Quantitative characterization of dielectric properties of nanoparticles using electrostatic force microscopy

We use a new method based on Electrostatic Force Microscopy (EFM) to perform quantitative measurements of the dielectric constants of individual carboxylated as well as non-functionalized polystyrene nanospheres. The EFM data record the oscillation phase of an atomic force microscope (AFM) cantilever as a function of the AFM tip position. In our experiments, the relative dielectric constant of the sample is measured from the EFM phase shifts vs the tip–surface separation, according to a simple analytical model describing the tip–surface interactions. We perform a comprehensive study of how the dielectric constant depends on the sphere diameter for both types of nanospheres. Our results demonstrate that the experimental method has a high-resolution for measuring the dielectric constant of nano/microbeads and other nanoscale materials and is simple to implement on standard atomic force microscopes. This non-invasive technique can be applied to measure the electrical properties of colloidal particles, polymers, interphases, and polymer nanocomposites.