Flame etching

Examination of flame-etched surfaces revealed only scattered torus-shaped ring and moat structures, 100-200m in diameter. These features probably result from differential resistance of anthraxolite and rare impurities to oxidation. 

Taking advantage of the fact that carbon fibers can be etched down to a size of approximately 100 nm by passing the fiber through a flame, Strein and Ewing (40) constructed polymer coated submicrometer disk electrodes from flame-etched carbon fibers. Electrodes with an apparent diameter as small as 124 nm were obtained. The flame-etched fibers had a very rough aspect (4). 

FIGURE 20.11 Schematic representation of the end-column amperometric detection system (1) the outlet of the separation capillary was etched to 13 pm i.d., (2) Ag/AgCl reference electrode, (3) flame-etched carbon fiber electrode, (4) buffer reservoir, and (5) separation capillary, 770 nm i.d. (Reprinted from Woods, L. A., et l.. Electroanalysis, 17, 1192, 2005. With permission.)... 

Electrophoretie paint insulation Flame etched C fiber Uncovered apex... 

Figure 6.3.5.1 Schematic drawing of a flame-etched carbon nanofiber electrode.

Figure 6J.5J Approach from air into liquid for a flame-etched carbon nanofiber with (A) and without (B) pinholes. The electrolyte is 1 mM ferrocenemethanol (FcOH) in 0.1 M KCl. Tips are held at 0.35 V vs. Ag/AgCl. Approach rate 200 nm sec . ...

The examination of the voltanunetric response at carbon fiber UMEs as a function of miCTOvial volume was undertaken by Clark et al. (89). The experimental volume was varied from about 4 nL to as little as 1 pL. For a 5 pm diameter electrode, the volammograms of ferrocenecarboxylic acid did not vary as a function of sample volume. The shape of the voltammograms was sigmoidal which is expected for disk microelectrodes scanned at slow rates (1-1000 mV/sec) under steady-state conditions (102). The half wave potential measured in the microvials was identical to that of ferrocenecarboxylic acid in bulk solution and the current value also matched the expected value. In addition, Clark et al. performed voltammetry with a 1 pm diameter flame etched carbon fiber electrode in a 1 pL vial however, no deviation from bulk solution behavior was apparent. 

Poor adhesion. Low energy surface. Apply primer to surface and re-bond. Try writing on the surface with a felt pen. If the ink globules, it is likely that the adhesive will do the same and a poor bond will result. In this case prepare the surface with a primer or try flame etching. 

For example, SWCNTs (Figure 7.2a) were coated on flame-etched carbon fiber nanoelectrodes and used as electrochemical sensors (Figure 7.2b). The (2NT-modified electrode, with tips ranging from 100 to 300 nm, exhibited overall detection capabilities in the nanomolar range, which is an order of magnitude lower than the conventional carbon fiber electrodes of similar geometry. These small electrodes would be well suited for electrochemical applications in ultra-low fluid volumes or biological systems such as tissue or cells. 

Strand AM, Venton BJ. Flame etching enhances the sensitivity of carbon-fiber microelectrodes. Anal Chem 2008 80 3708-15. 

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