Unusual redox behavior of a water soluble malonic acid derivative of C60: evidence for possible cluster formation

Guldi, Dirk M.; Hungerbuehler, Hartmut; Asmus, K.‐D.

doi:10.1021/j100036a026

Cited by 102 publications

(74 citation statements)

References 14 publications

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“…In PCBM charge absorption is characterized by two main bands: one with peak at 1.2 eV and shoulder at 1.35 eV, and a weaker band located at 2 eV. Our data is perfectly consistent with previa assignments of the absorption of fullerene anions 13 and photoinduced absorption ͑PA͒ spectroscopy at room temperature in C 60 films reported by Vardeny and co-workers. 14 In this latter work, these two bands are assigned to polaron subgap and intragap transitions, respectively.…”

Section: Resultssupporting

confidence: 91%

Subpicosecond photoinduced Stark spectroscopy in fullerene-based devices

et al. 2007

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We present a detailed study of the charge photogeneration and decay kinetics in ͓6,6͔-phenyl C61-butyric acid methyl ester by performing subpicosecond Stark spectroscopy measurements. Owing to the large photogenerated charge density and the strength of the applied field, progressive quenching of the Stark signal is observed during the first 20 ps, followed by a slow recovery at longer time scales. The quenching regime provides information on the average e-h separation and drift motion within the e-h pair whereas the recovery is related to the kinetics of charges and their recombination probability.

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Section: Resultssupporting

confidence: 91%

Subpicosecond photoinduced Stark spectroscopy in fullerene-based devices

et al. 2007

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“…Both of these fullerenes are readily soluble in water. However, it has been reported that some functionalized fullerenes may form aggregates in polar media at high concentrations (31,(42)(43)(44)(45). To verify the formation of aggregates, UV-visible absorption spectra of different concentrations of (γ-CyD) 2 /C 60 and C 60 (OH) 24 in aqueous solution were recorded.…”

Section: Resultsmentioning

confidence: 99%

Pristine (C₆₀) and Hydroxylated [C₆₀(OH)₂₄] Fullerene Phototoxicity towards HaCaT Keratinocytes: Type I vs Type II Mechanisms

Zhao

Bilski

et al. 2008

Chem. Res. Toxicol.

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The increasing use of fullerene nanomaterials has prompted widespread concern over their biological effects. Herein, we have studied the phototoxicity of γ-cyclodextrin bicapped pristine C 60 [(γ-CyD) 2 /C 60 ] and its water-soluble derivative C 60 (OH) 24 toward human keratinocytes. Our results demonstrated that irradiation of (γ-CyD) 2 /C 60 or C 60 (OH) 24 in D 2 O generated singlet oxygen with quantum yields of 0.76 and 0.08, respectively. Irradiation (>400 nm) of C 60 (OH) 24 generated superoxide as detected by the EPR spin trapping technique; superoxide generation was enhanced by addition of the electron donor nicotinamide adenine dinucleotide (reduced) (NADH). During the irradiation of (γ-CyD) 2 /C 60 , superoxide was generated only in the presence of NADH. Cell viability measurements demonstrated that (γ-CyD) 2 /C 60 was about 60 times more phototoxic to human keratinocytes than C 60 (OH) 24 . UVA irradiation of human keratinocytes in the presence of (γ-CyD) 2 /C 60 resulted in a significant rise in intracellular protein-derived peroxides, suggesting a type II mechanism for phototoxicity. UVA irradiation of human keratinocytes in the presence of C 60 (OH) 24 produced diffuse intracellular fluorescence when the hydrogen peroxide probe Peroxyfluor-1 was present, suggesting a type I mechanism. Our results clearly show that the phototoxicity induced by (γ-CyD) 2 /C 60 is mainly mediated by singlet oxygen with a minor contribution from superoxide, while C 60 (OH) 24 phototoxicity is mainly due to superoxide.

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“…It has been found that these derivatives can dissolve either in the form of monomers or as supramolecular aggregates. [8] In particular, water-soluble C 60 multiple adducts prefer to dissolve as monomers in water and aqueous organic solvents, [9][10][11] whereas monoadducts display a strong tendency to form clusters, [10,[12][13][14][15][16][17][18] depending upon the particular hydrophilic/hydrophobic balance in their molecular structures and the polarity [7] of the medium. The present work intends to identify reliable descriptors of the hydrophilic/hydro-chromatography (log k w ).…”

Section: Introductionmentioning

confidence: 99%