System fluorescent labeling of aerosol particles

Background

Aerosols, which are suspensions of fine solid or liquid particles in a gas, play a critical role in diverse fields such as environmental science, atmospheric chemistry, and health research. Understanding their physicochemical properties—such as pH, viscosity, and phase state—is essential for studying phenomena like air quality, climate change, virus transmission, and pulmonary drug delivery. However, the small size and low concentration of many aerosol particles make direct, in situ measurement of these properties extremely challenging. Fluorescence-based analytical techniques, particularly those using property-sensitive probe molecules, offer a promising approach due to their high sensitivity and non-destructive nature. Yet, many real-world aerosols, such as those found in ambient air or exhaled breath, cannot be pre-labeled with fluorescent probes during their formation, limiting the effectiveness of traditional fluorescence-based methods.

Current approaches to fluorescently labeling aerosols typically require premixing the probe molecules with the aerosol material before particle generation, a process that is unfeasible for naturally occurring or pre-existing aerosols. Alternative methods often rely on complex trapping or manipulation techniques that are not only labor-intensive but also limited in their applicability to a narrow range of particle types and sizes. These constraints hinder the study of ambient, exhaled, or otherwise unmodified aerosols, which are of significant interest in both environmental and biomedical contexts. As a result, there is a pressing need for a simple, broadly applicable method that enables post-generation fluorescent labeling of aerosols without requiring specialized instrumentation or altering the particles’ native state.

Technology

This technology enables the fluorescent labeling of aerosol particles by volatilizing a probe molecule—typically a fluorescent dye—so it condenses into or onto the particles as they pass through a controlled chamber. The process involves heating the probe, either dissolved in a solvent or as a solid, within a volatilization chamber to generate a gas-phase probe vapor without causing degradation. Aerosol particles, spanning a broad size range (approximately 1 nm to 10 mm), are then exposed to this vapor, allowing the probe molecules to partition into the particles. The system allows precise control over probe concentration (from 0.001% to 10% by mass) by adjusting the probe and solvent selection, as well as the chamber temperature. This approach is compatible with a wide variety of aerosol types and does not require premixing or complex trapping, making it suitable for in situ analysis of naturally occurring or exhaled aerosols.

What differentiates this technology is its versatility and simplicity in labeling aerosols post-generation, a significant advancement over traditional methods that require probes to be premixed with aerosol constituents—an impractical step for many real-world samples. The method is broadly applicable, functioning with diverse particle types (including non-spherical, absorbing, or uncharged aerosols) and a range of fluorescent probes sensitive to properties like polarity, pH, and viscosity. Experimental validation demonstrates that the fluorescence characteristics of labeled particles are consistent with those obtained via premixing, confirming the efficacy of the approach. The system’s modular design, compatibility with standard aerosol and fluorescence instrumentation, and ability to finely tune probe incorporation make it a powerful tool for health, environmental, and atmospheric research, enabling sensitive, non-destructive, and minimally invasive analysis of aerosol properties in situ.

Benefits

• Enables in situ, non-destructive fluorescent labeling of pre-existing or naturally occurring aerosol particles without the need for premixing.
• Applicable to a wide range of aerosol sizes (from ~1 nm to 10 mm) and types, including submicron, non-spherical, absorbing, or uncharged particles.
• Allows precise control of probe concentration within aerosols (0.001% to 10% by mass) via selection of probe, solvent, and temperature.
• Facilitates sensitive detection of aerosol physicochemical properties such as hygroscopicity, phase state, polarity, pH, and viscosity.
• Simple and versatile system compatible with standard aerosol and fluorescence measurement setups, requiring minimal specialized instrumentation.
• Validated experimentally with multiple probes and aerosol types, ensuring robustness and reproducibility.
• Supports broad applications in health (e.g., virus transmission, pulmonary drug delivery), environmental monitoring, and atmospheric chemistry research.

Applications

• Real-time environmental aerosol monitoring
• Exhaled breath particle analysis
• Pulmonary drug delivery research
• Atmospheric chemistry field studies
• Virus transmission aerosol tracking

Additional info

A system and method for labeling aerosol particles involves volatilizing a probe molecule from a solution or solid. Aerosol flow is exposed to the gas-phase probe, which then condenses onto or into the particles. This process enables in situ analysis of particle properties across a 1 nm to 10 mm size range, with controllable probe concentrations.