Organic Solvents C <sub> 60 </ Sub> Fluorescence Characteristics At Room Temperature And Fluorescence Emission Mechanism

Since an efficient preparation method for high pour C₆₀ having been discovered by Kratschmer and Huffman, the unique photophysical properties of C₆₀ have been extensively studied by scientists, especially, investigation on the fluorescence properties of C₆₀ is of great significance for exploiting novel fullerene-based photosensitive and luminescent materials. While, the intersystem crossing from singular state to the excited triplet state and the forbidden electronic transitions induced by the high symmetry produce a low fluorescence quantum yield of C₆₀, as leads to the difficulty of the experimental observation of C₆₀ fluorescence. Even though the symmetry of C₆₀ molecule could be reduced through lowing the temperature, and thus some high quality fluorescence spectra from C₆₀ solid films and C₆₀ in organic solvent have been obtained, the fluorescence from room-temperature C₆₀ is usually quite weak. Therefore, it is necessary to investigate the fluorescence properties and the luminescence mechanism of C₆₀ at room temperature.In this thesis, fluorescence properties of C₆₀ in CS₂, toluene, acetonitrile, DMSO, benzene and pyridine were studied at room temperature. It is exhibited that fluorescence bands from C₆₀ in organic solvents are generally located at 430 nm, 570 ran or 700 ran, additionally, the fine-structure of C₆₀ fluorescence spectrum is relative to the solvent. The solvent molecule with isolated electrons or conjugative structure of π electrons could induce a strong interaction with C₆₀, and the solvent-induced symmetry reduction of C₆₀ molecule may result in the increase of fluorescence radiation rate. Thus, a novel approach is provided for the fabrication of fullerene-based luminescent materials at room temperature.Even though a consensus on solvent effect seems to exist, theoretical or experimental evidences acquired so far are still not persuasive enough for revealing the origin of the rich and distinct fluorescence of C₆₀ in pyridine. In order to investigate the luminescence mechanism of C₆₀ in pyridine, fluorescence measurements combined with in-situ Transmission Electron Micrograph (TEM) observations were taken on C6o-pyridine system. It is exhibited that C₆₀ in different existence phases would contributes to three fluorescence emission centers, the bluefluorescence peaks centered at 440 nm originates from C₆₀ nanoparticles; the yellow-green...