ABSTRACT

Optical properties of nanoscaled phases of solid C60 are discussed. First, electronic and optical properties of C60 molecules and bulk crystals are briefly reviewed. Then, optical properties of C60 nanocrystals, nanowhiskers, and nanotubes are presented. Finally, photo-induced structural transformations of C60 nanowhiskers and nanotubes to polymeric and graphitic phases are described. It is pointed out that the electronic structures, and therefore the optical properties, of C60 are influenced strongly by its aggregated nanoscaled forms. The condensation of C60 molecules into nanoscaled forms play an intriguing role in the vibronic coupling of C60. 11.1 INTRODUCTION

One of the great interests in physical properties of fullerenes is to

clarify how the electronic structure can be tailored by condensing them into various solid forms. Although physical properties of C60 in its molecular and bulk solid states have been investigated extensively, the properties of intermediate state between bulk and molecular states, i.e., mesoscopic or aggregated nanoscaled state of solid C60, have not been understood well. Martin et al. observed the icosahedral (C60)n clusters (10 < n < 100) in the photoionization time-of-flight mass spectra in vacuum.1 Aggregation of C60 molecules to form (C60)n clusters (1 < n < 10) was also observed in solution.2,3 Some attempts were made to incorporate C60 into the pores of zeolites4-6 and porous glasses.7 However, those C60 clusters are too small to understand the properties of the mesoscopic state of solid C60. It has been necessary to make stable and well-dispersed nanometer-sized C60 crystals to investigate the electronic properties of the mesoscopic phase of solid C60.