Scanning Electrochemical Microscopy-Quartz Crystal Microbalance

SCANNING ELECTROCHEMICAL MICROSCOPY-QUARTZ CRYSTAL MICROBALANCE... 

Cliffel, D. E., Bard, A. J., Scanning electrochemical microscopy. 36. A combined scanning electrochemical microscope-quartz crystal microbalance instrument for studying thin films. Anal. Chem. 1998, 70, 1993-1998. 

While electrochemical methods provide powerful and sensitive ways of studying modified electrodes to provide information about electron-transfer kinetics and film porosity, they cannot provide information about structure or elemental composition. Thus complete characterization requires application of many of the nonelectrochemical methods described in Chapter 17. These encompass microscopy, high vacuum surface analysis, Raman and IR spectroscopy, and methods based on scanning probes, the quartz crystal microbalance, and measurements of contact angles. 

Such approximation is valid when the thickness of the polymeric layer is small compared to die thickness of die crystal, and the measured frequency change is small with respect to the resonant frequency of the unloaded crystal. Mass changes up to 0.05% of die crystal mass commonly meet this approximation. In die absence of molecular specificity, EQCM cannot be used for molecular-level characterization of surfaces. Electrochemical quartz crystal microbalance devices also hold promise for the task of affinity-based chemical sensing, as they allow simultaneous measurements of both tile mass and die current. The principles and capabilities of EQCM have been reviewed (67,68). The combination of EQCM widi scanning electrochemical microscopy has also been reported recently for studying die dissolution and etching of various thin films (69). The recent development of a multichannel quartz crystal microbalance (70), based on arrays of resonators, should further enhance die scope and power of EQCM. 

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). 

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]. 

Use of Electrochemical Quartz Crystal Microbalance (EQCM) 281 Use of Scanning Electrochemical Microscopy (SECM) 281 References 284... 

Since micro-gravimetry with the EQCM lacks specificity only the difference of cation and anion fluxes can be obtained by microgravimetry and therefore an independent measurement of specific ions is needed. Scanning electrochemical microscopy (SECM) coupled with a quartz crystal microbalance with independent potential control of the tip and substrate has been recently done by Cliffel and Bard [28]. In this experiment generation at the substrate (EQCM crystaj) working electrode and collection at the tip of an ultramicroelectrode (UNE) that was approached perpendicular to the EQCM crystal was employed with measurement of A/. Hillier and Ward [8] had previously used a scanning microelectrode to map the mass sensitivity across the surface of the QCM crystal. Reflection of longitudinal waves at the UME tip limits these experiments due to oscillations. 

V. Syritski, R.E. G3Tircsan3fi, A. Opik, and K. Toth, Synthesis and characterization of inherently conducting pol3Tners by using scanning electrochemical microscopy and Electrochemical Quartz Crystal Microbalance. Synth. Met., 152, 133 (2005). 

Recently a review has been published concerning the use of AFM, scanning electrochemical microscopy (SECM) and quartz crystal microbalance (QCM) as complementary techniques for the characterisation of enzyme-based bioanalytical platforms [42]. 

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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