Uptake and Collision Dynamics of Gas Phase Ozone at Unsaturated Organic Interfaces

Abstract

The uptake of gas phase ozone and the collision rate between ozone and double bonds at three different unsaturated organic interfaces with vapor are studied using classical molecular dynamics computer simulations. The organic systems are a self-assembled monolayer of 1-octenethiolate molecules adsorbed on a gold surface, liquid 1-tetradecene, and a monolayer of 1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine molecules adsorbed at the water liquid/vapor interface. The structural features of the neat organic systems are characterized and correlated with the dynamics in the presence of gas phase ozone molecules. The collision rate between ozone and a double bond is sensitive to several factors, including the extent of localization of the double bonds in the system and the distance that ozone diffuses into the organic phase. However, the average lifetime of a collision between ozone and a double bond is independent of the organic system. A comparison of the simulation results with experimental results from these systems shows good agreement. The results are discussed in the context of the oxidative processing of organic aerosols in the atmosphere.

A new mechanism for ozonolysis of unsaturated organics on solids: phosphocholines on NaCl as a model for sea salt particles

“…As discussed in detail by Tobias and coworkers, 78 this is due to trapping of ozone in the organic film, which increases the number of ozone-double bond collisions and hence the opportunity for reaction.…”

Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants, O3, NO3, and OH, on organic surfaces

“…The simulations also showed View Article Online that (possibly reactive) collisions of O 3 with CQC double bonds in organic systems were dependent upon the residence time of ozone on the organic surface before desorption, as well as the accessibility of unsaturated sites within the organic surface to ozone. 98 Specifically, the ozone collision probability with CQC bonds was found to be a factor of two lower for a vinylterminated SAM than for a liquid slab of 1-tetradecene. In the SAM, the CQC bonds are located at the gas-surface interface, allowing access to ozone without uptake into the organic phase.…”

“…Vieceli et al 98 employed time-resolved changes in atmosphericpressure ATR-IR band intensities as well as molecular dynamics simulations of alkene-terminated SAMs to describe the interaction of O 3 with a SAM. Their experimental results suggested a surprisingly long surface residence time for ozone: B7 s, which was many orders of magnitude longer that that shown by their simulations: B17 ps.…”

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

“…A counterbalancing effect of lowered anion concentrations may be trapping of oxidants such as ozone in the organic chains of the surfactants, which theory predicts leads to increased residence times and likelihood of reaction on the surface. 125 Clearly, there is a great deal more to be learned about both the physical and chemical properties of such complex systems.…”