Solvent-Mediated Shape Engineering of Fullerene (C₆₀) Polyhedral Microcrystals

Abstract

n-Heptanol bearing a long hydrocarbon chain is for the first time attempted as poor solvent for reprecipitation of fullerene C60 crystals, which unprecedentedly prompts the selective synthesis of well-faceted parallelepiped, hexagonal plate, cuboctahedron, octahedron C60 crystals, as well as their derivatives with varying degrees of edge- and corner-truncation. Our comprehensive investigations support that morphology evolution is systematically modulated by the solvent proportion of n-heptanol, where increasing the proportion of n-heptanol gradually tunes C60 growth behavior from thermodynamic to kinetic regime, and thus induces a general shape evolution from parallelepiped or truncated parallelepiped, to an intermediate shape like hexagonal plate or truncated octahedron or cuboctahedron, eventually into octahedron. We also prove the existence of n-heptanol molecules as high as 10 wt % inside the final C60 polyhedral crystals, which results in the extraordinarily PL enhancement as well as an obvious blue-shift of PL peaks when compared to that of the solvent-free crystal. Our study provides a fundamental understanding toward the solvent-mediated shape-control process for organic polyhedral crystals, enlightening on solvent-intercalate-induced unique properties.