Patent ID: 7504130

Claim:
A method for producing composite nanoparticles comprised of a nickel ferrite core surrounded with an outer layer of titania, which method comprises: a) dissolving an effective amount of a surfactant into a non-polar organic solvent and providing sufficient mixing to cause the formation of a reverse micelle microemulsion; b) dividing said reverse micelle microemulsion into a first fraction and a second fraction; c) blending into said first fraction an aqueous solution having dissolved therein: i) a water soluble nickel salt; and ii) a water soluble iron salt, wherein the concentration of nickel salt and the concentration of iron salt are in at least stoichiometric amounts that will result in the formation of NiFe 2 O 4 , thereby forming a metal salt microemulsion comprised of reverse micelles in a continuous non-polar organic phase, which reverse micelles are comprised of an aqueous core of metal salt solution encased in a surfactant shell; d) blending into said second fraction an effective amount of an aqueous precipitating agent solution, thereby resulting in the formation of a precipitating agent microemulsion comprised of reverse micelles in a continuous non-polar organic phase, which reverse micelles are comprised of an aqueous core of precipitating agent solution encased in a surfactant shell; e) blending at least a portion of the metal salt microemulsion with at least a portion of the precipitating agent microemulsion; thereby resulting in the precipitation of particles of NiFe 2 O 4 in the aqueous core of said reverse micelles and the formation of a NiFe 2 O 4 reverse micelle microemulsion; f) introducing into said NiFe 2 O 4 reverse micelle microemulsion an effective amount of an acidic titanium salt solution; g) heating said NiFe 2 O 4 reverse micelle microemulsion solution of step f) above at an effective temperature for an effective amount of time to form composite nanoparticles comprised of an inner core of NiFe 2 O 4 having an outer layer comprised substantially of TiO 2 ; h) extracting the composite nanoparticles by adding an effective amount of a higher alcohol to cause the nanoparticles to transfer to the higher alcohol phase and cause a colloidal dispersion; i) separating the colloidal dispersion alcohol phase from the non-polar solvent phase; j) centrifuging the colloidal dispersion of i) above to cause the composite nanoparticles to separate out of the colloidal dispersion; and k) collecting the composite nanoparticle product.