From 3D Hierarchical Microspheres to 1D Microneedles: The Unique Role of Water in Morphology Control of Ferrocenylpyrrolidine C60 Microcrystals

Abstract

Fullerene microcrystals have been well prepared by the conventional liquid-liquid interface precipitation (LLIP) method, and the crystal structures can be manipulated by solvent combination. Aromatic and alcoholic solvents are widely used as good and poor solvents, respectively in LLIP. However, water with higher polarity has been rarely utilized as a poor solvent for morphology engineering of fullerenes, especially in the morphology control of fullerene derivatives. Herein, water-regulated morphology of a fullerene derivative, ferrocenylpyrrolidine C60 (denoted as FC), is investigated via the LLIP method. By simply modulating the combinations of good solvent (aromatic isopropylbenzene, IPB) and poor solvents (alcohols), three-dimensional (3D) hierarchical microspheres of FC are obtained. Surprisingly, when water is introduced as one of poor solvents in the LLIP process, one-dimensional (1D) microneedles are prepared. The presence of water controls the liquid-liquid interface, the external environment and kinetics of crystal growth, thereby promoting the morphological evolution from 3D hierarchical microspheres to 1D microneedles. Moreover, the solvated 1D microneedles exhibit enhanced photoluminescence (PL) and photocurrent response in virtue of the highly ordered molecule arrangement and solvent (IPB) embedding in the crystal lattice. Water-regulated morphology engineering of FC provides a new strategy for the growth and morphology control of fullerene microcrystals.