法 (変位法) を, 大変位領域まで適用できるように拡張した方法を提案し, 実杭による水平載荷試験に基づき, その妥当性を検証したものである.まず, 杭体の非線形性は, 杭頭が先に降伏するという前提のもと, 杭頭付近に杭径分の塑性ヒンジ領域 (Ls) を仮定し, 杭体降伏後のバネ定数K1＊～K4＊をLsの関数とする式を提案した. 次に, 地盤の非線形性は等価線形化法で表現できることを明らかにし, 地盤種別ごとに非線形係数yを提案した. おわりに, 上記の杭体および地盤の非線形性の考え方を用いて, 実杭による水平載荷試験による荷重H～変位δ関係を解析し, 本方法が軸力変動を考慮した杭ラーメン法と同程度の推定精度を有していることを明らかにした.

Presence of inhomogeneous layered structures of ionic liquid (IL) molecules at IL/HOPG and IL/mica interfaces was directly detected and imaged by using frequency-modulation atomic force microscopy. High stability of the layered structures may disturb their interface applications to catalysis and electrochemistry.

In this article, we present a cost-sensitive approach to medical diagnosis based on fuzzy rule-based classification (Schaefer, Nakashima, Yokota, & Ishibuchi, 2007). While fuzzy rule-based systems have been mainly employed for control problems (Lee, 1990) more recently they have also been applied to pattern classification problems (Ishibuchi & Nakashima, 1999; Nozaki, Ishibuchi, & Tanaka, 1996). We modify a fuzzy rule-based classifier to incorporate the concept of weight which can be considered as the cost of an input pattern being misclassified. The pattern classification problem is thus reformulated as a cost minimisation problem. Based on experimental results on the Wisconsin breast cancer dataset, we demonstrate the efficacy of our approach. We also show that the application of a learning algorithm can further improve the classification performance of our classifier.

We report evolution of electric characteristics of an electric double layer field-effect transistor based on the ionic liquid/rubrene single crystal interfaces. In contrast to usual devices, the field effect mobility was found to gradually increase with time for a day, followed by minor long-term fluctuations. Although the details of the evolution were somewhat device dependent, the final values of the mobility turned out to be 3–4 times larger irrespective of the initial values. These observations are explained by the evolution of the flat interface by defect-induced spontaneous dissolution of rubrene molecules at the ionic liquid/rubrene single crystal interfaces, revealed by frequency modulation atomic force microscopy.

In this paper we examine the performance of fuzzy rule-based systems with classification priority for medical diagnosis problems. The assumption in this paper is that a classification priority is given a priori for each class in a pattern classification problem. Our fuzzy rulebased system consists of a set of fuzzy if-then rules that are automatically generated from a set of given training patterns. The consequent class of fuzzy if-then rules are decided based on the number of covered training patterns for each class. We apply the fuzzy classifier with class priority to two medical diagnosis problems: appendix diagnosis and breast cancer diagnosis, and compare its performance with that of a conventional fuzzy rule-based systems.

Electroactive tetrathiafulvalene thiol, specially designed to pursue an intermolecular electronic coupling, was embedded in an n-alkanethiol SAM matrix as islands and was studied under potential control using in situ scanning tunneling microscopy. The apparent height of the islands increased with the island size, irrespective of the oxidation state of the tetrathiafulvalene backbones. This behavior can be rationalized on the basis of the strong intermolecular electronic coupling that creates efficient intermolecular conduction paths.

Surface processing of a rubrene single crystal immersed in ionic liquids is valuable for further development of low voltage transistors operated by an electric double layer. We performed a precise and clean surface processing based on the tip-induced dissolution of rubrene molecules at the ionic liquid/rubrene single crystal interfaces by using frequency modulation atomic force microscopy. Molecular resolution imaging revealed that the tip-induced dissolution proceeded via metastable low density states derived from the anisotropic intermolecular interactions within the crystal structure.

A simple, mild, reproducible, and controllable nanodeposition method for ionic liquids (ILs) by ejection of IL solution through a high-speed electromagnetic valve (pulse valve) to a substrate under vacuum is proposed (pulse-valve method). Sequential deposition of an IL [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM-TFSI)] on Au(111) substrates from its methanol solution was examined by adopting the pulse-valve method and the deposited IL films were analyzed by X-ray photoelectron spectroscopy (XPS) and tapping-mode atomic force microscopy (AFM). The amount of IL deposited per a pulse was successfully reduced to less than an equivalent thickness of 0.2 nm. The deposited IL was homogeneously distributed over a substrate area of 1 × 1 cm2 substrate area and the deposited amount was reproducible for independent depositions.

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