Wednesday, November 7, 2007 - 2:00 PM
321-8
The Effect of Carbon Nanomaterials and Other Black Carbon Materials on the Molecular-Motion and Bioavailability of Benzene.
Tu N. Pham1, Samer AbuBakr2, Kathleen E. Duncan3, Margaret Eastman4, and Mark Nanny1. (1) School of Civil Engineering and Environmental Science, The University of Oklahoma, 202 West Boyd Str Room 334, Norman, OK 73019, (2) The department of Botany and Microbiology, The University of Oklahoma, 770 Van Vleet Oval, Norman, OK 73019, (3) Department of Botany and Microbiology, The University of Oklahoma, 770 Van Vleet Oval, Norman, OK 73019, (4) Department of Chemistry, Oklahoma State University, Stillwater, OK 74078
Deuterium (2H) static, solid-state nuclear magnetic resonance (NMR) experiments have characterized the molecular motion of benzene-d6 associated with various black carbon materials including nanocarbon particles, single-walled nanotubes, and multi-walled nanotubes. NMR results demonstrate that diverse molecular motions of benzene-d6 associated with these materials range from highly isotropic motion resulting from diffusion within pores or rapid translocation on the surface as seen with carbon nanoparticles, graphite, and soot, to mildly restrained motion as observed with nanotubes, to restrained motion observed with char and activated carbon. Activation energies and rotational rates of isotropic motion as well as the wobble angle and rotational rates of constrained motions are calculated using a spectral fitting model capable of quantifying simultaneous, multiple motional modes. These results provide a quantitative, molecular-scale view of the multiple motional modes occurring between benzene and the various black carbon materials. It is hypothesized that the interaction mechanisms between benzene and black carbon materials responsible for controlling bioavailability can be identified by using 2H NMR method. Results will be presented using a model microbial system to examine the effect of black carbon materials on the bioavailability of benzene to the benzene-degrading microbe Pseudomonas putida strain F1. Molecular motion of benzene and the corresponding thermodynamic parameters will be contrasted before and after sample incubation with strain F1 to identify modes of molecular motion susceptible to biodegradation. Benzene molecules resistant to biodegradation will be characterized according to their molecular motion behavior and the corresponding thermodynamic parameters of this motion. This model system allows the bioavailability of benzene associated with black carbon materials, both macro- and nano-, to be characterized as a function of molecular-scale interactions and molecular motion of the contaminant molecule.