Aerosol Optical Tweezer (AOT)

The aerosol optical tweezer (Biral AOT-100) is used to examine the chemical characteristics and physiochemical properties of individual aerosol droplets. Coupled with cavity enhanced Raman spectroscopy, the AOT allows for the real time measurement of chemical composition as well as physiochemical properties, such as particle size and refractive index. The method involves the contactless levitation of a single aerosol droplet that enables the particle to be analyzed for long periods of time (hours or even days). The instrument is equipped with the means to continuously control and monitor the trapping environment, including the humidity of the gaseous medium in which the particle is suspended as well as the flow of reagent gases, permitting changes in the particle’s properties to be monitored as an experiment proceeds.

Single particle measurements provide insights into the physicochemical properties and reactivity of single droplets that are otherwise reported as averaged values when studied using ensemble methods. The AOT-100 is to be used by the Grassian group to study the pH-dependent chemistry of transition metal catalyzed reactions of atmospheric significance within individual droplets as well as the chemistry of mineral dust inclusions within droplets. Future studies will potentially include enzyme reactions of atmospheric significance within individual sea spray aerosol particles.