Process for preparing nanocomposite particles

A process for preparing composite particle dispersions comprising:

• dispersing a plurality of core particles in a first aqueous solution wherein the core particles do not irreversibly self-flocculate, the first solution having a pH sufficiently different from the isoelectric point such that the core particle zeta potential is at least +/-20 millivolts,
• adding an amount of polymer to the dispersion of core particles, wherein the polymer has an affinity for the dispersed core particles, the polymer having a potential opposite that of the dispersed core particles,
• removing the excess polymer by a) centrifuging the solution, thereby forming a supernatant solution which comprises non-adsorbed excess polymer and a residual solution containing polymer-coated core particles, b) removing the supernatant solution, c) re-dispersing the residual solution in a pure aqueous solution, and d) repeating steps a) through c) as necessary until the excess polymer in the supernatant solution is substantially eliminated, and
• a suspension of shell particles having a size between 1 and 100 nm dispersed in a second aqueous solution is added to the solution of polymer-coated core particles, and excess shell particles are subsequently removed by a) centrifuging the solution, thereby forming a supernatant solution which comprises non-adsorbed excess shell particles and a residual solution containing shell particle-coated composite particles, b) removing the supernatant solution, c) re-dispersing the residual solution in a pure aqueous solution, and d) repeating steps a) through c) as necessary until the excess shell particles are substantially eliminated.