Neutron bombardment of C₆₀ and C₇₀ fullerenes: A spectroscopic and calorimetric study

ABSTRACT

C₆₀ and C₇₀ fullerenes were neutron-bombarded to an integral dose of 3.28×10¹⁶ n cm⁻². After the neutron treatment the trichloromethane soluble fraction was determined spectrophotometrically and C₆₀ insoluble fraction was found at 3.8% while the insoluble fraction of C₇₀ 17.9%. The formation of the CHCl₃ insoluble fraction is due to polymerization and incipient amorphization of the neutron-bombarded fullerenes where C₇₀ appears more sensitive to radiation damage than C₆₀. Raman spectroscopy was used for the characterization of the irradiated fullerenes as well as electron spin resonance (ESR) and electronic absorption spectroscopy on solid samples. Differential scanning calorimetry (DSC) to 630°C was employed for the determination of the Wigner energy of the neutron-damaged fullerenes. The results are consistent with a higher level of radiation damage reached by C₇₀ in comparison to C₆₀ at the same neutron dose.

KEYWORDS:

• Fullerenes
• Neutron damage
• Wigner energy
• Raman spectroscopy
• ESR
• Electronic absorption spectroscopy
• DSC

Acknowledgments

We wish to thank Dr. Michele Prata from LENA, Laboratorio Energia Nucleare Applicata in Pavia, for the kind assistance in the neutron irradiation experiments.