Electrophoretic paint insulation

To probe for pinholes in the electrophoretic paint insulation, the carbon nanofiber electrodes are tested with a scanning electrochemical microscope (SECM, see Chapter 12)... 

Figure 10.17 Microelectrodes array formed through chemical etching. (Al) SEM of an 1141-electrode titanium alloy electrode array, (A2) SEM image of a parylene-coated assembly of platinum-coated electrodes (181), (Bl) SEM of an etched optical imaging fiber bundle, and (B2) SEM of a with gold covered and with electrophoretic paint insulated microelectrode array (with permission from reference (34)).

Qiao, Y, Chen, J., Guo, X. L. et al. 2005. Fabrication of nanoelectrodes for neurophysiology Cathodic electrophoretic paint insulation and focused ion beam milling. Nanotechnology 16 1598-1602. 

FIG. 1 Steps involved in constructing an SECM/AFM tip (a) Pt microwire inserted in holder (b) electrochemical etching (c) compression to form cantilever component (d) insulation of electrode and cantilever with electrophoretic paint followed by heating to expose tip (e) attachment to commercial AFM chip. (From Ref. 3.)... 

Unwin and coworkers [11] have developed a straightforward approach for fabricating platinum microelectrodes with tip sizes as small as a few nanometers. Their innovation is to use an electrophoretic paint to insulate the electrode walls while leaving an electrochemicaUy active tip exposed. These electrodes have excellent properties for use in scanning electrochemical microscopy (SECM), discussed further in Chapter 3.3. 

A highly significant recent development is the integration of atomic force microscopy with SECM (AFM-SECM) [220]. Further details are described in Chapter 3.2 of this volume. An etched Pt wire was flattened and then insulated with electrophoretic paint. This probe acts as the cantilever in AFM and as the SECM tip providing dual force-sensing and electrochemical capabilities. Submicron resolution for SECM and for topography by AEM was achieved for test samples of track-etched polycarbonate membranes and ionic crystal surfaces. As the resolution of the technique improves and it is combined with other scanning probes, it seems likely that SECM can be applied in an ever-wider spectrum of scientific fields. 

Figure 6.3.4.1 Schematic of the setup for the fabrication of Pt conical UMEs. (a) A Pt wire is sealed into glass capillary, (b) The etched wire is insulated with electrophoretic paint.

Figure 6.3.4.S The electrochemical approach curves of a Pt UME insulated with electrophoretic paint to an air/solution interface, (a) Electrode insulation is good, (b) Electrode insulation is poor. The solution contained 10 mM K3pe(CN)5 and 0.1 M KCl. The tip potential was 0.1 V vs. Ag/AgCl. (The data was from the Electrochemistry Laboratory of the Department of Chemistry and Biochemistry, University of Austin at Texas.)...

Figure 6.3.S.4 SEM image of a carbon nanofiber after insulation with electrophoretic paint. Beam energy is 5.00 kV and the focal distance is 11 mm.

Cathodic electrophoretic paint is the preferred polymeric material used to insulate the carbon fibers as the negative potentials required for deposition avoid any possibility of further oxidative dissolution of the carbon fiber. The usual approach for electrophoretic deposition is to suspend the article being coated in an appropriate suspension of polymer particles and polarising the iton versus a secondary electrode. 

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