Page 214 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

Reactive Oxygen Species Generation on Nanoparticulate Material 199

Figure 5.31 Reduction potential of increasing number of functional groups
relative to the ground state C 60 .

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However, the energy of C 60 is approximately 1.5 V higher than C 60
and as a result all functionalized triplet states remain easier to reduce
than ground state C 60 despite the negative trend in their reduction
potentials.
As a result, the change in reduction potential for monofunctionalized/
encapsulated forms of C 60 have lower rates of reduction than the
unfunctionalized/encapsulated C 60 [80]. The type of addend does seem
to make a significant difference. Cages with positively charged amino
functional groups are more susceptible to reduction than the nega-
tively charged carboxyl groups.
In the case of fullerol, the reduction potential is estimated between
0.358 and 0.465 V vs. NHE ( 0.600 and 0.707 vs. SCE), indicating
the reduction potential decrease with addition of addends (Figure 5.33) has
a limit. Fullerol has been shown to produce type I (Eq. 103) superoxide in

Figure 5.32 Relative triplet energy with increasingly functionalized C 60 cage.