ABSTRACT
This chapter focuses on the effect of nonadsorbed nanoparticles, since in many ways the resulting impact on dispersion stability is much more interesting and complex than that produced from adsorbed nanoparticles. It presents an overview of some of the work that has been performed in these systems, starting with the pioneering work of Asakura and Oosawa and ending with some recent discoveries. The Asakura—Oosawa force can be derived via two different approaches. The first involves calculating the bulk osmotic pressure solution acting on a circular plate with a radius equal to the size of the exclusion region between the two spheres. The second approach involves calculating the reduction in the system volume that is excluded from the macromolecules upon approach of the two particles. Developments in experimental tools for detecting colloidal forces have allowed direct measurement of the depletion force and depletion energy in a variety of experimental systems.
