| AVS 65th International Symposium & Exhibition | |
| In-situ Microscopy, Spectroscopy, and Microfluidics Focus Topic | Monday Sessions |
| Session MM+AS+NS+PC+SS-MoA |
| Session: | X-ray and Electron Spectromicroscopy in Liquids and Gases & Flash Networking Session |
| Presenter: | Jared Bruce, University of California, Irvine |
| Authors: | J.P. Bruce, University of California, Irvine J.C. Hemminger, University of California, Irvine |
| Correspondent: | Click to Email |
Transition metals in aqueous solution have been investigated by a multitude of techniques and are a cornerstone of many aspects of chemistry. Recently, the atmospheric chemistry community has begun to shift their attention to iron, manganese and copper containing aqueous solutions due to their propensity to generate hydroxyl radicals at the air/water interface through a Fenton mechanism. Understanding the chemical state of the transition metal present at the air/water interface, in addition to the distribution as a function of depth, would provide critical insight to the active species of hydroxyl generation. Solvation effects have been shown to significantly affect the distribution of small ions as a function of depth from the vacuum/water interface; first through molecular dynamics (MD) simulations then corroborated by liquid – jet X – ray photoelectron spectroscopy (LJ-XPS). Solvation of transition metals in aqueous solution have added complexity compared to small ions because of complexation of ligands and equilibria with the surrounding solvent.
In our work, using both a lab – based LJ - XPS and synchrotron measurements at the Advanced Light Source, we have shown the distribution of chemical states on a model Fenton reagent, Fe2+(aq), change with depth relative to the air/liquid interface. The chemical state is also sensitive to “spectator” ions in the solution. The presence of Cl- leads to a binding energy shift in the Fe 2p spectra and a change in the distribution as a function of depth. This is also observed in the Cl 2p spectrum where a binding energy shift of 0.3 eV indicates the presence of an inner sphere Cl that follows the distribution change in the Fe 2p spectrum