Size-Dependent Sigmoidal Reaction Kinetics for Pyruvic Acid Condensation at the Air-Water Interface in Aqueous...

Area of Science:

• Chemical kinetics
• Atmospheric chemistry
• Physical chemistry

Background:

• Pyruvic acid (PA) chemistry is limited in bulk solutions but occurs in microdroplets.
• Microdroplets offer unique environments for chemical reactions.
• The air-water interface plays a crucial role in atmospheric chemistry.

Purpose of the Study:

• Investigate the chemistry of pyruvic acid (PA) in aqueous microdroplets.
• Determine the reaction mechanism and kinetics of PA condensation.
• Understand the role of microdroplet size and the air-water interface.

Main Methods:

• In situ micro-Raman spectroscopy was used.
• Experiments were conducted in a controlled environmental cell (humidity and temperature).
• Aqueous microdroplets of pyruvic acid were studied.

Main Results:

• Pyruvic acid (PA) undergoes condensation to form zymonic acid.
• The reaction exhibits size-dependent sigmoidal kinetics (induction, reaction, completion).
• Reaction kinetics are linked to surface area and surface-to-volume ratio, indicating interface involvement.

Conclusions:

• The air-water interface is critical for pyruvic acid condensation in microdroplets.
• Size-dependent sigmoidal kinetics in microdroplets highlight reaction complexity.
• Droplet dynamics, influenced by composition and humidity, affect reaction pathways.