Three-Dimensional "Star of David"-Shaped Fullerene (C60) Microstructures: Controlled Synthesis, Photoluminescence, and Photoelectrochemical Properties

Fullerene micro-/nanostructures with controllable dimensions and explicit morphologies have been widely studied, but such architectures without definitely exposed facets have rarely been reported because of the difficulties in regulating the diffusion behaviors of fullerene molecules at the interfaces. Herein, assuming that solvent viscosity may exert a decisive effect on the diffusion of C-60 molecules and thus the morphologies of C-60 crystals, we chose the high-viscosity isobutyl alcohol (IBA) and anisole as the poor and good solvents, respectively, to synthesize the unprecedented three-dimensional "Star of David"-shaped C-60 microcrystals (SOD) which consist of two oppositely linked quadripods with a common vertex merged together. The curved surface of SOD is obviously different from those of the previously reported fullerene micro-/nanostructures which all show clear crystalline facets. The decisive effect of viscosity on the formation of SOD has been verified by introducing ultrasonication or increasing the concentration of C-60 which promotes the diffusion of C-60 molecules and thus weakens the restrictive effect of the high-viscosity IBA molecules so that well-faceted octahedral microcrystals are formed. We also found that the photoluminescence and photoelectrochemical behaviors of C-60 crystals depend strongly on their surface curvatures, providing a strategy to regulate the photophysical properties to ensure their potential applications as photodetectors. This study reveals for the first time the effect of solvent viscosity on the morphology of C-60 crystals, providing valuable information about the formation mechanism of fullerene micro-/nanostructures.