Water Science Research Institute, Beijing Normal University, 19 Xinjiekouwai Street, Haidian District, Beijing 100875, China.
Research Center for Cleaner Production and Circular Economy, Chinese Research Academy of Environmental Sciences, 8 Dayangfang, Anwai Beiyuan, Chaoyang District, Beijing 100012, China.
Langmuir. 2023 Jul 4;39(26):9144-9153. doi: 10.1021/acs.langmuir.3c00847. Epub 2023 Jun 19.
Absorption spectra are fundamental bases for the qualitative and quantitative analysis of the target chemical, and the development of an analytical model can be improved by studying its characteristics and rules. In the present study, the electronic excitation characteristics of phosphate anions (HPO, HPO, and PO) were analyzed based on the charge-transfer spectrum. In addition, the absorption spectra of phosphate anions at the energy level of PBE0/6-311+G (d,p) were recorded based on the time-dependent density functional theory (TD-DFT) method. Different (HPO)·(HO) molecular clusters were theoretically constructed, and the combined TD-DFT method and independent gradient model revealed that red shift of the maximum absorption wavelength (λ) with the increase of phosphate anion concentration (0-10 mM) may be caused by the decrease of hydrogen bond interaction. In addition, the prominent dispersion in the short-wave region mainly resulted in the red shift of λ with the increase in optical path length (1-100 mm). Moreover, with the increase in spectral bandwidth (0.4-3.0 nm), λ slightly blue-shifted because of the increase in energy through the slit, and repeatability of the corresponding absorbance measurement at λ gradually improved. As the spectral bandwidth increased, light monochromaticity became poor, resulting in the decrease of the linearly fitted correlation coefficient of the concentration-absorbance curve. Finally, the multivariate analysis of variance results showed that the optical path length was the most significant factor that influenced the absorption spectral characteristics of phosphate anions. This study provides a basis for the qualitative and quantitative analysis of phosphate anions by using absorption spectra and also renders a theoretical reference for absorption spectroscopy of other chemicals.
吸收光谱是目标化学物质定性和定量分析的基础，通过研究其特征和规律，可以改进分析模型的开发。本研究基于电荷转移光谱分析了磷酸根阴离子（HPO、HPO 和 PO）的电子激发特性。此外，还基于含时密度泛函理论（TD-DFT）方法记录了在 PBE0/6-311+G（d，p）能级下磷酸根阴离子的吸收光谱。理论构建了不同的（HPO）·（HO）分子簇，组合的 TD-DFT 方法和独立梯度模型表明，随着磷酸根阴离子浓度（0-10 mM）的增加，最大吸收波长（λ）的红移可能是由于氢键相互作用的减弱所致。此外，在短波长区域的显著色散主要导致 λ随着光程长度（1-100 mm）的增加而红移。此外，随着光谱带宽（0.4-3.0 nm）的增加，由于通过狭缝增加了能量，λ略有蓝移，并且在 λ处相应吸光度测量的重复性逐渐提高。随着光谱带宽的增加，光的单色性变差，导致浓度-吸光度曲线的线性拟合相关系数降低。最后，多元方差分析结果表明，光程长度是影响磷酸根阴离子吸收光谱特征的最显著因素。本研究为利用吸收光谱对磷酸根阴离子进行定性和定量分析提供了依据，也为其他化学物质的吸收光谱学提供了理论参考。
