Abstract
We report a state-of-the-art gas-phase electrophoresis method for the characterization of nanosheet graphene oxide, metal-organic frameworks (MOF), and ceramic nanoparticle aggregates in the form of nanomaterial suspension. In this study, electrospray-differential mobility analysis (ES-DMA) is used to quantify number concentration and dimensional properties, analyze the reversibly dis-assembly and de-aggregation processes and ligand-nanoparticle interactions to colloidal stability of nanomaterial. Transmission electron microscopy and scanning electron microscopy are employed orthogonally to provide complementary data and imagery of nanomaterial. Results show that the equivalent mobility sizes, size distributions, and number concentrations of these functional nanomaterials are able to be successfully measured by ES-DMA. Aggregation, de-aggregation, and dis-assembly processes of nanomaterial colloids are strongly correlated to the zeta potential and isoelectric point of nanomaterials, dissociation constant of the functional ligands, and the pH in the environment, providing an effective route to control the primary size as well as the size homogeneity. This prototype study demonstrates a proof of concept of using ES-DMA to quantitatively characterize nonspherical functional nanomaterials. The results provide beneficial guidelines for the aqueous formulation chemistry of nanomaterial-based platforms (e.g., metalation in MOF) and the subsequent electrospray-assisted device integration.