Uptake of Molecules by Polyaromatic Hydrocarbon Nanoparticles

Polycyclic aromatic hydrocarbons (PAHs) are omnipresent in the Earth's atmosphere and detected in many regions of the interstellar space. Large PAH clusters (nanoparticles) can mimic soot and aerosol particles in the Earth's atmosphere as well as PAH ice grains in space. We investigate PAH nanoparticles in a molecular beam experiment and the uptake of different atmospherically and astrochemically relevant molecules by these nanoparticles. In our recent article [J. Phys. Chem. Lett. 2022, 13, 3781-3788], we have established a new method to determine the relative uptake ratios for hydrogen-bonding molecules on benzene nanoparticles of average radius of about 2 nm. Here, we extend the method from benzene nanoparticles to more complex PAH N of naphthalene, anthracene, phenanthrene, and pyrene, including also the five-membered ring containing PAHs indene and fluoranthene. The uptake of small molecules water, methanol, ethanol, ammonia, methane, oxygen, and carbon dioxide is investigated, and uptake ratios are determined to assess differences in the pickup of these molecules by PAH nanoparticles. We discuss the mobility and coagulation of the molecules on these nanoparticles. Investigating the uptake and accommodation of different molecules on PAH nanoparticles is desirable for a molecular-level understanding of the chemistry of soot and aerosol particles in the Earth's atmosphere as well as PAH ice grains in the interstellar space, where they interact with different molecules.