Ratiometric Optical Sensing of Aerosol Phase State with Excited-State Intramolecular Proton Transfer Probes.

Area of Science:

• Environmental Science
• Chemistry
• Physics

Background:

• Phase transitions in aerosols influence virus transmission and atmospheric phenomena.
• Measuring the phase state of small aerosols is experimentally challenging.
• Fluorescence probe spectroscopy is a key technique for in situ aerosol analysis.

Purpose of the Study:

• To demonstrate a novel, highly sensitive method for determining aerosol phase state using ESIPT probes.
• To investigate the sensitivity of ESIPT probes to various chemical environments in aerosols.
• To overcome limitations of previous methods relying on solvatochromic probes.

Main Methods:

• Utilized excited-state intramolecular proton transfer (ESIPT) probes, specifically 2-(2-benzofuranyl)-3-hydroxychromone.
• Analyzed mixed organic/inorganic aerosols to observe phase transitions (solid-liquid, liquid-liquid).
• Investigated the influence of aerosol chemical composition, particularly Na+ and Cl- ions, on probe response.

Main Results:

• ESIPT probes exhibited a dual-emission peak intensity ratio highly sensitive to aerosol phase state.
• The probe demonstrated sensitivity to both solid-liquid and liquid-liquid phase transitions.
• Sensitivity was particularly linked to the presence of sodium (Na+) and chloride (Cl-) ions.

Conclusions:

• ESIPT-based fluorescent sensing provides a sensitive and simple method for real-time analysis of submicron aerosol phase state.
• This technique has significant potential for studying aerosols relevant to respiratory health and atmospheric science.
• The findings pave the way for improved understanding of aerosol behavior and its environmental and health impacts.