Spontaneous Iodide Activation at the Air–Water Interface of Aqueous Droplets
Yunlong Guo, Kangwei Li, S. Perrier, Taicheng An, D. J. Donaldson, C. George
Abstract
We present experimental evidence that atomic and molecular iodine, I and I 2, are produced spontaneously in the dark at the air–water interface of iodide-containing droplets without any added catalysts, oxidants, or irradiation. Specifically, we observe I 3 – formation within droplets, and I 2 emission into the gas phase from NaI-containing droplets over a range of droplet sizes. The formation of both products is enhanced in the presence of electron scavengers, either in the gas phase or in solution, and it clearly follows a Langmuir–Hinshelwood mechanism, suggesting an interfacial process. These observations are consistent with iodide oxidation at the interface, possibly initiated by the strong intrinsic electric field present there, followed by well-known solution-phase reactions of the iodine atom. This interfacial chemistry could be important in many contexts, including atmospheric aerosols.