Interactions between nanoparticles in nanosuspension

Nanoparticles are particles with a characteristic dimension below 100 nm. The properties of nanoparticles differ substantially from those of "big" colloidal particles (size bigger than 1 μm) because radius of surface forces, which is around 100 nm, is greater than or comparable with the nanoparticles size. The latter means that each nanoparticle could be completely covered by the surface forces of the neighbouring particles at small enough separation. It also means that the well-known Derjaguin approximation cannot be applied directly and some modifications are required. Pairwise interaction between nanoparticles can be used only at an extremely low volume fraction of nanoparticles (below some critical volume fraction, which is ~0.02%), and above this concentration a new theory based on many-particle interactions should be applied, which is yet to be developed. Some recent progress in the area of interaction between nanoparticles is reviewed and the properties of nanosuspensions based on interaction between nanoparticles are described. The authors have not attempted to cover all available literature in the area but instead have tried to underline the fundamental problems in the area which need to be addressed.