Electrochemical scanning tunneling microscopy

Fig. VIII-2. Scanning tunneling microscopy images illustrating the capabilities of the technique (a) a 10-nm-square scan of a silicon(lll) crystal showing defects and terraces from Ref. 21 (b) the surface of an Ag-Au alloy electrode being electrochemically roughened at 0.2 V and 2 and 42 min after reaching 0.70 V (from Ref. 22) (c) an island of CO molecules on a platinum surface formed by sliding the molecules along the surface with the STM tip (from Ref. 41).

Section 6.2.1 offers literature data on the electrodeposition of metals and semiconductors from ionic liquids and briefly introduces basic considerations for electrochemical experiments. Section 6.2.2 describes new results from investigations of process at the electrode/ionic liquids interface. This part includes a short introduction to in situ Scanning Tunneling Microscopy. 

FIGURE 2-15 Design of a system for in-situ electrochemical scanning tunneling microscopy. 

Electrochemistry is the basis of many important and modem applications and scientific developments such as nanoscale machining (fabrication of miniature devices with three dimensional control in the nanometer scale), electrochemistry at the atomic scale, scanning tunneling microscopy, transformation of energy in biological cells, selective electrodes for the determination of ions, and new kinds of electrochemical cells, batteries and fuel cells. 

Sorenson TA, Lister TE, Huang BM, Stickney JL (1999) A comparison of atomic layers formed by electrodeposition of selenium and tellurium Scanning tunneling microscopy studies on Au(lOO) and Au(lll). J Electrochem Soc 146 1019-1027... 

Landman, U., and W. D. Luedtke, Consequences of tip-sample interactions, in Scanning Tunneling Microscopy III, R. Wiesendanger and H. J. Guntherodt Eds., Springer-Verlag, Berlin, 1993. Lorentz, W. J., and W. Plieth, Eds., Electrochemical Nanotechnology, Wiley-VCH, New York, 1996. 

We have found new CO-tolerant catalysts by alloying Pt with a second, nonprecious, metal (Pt-Fe, Pt-Co, Pt-Ni, etc.) [Fujino, 1996 Watanabe et al., 1999 Igarashi et al., 2001]. In this section, we demonstrate the properties of these new alloy catalysts together with Pt-Ru alloy, based on voltammetric measurements, electrochemical quartz crystal microbalance (EQCM), electrochemical scanning tunneling microscopy (EC-STM), in situ Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). 

As mentioned above, the methods based on detection of electrons or ions or probing the electrode surface by these particles are generally handicapped by the necessity to move the studied electrode into vacuum, i.e. to work ex-situ. There are, however, two important exceptions to this rule electrochemical mass spectrometry and electrochemical scanning tunnelling microscopy. 

Haiss W, Albrecht T, van Zalinge H, Higgins SJ, Bethell D, Hobenreich H, Schiffrin D J, Nichols RJ, Kuznetsov AM, Zhang J, Chi Q, Ulstrup J (2007) Single-molecule conductance of redox molecules in electrochemical scanning tunneling microscopy. J Phys Chem Bill 6703-6712... 

Gichuhi, A. Shannon, C. Perry, S. 1999. A scanning tunneling microscopy and X-ray photoelectron spectroscopy study of electrochemically grown ZnS mono-layers on Au(lll). Langmuir 15 5654-5661. 

Shaikhutdinov, S.K., Moller, F.A., Mestl, G. and Behm, R.J., Electrochemical deposition of platinum hydrosol on graphite observed by scanning tunneling microscopy, J. Catal., 163,492, 1996. 

N. Kuiiyama, D. Chartouni, M. Tsukahara, K. Takahashi, H.T. Takeshita, H. Tanaka, L. Schlapbach, T. Sakai, I. Uehara, Scanning tunneling microscopy in situ observation of phase-selective cathodic hydrogenation of a V-Ti-Ni-based multiphase alloy electrode, Electrochem. Solid-State Lett. 1 (1998) 37-38. 

A number of methods are available for the characterization and examination of SAMs as well as for the observation of the reactions with the immobilized biomolecules. Only some of these methods are mentioned briefly here. These include surface plasmon resonance (SPR) [46], quartz crystal microbalance (QCM) [47,48], ellipsometry [12,49], contact angle measurement [50], infrared spectroscopy (FT-IR) [51,52], Raman spectroscopy [53], scanning tunneling microscopy (STM) [54], atomic force microscopy (AFM) [55,56], sum frequency spectroscopy. X-ray photoelectron spectroscopy (XPS) [57, 58], surface acoustic wave and acoustic plate mode devices, confocal imaging and optical microscopy, low-angle X-ray reflectometry, electrochemical methods [59] and Raster electron microscopy [60]. 

A detailed electrochemical study of Ni(l 11) electrodes in H2SO4 solution in conjunction with in situ scanning tunneling microscopy (STM) and in situ surface X-ray scattering methods (SXS, x-ray diffraction and x-ray reflectivity) was carried out by Scherer et al. [18]. 

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