My current research interests and program focus on the characterization and multiscale modeling of nanoparticles and colloids in natural and engineered environmental systems.  Environmentally relevant particles of interest consist of supramolecular assemblies with characteristic length scales of 1nm to 10 mm.  These include naturally occurring abiotic/biotic macromolecules, nanoparticles and colloids.  In natural environmental systems, fulvic acids, humic acids and their supramolecular aggregates have a significant impact on water quality.  They control contaminant mobility, reactivity and bioavailability in natural environmental systems.  Nanoparticles can also be designed and synthesized to act as (i) separation and reaction media for organic/inorganic pollutants and (ii) scaffolds and delivery vehicles for bioactive compounds; thus providing unprecedented opportunities to develop more efficient and cost effective water treatment processes.  The toxicity of anthropogenic chemicals depends to a large extent on their interactions with biological nanostructures such as proteins and DNA.  The fate, transport and toxicity of synthetic nanomaterials (e.g., carbon nanotubes, molecular wires, etc) will determine to large extent regulatory and public acceptance of Nanotechnology.  Since 2000, I have been leading the development and implementation of a collaborative research program in Nanoscale Environmental Science and Technology (NEST) between (i) the Materials and Process Simulation Center of the Beckman Institute of the California Institute of Technology and (ii) the Department of Civil Engineering at Howard University.  This program is currently funded through grants from the National Science Foundation (NSF), the Environmental Protection Agency (EPA), the Department of Energy (DOE) and the National Water Research Institute.  The overall objectives of our NEST research program are to:

1. Characterize the structures and functions of environmentally relevant abiotic/biotic macromolecules, nanoparticles and colloids;
2. Develop and evaluate functional nanomaterials for treatment of water contaminated by mixtures of organic/inorganic pollutants,         radionuclides and biological contaminants; and 
3. Develop and validate quantitative tools for assessing the fate, transport and toxicity of nanomaterials.

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