People

Professor, Department of Chemistry

Professor, Department of Mechanical Engineering

Courtesy Appointment, Civil and Environmental Engineering

Associate Director, Institute for Green Science

Ryan started his research group in environmental chemistry at Carnegie Mellon University in 2012, as part of the Center for Atmospheric Particle Studies. He conducted his postdoctoral research with Sonia Kreidenweis and Paul DeMott in the Department of Atmospheric Science at Colorado State University, after completing his Ph.D. in atmospheric chemistry with Kimberly Prather in the Department of Chemistry & Biochemistry at the University of California, San Diego. Ryan engaged in undergraduate research with Kimberly Strong, Scott Mabury, and Jonathan Abbatt while completing his Hon.B.Sc. in environmental chemistry at the University of Toronto. Ryan has a joint faculty appointment in the Department of Chemistry and the Department of Mechanical Engineering at CMU, and is the Associate Director of the Institute for Green Science.

Ryan leads a group of chemists and engineers that work together to investigate the chemistry that tiny aerosol particles experience in the atmosphere. We seek to understand the role that chemistry catalyzed by aerosols plays in changing air pollution and impairing air quality. We study how these reactions change critical properties of the particles that alter how they create and change clouds, and the role of aerosol chemistry in changing the planet’s climate and energy budget. Our aerosol experiments are facilitated by the new methods and instruments we engineer that can probe individual particles one-at-a-time, using aerosol optical tweezers, laser ablation mass spectrometry, and microfluidics. The multiphase chemical evolution of biomass-burning aerosol produced from trees and tall grasses is a major current focus, along with investigating how this chemistry alters the ice nucleating particles emitted by biomass combustion. Our optical tweezers experiments allow us to uniquely determine how a particle’s chemistry and properties such as pH and phase separations evolve over hours of reactions with trace gases, and how this in turn alters the particle’s ability to further accelerate chemical reactions. As part of the Institute for Green Science, we are developing advanced water purification technologies for the removal of persistent micropollutants.

Graduate Student (PhD, Chemistry)

Riley is a PhD student in the Chemistry department who joined the Sullivan group in Fall 2019. She graduated from Kent State University in 2019 with BS degrees in Chemistry and Environmental & Conservation Biology, where she investigated the effects of road salt runoff on constructed wetlands. Her research currently focuses on using the aerosol optical tweezers to probe atmospherically relevant systems and observe droplet-accelerated chemistry as it relates to oxidative remediation of persistent pollutants.

Graduate Student (PhD, Mechanical Engineering)

Wendy is a Mechanical Engineering PhD student who joined the Sullivan group in Fall 2020. She completed a B.S. in Mechanical Engineering at Universidad del Turabo- Gurabo, Puerto Rico and an M.S. in Mechanical Engineering at University of New Mexico (UNM)- Albuquerque. While at UNM and during her internship with Sandia National Labs, Wendy researched the emissivity of aerosol deposited and painted-on thermographic phosphors, as well as combining these thermographic phosphors with laser diagnostics techniques to obtain surface temperatures and expansion/displacement (strain) measurements. Her current research focuses on enhancing the light scattering signal and detection of the laser ablation aerosol time-of flight (LAAPTOF) mass spectrometer.