Superfund Research Program

Combustion-Generated Nanoparticles and Pollutant Formation (ARRA Funded)

Project Leader: Erwin D. Poliakoff
Grant Number: P42ES013648
Funding Period: 2009-2011

Project-Specific Links

Final Progress Reports

Year:   2010 

The major thrust of Dr. Poliakoff's work is developing an understanding of how metal oxide nanoclusters that are present in the environment produce other chemical species – particularly relatively stable radicals that are bound to these metal oxides. Researchers refer to these surface bound radicals as EPFRs, which is an acronym for Environmentally Persistent Free Radicals. In order to understand the chemical properties of these EPFRs, it is crucial to comprehend the nature of the metal oxide nanoclusters themselves, as well as the interactions between these nanoclusters and the molecules that adsorb to them that result in the production of EPFRs. The development of a fundamental microscopic picture of these interactions is the goal of Dr. Poliakoff's research team. More specifically, their efforts are concentrated on three major issues. First, the researchers have developed experiments that help them understand the structure of the metal oxide nanoclusters, i.e., the geometric arrangement of atoms that form the clusters to which the radicals are bound. Second, the research group focused on the electronic properties of the metal oxide nanoclusters, which in this context, refers to how equally electrical charge is distributed throughout the clusters. Third, they study how molecules, which bind to the metal oxide clusters and form radicals, affect how electrons are distributed in these complexes.

Significant progress has been achieved on all three of these avenues of study. Specifically, the researchers use x-ray spectroscopy in order to glean the information that is described above, and they have refined their x-ray experiments to obtain useful information on these topics. For example, the researchers varied the size of the metal oxide clusters, and have determined that the degree of crystallinity actually increases as the size of the cluster decreases in some instances. This result is counterintuitive, and it is likely to lead to a deeper understanding of how the EPFRs are formed. Similarly, they have acquired data showing that copper oxide nanoclusters are more ionic than the more typical macroscopically available copper oxide that is found in everyday life. This, too, is likely to be significant, and lead to an understanding of the chemical species that have health impacts in everyday lives. The researchers have focused most of their efforts on copper oxide nanoclusters on silica supports, and more recently, have started to branch out to other metal oxides, and other supports. In general, the researchers are finding that the planned x-ray spectroscopy experiments are providing the type of useful microscopic insights that were hoped for.