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摘要
Polycyclic aromatic hydrocarbon compound, 1,2ˋ:ˋ3,4-dibenzanthracene, is spectroscopically analyzed in ethanol. Ultraviolet absorption spectra were taken and fluorescence measurements were performed. From absorption and emission spectra, Stokes%26apos; lines were clearly discernible and these shifts were recorded. Being a carcinogenic compound, the detection of 1,2ˋ:ˋ3,4-dibenzanthracene presence in the environment as a pollutant with adverse genotoxic effects is vital. 1. Introduction Absorption and emission spectroscopy of dibenzanthracene (DBA) isomers such as 1,2,5,6-DBA, 1,2,7,8-DBA have been analyzed in polymer matrices [1, 2]. Amorphous solids such as polymethlymethracrylate remain relatively rigid even at high temperatures and DBA molecules cannot move freely in such solids, thus making them ideal for time resolved absorption and fluorescence spectra studies of DBA isomers. Singlet and triplet electronic absorption and prompt fluorescence can be readily observed. However, DBA in solvents such as ethanol is much more complicated for absorption and fluorescence spectroscopy. We aim to fill this gap by taking ultraviolet (UV) absorption spectroscopy, fluorescence emission spectroscopy, and Fourier Transform infra-red spectroscopy of 1,2ˋ:ˋ3,4-dibenzanthracene in ethanol. We also show Stokes＊ shifts in the fluorescence spectroscopy by measuring the quantum efficiency of the 1,2ˋ:ˋ3,4-dibenzanthracene and ethanol solution. The molecular structure of 1,2ˋ:ˋ3,4-dibenzanthracene is shown in Figure 1. Figure 1: 1,2ˋ:ˋ3,4-dibenzanthracene. Absorption of light by the molecule excites the molecule to one of the upper electronic singlet states from ground state. Most of the molecules reside in the lowest vibrational state at room temperature and absorption of light initiates upward transitions from this level to higher levels. When the molecule reaches the first excited singlet state, the molecule can return to any one of the vibrational levels of the ground state by emitting fluorescence. Part of the excited molecules can also return to ground state following other mechanisms such as through quenching processes, photochemical changes, or conversion to triplet state. Hence, fluorescence efficiency becomes less than one [3每12]. In particular, fluorescence spectroscopy of 1,2ˋ:ˋ3,4-dibenzanthracene reveals clear Stokes＊ shifts when the molecule is excited in UV. 2. Materials and Methods 1,2ˋ:ˋ3,4-dibenzanthracene, was of AccuStandard reagent grade, used as received without any further purification and was mixed with ethanol at atmospheric pressure. The concentration
