60
1
2
1
3
3
3
1, 2
1
. Chemistry and Physics Department, SUNY College at Old Westbury, Old Westbury, NY 11568,
2
. Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217,
3
.
Department of Biology, Jackson State University, Jackson, MS 39217
The stock C
60
water suspension (10 -6 -10 -4 M) is prepared in a 0.5 M KNO
3
solution containing 20% DMSO for cyclic voltammetric measurements, and in a 0.8% (W/V) saline solution
(or 0.14 M NaCl) containing 1% DMSO for superoxide detection. The above mixtures are subjected to sonication for several hours, which resulted in the formation of water-stable C
60
aggregates.
O
2
.-
is detected by a modified NBT method.( 1, 2 ) NBT exists as an oxidant (light yellow)
and reacts with O
2
. rapidly at weakly acidic pH to form formazon (dark blue). The generation of
O
2
. is monitored by measuring the formation of formazon at 560 nm. Briefly, to a saline solution
(1.6 mL), 0.20 mL 1.0 mM NBT (in pH 6.8, 50 mM phosphate buffer), 0.20 mL 5.0 mM NADH (in pH 7.0 saline solution) and 0.020 mL 1.4x10
-4 M C
60
are added and thoroughly mixed. The above mixture is irradiated at 365 nm for up to 2 hours and measured spectroscopically at appropriate time intervals. The amount of O
2
. produced is estimated using an extinction coefficient of formazon
1.3x10
5 M -1 cm -1 .
1

The cyclic voltammetric experiments are performed in a three electrode chemical cell at a scan rate of 0.5 V/s for the potential range between 0.2 V and -1.4 V. The working electrode is a 3 mm diameter glassy carbon electrode. The auxiliary electrode is a 10 µm diameter platinum wire electrode. All potentials are measured versus an Ag/AgCl reference electrode for 7x10 -5 M C
60
in
20% DMSO aqueous solution in the presence of 0.5 M KNO
3
as supporting electrolytes. The glassy carbon electrode is polished with 0.05 micron titania powder and rinsed thoroughly with water. The cyclic voltammetric measurements are taken after stirring the C
60
solutions for 1 hour to allow the adsorption of C
60
onto the surface of the working electrode.
. Cyclic voltammogram of 7.0x10
-5 M C
60
in 20% DMSO aqueous solution containing
0.5 M KNO
3
as supporting electrolytes, using a glassy carbon working electrode, a platinum wire counter electrode and an Ag/AgCl reference electrode at a scan rate of 0.5 V/s. The arrows indicate sweep directions.
2

. The effect of 6-TG (2x10 -4 M) on visible light/C
60
(9x10 -5 M)-induced DMA (6x10 -3
M) photooxidation in air-saturated 2:1 C
6
D
6
/d-DMSO solutions containing 2.5 M CH
3
COOH. 1, 2 and 3: DMA upon irradiation for 0, 10 and 40 minutes in the presence of 6-TG with DMA conversion yields of 0, 11% and 47%, respectively; 4, 5 and 6: DMA upon irradiation for 0, 10 and
40 minutes in the absence of 6-TG with DMA conversion yields of 0, 13% and 56%, respectively.
3

. Accumulated conversion yield of 6 µmole DMA to DMA endoperoxide versus visible light irradiation time for 0.08 µmole C
60
in the absence (black line) and presence (red line) of 0.2
µmole 6-TG in an air-saturated 2:1 C
6
D
6
/d-DMSO solution containing 7 mM HCl.
. Accumulated conversion yield of 6 µmole DMA to DMA endoperoxide versus visible light irradiation time for 0.08 µmole C
60
in the absence (black line) and presence (red line) of 0.2
µmole 6-TG in an air-saturated 2:1 C
6
D
6
/d-DMSO solution containing 2.5 M CH
3
COOH
4

1.
2.
Benon H. J. Blelski, Grace G. Shiue, and Bajuk, S. (1980) Reduction of Nitro Blue Tetrazolium by COP- and O2- Radicals, J. Phys. Chem. 84, 830-833.
Rui-heng Liu, Shi-yu Fu, Huai-yu Zhan, and Lucia, L. A. (2009) General Spectroscopic Protocol to
Obtain the Concentration of the Superoxide Anion Radical, Ind. Eng. Chem. Res. 48, 9331-9334.
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