Developing instruments to confine and characterize aerosol on the single particle level.
Designing and building instrumentation provide freedom to take on new problems. I have worked with traditional and holographic optical tweezers, a dual-beam optical trap, and a photophoretic trap. These variations allow for the confinement of different types of solid and liquid particles (absorbing and non-adsorbing) and even non-spherical particles, in a contactless environment mimicking atmospheric conditions. Confined particles can be characterized with angular Mie scattering, cavity-enhanced Raman scattering, broadband scattering, and optical imaging to retrieve the physical (size and refractive index) and the chemical (Raman scattering) information. Often, how these properties change in response to a change in ambient conditions provides insight into aerosol properties. Find out more.
Atmospheric Nano- and Microplastics
Understanding the impacts of atmospheric plastics on aerosol properties and processes.
Field studies have found nano- and microplastics in urban centre atmospheric fallout, remote terrestrial locations and aloft in the atmosphere. Evidence suggests that these plastics can undergo long range atmospheric transport, but their impact on aerosol properties and processes is not yet understood. Plastics have a range of densities, chemical properties, colours and morphologies, and environmental aging can alter these properties. New techniques are required to characterize droplets with plastic inclusions in order to understand the processes and chemistry that occur in mixed phase droplets. Find out more.
Aerosal Surface Tension
Measuring the surface tension in droplets to understand the impacts of bulk to surface partitioning of surfactants in finite volume droplets.
Surfactants have been identified in sea water and sea spray aerosol where they interact with co-solutes and may lower the surface tension of aerosol droplets which decreases the barrier to cloud droplet activation. Due to the large surface to volume ratio in picoliter droplets compared to bulk solutions, surfactant from the droplet bulk must partition to the interface, decreasing the droplet bulk concentration and altering the surface tension. This partitioning depends on the properties of the surfactant as well as the co-solutes with which it interacts. The co-solute identity may affect the critical micelle concentration (CMC), the diffusion coefficient of the surfactant and thus the partitioning dynamics as well as its surface excess and molecular area on the surface. In addition, the incorporation of solid inclusions, offering additional interfaces for surfactant adsorption, may also affect aerosol surface tension
- Bain, A. (2022) Buoyancy and Brownian motion of plastics in aqueous media: Predictions and implications for density separation and aerosol internal mixing state Environmental Science: Nano https://doi.org/10.1039/D2EN00525E
- Yin, H., Dou, J,. Klein, L., Krieger, U. K., Bain, A., Wallace, B. J., Preston, T. C. & Zuend, A. (2022) Extension of the AIOMFAC model by iodine and carbonate species: applications for aerosol acidity and cloud droplet activation. Atmospheric Chemistry & Physics, 22, 973–1013. https://doi.org/10.5194/acp-22-973-2022
- Bain, A. & Preston, T. C. (2021) Hygroscopicity of microplastics and mixed microplastic-ammonium sulfate systems. Environmental Science & Technology, 55(17), 11775–11783. https://doi.org/10.1021/acs.est.1c04272
- Bain, A., & Preston, T. C. (2020) The wavelength-dependent optical properties of weakly absorbing aqueous aerosol particles. Chemical Communications, 56, 8928–8931. https://doi.org/10.1039/d0cc02737e
- Price, C. L., Bain, A., Wallace, B. J., Preston, T. C. & Davies, J. F. (2020) Simultaneous retrieval of the size and refractive index of suspended droplets in a linear quadrupole electrodynamic balance. The Journal of Physical Chemistry. A, 124(9), 1811–1820. https://doi.org/10.1021/acs.jpca.9b10748