Surfactant-Triggered Nanoarchitectonics of Fullerene C60 Crystals at a Liquid-Liquid Interface.

Here, we report the structural and morphological modulation of fullerene C60 crystals induced by nonionic surfactants diglycerol monolaurate (C12G2) and monomyristate (C14G2). C60 crystals synthesized at a liquid-liquid interface comprising isopropyl alcohol (IPA) and a saturated solution of C60 in ethylbenzene (EB) exhibited a one-dimensional (1D) morphology with well-defined faceted structure. Average length and diameter of the faceted rods were ca. 4.8 μm and 747 nm, respectively. Powder X-ray diffraction pattern (pXRD) confirmed a hexagonal-close packed (hcp) structure with cell dimensions ca. a = 2.394 nm and c = 1.388 nm. The 1D rod morphology of C60 crystals was transformed into "Konpeito candy-like" crystals (average diameter ca. 1.2 μm) when the C60 crystals were grown in the presence of C12G2 or C14G2 surfactant (1%) in EB. The pXRD spectra of "Konpeito-like" crystals could be assigned to the face-centered cubic (fcc) phase with cell dimensions ca. a = 1.4309 nm (for C12G2) and a = 1.4318 nm (for C14G2). However, clusters or aggregates of C60 lacking a uniform morphology were observed at lower surfactant concentrations (0.1%), although these crystals exhibited an fcc crystal structure. The self-assembled 1D faceted C60 crystals and "Konpeito-like" C60 crystals exhibited intense photoluminescence (PL) (∼35 times greater than pC60) and a blue-shifted PL intensity maximum (∼15 nm) compared to those of pC60, demonstrating the potential use of this method for the control of the optoelectronic properties of fullerene nanostructures. The "Konpeito-like" crystals were transformed into high surface area nanoporous carbon with a graphitic microstructure upon heat-treatment at 2000 °C. The heat-treated samples showed enhanced electrochemical supercapacitance performance (specific capacitance is ca. 175 F g-1, which is about 20 times greater than pC60) with long cyclic stability demonstrating the potential of the materials in supercapacitor device fabrication.