Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
J Phys Chem A. 2012 Mar 15;116(10):2519-28. doi: 10.1021/jp3002417. Epub 2012 Mar 6.
The adsorption of gas-phase naphthalene and ozone molecules onto air/ice interfaces coated with different surfactant species (1-octanol, 1-hexadecanol, or 1-octanal) was investigated using classical molecular dynamics (MD) simulations. Naphthalene and ozone exhibit a strong preference to be adsorbed at the surfactant-coated air/ice interfaces, as opposed to either being dissolved into the bulk of the quasi-liquid layer (QLL) or being incorporated into the ice crystals. The QLL becomes thinner when the air/ice interface is coated with surfactant molecules. The adsorption of both naphthalene and ozone onto surfactant-coated air/ice interfaces is enhanced when compared to bare air/ice interface. Both naphthalene and ozone tend to stay dissolved in the surfactant layer and close to the QLL, rather than adsorbing on top of the surfactant molecules and close to the air region of our systems. Surfactants prefer to orient at a tilted angle with respect to the air/ice interface; the angular distribution and the most preferred angle vary depending on the hydrophilic end group, the length of the hydrophobic tail, and the surfactant concentration at the air/ice interface. Naphthalene prefers to have a flat orientation on the surfactant coated air/ice interface, except at high concentrations of 1-hexadecanol at the air/ice interface; the angular distribution of naphthalene depends on the specific surfactant and its concentration at the air/ice interface. The dynamics of naphthalene molecules at the surfactant-coated air/ice interface slow down as compared to those observed at bare air/ice interfaces. The presence of surfactants does not seem to affect the self-association of naphthalene molecules at the air/ice interface, at least for the specific surfactants and the range of concentrations considered in this study.
采用经典分子动力学（MD）模拟研究了不同表面活性剂物种（1-辛醇、1-十六醇或 1-辛醛）涂覆的空气/冰界面对气相萘和臭氧分子的吸附。与溶解在准液相层（QLL）的主体或掺入冰晶体中相比，萘和臭氧强烈倾向于被吸附在涂覆有表面活性剂的空气/冰界面上。当空气/冰界面涂覆有表面活性剂分子时，QLL 变得更薄。与裸空气/冰界面相比，萘和臭氧在涂覆有表面活性剂的空气/冰界面上的吸附增强。萘和臭氧都倾向于溶解在表面活性剂层中并靠近 QLL，而不是吸附在表面活性剂分子的顶部并靠近体系的空气区域。表面活性剂倾向于相对于空气/冰界面以倾斜角度取向；角分布和最优选的角度取决于亲水头基、疏水性尾部的长度以及空气/冰界面处的表面活性剂浓度。萘在涂覆有表面活性剂的空气/冰界面上优先具有平面取向，除非在空气/冰界面处的 1-十六醇浓度较高时；萘的角分布取决于特定的表面活性剂及其在空气/冰界面处的浓度。与在裸空气/冰界面上观察到的相比，萘分子在涂覆有表面活性剂的空气/冰界面上的动力学速度减慢。至少对于本研究中考虑的特定表面活性剂和浓度范围，表面活性剂的存在似乎不会影响萘分子在空气/冰界面上的自组装。
