Solid, Semisolid, and Liquid Phase States of Individual Submicrometer Particles Directly Probed Using Atomic Force...

Area of Science:

• Atmospheric chemistry and physics
• Materials science
• Physical chemistry

Background:

• The climate impact of aerosol particle phase states is poorly understood, particularly for submicrometer particles.
• Current experimental methods face size limitations in assessing fine aerosol particle phase states.

Purpose of the Study:

• To present a novel atomic force microscopy (AFM) technique for directly probing the phase states of individual submicrometer aerosol particles.
• To quantify phase state transitions as a function of relative humidity (RH) and temperature.

Main Methods:

• Utilizing AFM with nanoindentation and nano-Wilhelmy methodologies on individual sucrose particles.
• Measuring Young's modulus and surface tension as a function of RH.
• Analyzing force profiles, indentation depth, and viscoelastic response to determine particle phase states.

Main Results:

• Successfully quantified Young's modulus and surface tension of sucrose particles across varying RH.
• Demonstrated that force profiles provide qualitative and quantitative assessments of solid, semisolid, and liquid phases.
• Identified three distinct phase states and their transitions for sucrose particles based on RH and viscosity.

Conclusions:

• The developed AFM technique can effectively identify and quantify phase states and transitions in submicrometer aerosol particles.
• This methodology offers a direct approach to study aerosol phase behavior, improving climate models.
• The technique holds potential for investigating other atmospherically relevant systems.