Environmental Engineering Reference
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covalently attached to a Au electrode via cysteamine and the other to the flavin group
of glucose oxidase [Patolsky et al., 2004]. Such a carbon nanotube “forest” electrode
has also been applied to peroxidases [Gooding et al., 2003; Yu et al., 2003].
Of direct interest for biofuel cell applications are the reported reduction of O 2 by
multi-copper oxidases on carbon nanotube electrodes [Yan et al., 2006; Zheng
et al., 2006] and the oxidation of H 2 by hydrogenase covalently bound to carbon nano-
tubes [Alonso-Lomillo et al., 2007]. The hydrogenase/nanotube anode is extremely
stable (.1 month), and shows 33-fold enhanced enzyme coverage compared with
similarly treated graphite of the corresponding geometric surface area. A. vinosum
Figure 17.21 Allochromatium vinosum [NiFe]-hydrogenase adsorbed onto single-walled
carbon nanotubes pretreated with polymyxin. (a) Tapping-mode atomic force microscopy
image of carbon nanotubes grown on Si/SiO 2 by chemical vapor deposition (according to
the method of [Kong et al., 1998]). Nanotubes were first incubated with 0.2 mg mL 21 poly-
myxin and then with 20 nm hydrogenase. (b) Cyclic voltammograms recorded at 5 mV s 21
showing electrocatalysis by a dense layer of carbon nanotubes [Heering et al., 2006], treated
with 50 mg mL 21 polymyxin and then with 0.5 mM hydrogenase. The solid trace was recorded
under argon, the dash - dotted trace with 0.4 mM H 2 in solution, and the dashed trace with
0.2 mM of the inhibitor CO. The buffer was 15 mM MES containing 100 mM NaCl, pH
5.7, and the macroscopic electrode area was 10 mm 2 .
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