Examples of AFM Analysis and

Imaging Enzyme Fuel Cell Materials The most common application of AFM is imaging the surface of electrode materials. Dispersion of enzyme immobilized to electrode surfaces can be qualitatively determined and, in some cases, attachment of enzyme and additives (e.g., CNT) can be quantified. Different loadings of MWCNT 

FIGURE 13.13 AFM images of (a) bare HOPG, (b) first polyterthiophene monomer, and (c) second Fe-containing polyterthiophene monomer synthesized on HOPG surfaces. (Adapted with permission from Ref. [62]. Copyright 2010, Elsevier.) 

The actual diameter of an object d) smaller than the tip radius has an imaged diameter (D) when the radius of the tip (r) and the height Qi) are considered. Hence, the apparent enzyme diameter of 26 nm, calculated to be an actual radius of 4.5 nm for the enzyme, is in close agreement with an enzyme monolayer thickness of 8nm calculated from force measurements and the reported diameter of the T. versicolor laccase [67]. From values of the observed electric current and electrode surface area (measured by direct electrochemistry and capacitance analysis, respectively) and the enzyme density calculated from the average area per enzyme molecule derived from AFM height images, the current per enzyme molecule was calculated to be 5xlO pA. 

---