Häusler Thomas, Gebhardt Paul, Iglesias Daniel, Rameshan Christoph, Marchesan Silvia, Eder Dominik, Grothe Hinrich
Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria.
Department of Chemical and Pharmaceutical Sciences, Università degli studi di Trieste, 34127 Trieste, Italy.
J Phys Chem C Nanomater Interfaces. 2018 Apr 19;122(15):8182-8190. doi: 10.1021/acs.jpcc.7b10675. Epub 2018 Mar 1.
Aerosols can act as cloud condensation nuclei and/or ice-nucleating particles (INPs), influencing cloud properties. In particular, INPs show a variety of different and complex mechanisms when interacting with water during the freezing process. To gain a fundamental understanding of the heterogeneous freezing mechanisms, studies with proxies for atmospheric INPs must be performed. Graphene and its derivatives offer suitable model systems for soot particles, which are ubiquitous aerosols in the atmosphere. In this work, we present an investigation of the ice nucleation activity (INA) of different types of graphene and graphene oxides. Immersion droplet freezing experiments as well as additional analytical analyses, such as X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy, were performed. We show within a group of samples that a highly ordered graphene lattice (Raman G band intensity >50%) can support ice nucleation more effectively than a lowly ordered graphene lattice (Raman G band intensity <20%). Ammonia-functionalized graphene revealed the highest INA of all samples. Atmospheric ammonia is known to play a primary role in the formation of secondary particulate matter, forming ammonium-containing aerosols. The influence of functionalization on interactions between the particle interface and water molecules, as well as on hydrophobicity and agglomeration processes, is discussed.
气溶胶可作为云凝结核和/或冰核粒子（INPs），影响云的特性。特别是，INPs在冻结过程中与水相互作用时表现出各种不同且复杂的机制。为了从根本上理解异质冻结机制，必须使用大气INPs的替代物进行研究。石墨烯及其衍生物为大气中普遍存在的气溶胶——烟尘颗粒提供了合适的模型系统。在这项工作中，我们对不同类型的石墨烯和氧化石墨烯的冰核活性（INA）进行了研究。进行了浸没液滴冻结实验以及额外的分析，如X射线光电子能谱、拉曼光谱和透射电子显微镜。我们在一组样品中表明，高度有序的石墨烯晶格（拉曼G带强度>50%）比低有序的石墨烯晶格（拉曼G带强度<20%）能更有效地支持冰核形成。氨功能化石墨烯在所有样品中显示出最高的INA。已知大气中的氨在二次颗粒物的形成中起主要作用，形成含铵气溶胶。讨论了功能化对颗粒界面与水分子之间相互作用以及对疏水性和团聚过程的影响。
