Fluorescence Characteristics of Carbazole-Anthracene, Carbazole-Phenanthrene Mixed Crystalst

Abstract

In order to study the purity of carbazole, the evaporated thin films of carbazole-anthracne and carbazole-phenanthrene mixed crystals containing 10^-8∼10^-8 mol/mol of anthracene and of phenanthrene, respectively, were prepared on quartz plates. Commercial carbazole was purified by treatment with maleic anhydride and chloranil, with metallic sodium in 1-pentanol, followed by chromatography on an alumina column. It was finally zone-refined. The fluorescence spectra, the fluorescence lifetimes and the time-resolved. fluorescence spectra were measured both at room and liquid nitrogen temperatures.
Anthracene of the concentration less than 10^-7 mol/mol in the carbazole can be detected by the fluorescence spectra, and anthracene, less than 10^-9 mol/mol, can be detected by the timeresolved fluorescence spectra. However, it was difficult to measure the, concentration of anthracene in the carbazole by the fluorescence lifetimes, because their fluorescence were in the same range. The - phenanthrene less than 10^-5mol/mol in the carbazole can be detected by the fluorescence spectra, that of less than 10^-6 mol/mol bry the time-resolved fluorescence spectra, and that of less than 10^-7 mol/mol by the fluorescence life times. It was concluded that the concentration of anthracene and plienanthrene: containeci in 'corn mercial carbazole as impurities could be decreased to less than 10^-9mol/mol and 10^-7mol/mol, respectively, by the method described above.