2-Methyltetrol sulfate ester-initiated nucleation mechanism enhanced by common nucleation precursors: A theory study.

Aerosol samples from all over the word contained 2-methyltetrol sulfate ester (MTS). We investigated the role of MTS in new particle formation (NPF) with aerosol nucleation precursors, including sulfuric acid (SA), water (W), ammonia (N), methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA). The analysis was performed using quantum chemical approach, kinetic calculation and molecular dynamics (MD) simulations. The results proved that the molecular interactions in the clusters were mainly H-bonds and electrostatic interaction. The negative Gibbs free energy changes for all the studied MTS-containing clusters indicated that the formation of these clusters was thermodynamically favorable. The stability of the clusters was evaluated according to the total evaporation rate. Here, (MTS)(SA) and (MTS)(W) were the most and least stable cluster, respectively. MD simulations were used for time and spatial analysis of the role of the MTS-SA system. The results indicated that MTS can self-aggregate or absorb SA molecules into clusters, larger than the size of the critical cluster (approximately 1 nm), suggesting that MTS can initiate NPF by itself or together with SA.