The Diagnostics of Laser-Induced Fluorescence (LIF) Spectra of PAHs in Flame with TD-DFT: Special Focus on Five-Membered Ring.
The Diagnostics of Laser-Induced Fluorescence (LIF) Spectra of PAHs in Flame with TD-DFT: Special Focus on Five-Membered Ring.
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DOI：
10.1021/acs.jpca.5b10114
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发表时间：
2015-12
期刊：
影响因子：
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通讯作者：
Peng Liu;Zhenwu He;Gao‐Lei Hou;B. Guan;He Lin;Zhen Huang
中科院分区：
文献类型：
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作者：
Peng Liu;Zhenwu He;Gao‐Lei Hou;B. Guan;He Lin;Zhen Huang
采用密度泛函理论（DFT）、含时密度泛函理论（TD-DFT）和预混火焰模拟方法，研究了从苯乙炔到红宝石烯等13种气相多环芳烃的电子发射特性，并对火焰中多环芳烃的激光诱导荧光（LIF）光谱进行了诊断。结果表明，五元环多环芳烃的最大发射波长位于可见光区，且对碳原子数不敏感。而不含五元环的多环芳烃由于HOMO-LUMO能隙减小，荧光波长随碳原子数的增加而增加.此外，线性排列的不含五元环的多环芳烃的荧光波长比非线性排列的多环芳烃的荧光波长长。根据Franck-Condon原理，得到了振动分辨的电子荧光光谱。结果表明，含五元环的多环芳烃的荧光带宽比不含五元环的多环芳烃的荧光带宽宽得多。多环芳烃的浓度计算采用预混平焰模型与KM 2机制。根据荧光光谱带宽和多环芳烃的浓度，绘制了火焰中多环芳烃的潜在荧光分布图。根据多环芳烃的荧光分布图，可以区分特定的多环芳烃。结果表明，萘是火焰中312-340 nm区域荧光的主要来源。1-乙炔基萘是最有可能发射位于360-380 nm区域的荧光的候选者。波长大于500 nm的荧光信号可能是五元环多环芳烃的荧光信号。该研究有助于提高LIF技术对多环芳烃的选择性，特别是在可见光区。
The electronic emission characteristics of 13 gas-phase PAHs, ranging from phenlylacetylene to rubicene, were investigated to diagnose laser-induced fluorescence (LIF) spectra of PAHs in flame by DFT, TD-DFT, and premixed flame modeling methods. It was found that the maximum emission wavelengths of the PAHs with five-membered ring are located in visible region and insensitive to the number of C atoms. However, the fluorescence wavelengths of the PAHs without five-membered rings increase with the number of C atoms due to the reduced HOMO-LUMO gap. In addition, the fluorescence wavelength of the PAHs without five-membered rings with linear arrangement is longer than that of PAHs with nonlinear arrangement. According to the Franck-Condon principle, the vibrationally resolved electronic fluorescence spectra were obtained. The results show that fluorescence bandwidth of the PAHs with five-membered rings is much broader than that of the PAHs without five-membered rings. The concentration of PAHs was calculated by using the premixed flat-flame model with KM2 mechanism. On the basis of the fluorescence bandwidth and the concentration of the PAHs, the potentially fluorescence distribution of PAHs in flame was mapped. One can distinguish the specific PAHs according to the mapped fluorescence distribution of PAHs in this study. It was found that naphthalene should be responsible for the fluorescence located in the 312-340 nm region in the flame. 1-Ethynylnaphthalene is the most possible candidate to emit the fluorescence located in the 360-380 nm region. The fluorescence signals with the wavelength longer than 500 nm are likely emitted by the PAHs with five-membered rings. This study contributes to enhance the selectivity of PAHs in LIF technology, especially in the visible region.