Tip Generation-Substrate Collection Mode

Fig. 37.3. Schematics of the GC mode, (a) Substrate-generation/tip-collection mode and (b) tip-generation/substrate-collection mode.

Recently, Colley et al. [104] studied the distribution of electrochemical activity in microarray electrodes. The array contained 50-pm diameter boron-doped regions spaced 250 pm apart in an intrinsic diamond disk. Reaction rate imaging was done in the substrate generation/tip collection mode. The electroactive boron doped regions were biased at a suitable potential to reduce the mediator, [Ru(NH3)6]3+, and the product of the reduction reaction was collected at the tip. Two-dimensional scans over different regions (Fig. 21) revealed wide variations in local electroactivity. 

Recently, the substrate-generation/tip-collection mode of SECM was exploited to confirm the release of oligomers by PEDOT films electrogenerated from aqueous solutions... 

A number of SECM modes of operation are possible [28,48]. The tip can be used to detect a species generated at the substrate surface (substrate generation/tip collection mode or SG/TC mode), a method that is particularly useful in corrosion studies. Alternatively, the tip generation/substrate collection (TG/SC) mode is usefiil for kinetic measurements. Additional information may be obtained by... 

Sanchez-Sanchez CM, Rodriguez-Lopez J, Bard AJ (2008) Scaiming electrochemical microscopy. 60. Quantitative calibration of the SECM substrate generation/tip collection mode and its use for the study of the oxygen reduction mechanism. Anal Chem 80(9) 3254-3260... 

Martin RD, Unwin PR (1998) Theory and experiment for the substrate generation tip collection mode of the scanning electrochemical microscope application as an approach for measuring the diffusion coefficient ratio of a redox couple. Anal Chem 70 (2) 276-284. doi 10.102l/ac97068Ip... 

To study the kinetics of electron transfer, SECM can be operated in two modes a feedback mode (53, 69) and a substrate generation-tip collection mode (53). In the feedback mode, a mediator redox couple is required to probe the interface. The tip is poised to a potential well above Eredox- The steady-state current observed due to hemispherical diffusion of O toward the tip is expressed as (Figure 9.29a)... 

Martin, R. D., Unwin, P. R. 1998. Scanning electrochemical microscopy. Kinetics of chemical reactions following electron-transfer measured with the substrate-generation-tip-collection mode. J Chem Soc Faraday Trans 94 753-759. 

An important example of an ET process with coupled homogeneous reactions is reduction oxygen with DMFc at the water-DCE interface [93]. The substrate generation/tip collection mode of... 

There are several similarities between the classical amperometric and voltammetric measurements performed at microelectrodes and the substrate generation-tip collection modes of SECM, for example, in both cases, a microelectrode in close proximity to a cell membrane is used to oxidize (or reduce) the molecules ejected from the cell to obtain information on cellular functions at the single cell level. However, the use of a SECM provides additional dimensions through the feedback and imaging modes. Such measurements are crucial in establishing SECM as a quantitative bio-analytical microscopy and its ability to perform time-lapse cell response measurements. As such. Chapter 12 focuses exclusively on SECM studies performed on living systems. 

Fig. 14 Epidermal growth factor receptor (EGFR) image on single Chinese ovary (CHO) cell. Alkaline phosphatase was used as label in sandwich immune stile. PAP was detected in substrate generating tip collecting mode. Cell with EGRF (left), normal cell (right) [143]...

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