Detecting pH of Sub-Micrometer Aerosol Particles Using Fluorescent Probes

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Analytical Chemistry

Background:

• Atmospheric aerosol particle acidity is crucial for chemical processes and environmental effects.
• Existing pH measurement methods are inadequate for suspending submicron particles.

Purpose of the Study:

• To develop a novel method for quantifying the pH of aerosol particles in continuous flow.
• To enable real-time pH measurement of submicron atmospheric particles.

Main Methods:

• Development of an aerosol fluorescence cell (AFC).
• Utilizing fluorescent pH probes (fluorescein, Oregon green 488) and ratiometric analysis.
• Employing two diode laser excitation wavelengths (450 and 488 nm).

Main Results:

• The AFC method successfully quantified aerosol particle pH in the range of 2-7.
• AFC measurements showed good agreement with pH indicator paper methods.
• The AFC approach is applicable to particles as small as 80 nm in diameter.

Conclusions:

• The AFC method provides a reliable way to measure the pH of submicron aerosol particles.
• This technique can be applied to both laboratory standards and atmospherically relevant samples.
• The AFC represents a significant advancement in atmospheric aerosol characterization.