Real-time sampling and identification of airborne chemicals using optical tweezers

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A new analytical approach for real-time sampling, identifying and quantifying specific ambient aerosol components found in atmospheric particulate matter, including the potential to analyse the presence of chemical warfare agents (CWAs), will be developed. This approach will be used to investigate and refine the physicochemical properties (e.g. Henry's law constants, hydrolysis rate constants) that govern the atmospheric lifetimes of atmospheric species as well as possible CWAs. Ambient organic compounds from anthropogenic pollution sources are present in the atmosphere in both the vapour/gas phase or as dispersed solid particles or liquid droplets. Similarly, CWAs if released would be expected to be dispersed between the vapour and particle phase. Thus, sampling and characterisation of ambient air to enable detection of a hazardous compounds must be rapid and responsive to changes in gas/aerosol particle composition. The identification of potential CWAs must be specific, discriminating successfully from background ambient species, and leading to the robust, unambiguous identification of the agent. Any new technique should be multiplexed, allowing the identification of a broad range of hazards as well as background compounds in the same analysis, and able to sample and analyse both gas phase species and condensed phase particles (typically >100 nm in diameter). A single aerosol probe droplet can allow responsive and rapid sampling of gas phase and particle phase species from an airflow (second timescale), can be ultra-small in volume (less than pL) requiring little sample, and can be readily configured with conventional analytical techniques such as Raman spectroscopy. Here, we will develop the use of aerosol optical tweezers to isolate a single probe aerosol droplet (or even an array of probe droplets) for an indefinite period of time to act as an ultra-sensitive sampling volume of ambient particles or gas constituents to detect, identify and characterise species present in ambient aerosols.