Khan Muhammad Farooq Saleem, Akbar Mona, Wu Jing
State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China.
J Fluoresc. 2024 Aug 26. doi: 10.1007/s10895-024-03905-4.
Polyaromatic hydrocarbons (PAHs) are widely spread pollutants in the environment, including soil and water. Anthracene (anth) and phenanthrene (phen) pose severe health impacts on human lives due to their carcinogenic nature by increasing cancer risk to the skin, lungs, and bladder. Fluorescence spectroscopy is a promising , efficient and straightforward tool for characterizing these trace PAHs in water. Therefore, the current work provides a detailed insight into the fluorescence properties of anth and phen in water. The fluorescence EEMs (excitation-emission matrices) of anth showed emissions at 380 nm, 400 nm, and 425 nm with single excitation at 250 nm, whereas phen showed two emissions < 380 nm, at 350 nm and 365 with single excitation at 250 nm. Then the theoretical EX/EM wavelengths were calculated by DFT and CIS-B3LYP for these compounds in water. The environmental effect of pH variation on fluorescence EEM shows a significant difference in fluorescence intensity without changing in peak locations, with highest fluorescence intensity at neutral pH than acidic and alkaline. Furthermore, the theoretical pH effect was described for the first time by simulating the protonated (+ 1), deprotonated (-1) and neutral molecules in water at the DFT level of theory. The variation in simulated oscillator strengths was similar in trend with the experimental fluorescence intensity of these compounds. The HOMO-LUMO were calculated to obtain the energy gap, molecular softness, molecular hardness, electronic potential and electrophilicity of anth and phen. To find the fluorophore contribution, the fluorescence of homogeneous mixture of both isomers was analyzed, which showed an enhanced fluorescence intensity of anth by 12-20%, whereas a decrease of 9-14% was observed in phen. This study describes that the fluorescence technique could be a fast and easy method to distinguish and identify PAHs isomers (anth and phen) in water.
多环芳烃（PAHs）是环境中广泛存在的污染物，包括土壤和水体。蒽（anth）和菲（phen）具有致癌性，会增加皮肤、肺部和膀胱的癌症风险，对人类健康构成严重影响。荧光光谱法是一种很有前景、高效且直接的工具，可用于表征水中的这些痕量多环芳烃。因此，当前的工作详细深入地研究了蒽和菲在水中的荧光特性。蒽的荧光EEMs（激发 - 发射矩阵）在250 nm单激发下，在380 nm、400 nm和425 nm处有发射峰，而菲在250 nm单激发下，在380 nm以下有两个发射峰，分别在350 nm和365 nm处。然后通过DFT和CIS - B3LYP计算了这些化合物在水中的理论激发/发射波长。pH变化对荧光EEM的环境影响表明，荧光强度有显著差异，但峰位置不变，中性pH下的荧光强度高于酸性和碱性条件。此外，首次通过在DFT理论水平上模拟水中的质子化（+1）、去质子化（-1）和中性分子来描述理论pH效应。模拟的振子强度变化趋势与这些化合物的实验荧光强度相似。计算了蒽和菲的HOMO - LUMO以获得能隙、分子柔软度、分子硬度、电子势和亲电性。为了找到荧光团的贡献，分析了两种异构体均匀混合物的荧光，结果表明蒽的荧光强度增强了12 - 20%，而菲的荧光强度下降了9 - 14%。这项研究表明，荧光技术可能是一种快速简便的方法，用于区分和识别水中的多环芳烃异构体（蒽和菲）。
