Wider research context
Atmospheric new particle formation (NPF) is a global phenomenon impacting climate and air quality. Oxygenated organics and sulfuric acid are the major trace vapors involved in the process of molecular clustering and initial cluster growth. However, it remains unclear which organic molecules participate in these processes, leading to major uncertainties in climate change predictions and air quality measures. A missing piece of knowledge is structural information of the relevant compounds as atmospheric nucleation processes are currently almost exclusively investigated by mass spectrometry.
Objectives
This project aims at performing the first matrix-isolation infrared spectroscopy experiments of organic clusters relevant for atmospheric nucleation, establishing a new approach in NPF studies. The project resolves the structural arrangements of organic-inorganic clusters and explores the precision of QC cluster calculations. We provide first estimates of the functionalization of organic aerosols during the initial steps of growth. Altogether, this improves NPF-related process models resulting in more accurate descriptions of organic aerosol formation.
Methods
The project explores three different experimental approaches for preparing matrix-isolated organic-inorganic clusters and two different approaches in analyzing nanoparticle composition through matrix-freezing. We characterize the infrared spectra of an array of different small organic molecules clustering with sulfuric acid, identifying the most stable dimer arrangements. This allows for the comparison with ultra-high precision QC vibrational mode predictions including matrix-shifts, providing first experimental counterparts to the widely used QC cluster binging energy calculations. In addition, we measure the average organic functionalization of differently sized nanoparticles from representative organic NPF precursors. This is used as input for nanoparticle growth models such as the volatility basis set.
Innovation
The project introduces a novel approach to the phyisco-chemical analysis of clusters and nanoparticles associated with NPF with the potential for a wide field of applications beyond the project duration. Experimental information on the structure of the first embryonic clusters is still missing, and sub-10 nm nanoparticle composition analysis is considered one of the grand challenges in NPF studies.
Primary researchers involved
The project is led by Asst.-Prof. Dr. Dominik Stolzenburg at TU Wien, brings in expertise on nanoparticle and gas-phase precursor measurement techniques and the involvement of organics in NPF processes. He is supported by in-house cooperation partners Prof. Hinrich Grothe and Asst.-Prof. Maren Podewitz experts in matrix-isolation experiments and QC calculations, respectively. Cooperation partner Assoc.-Prof. Paul Winkler at the University of Vienna provides support for the experimental work on nanoparticle matrix freezing.
