Ryan Sullivan

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.

Luke Monroe

Graduate Student (PhD, Chemistry)

Luke graduated from Towson University in 2018 with a B.S. in chemistry after spending five years in the Marine Corps as an Arabic linguist. He is currently pursuing his Ph.D in chemistry. Luke uses single particle instrumentation to explore the chemical properties of model and real aerosol particles, as well as explore those effects on ice nucleation.

Riley Weatherholt

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.

Darren Cheng

Darren Cheng

Graduate Student (PhD, Mechanical Engineering)

Darren joined the Sullivan group in Fall 2020, after graduating from the University of Michigan with a B.S. in Mechanical Engineering in 2017. In the three years in between, Darren worked as a process and tooling engineer for inkjet cartridge manufacturing at HP Inc. Darren’s research interests currently include investigating novel ionization methods to study aerosol droplet chemistry.

Wendy Flores-Brito

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.

Graham Thornhill

Graham Thornhill

Graduate Student (PhD, Chemistry)

Graham graduated with a B.S. in Chemistry in May of 2019 from the University of Georgia where he researched the optical properties of ambient atmospheric aerosols. He joined the Sullivan group in Fall 2020 where he now uses the Aerosol Optical Tweezers to investigate the various chemical processes and properties of model and real aerosol particles.

Group Photos

Sullivan Group in September 2021
Ryan Sullivan, Guy Symonds, Victoria Patella, Luke Monroe, Graham Thornhill, Wendy Flores-Brito, Riley Weatherholt, Bailey Bowers

Sullivan Group in November 2020

via Zoom

Sullivan Group in November 2019
Ryan Sullivan, Lydia Jahl, Bailey Bowers, Luke Monroe, Riley Weatherholt, Tom Brubaker, Leif Jahn

Sullivan Group in July 2018
Sara Graves, Lydia Jahl, Hallie Boyer, Bailey Bowers, Ryan Sullivan, Mike Polen, Tom Brubaker, Leif Jahn, Qing Ye

Sullivan Group in 2016
Adam Ahern, Hassan Beydoun, Tom Brubaker, Mike Polen, Leif Jahn, Kyle Gorkowski, Lydia Jahl, Qing Ye, Ryan Sullivan


Sullivan Group in April 2015
Qing Ye, Ryan Sullivan, Kyle Gorkowski, Hassan Beydoun, Mike Polen, Mark Aboff, Emily Lawlis, Adam Ahern, Leif Jahn


Sullivan Group in May 2014
Qing Ye, Hassan Beydoun, Ryan Sullivan, Kyle Gorkowski, Adam Ahern, Mike Polen


Sullivan Group in September 2013
Mike Polen, Kyle Gorkowski, Mark Aboff, Peter Leeman, Adam Ahern, Ryan Sullivan, Hassan Beydoun, Qing Ye, Victoria Hofbauer


Bailey Bowers

PhD, Chemistry, 2022

Thesis: Understanding Everyday–Everywhere Chemicals and their Transformation Products via High-Resolution Mass Spectrometry of Environmentally-Relevant Matrices

Currently: Visiting Assistant Professor of Chemistry at Earlham College

Guy Symonds

BS/MS, Chemistry, 2022

Thesis: A Characterization of Ice Nucleating Activity on Southern Great Plains Mineral Dusts and Proof of Concept for a Novel Microfluidics to Spectromicroscopy Integration for Ice Nucleation Studies 

Currently: PhD Student at University of Colorado Boulder

Will Fahy

BS/MS, Chemistry, 2021

Thesis: The Impact of Atmospheric Processing on the Ice Nucleating Activity and Physicochemical Properties of Volcanic Ash

Currently: PhD Student in Environmental Chemistry at University of Toronto

Tom Brubaker

PhD, Mechanical Engineering, 2021

Thesis: The Development of Microfluidic Methods for Measuring the Ice Nucleating Capabilities of Single-Particle-Droplets Directly Sampled from an Aerosol

Currently: Senior Engineer at 

Lydia Jahl

PhD, Chemistry, 2020

Thesis: Understanding the Sources and Transformations of Ice Nucleating Particles and Trace Reactive Gases in Biomass-Burning Emissions

Currently: Science & Policy Fellow, Green Science Policy Institute

Zuowei Wen

MS-R, Mechanical Engineering, 2020

Thesis: CFD Oriented Design in Aerosol Optical Tweezers and Microfluidic-Chip

Currently: PhD Student in Mechanical Engineering at University of Michigan

Leif Jahn

PhD, Chemistry, 2020

Thesis: Biomass-Burning and Volcanic Ash Aerosols: Atmospheric Aging, Chemical Reactivity, and Ice Nucleation Ability

Currently: Postdoctoral Research Associate at UT Austin in the Misztal and Hildebrandt Ruiz groups

Hallie Chelmo (Boyer)

Dreyfus Postdoctoral Fellow 2017 - 2019

Currently: Assistant Professor of Mechanical Engineering, University of North Dakota

Qing Ye

PhD, Chemistry and Engineering & Public Policy, 2019

Thesis: Atmospheric Organic Aerosols: Formation, Mixing and Human Exposure

Currently: Scientist, National Center for Atmospheric Research (NCAR)

Mike Polen

PhD, Chemistry, 2018

Thesis: Investigating the Chemistry and Chemical Aging that Affects Ice Nucleating Particles in the Atmosphere

Currently: Lecturer in Chemistry at McDaniel College

Kyle Gorkowski

PhD, Civil and Environmental Engineering, 2017

Thesis: The Morphology and Equilibration of Levitated Secondary Organic Particles Under Controlled Conditions

Currently: Postdoctoral Research Associate at Los Alamos National Laboratory

Hassan Beydoun

PhD, Mechanical Engineering, 2017

Thesis: Advances in heterogeneous ice nucleation research: Theoretical modeling and measurements

Currently: Staff Scientist at Lawrence Livermore National Labs in the Cloud Processes group in the Atmospheric, Earth, and Energy Division (AEED)

Adam Ahern

PhD, Chemistry, 2017

Thesis: Atmospheric Aging of Biomass-Burning Aerosol: Oxidants, Oxidation Products, and Measurement Methods

Currently: Research Scientist, Cooperative Institute for Research in Environmental Sciences (CIRES)

Peter Leeman

MS, Mechanical Engineering, 2014

Thesis: Excimer laser beam homogenization to achieve mass quantitative single-particle mass spectrometry

Currently: a photographer and filmmaker in Pittsburgh

Undergraduate Alumni

Victoria Patella (Chemistry, 2022) Spring 2021 - Fall 2021

Alex Adams (Mechanical Engineering, 2023) Fall 2020 - Spring 2021

Katie Ziegler (Chemistry, 2021)  Spring 2020 - Spring 2021

Remy Goldberg (Chemistry, 2023)  Spring 2020 - Summer 2020

Vinnie Silverman (Chemistry, 2020)  Spring 2018 - Spring 2020

Brian Woolley (Chemical Engineering, 2023)  Summer 2019

Jonathan Goodstein (Chemistry, 2021)  Spring 2019

Sara Graves (Physics, 2019)  Spring 2018 - Spring 2019

Darien Skifstad (Mechanical Engineering, 2020)  Summer 2018

Jason Kwak (Chemistry, 2019)  Summer 2018

Perry Cheng (Civil and Environmental Engineering, 2019)  Fall 2017 - Spring 2018

Vinay Ekamaram (Mathematics, 2018)  Summer 2017 - Spring 2018

Joshua Somers (Chemistry, 2019)  Summer 2017 - Fall 2017

Chun Ming (Jeffrey) Zhang (Mechanical Engineering, 2020)  Spring 2017

Anirudh Narain (Chemistry, 2017)  Summer 2016 - Fall 2016

Rushi Dave (Chemistry, 2017)  Spring 2016 - Spring 2017

Emily Lawlis (Chemistry, 2016)  Summer 2014 - Fall 2015

Holly Stokes (Chemistry, 2016)  Fall 2015

Mark Aboff (Mechanical Engineering, 2015)  Fall 2013 - Spring 2015

Mahir Kothari (Chemistry, 2015)  Summer 2014

Madeline Hartman (Chemistry, 2015)  Summer 2013

Joanna Sokoloski (Chemistry, 2014)  Spring 2013