Behavior of Polymer Coated ZnO Nanoparticles in Soil.

 

 

Behavior of polymer coated ZnO nanoparticles in soil

 

Z. Elhaj Baddar¹ and J.M. Unrine¹

¹ University of Kentucky, department of plant and soil sciences

Abstract

ZnO nanoparticles may find their way into agricultural soils through a number of different pathways, both intentionally and unintentionally.  The objective of this study was to develop ZnO nanoparticles (NPs) with varied polymer coatings to investigate the role of surface chemistry on ZnO nanoparticle behavior in soil.  We synthesized ZnO NPs using alkaline precipitation of ZnO from ZnCl₂ dissolved in water.  We stabilized the ZnO NPs against aggregation electrostatically by conferring a charge to the particles using phosphate, sterically by adding a nonionic polymer (dextran), and electrosterically which is a combination of both and utilizes polyelectrolyte coatings (dextran sulfate).  The ZnO NPs were characterized using several analytical techniques, such as dynamic light scattering (DLS) for the determination of the hydrodynamic diameter of the NPs and aggregates in suspension,  electrophoretic mobility to approximate the zeta potential of the particles, transmission electron microscopy (TEM) to determine primary particle size and shape, and X-ray diffraction (XRD) to characterize crystal structure. TEM micrographs of triplicate batches were highly reproducible and showed that the primary particle diameter of ZnO NPs (coated and uncoated) varied between (20-30) nm depending on the coating used. Coating type and ratio of Zn to coating (m/m) had little effect on particle diameter.  XRD analysis showed that the particles were zincite structured ZnO. Effects of different coating materials on the aggregation state (as measured by DLS) of ZnO NPs as a function of ionic strength showed that electrosterically stabilized ZnO NPs were more resistant to aggregation compared to other coated and uncoated NPs. Currently, we are investigating the behavior of the synthesized ZnO NPs in soil under different conditions and preliminary results will presented.