Generation-Collection Mode Imaging

FIG. 15 Image improvement in generation-collection mode imaging as introduced by Engstrom et al. (66) (schematics prepared by the chapter authors). 

The imaging of enzyme activity at insulating supports can be achieved via feedback or generation-collection modes as described in Secs. I.C and I.D. 

Fig. 4 Schematics of the feedback mode (a) and the generation-collection mode (b) of SECM for imaging and...

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. 

For surface analysis all SECM modes—the feedback, generation/collection, and direct modes—have been used to visualize lateral differences in heterogeneous electron transfer properties. At this point, we shall briefly review a few aspects of surface imaging concerning the acquisition and interpretation of data that are relevant for most experiments before presenting individual studies. Details of SECM imaging are discussed in Chapter 4. 

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