Hadizadeh Mohammad Hassan, Xu Fei
Environment Research Institute, Shandong University, Qingdao, 266237, China.
International Center for Quantum Design of Functional Materials (ICQD), University of Science and Technology of China, Hefei, 230026, Anhui, China.
Sci Rep. 2025 Jul 19;15(1):26219. doi: 10.1038/s41598-025-10911-4.
Water nanodroplets act as microreactors, driving critical processes in atmospheric chemistry, pollutant degradation, and aerosol formation. This study utilizes ab initio molecular dynamics (AIMD) simulations to unravel the thermally induced behavior of hydroxyl (OH) radicals within water nanodroplets across temperatures ranging from 300 K to 400 K. Elevated temperatures significantly weaken the hydrogen-bonding network, enhance OH radical mobility, and promote interfacial reactivity. The energy barriers for hydrogen transfer events decrease from ~ 4 kcal/mol at 300 K to ~ 2.5 kcal/mol at 400 K, facilitating rapid migration of OH radicals from the droplet interior to the air-water interface. Thermal energy also induces droplet deformation, as reflected by an increase in the asphericity parameter, further amplifying interfacial dynamics. Despite these thermal perturbations, OH radicals maintain a consistent orientation at the interface, stabilized by interfacial forces and localized hydrogen bonding. These findings provide molecular-scale insights into temperature-dependent radical dynamics with broad implications for atmospheric oxidation, plasma-liquid interactions, and environmental chemistry.
水纳米液滴充当微反应器，驱动大气化学、污染物降解和气溶胶形成中的关键过程。本研究利用从头算分子动力学（AIMD）模拟来揭示水纳米液滴中羟基（OH）自由基在300 K至400 K温度范围内的热诱导行为。升高的温度显著削弱氢键网络，增强OH自由基的迁移率，并促进界面反应性。氢转移事件的能垒从300 K时的约4 kcal/mol降至400 K时的约2.5 kcal/mol，促进了OH自由基从液滴内部快速迁移到气-水界面。热能还会引起液滴变形，这通过非球形度参数的增加得以体现，进一步放大了界面动力学。尽管存在这些热扰动，但OH自由基在界面处保持一致的取向，由界面力和局部氢键稳定。这些发现为温度依赖性自由基动力学提供了分子尺度的见解，对大气氧化、等离子体-液体相互作用和环境化学具有广泛影响。
