ABSTRACT
Probing electrochemical reactions at surfaces with nanometer resolution is one of the major goals of nanoelectrochemistry. Scanning electrochemical microscopy (SECM)1 is, as detailed in Chapter 18, a promising way to achieve this goal, provided experimental approaches are designed to endow SECM with nanometer resolution capabilities. Among these approaches, one is to couple SECM with some other local probe technique known for its robustness and inherent nanoscale resolution. A particularly attractive technique for this is atomic force microscopy (AFM),2 introduced in 1986 by Binning et al., and which has now become one of the most popular local probe techniques for the nanoscale characterization of surfaces. Coupling SECM with AFM can seem a priori simple: it sufces to endow the nanoprobes commonly used in AFM with current measuring capabilities, that is, to design combined AFM tips which can also act as SECM-microelectrode probes. Of course things are not that simple and fabrication of such AFM-SECM probes has proved to be a formidable challenge.3,4 Indeed to date, many of the publications related to AFM-SECM (or SECM-AFM, some
21.1 Introduction .......................................................................................................................... 749 21.2 Working Principle of AFM-SECM: What AFM Brings to SECM? .................................... 750 21.3 Availability of Combined AFM-SECM Probes: A Key Issue .............................................. 753 21.4 Development and Applications of AFM-SECM for Nanoelectrochemistry ........................ 753
21.4.1 Imaging Dissolution Processes ................................................................................. 753 21.4.2 Functional Imaging of Electroactive Sites on a Surface ........................................... 755 21.4.3 Imaging Enzyme Activity ......................................................................................... 760 21.4.4 Imaging Transport Processes through Micropores .................................................. 764 21.4.5 Substrate Patterning Using AFM-SECM ................................................................. 766 21.4.6 Quantitative Measurements with AFM-SECM ........................................................ 768
21.5 Touching Surface-Attached Macromolecules with a Microelectrode: Mt/AFM-SECM ..... 769 21.6 Attaching a Redox Mediator to an AFM-SECM Tip for the Functional
Probing of Nanosystems: Tarm/AFM-SECM ...................................................................... 776 21.7 Alternative/Improved Strategies for Fabricating AFM-SECM Probes ................................ 778
21.7.1 Probes with the Microelectrode Recessed from the (Insulating) Tip Extremity ..... 778 21.7.2 Probes with the Microelectrode Located at the Tip Extremity ................................ 780
21.7.2.1 Conically Shaped Probes ........................................................................... 780 21.7.2.2 Needle-Like Probes ................................................................................... 782
21.8 Conclusion ............................................................................................................................ 784 References ...................................................................................................................................... 785
authors preferring this later acronym) actually solely report on suitable fabrication methods for the combined probes. Here, we will primarily focus on the successful applications of AFM-SECM for the nanoscale characterization of electroactive systems while describing briey the corresponding probe fabrication methods along the way. The newest techniques for fabricating AFM-SECM probes will then be examined separately in more detail. Most of all we intend to show that coupling SECM with AFM can bring much more than resolution enhancement: AFM-SECM makes possible the nanoscale exploration of electrochemical (or electrochemically transduced) processes impossible to reveal by mere AFM or SECM.
