AVS 57th International Symposium & Exhibition
    Nanometer-scale Science and Technology Monday Sessions
       Session NS-MoA

Paper NS-MoA9
Environmental Effects on Nanoparticle Properties and Chemical Reactivity

Monday, October 18, 2010, 4:40 pm, Room La Cienega

Session: Nanomaterials in the Environment
Presenter: D.R. Baer, Pacific Northwest National Laboratory
Authors: D.R. Baer, Pacific Northwest National Laboratory
J.E. Amonette, Pacific Northwest National Laboratory
A. Dohnalkova, Pacific Northwest National Laboratory
M.H. Engelhard, Pacific Northwest National Laboratory
R.L. Penn, University of Minnesota
P. Nachimuthu, Pacific Northwest National Laboratory
J. Liu, Pacific Northwest National Laboratory
J.T. Nurmi, Oregon Health and Sciences University
P.G. Tratnyek, Oregon Health and Sciences University
C.M. Wang, Pacific Northwest National Laboratory
Correspondent: Click to Email
Nanoparticles of many types are increasingly used in a variety of applications. Parts of our work have focused on the reactions of Fe metal-core oxide-shell nanoparticles with water and solution contaminants that may be found in ground water. An important factor in understanding the ability of such particles to reduce environmental contaminants and the ultimate fate of such particles is knowledge of how the particles and their properties change with time in a variety of environments. Our work has demonstrated that these particles can change rapidly over periods of hours to days in water. Our research has focused attention on three aspects of these time dependent phenomena: 1) developing the ability to extract particles from solution, thereby stopping the reaction process and preserving, to the extent possible, the chemical and structural information; 2) how changes in the solution (adding buffers and organics) alter particle reactivity and aging in solution; and 3) using in situ methods to track particle changes and chemical properties. A variety of ex situ methods have been used to characterize the particles, including XPS, TEM, BET and XRD. Electrochemistry measurements have been used as an in situ real-time method. The method of sample extraction involves handling samples in a nitrogen atmosphere, a solvent rinse, and vacuum pumping to remove excess solvent. Even when particles appear dry, aggregates of particles may retain significant solvent. In addition to examining the influence of a variety of common buffers, we have examined the impact of natural organic material on the oxidation and chemical behavior of nanoparticles. Although natural organic matter (NOM) slows aging of the particles, the NOM coating helps the particles migrate relatively quickly through soil. Electrochemical measurements of various types including the open-circuit potential demonstrate the time dependence of particle changes and highlight the effects of varying environments on particle properties. Surface-potential measurements also highlight the impact of differing solutions on particle behavior.