In the Bain Aerosol Research group, we investigate the chemical and physical properties of aerosol droplets. Due to the small size and large surface-area-to-volume ratio, as well as their contactless environment, aerosol droplets can have distinct physical properties from their macroscopic counterparts. To investigate these unique properties, we utilize a combination of single-particle spectroscopy and bulk phase techniques.
Research Interests
Aerosol Surface Tension​
Instrument Development​
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Developing instruments to confine and characterize single aerosol particles.
Designing and building instrumentation provides freedom to tackle new problems. We specialize in optical trapping, which uses a highly focused laser beam to trap aerosol particles. We currently have holographic optical tweezers in the lab, which allow us to trap and manipulate multiple particles at once. 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) as well as the chemical (Raman scattering) information. We can use changes in these light scattering signals to determine a host of other aerosol properties, and how these properties change in response to a change in ambient conditions provides. Find out more.
Aerosol Optical Properties
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Measuring and modelling the refractive index of aerosol as a function of water content and optical wavelength.
Aerosols in the atmosphere scatter and absorb solar radiation and impact Earth's radiative balance. The refractive index is a complex number that relates to these two processes. Sea spray is weakly absorbing in the visible region and predominantly scatters. In contrast, brown carbon aerosol absorbs strongly in the near UV and into the short wavelength portion of the visible spectrum. Using the cavity-enhanced Raman spectra of
Atmospheric Micro- and Nanoplastics
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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. We are developing new techniques to characterize droplets with plastic inclusions in order to understand the processes and chemistry that occur in mixed phase droplets. Find out more.
Surfactant Partitioning in Aerosol Droplets
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Understanding the impact of surfactant partitioning on aerosol properties
Surfactants have been identified in seawater 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 and
aerosol droplets under different relative humidity conditions, we develop models for the wavelength- and composition-dependent optical properties. We use these tools to investigate tropospheric aerosol surrogates, as well as materials of interest for stratospheric aerosol injection (SAI). Find out more.
water activity. This partitioning depends on the properties of the surfactant as well as the cosolutes 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. We measure surface tension directly in the aerosol phase to help understand these processes. Additionally, we are working to understand the impact of strong surfactants on water activity. Together, these measurements allow us to better understand how strong surfactants impact aerosol hygroscopicity and cloud droplet activation. Find out more.
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