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Time-Dependent Density Functional Theory Investigation of the UV–Vis Spectra of Organonitrogen Chromophores in Brown Carbon
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2020-02-10 , DOI: 10.1021/acsearthspacechem.9b00328 Jin Y. Chen 1 , Emmy Rodriguez 2 , Huanhuan Jiang 2 , Kunpeng Chen 2 , Alexander Frie 2, 3 , Haofei Zhang 1, 4 , Roya Bahreini 1, 2, 4 , Ying-Hsuan Lin 1, 2
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2020-02-10 , DOI: 10.1021/acsearthspacechem.9b00328 Jin Y. Chen 1 , Emmy Rodriguez 2 , Huanhuan Jiang 2 , Kunpeng Chen 2 , Alexander Frie 2, 3 , Haofei Zhang 1, 4 , Roya Bahreini 1, 2, 4 , Ying-Hsuan Lin 1, 2
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The ability of brown carbon (BrC) in aerosols to absorb solar radiation is an important but highly uncertain factor in climate forcing. The uncertainties are partially due to incomplete characterization of BrC chromophores and lack of authentic standards to confirm light absorption. Organonitrogen species are crucial components in atmospheric aerosols, but their light-absorbing properties remain to be fully characterized. To facilitate the molecular characterization of BrC chromophores, time-dependent density functional theory (TD-DFT) based computational chemistry approaches were used in this study to predict the light absorption spectra of 16 organonitrogen species, including nitroaromatics, nitro-heterocyclic compounds, organonitrates, and Maillard-type reaction products in BrC. Effects of basis sets, functionals, solvation, and pH on light absorption properties of these compounds were evaluated. Predicted absorption spectra were compared with experimental measurements. Overall, the PBE0 and B3LYP functionals tend to outperform PBE and CAM-B3LYP on the predicted absorption spectra of studied compounds. Absorbance calculated in water and methanol (bulk solvents) varies up to 2 nm (0.03 eV). Absorbance calculated in gas phase (vacuum state) blue-shifts in comparison to solvation. Absorbance of weak acids (e.g., nitrophenols) is enhanced under basic conditions, and the absorption spectra can be predicted by the fractions of conjugate acid–base species. Results from this study demonstrate that a combined use of TD-DFT predictions and experimental measurements of light absorption can allow for a rapid and reliable determination of potential chromophores in BrC when authentic standards are not available.
中文翻译：
棕碳中有机氮发色团的紫外-可见光谱的时变密度泛函理论研究
气溶胶中的褐碳（BrC）吸收太阳辐射的能力是气候强迫中一个重要但高度不确定的因素。不确定性部分是由于BrC发色团的不完全表征以及缺乏确定光吸收的真实标准所致。有机氮物质是大气气溶胶中的关键成分，但它们的光吸收性能仍有待充分表征。为了促进BrC发色团的分子表征，本研究中使用了基于时变密度泛函理论（TD-DFT）的计算化学方法来预测16种有机氮物质的光吸收光谱，包括硝基芳族化合物，硝基杂环化合物，有机硝酸盐，和BrC中的美拉德型反应产物。基础集，功能，溶剂化的影响，以及pH对这些化合物的光吸收性质的评价。将预测的吸收光谱与实验测量值进行比较。总体而言，在研究化合物的预测吸收光谱上，PBE0和B3LYP的功能往往优于PBE和CAM-B3LYP。在水和甲醇（本体溶剂）中计算出的吸光度变化最大为2 nm（0.03 eV）。与溶剂化相比，以气相（真空状态）蓝移计算的吸光度。在碱性条件下，弱酸（例如，硝基苯酚）的吸收率会提高，并且吸收光谱可以通过共轭酸碱物种的分数来预测。
更新日期：2020-02-10
中文翻译：
棕碳中有机氮发色团的紫外-可见光谱的时变密度泛函理论研究
气溶胶中的褐碳（BrC）吸收太阳辐射的能力是气候强迫中一个重要但高度不确定的因素。不确定性部分是由于BrC发色团的不完全表征以及缺乏确定光吸收的真实标准所致。有机氮物质是大气气溶胶中的关键成分，但它们的光吸收性能仍有待充分表征。为了促进BrC发色团的分子表征，本研究中使用了基于时变密度泛函理论（TD-DFT）的计算化学方法来预测16种有机氮物质的光吸收光谱，包括硝基芳族化合物，硝基杂环化合物，有机硝酸盐，和BrC中的美拉德型反应产物。基础集，功能，溶剂化的影响，以及pH对这些化合物的光吸收性质的评价。将预测的吸收光谱与实验测量值进行比较。总体而言，在研究化合物的预测吸收光谱上，PBE0和B3LYP的功能往往优于PBE和CAM-B3LYP。在水和甲醇（本体溶剂）中计算出的吸光度变化最大为2 nm（0.03 eV）。与溶剂化相比，以气相（真空状态）蓝移计算的吸光度。在碱性条件下，弱酸（例如，硝基苯酚）的吸收率会提高，并且吸收光谱可以通过共轭酸碱物种的分数来预测。
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