Abstract
Both ethanol solutions and evaporated thin films of mixed crystals containing pure anthracene in pure phenanthrene were prepared in various mole concentrations. By measuring fluorescence spectra and life times of these samples, the limit of determination for anthracene in phenanthrene was quantitatively investigated. The method of fluorescence spectra: the relative intensity ratios of fluorescence spectra changed depending on the concentrations of anthracene in these samples. In the case of ethanol solutions, the concentration could be quantitatively measured to 10-6 mol/mol by using relative intensity ratios of the 423 nm-peak to the 366 nm-peak. In the case of evaporated thin films, the concentration could be quantitatively measured to 10-8 mol/mol by using the ratios of the 410 nm-peak to the 370 nm-peak. The method of fluorescence life times : the fluorescence life times changed with the concentrations of anthracene in the samples. The average life time of fluorescnece of pure phenanthrene was 69.6 ns {in the region of (360440) nm}. The average life time of pure anthracene was 19.9 ns {in the region of (380500) nm}. The average life times of mixed crystals were as follows; 10-3mol/mol20.5ns, 10-5mol/mol42.8ns, 10-7 mol/mol53.4 ns, 10-9 mol/mol59.6ns. Therefore, the lower limit of determination for anthracene in phenanthrene was decreased to less than 10-9 mol/mol. Furthermore, it was found that the fluorescence life times of phenanthrene reported in literatures were largely effected by impurities, comparing with the life times presented in this report.
