Controllable preparation and disorder-dependent photoluminescence of morphologically different C60 microcrystals*

Abstract

Different C60 crystals were synthesized by precipitation from a mixture of the good solvent m-xylene and the poor solvent isopropyl alcohol. The samples were characterized by scanning electron microscopy (SEM), Raman spectroscopy, thermogravimetric analysis, and high resolution transmission electron microscope (HRTEM). We found that the morphologies and sizes of the samples could be controlled by adjusting the volume ratio between the good and poor solvents. Especially, an unexpected short flower column-like crystal was synthesized at low ratios (from 1:6 to 1:12). Room temperature photoluminescence (PL) and HRTEM studies of the C60 crystal samples reveal that the PL efficiency of the crystals decreases with increasing crystalline order and that the disordered C60 crystals synthesized at the ratio of 1:2 show 10 times higher PL efficiency than that of pristine C60. The mechanism of the growth process of these C60 crystals was also studied by replacing the good solvents m-xylene with toluene and mesitylene.