Atmospherically relevant core-shell aerosol studied using optical trapping and Mie scattering.

Area of Science:

• Atmospheric Chemistry
• Optical Physics
• Materials Science

Background:

• Aerosols play a critical role in atmospheric processes, including climate and air quality.
• Understanding the morphology and optical properties of aerosols is crucial for accurate atmospheric modeling.
• Core-shell aerosol structures are hypothesized to exist in the atmosphere, but direct experimental confirmation and characterization are challenging.

Purpose of the Study:

• To experimentally confirm the existence of solid core-liquid shell aerosol morphology.
• To demonstrate the capability of optical trapping for aerosol characterization.
• To precisely measure the physical dimensions and optical properties of core-shell aerosols.

Main Methods:

• Utilizing a counter-propagating optical trap to confine aerosols.
• Employing Mie spectroscopy for detailed particle analysis.
• Synthesizing solid silica core-liquid oleic acid shell aerosols for experimentation.

Main Results:

• Successfully trapped solid core-liquid shell aerosols, providing evidence for their atmospheric relevance.
• Achieved high-precision measurements of core radius (0.5 nm) and film thickness (1 nm).
• Determined wavelength-dependent refractive indices for both silica (core) and oleic acid (shell) components.

Conclusions:

• Optical trapping is a viable technique for studying aerosol morphology and properties.
• Mie spectroscopy offers high precision for characterizing core-shell aerosol structures.
• The findings contribute to a better understanding of atmospheric aerosol composition and behavior.