Data from: Quantifying the viscosity of individual submicrometer semisolid particles using atomic force microscopy. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

Publication abstract: Atmospheric aerosols’ viscosities can vary significantly depending on their composition, mixing states, relative humidity (RH) and temperature. The diffusion timescale of atmospheric gas phase molecules into aerosols is governed by the aerosols’ viscosity, which affects heterogeneous chemistry and the climate. Quantifying semisolid aerosol viscosity is crucial as they are prevalent in the atmosphere and have a wide range of viscosities and diffusion time scales. Currently, direct viscosity measurements of submicrometer individual atmospheric aerosols are limited, largely due to inherent size limitations present in present experimental techniques. Herein, we present a method that utilizes atomic force microscopy (AFM) to directly quantify viscosity of individual submicrometer semisolid particles as a function of RH. The method is based on AFM force spectroscopy measurements coupled with the Kelvin-Voigt viscoelastic model. Using glucose, sucrose, and raffinose as model systems, we demonstrate the accuracy of the AFM method within the viscosity range of ~104 – 107 Pa s. The method is applicable to individual particles with sizes ranging from tens of nanometers to several micrometers. Furthermore, the method does not require a prior knowledge on the composition of studied particles. We anticipate that future measurements utilizing the AFM method on real atmospheric aerosols at various RH are expected to aid in our understanding on the range of aerosols’ viscosities, the extent of particle-to-particle viscosity variability, and how these contribute to the particle diversity observable in the atmosphere.