Electrochemical quartz crystal microbalance fundamentals

Fundamental frequency of the resonator Correlation function for surface roughness Root mean square height of a roughness Wave vector of shear waves in quartz, (Uy pq//rq Correlation length of surface roughness Thickness of the liquid film Thickness of interfacial layer Molecular dynamics Pressure in a liquid Quartz crystal microbalance Hydrodynamic roughness factor Electrochemical roughness factor Coordinates (normal and lateral)... 

The literature concerning the quartz crystal microbalance (QCM) and its electrochemical analog, the electrochemical EQCM, is wide and diverse. Many reviews are available in the Uterature, discussing the fundamental properties of this device and its numerous appUcations, including its use in electrochemistry [1-7]. In this chapter we focus on the effect of interfacial properties on the QCM response, specifically when the device is immersed in a fiquid. 

The understanding of the electrochemical phenomena underlying corrosion processes provides a basis for experimental techniques that allow simple and accurate measures of corrosion rates. The electrochemical fundamentals are discussed in Sects. 1.2-1.4 of this volume and in other volumes of this series. This chapter wiU discuss a wide range of experimental techniques commonly used in the field of corrosion and issues associated with their use. Electrochemical techniques will be the focus, but some nonelectrochemical techniques will also be discussed. Electrochemical techniques take advantage of our ability, with modern instrumentation, to utilize feedback control and measure very small currents. These techniques allow highly sensitive measurements that far exceed the capabilities of most nonelectrochemical techniques based on, for instance, weight loss or appearance. On the other hand, some nonelectrochemical techniques are also extremely sensitive to small amounts of material loss. An example is the quartz crystal microbalance (QCM), which provides submonolayer sensitivity as will be described in the following sections. 

Various planar membrane models have been developed, either for fundamental studies or for translational applications monolayers at the air-water interface, freestanding films in solution, solid supported membranes, and membranes on a porous solid support. Planar biomimetic membranes based on amphiphilic block copolymers are important artificial systems often used to mimic natural membranes. Their advantages, compared to artificial lipid membranes, are their improved stability and the possibility of chemically tailoring their structures. The simplest model of such a planar membrane is a monolayer at the air-water interface, formed when amphiphilic molecules are spread on water. As cell membrane models, it is more common to use free-standing membranes in which both sides of the membrane are accessible to water or buffer, and thus a bilayer is formed. The disadvantage of these two membrane models is the lack of stability, which can be overcome by the development of a solid supported membrane model. Characterization of such planar membranes can be challenging and several techniques, such as AFM, quartz crystal microbalance (QCM), infrared (IR) spectroscopy, confocal laser scan microscopy (CLSM), electrophoretic mobility, surface plasmon resonance (SPR), contact angle, ellipsometry, electrochemical impedance spectroscopy (EIS), patch clamp, or X-ray electron spectroscopy (XPS) have been used to characterize their... 

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