University of Kent at Canterbury, Canterbury, United Kingdom.
J Chem Phys. 2012 Feb 7;136(5):054704. doi: 10.1063/1.3681400.
Heterogeneous nucleation of liquid from a gas phase on nanoparticles has been studied under various saturation ratios and nuclei size. The probability of liquid droplet nucleation, especially at a low degree of deviation from equilibrium, was measured for both atmospheric aerosol particles and engineered nanoparticles Cr(2)O(3). The concept of a critical saturation ratio and the validity of the one-to-one relationship between the nuclei number and the number of droplets were examined. A transient zone between no nucleation and established nucleation termed the surface area controlled nucleation was observed. In this zone, the probability of stable phase formation is determined by the surface area of nuclei. There are two distinctive features of the surface area controlled nucleation: the nucleation probability is much less than 1 and is proportional to the surface area of nuclei. For condensation particle counters (CPCs) counting nanoparticles, these features mean that counts measured are proportional to the surface area of nanoparticles and, therefore, the CPCs counts can be calibrated to measure the surface area.
气相在纳米颗粒上异质成核已在各种过饱和度和核大小下进行了研究。对大气气溶胶颗粒和工程纳米颗粒 Cr(2)O(3)，测量了尤其是在偏离平衡程度较低时的液滴成核概率。检验了临界过饱和度的概念以及核数与液滴数之间一一对应关系的有效性。观察到了无成核到已建立成核之间的暂态区，称为表面积控制成核。在此区域中，稳定相形成的概率取决于核的表面积。表面积控制成核有两个显著特征：成核概率远小于 1，并且与核的表面积成正比。对于用于计数纳米颗粒的凝结核计数器 (CPC)，这些特征意味着测量的计数与纳米颗粒的表面积成正比，因此，CPC 计数可以进行校准以测量表面积。
