Understanding the Behavior of Charged Nanoparticles in Water

Nanoparticles have been extremely useful in the treatment of diseases, such as cancer and bacterial infections, as well as for cleaning up pollutants like oil or minerals from water. Since it is hard to image any water-based solution in electron microscope, the behavior of charged nanoparticles in water is not well understood. This has been a barrier to the development of applications for nanoparticles.
The focus of the work presented here is to examine charge screening of positive and negatively charged gold nanoparticles (+/- AuNP) in water with different concentrations of salt. Aggregation and flocculation will be studied using a combination of transmission electron microscopy (TEM) and scanning transmission electron microscope (STEM), using liquid cells fabricated from nanoparticles in various solutions encapsulated by graphene. The degree of aggregation is determined by measuring the radial distribution function (RDF) of a field of particles in an image. RDF is directly related to the surface charges of nanoparticles. This information yields a much better understanding of the aggregation behavior of nanoparticles in water.