Chemically Resolving the Growth of Gas Phase Clusters into Nanoparticles

化学学部的环境化学科学项目资助了加州大学欧文分校化学系的詹姆斯·史密斯教授的这项研究。史密斯教授和他的学生研究大气中小分子簇的生长和化学成分的变化。这些团簇可以生长成纳米大小的粒子。该项目的目标是首次直接观察大气纳米团簇（ANs）中发生的成分变化，并在分子水平上理解控制这些过程的相互作用。这一基本认识使预测粒子如何在自然或受人类活动影响的若干大气环境中形成和演化成为可能。了解簇的演化对于建立AN生长速率和生存概率的模型是必要的，反过来，这与纳米颗粒对空气质量和气候的影响有关。该项目包括一个研究生和本科生配对的同伴指导计划。这种伙伴关系有助于为本科生未来在STEM领域的职业生涯做好准备。采用实验室实验和计算化学模拟相结合的方法研究了大气纳米粒子（AN）的形成和演化。实验室实验探索氨和有机碱与硫酸反应中氨的形成和演化。实验集中于苯甲酸、乙二醛等有机化合物与已知化合物簇之间的反应。实验观察与计算化学计算相结合，阐明了簇和AN生长机制。这些模拟探索了特定的过程，如质子转移反应和微量水在不同大小的团簇中的作用，可达几纳米，以及不同的初始团簇组成。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Environmental Chemical Sciences Program of the Chemistry Division funds this research by Professor James Smith of the Chemistry Department at the University of California, Irvine. Professor Smith and his students study the growth and change in chemical composition of small molecular clusters in the atmosphere. These clusters can grow to become nanometer-sized particles. The goal of this project is to directly observe, for the first time, compositional changes that occur in atmospheric nanoclusters (ANs) and to understand, at a molecular level, the interactions that control these processes. This fundamental understanding makes it possible predict how particles form and evolve in a number of atmospheric environments that are natural or influenced by human activities. Understanding the evolution of clusters is necessary for creating models of AN growth rates and survival probabilities and in turn, correlates to nanoparticle impacts on air quality and climate. This project includes a peer mentorship program that pairs graduate and undergraduate students. This partnership helps prepare undergraduate students for future careers in STEM. The formation and evolution of atmospheric nanoparticles (AN) are studied using a combination of laboratory experiments and computational chemistry simulations. Laboratory experiments explore AN formation and evolution from reactions of ammonia and organic bases with sulfuric acid. Experiments focus on reactions between organic compounds such as benzoic acid and glyoxal and clusters of known composition. Experimental observations are performed in concert with computational chemistry calculations that elucidate cluster and AN growth mechanisms. These simulations explore specific processes such as proton transfer reactions and the role of trace water in clusters of various sizes, up to several nanometers, as well as for different initial cluster compositions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.