Nanoparticle growth by particle-phase chemistry
Nanoparticle growth by particle-phase chemistry
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DOI：
10.5194/acp-18-1895-2018
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发表时间：
2018-02-09
影响因子：
6.3
通讯作者：
Johnston, Murray V.
中科院分区：
文献类型：
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作者：
Apsokardu, Michael J.;Johnston, Murray V.
通过使用动力学生长模型研究了颗粒相化学改变分子组成和提高2-100 nm直径范围内纳米颗粒生长速率的能力。所包括的分子组分是硫酸、氨、水、非挥发性有机化合物和半挥发性有机化合物。分子组成和生长速率进行比较的颗粒单独的分区与那些增长的组合的分区和两个有机分子之间的颗粒相的吸积反应。颗粒相化学导致分子组成的变化，这是粒径依赖性的，当反应涉及半挥发性分子时，颗粒的生长速度比单独分配快。这些效应对于直径大于约20 nm的颗粒最为显著。模拟结果提供了一个基本的基础，了解最近的实验测量的二次有机气溶胶的分子组成表明，吸积反应产物的形成线性增加，增加气溶胶体积表面积。它们还允许这些系统的反应速率常数的初步估计。对于由环状二甲基硅氧烷（D-5）的OH氧化或β-蒎烯的臭氧分解产生的二次气溶胶，需要10（-3）到10（-1）M-1 s（-1）量级的低聚速率常数来解释实验结果。这些值与先前测量的氢过氧化物和/或过氧酸在凝聚相中的反应速率常数一致。
The ability of particle-phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2-100 nm diameter range is investigated through the use of a kinetic growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound, and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle-phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particles larger than about 20 nm in diameter. The modeling results provide a fundamental basis for understanding recent experimental measurements of the molecular composition of secondary organic aerosol showing that accretion reaction product formation increases linearly with increasing aerosol volume-to-surface-area. They also allow initial estimates of the reaction rate constants for these systems. For secondary aerosol produced by either OH oxidation of the cyclic dimethylsiloxane (D-5) or ozonolysis of beta-pinene, oligomerization rate constants on the order of 10(-3) to 10(-1) M-1 s(-1) are needed to explain the experimental results. These values are consistent with previously measured rate constants for reactions of hydroperoxides and/or peroxyacids in the condensed phase.