Abstract
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.
Highlights
Nanostructured polymers, such as polymer blends, colloidal spheres, and nanoparticle composites with diameters of the order of tens to hundreds of nanometers, are used in a wide range of applications, such as fabrication of photonic bandgap crystals and threedimensional porous materials,1,2 chemical sensors,3,4 materials for drug delivery, screening, and tissue restoration,5,6 as well as major components of industrial products, such as coatings, papers, and inks.2,7 The functional utility of these complex systems is determined by their composition and size and their optical, mechanical, and electrical properties.1–8 Novel experimental techniques are required to quantitatively measure these properties at the local scale.Atomic Force Microscopy (AFM) is a powerful tool to investigate the topographical, mechanical, and electrical properties of nanoscale materials and composites
We adopt the standard AFM software (MFP3D)25 convention that all phase shifts are measured with respect to this value, which results in an overall positive phase shift above the substrate [Eq (2)]
We have developed a novel high-resolution technique based on electrostatic force microscopy to quantitatively measure the dielectric constants for nanospheres of different diameters
Summary
Nanostructured polymers, such as polymer blends, colloidal spheres, and nanoparticle composites with diameters of the order of tens to hundreds of nanometers, are used in a wide range of applications, such as fabrication of photonic bandgap crystals and threedimensional porous materials, chemical sensors, materials for drug delivery, screening, and tissue restoration, as well as major components of industrial products, such as coatings, papers, and inks. The functional utility of these complex systems is determined by their composition and size and their optical, mechanical, and electrical properties. Novel experimental techniques are required to quantitatively measure these properties at the local scale. We develop a novel technique based on EFM, which, together with a simple electrostatic model, allows us to measure the dielectric constants of individual non-functionalized and carboxyl-terminated polystyrene nanospheres as a function of sphere diameter. The values of the dielectric constant obtained for carboxyl-terminated polystyrene nanospheres with small diameters (D < 250 nm) are significantly smaller than the corresponding values obtained for non-functionalized polystyrene spheres of similar diameters. These results demonstrate that EFM can be used to distinguish between the dielectric properties of nano-objects of similar size and shape and have significant implications for quantitative measurements of nanoparticles and complex core–shell nanocomposite materials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
