Disperse the nanoparticles - increase the stabilization of the disperse system. This can be done by changing the concentration of electrolyte, рН, surfactant, high-molecular compound, adding or changing the dispersant, the influence of the magnetic field. I do not mean the crushing on which energy is necessary.
The only dispersing agent is energy. Chemicals added to the system are either wetting agents or stabilizers. The steps in making a stable dispersion are wetting, separation (the key step and sonication is the most effective), and stabilization. One possible exception is stress corrosion milling. Look at:
Nov 11th, 2008. Dispersion and nanotechnology http://tinyurl.com/hpywsge
Using mechanical strength by high shear disperser equipment . in this case the viscosity of your solution must be increased either by high concentration either by using thickeners ( cellulosic?)