Waller Sarah E, Yang Yi, Castracane Eleanor, Racow Emily E, Kreinbihl John J, Nickson Kathleen A, Johnson Christopher J
Department of Chemistry , Stony Brook University , 100 Nicolls Road , Stony Brook , New York 11794 , United States.
J Phys Chem Lett. 2018 Mar 15;9(6):1216-1222. doi: 10.1021/acs.jpclett.8b00161. Epub 2018 Feb 26.
Acid-base cluster chemistry drives atmospheric new particle formation (NPF), but the details of the growth mechanisms are difficult to experimentally probe. Clusters of ammonia, alkylamines, and sulfuric acid, species fundamental to NPF, are probed by infrared spectroscopy. These spectra show that substitution of amines for ammonia, which is linked to accelerated growth, induces profound structural rearrangement in clusters with initial compositions (NH) (HSO) (1 ≤ n ≤ 3). This rearrangement is driven by the loss of N-H hydrogen bond donors, yielding direct bisulfate-bisulfate hydrogen bonds, and its onset with respect to cluster composition indicates that more substituted amines induce rearrangement at smaller sizes. A simple model counting hydrogen bond donors and acceptors explains these observations. The presence of direct hydrogen bonds between formal anions shows that hydrogen bonding can compete with Coulombic forces in determining cluster structure. These results suggest that NPF mechanisms may be highly dependent on amine identity.
酸碱簇化学驱动大气新粒子形成（NPF），但其生长机制的细节难以通过实验探究。氨、烷基胺和硫酸的簇是NPF的基本物种，通过红外光谱对其进行探测。这些光谱表明，用胺取代氨与加速生长有关，会在初始组成为(NH) (HSO) （1≤n≤3）的簇中引发深刻的结构重排。这种重排是由N-H氢键供体的损失驱动的，产生直接的硫酸氢根-硫酸氢根氢键，并且其相对于簇组成的起始表明，取代程度更高的胺在更小尺寸时就会引发重排。一个计算氢键供体和受体的简单模型解释了这些观察结果。形式阴离子之间直接氢键的存在表明，在确定簇结构时，氢键可以与库仑力竞争。这些结果表明，NPF机制可能高度依赖于胺的特性。
