Nanosuspensions are nanosized submicron particles which are insoluble. They are suspended and dispersed (collide) in any fluid. Examples: fog, mist, smoke, pigmented ink and paint, and so on.
Gold nano particles in a solution (Gold nanoparticles: Optical properties and implementations in cancer diagnosis and photothermal therapy, Journal of Advanced Research Volume 1, Issue 1, January 2010, Pages 13-28)
Can this phenomenon be explained better by considering both gravitational repulsion and attraction forces?