Ice Nucleation Activity of Graphene and Graphene Oxides.

Thomas Häusler,Dominik Eder,Christoph Rameshan,Paul Gebhardt,Daniel Iglesias,Silvia Marchesan,Hinrich Grothe

doi:10.1021/acs.jpcc.7b10675

Thomas Häusler, Dominik Eder + Show 5 more

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https://doi.org/10.1021/acs.jpcc.7b10675

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Abstract

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.

Highlights

At temperatures below −35 °C, ice forms via the homogeneous nucleation of supercooled droplets or heterogeneous nucleation on ice-nucleating particles (INPs).[1−3] At temperatures above −35 °C, heterogeneous nucleation is considered to be the dominant mechanism.[3,4] INPs play a major role in the ice forming process in clouds
We investigated a variety of functionalized and nonfunctionalized graphene and graphene oxide materials with different chemical and structural characteristics to evaluate the dependence of the ice nucleation activity (INA) on the surface chemistry, micromorphology, and nanomorphology
The samples were divided into two groups according to their chemical characteristics: (i) graphene, including G-non, G-NPr3+I−, and G-NPr3+OH−, and (ii) graphene oxides, including GO-DE, GO-SA, GO-nano, and GO-NH2. ncanos dmGvrpGaala-uprNeehsdPern3ot+efoO

Summary

Introduction

At temperatures below −35 °C, ice forms via the homogeneous nucleation of supercooled droplets or heterogeneous nucleation on ice-nucleating particles (INPs).[1−3] At temperatures above −35 °C, heterogeneous nucleation is considered to be the dominant mechanism.[3,4] INPs play a major role in the ice forming process in clouds. The composition and origin of INPs have been studied intensively over the past few decades, as summarized, for example, by Murray et al.[5] the microscopic and molecular mechanisms of heterogeneous ice nucleation are complex and remain poorly understood. Necessary attributes, such as the ice-like structure or hydrophobicity of the INP, can rarely be applied.[3] Factors controlling heterogeneous processes have been investigated intensively, but the knowledge remains fragmentary.[5] To answer the major question of ice nucleation what makes an effective ice-nucleating site? More laboratory and atmospheric data are required.[6]

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