| AVS 55th International Symposium & Exhibition | |
| In Situ Microscopy and Spectroscopy: Interfacial and Nanoscale Science Topical Conference | Wednesday Sessions |
| Session IS+NS+TR-WeA |
| Session: | In Situ Microscopy and Spectroscopy – Interfacial Science and Catalysis |
| Presenter: | D.R. Baer, Pacific Northwest National Laboratory |
| Authors: | D.R. Baer, Pacific Northwest National Laboratory P.G. Tratnyek, Oregon Health & Science University J.T. Nurmi, Oregon Health & Science University J.E. Amonette, Pacific Northwest National Laboratory P. Nachimuthu, Pacific Northwest National Laboratory C.M. Wang, Pacific Northwest National Laboratory M.H. Engelhard, Pacific Northwest National Laboratory A. Sharma, University of Idaho Y. Qiang, University of Idaho |
| Correspondent: | Click to Email |
In many circumstances nanoparticles are transformed by their environment. These transformations may impact particle structure, involve the formation of surface or contamination layers or alter important particle chemical or physical properties critical for specific applications. In our studies of nanoparticulate iron in aqueous solution related to contaminant transport in the environment, we need to understand the nature of the transformations and the time frame over which they occur. We are also working to develop methods to control (increase or decrease) the rate of these changes. We find that real-time in situ measurements are essential in addition to some batch ex-situ measurements to fully characterize the transformation. Determining minimum combination of in-situ and ex-situ measurements that provides the essential information is a challenge. We have used electrochemical potential and gas production (hydrogen production) to observe the real-time dependence of particle reaction properties. These have been correlated with batch ex-situ measurements, often involving anaerobic sample handling, of surface composition (XPS), particle phase composition and structure (XRD and TEM) and reaction rates with probe molecules (carbon tetrachloride). Real time in situ measurements are increasingly important as we develop ways to alter the particles with the intent of controlling the transformation rate of particles in aqueous solution. Initial data indicates that sulfur and transition metal doping of the particles significantly alters the overall reactivity and the interaction with contaminants. We are currently examining the impact of sulfur and transition metal additions as well as changes in oxide shell thickness on the reaction lifetime of core-shell iron nanoparticles. Because of a need to provide additional types of time-dependent information we are applying microbeam XRD and TEM in closed cells to examine these particles as they change in solution. This work is supported by the US Department of Energy Offices of Basic Energy Science and Biological and Environmental Research. A portion of the work has been conduced the the EMSL, a US DOE national user facility.