Surface area controlled heterogeneous nucleation.

Area of Science:

• Physical Chemistry
• Aerosol Science
• Nanoparticle Research

Background:

• Heterogeneous nucleation of liquid from a gas phase on nanoparticles is crucial for aerosol formation and atmospheric processes.
• Understanding nucleation behavior under varying conditions, including saturation ratios and particle sizes, is essential for accurate atmospheric modeling and nanoparticle characterization.

Purpose of the Study:

• To investigate the probability of liquid droplet nucleation on nanoparticles across different saturation ratios and sizes.
• To examine the critical saturation ratio and the relationship between nuclei number and droplet number.
• To identify and characterize a transient nucleation zone and its implications for nanoparticle measurement techniques.

Main Methods:

• Experimental measurement of liquid droplet nucleation probability on atmospheric aerosol particles and engineered chromium(III) oxide (Cr(2)O(3)) nanoparticles.
• Systematic variation of saturation ratios and nanoparticle nuclei size during nucleation experiments.
• Analysis of nucleation phenomena, including the critical saturation ratio and the surface area controlled nucleation zone.

Main Results:

• A transient zone, termed surface area controlled nucleation, was identified between no nucleation and established nucleation.
• In this zone, nucleation probability is less than 1 and directly proportional to the surface area of the nuclei.
• Observed nucleation behavior suggests that condensation particle counter (CPC) counts are proportional to nanoparticle surface area.

Conclusions:

• The study reveals a distinct surface area controlled nucleation regime for liquid formation on nanoparticles.
• This finding validates the proportionality between CPC counts and nanoparticle surface area.
• Condensation particle counters can be calibrated to accurately measure nanoparticle surface area based on these nucleation characteristics.