This project addresses: 1.) The role of combustion-generated metal oxide nanoparticles in the formation/growth of primarily carbonaceous nanoparticles and 2.) The role of metal oxides condensed on growing nanoparticles in the formation of organic pollutants. Ni and Cu have been identified as important metals for initial study. The reactivity of their oxides under a range of conditions is being studied using a variety of experimental techniques. Dendrimeric synthesis techniques is used to create 1-3 nm metal oxide nanoparticles with and without associated carbonaceous layers; sol-gel techniques are used to create thin metal-oxide films on carbon and silica. The reactions of organic chemicals with these nanoparticle surrogates from 200 to 1100 C under oxidative and pyrolytic conditions are studied using a high-temperature flow reactor coupled with GC-MS, EPR, and FTIR analysis. Metal-catalyzed PAH formation is studied using HPLC-UV absorption. The nature of the metal oxides and their chemical binding is characterized using x-ray spectroscopic techniques at the LSU synchrotron facility. Ab initio modeling techniques are used to assess nanoparticle geometries, reaction sites, possible reaction mechanisms, and how they may vary as a function of particle size and metal identity. It has been estimated that over 650,000 people die prematurely in the US each year due to exposure to airborne fine particles. PM2.5, defined as particles with a mean aerodynamic diameter of less than 2.5 microns, have been shown to initiate cardiopulmonary disease and cancer in exposed populations. It has been realized only recently, however, that submicron, combustion-generated nanoparticles are the likely cause (alone or in combination with other pollutants) for the majority of these deaths and associated illnesses. Although health-effects research programs have been initiated by NIH and EPA, the causative agents remain unknown and progress is hindered by lack of understanding of the complex composition and reactivity of combustion-generated nanoparticles. The impetus of this program is practical, viz. to understand the origin and nature of combustion-generated nanoparticles so that their environmental impact can be minimized. The goal is contribute to the understanding of the chemical factors impacting the health effects of combustion-generated nanoparticles so that their effects can be mitigated or eliminated through combustion control.
