Bathochromic shift in the UV-visible absorption spectra of phenols at ice surfaces: insights from first-principles calculations

Some organic pollutants in snowpack undergo faster photodegradation than in solution. One possible explanation for such effect is that their UV-visible absorption spectra are shifted toward lower energy when the molecules are adsorbed at the air-ice interface. However, such bathochromic shift is difficult to measure experimentally.
Here we employ a multiscale/multimodel approach that combines classical and first-principles molecular dynamics, quantum chemical methods and statistical learning to compute the light absorption spectra of two phenolic molecules in different solvation environments at the relevant thermodynamic conditions.
Our calculations provide an accurate estimate of the bathochromic shift of the lowest-energy UV-visible absorption band when these molecules are adsorbed at the air-ice interface, and they shed light into its molecular origin.

积雪层中的部分有机污染物的光降解速率快于溶液体系。针对该现象的一种合理解释是：当分子吸附于气-冰界面时，其紫外-可见吸收光谱（UV-visible absorption spectra）会向低能方向偏移。然而，这类红移（bathochromic shift）难以通过实验手段测得。
本研究采用多尺度多模型联用方法，结合经典分子动力学与第一性原理分子动力学（first-principles molecular dynamics）、量子化学方法及统计学习手段，在相关热力学条件下，计算两种酚类分子在不同溶剂化环境中的光吸收光谱。
本研究的计算结果精准估算了当这些分子吸附于气-冰界面时，其最低能紫外-可见吸收带的红移，并阐明了该现象的分子起源。