Photophysical and Nonlinear Absorptive Optical Limiting Properties of [60]Fullerene Dimer and Poly[60]fullerene Polymer

Abstract

A systematic study of the photophysical properties and nonlinear absorptive optical limiting responses of the [60]fullerene dimer (C60 dimer) and poly[60]fullerene (poly-C60) polymer in room-temperature solutions is reported. The results are compared with those of C60 and representative C60 derivatives. While the absorption, fluorescence (spectrum, quantum yield, lifetime), and photoinduced electron-transfer properties of the C60 dimer are somewhat different from those of C60, they are qualitatively similar to those of other C60 derivatives. The triplet−triplet absorption of the C60 dimer is noticeably weaker than those of C60 and other C60 derivatives, corresponding to lower optical limiting responses of the C60 dimer at 532 nm. However, the photophysical and nonlinear absorptive optical limiting properties of the poly-C60 polymer are significantly different. The polymer solution shows much weaker fluorescence, barely detectable triplet-state absorption, and marginal optical limiting response. The different excited-state and nonlinear optical properties of the poly-C60 polymer are explained in terms of new excited singlet-state decay pathways in the polymer that are not available in monomeric and dimeric C60 molecules. In addition, the issue concerning significant excited-state fullerene cage−cage interactions in the C60 dimer and poly-C60 polymer is discussed.