Significant uncertainties still remain over our ability to accurate predict the overall aerosol effect on the climate and atmosphere. One reason originates from a limited number of direct physical-chemical data for submicrometer-sized aerosol particles that can be in different physical phase states. One of the important challenges is development of innovative tools to study individual submicrometer particles as a function of relative humidity under ambient pressure. Here, we present atomic force microscopy (AFM) methodologies on a series of model aerosol systems that provide the capability to identify and correlate the 3D morphology, phase state and viscoelastic properties of aerosol particles on a single particle basis. We establish quantitative framework using AFM force spectroscopy towards differentiation of the physical phase states of individual particles without prior knowledge of their chemical identity. We show the aspect ratio of individual particles can be used as a measure of the extent of the particle spreading due to impaction with the solid substrate and in turn assess their phase state. Therefore, we introduce the ability to identify the phase state of individual substrate deposited particles, irrespective of the microscopy technique used, which can subsequently be further validated by more quantitative AFM force spectroscopy.

Study of 3D morphology, phase state and viscoelastic properties of individual substrate-deposited particles

2019 Fall National Meeting

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