Optically Trapped, Single-Particle Reactor for the Study of Heterogeneous Chemistry
YUKAI AI, Chuji Wang, Gorden Videen, Yong-Le Pan,
Mississippi State University Abstract Number: 242
Working Group: Aerosol Physics
AbstractMercury is a neurotoxin that impacts human health and the health of ecosystems globally. Mercury exists in the atmosphere in three major forms: elemental mercury, gaseous oxidized mercury, and particulate-bound mercury. To date, gaseous-phase mercury chemistry has been extensively studied. However, mercury's heterogeneous and surface chemistry, which is mostly related to the particulate bond mercury, and is associated with chemical reactions at atmospherically relevant surfaces, such as aerosols, air-water interfaces, etc., has been much less investigated. This is mainly due to the experimental difficulties in making accurate measurements, for example, due to the wall effect and surface interferences.
In this study, we created a micron-sized, single-particle reactor (SPR) freely trapped in air using optical trapping of a single particulate-bound mercury particle that was formed by mixing Hg(II) halides (HgX
2, X
2=Cl
2, Br
2 or BrCl) with single-walled carbon nanotubes (SWCNT). We observed chemical reactions on the surface of SPRs (HgX
2 contained single SWCNT particles) in the O
3 environment under the radiation of 532-nm light, based on Raman spectra changes. We propose a reaction mechanism: Hg(II)X
2 (solid) + O → Hg(I)X + XO, XO + O → O
2 + X on the surface of the SPR. This SPR technique may serve as a new reaction platform for the study of surface and heterogeneous chemistry in the simulated atmospheric state.