electrochemical imaging
- Introduction
- Bias Modulated - Scanning Ion Conductance Microscopy (SICM)
- Scanning Electrochemical Cell Microscopy (SECCM)
- Scanning Electrochemical Microscopy (SECM)
- Combined SICM-SECM
IntroductionThe ability to visualise surfaces and interfaces is of critical importance to understaning the dynamic processes that occur at these interfaces and in understanding to complex interactions involved. The versatility of the techniques are vast and versatile in the systems that can be immaged. Historically scanning probe techniques have been limited to determining the surface topography, however recent advances now mean researchers can simultainiously determin many other surface characteristics at the same time. In the Electrochemistry and Interfaces group at Warwick, we have developed several imaging methods here ourselves in order to image the systems we study. We have available many techniques for the fabrication and characterisation of new probes. |
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Top: Laser Pulling of Glass Pipettes Middle: Focused Ion Beam milling of tip geometry Bottom: Carbon Filling of Glass Pipettes |
Bias Modulated Scanning Ion Conductance Microscopy (SICM)Scanning ion conductance microscopy (SICM) is regularly used to determine, in a noncontact manner, the topography of a sample. We have developed a new method Bias Modulated scanning Ion Conductance Microscopy (BM-SICM) which, by oscillating the applied bias between the SICM nanopipet probe and the reference electrode in the bulk solution generates a feedback signal to control the distance between the end of a nanopipet and a surface. This development eliminates the need to physically oscillate the probe to generate an oscillating ion current feedback signal, as needed for conventional SICM modes. Moreover, bias modulation allows a feedback signal to be generated without any net ion current flow and phase-detection opens up the mode to the prospect of faster imaging. Bias Modulated Scanning Ion Conductance Microscopy |
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Scanning Electrochemical Cell Microscopy (SECCM)This technique is a highly localized electrochemical measurements and imaging technique using a simple, mobile theta pipet cell. Each channel is filled with electrolyte solution and a Ag/AgCl electrode, between which a bias is applied, resulting in a conductance current across a thin meniscus of solution at the end of the pipet, which is typically deployed in air or a controlled gaseous environment. When the pipet is oscillated, an oscillating component in the conductance current is generated. This oscillating current component can be used to maintain gentle contact of the solution from the pipet cell with the surface and as a set point for high resolution topographical imaging with the pipet. Simultaneously, the mean conductance current that flows between the pipet channels can be measured and is sensitive to the local nature of the interface, informing one, for example, on wettability and ion flow into or out of the surface investigated. Conductor or semiconductor surfaces can be connected as a working electrode, with one of the electrodes in the pipet serving as a quasi-reference electrode. This pipet cell then constitutes part of a dynamic electrochemical cell, with which direct voltammetric−amperometric imaging can be carried out simultaneously with conductance and topographical imaging. This provides multifunctional electrochemical maps of surfaces and interfaces at high spatial resolution. Localized High Resolution Electrochemistry and Multifunctional Imaging: Scanning Electrochemical Cell Microscopy |
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Scanning Electrochemical Microscopy (SECM) |
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Combigned SICM-SECMThe easy and cheep fabrication and use of nanoscale dual function pH-scanning ion conductance microscopy (SICM) probes has been developed here at Warwick. One Example of this type of probe incorporate an iridium oxide coated carbon electrode for pH measurement and an SICM barrel for distance control, enabling simultaneous pH and topography mapping. The fabricated probes, with pH and SICM sensing elements are typically on the 100 nm scale. The capability of the pH-SICM probe was demonstrated by detecting both pH and topographical changes during the dissolution of a calcite microcrystal in aqueous solution. This system illustrates the quantitative nature of pH-SICM imaging, because the dissolution process changes the crystal height and interfacial pH (compared to bulk), and each is sensitive to the rate. Fabrication and Characterization of Dual Function Nanoscale pH-Scanning Ion Conductance Microscopy (SICM) Probes for High Resolution pH Mapping B. P. Nadappuram, K. McKelvey, R. Al-Botros, A. W. Colburn, and P. R. Unwin, Anal. Chem., 2013, 85(17), 8070–8074. |
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