Evidence for Faradaic Processes in Scanning Probe Microscopy on Mica in Humid Air

Forouzan, Fardad; Bard, Allen J.

doi:10.1021/jp972728g

Cited by 45 publications

(29 citation statements)

References 25 publications

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“…The results are obtained for quasi infinitely large samples of uniform reactivity. This is indeed a good approximation of experimental results if the radius of the investigated sample region is large enough (r S ≥ r T + 1.5 d) [52,72]. If sample regions are smaller than that criterion, i T lies between the limiting cases for a specific RG shown in Figure 4.…”

Section: (7)supporting

confidence: 75%

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Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

Pust¹,

Maier²,

Wittstock³

2008

Zeitschrift Für Physikalische Chemie

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Scanning Electrochemical Microscopy (SECM) . Catalytic Electrodes .Electrochemical Energy Conversion . Fuel Cells . Oxygen Reduction Reaction . CorrosionScanning electrochemical microscopy (SECM) has developed into a very versatile tool for the investigation of solid-liquid, liquid-liquid and liquid-gas interfaces. The arrangement of an ultramicroelectrode (UME) in close proximity to the interface under study allows the application of a large variety of different experimental schemes. The most important have been named feedback mode, generation-collection mode, redox competition mode and direct mode. Quantitative descriptions are available for the UME signal, depending on different sample properties and experimental variables. Therefore, SECM has been established as an indispensible tool in many areas of fundamental electrochemical research. Currently, it also spreads as an important new method to solve more applied problems, in which inhomogeneous current distributions are typically observed on different length scales. Prominent examples include devices for electrochemical energy conversion such as fuel cells and batteries as well as localized corrosion phenomena. However, the direct local investigation of such systems is often impossible. Instead, suitable reaction schemes, sample environments, model samples and even new operation modes have to be introduced in order to obtain results that are relevant to the practical application. This review outlines and compares the theoretical basis of the different SECM working modes and reviews the application in the area of electrochemical energy conversion and localized

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Section: (7)supporting

confidence: 75%

“…While this conceptual difference appears to be clear, particular experiments trigger intensive debates [68][69][70][71][72][73]. The general similarity of the instrumentation provoked some "jargon" in SECM.…”

Section: Secm Instrumentation and Basic Concepts 21 Instrumentationmentioning

confidence: 99%

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

Pust¹,

Maier²,

Wittstock³

2008

Zeitschrift Für Physikalische Chemie

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“…Following the work of Guckenberger et al (3), we recently carried out some preliminary SECM measurements on mica surface in humid air and reported the imaging of a Nafion thin film (4) and the deposition of silver nanostructures (5). In this paper, we describe the imaging of biological samples (DNA and some structurally well-characterized protein molecules) with this technique.…”

mentioning

confidence: 96%

“…As shown by Guckenberger et al (3), imaging is possible within this thin liquid layer. As we have discussed previously (4,5), the current that passes between tip and contact is a faradaic one, based on EC reactions that take place within the thin liquid layer. In this case, very high resolution can be attained with a tip without insulation, because only the end of the tip is in contact with the liquid layer.…”

mentioning

confidence: 99%

Imaging of biological macromolecules on mica in humid air by scanning electrochemical microscopy

Fan

Bard

1999

Proc. Natl. Acad. Sci. U.S.A.

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111

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Imaging of DNA, keyhole limpet hemocyanin, mouse monoclonal IgG, and glucose oxidase on a mica substrate has been accomplished by scanning electrochemical microscopy with a tungsten tip. The technique requires the use of a high relative humidity to form a thin film of water on the mica surface that allows electrochemical reactions to take place at the tip and produce a faradaic current (Ϸ1 pA) that can be used to control tip position. The effect of relative humidity and surface pretreatment with buffer solutions on the ionic conductivity of a mica surface was investigated to find appropriate conditions for imaging. Resolution of the order of 1 nm was obtained.H igh-resolution imaging of nanostructured materials, especially soft and sensitive biological samples, poses a great challenge in material science and biology. The structures of individual biological molecules at nanometer-scale resolution have been traditionally studied by high-resolution electron microscopy and x-ray crystallography. However, these techniques often require difficult sample-preparation procedures and potentially damaging experimental conditions or depend on the availability of obtaining crystalline samples. The atomic-force microscope has been extensively used to image biological samples and is especially convenient because the molecules can be observed under ambient or physiological conditions. However, atomic-force microscopy does not provide chemical information, and special precautions are required to prevent the tip from damaging or altering the sample. In the family of scanning probe microscopes (1), the scanning electrochemical (EC) microscope (SECM) allows for both structural and chemical information of the surface (so-called chemical imaging). However, the application of SECM has largely focused on analytical investigations, e.g., in studies of interfacial kinetics, rather than as a highresolution imaging tool (2). In the amperometric mode, the SECM is similar to the better-known scanning tunneling microscope (STM), in that it measures the current flow through a conductive tip. However, it differs from the STM in that the current response is an EC one, and the sample is interrogated by solution species generated or reacting at the tip rather than by a strong interaction with the tip itself.The resolution attainable with a SECM is largely governed by the tip size and the distance between tip and sample. Most SECM measurements are carried out with the sample under a thick liquid layer; under these conditions, the tip must be sheathed in an insulator so that only the very end is exposed to solution to achieve high resolution. SECM measurements can also be carried out in ambient or humid air. When a substrate, like mica, with a hydrophilic surface is exposed to air, a thin layer of water forms on the surface. As shown by Guckenberger et al. (3), imaging is possible within this thin liquid layer. As we have discussed previously (4, 5), the current that passes between tip and contact is a faradaic one, based on EC reactions that take ...

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“…Most SPL techniques are negative printing methods that rely on scanning probe instruments to pattern substrate surface by selectively removing the pre-coated organic resist layer or self-assembled monolayers (SAMs). They include mechanical scratching [52,53], anodization of Si surfaces [54,55], electrochemical decomposition of SAM [56][57][58][59], electric field-induced chemical reactions [60,61], and electrochemical reactions in solution using electrochemical Scanning Tunnel Microscope (STM) tips [62][63][64][65][66][67][68]. Subsequent etching, adsorption or electroforming steps allow the transfer of nanoscale patterns to the substrate.…”

Section: Scanning Probe Lithography (Spl)mentioning

confidence: 99%

Nanoscale Polymer Fabrication for Biomedical Applications

Lee

BioMEMS and Biomedical Nanotechnology

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Evidence for Faradaic Processes in Scanning Probe Microscopy on Mica in Humid Air

Cited by 45 publications

References 25 publications

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

Imaging of biological macromolecules on mica in humid air by scanning electrochemical microscopy

Nanoscale Polymer Fabrication for Biomedical Applications

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