Differential
Photoactivity of Aqueous [C<sub>60</sub>] and [C<sub>70</sub>] Fullerene
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Abstract
Many
past studies have focused on the aqueous photochemical properties
of colloidal suspensions of C<sub>60</sub> and various [C<sub>60</sub>] fullerene derivatives, yet few have investigated the photochemistry
of other larger cage fullerene species (e.g., C<sub>70</sub>, C<sub>74</sub>, C<sub>84</sub>, etc.) in water. This is a critical knowledge
gap because these larger fullerenes may exhibit different properties
compared to C<sub>60</sub>, including increased visible light absorption,
altered energy level structures, and variable cage geometries, which
may greatly affect aggregate properties and resulting aqueous photoactivity.
Herein, we take the first steps toward a detailed investigation of
the aqueous photochemistry of larger cage fullerene species, by focusing
on [C<sub>70</sub>] fullerene. We find that aqueous suspensions of
C<sub>60</sub> and C<sub>70</sub>, nC<sub>60</sub> and nC<sub>70</sub>, respectively, exhibit many similar physicochemical properties,
yet nC<sub>70</sub> appears to be significantly more photoactive than
nC<sub>60</sub>. Studies are conducted to elucidate the mechanism
behind nC<sub>70</sub>’s superior <sup>1</sup>O<sub>2</sub> generation, including the measurement of <sup>1</sup>O<sub>2</sub> production as a function of incident excitation wavelength, analysis
of X-ray diffraction data to determine crystal packing arrangements,
and the excited state dynamics of aggregate fullerene species via
transient absorption spectroscopy
