Polymer-encapsulated magnetic nanoparticles

Abstract

Magnetic particles have a particle size of 500 nm of less and include a core and a polymer coating that surrounds and encapsulates the core. The core includes a metal, metal alloy, or metal oxide of at least one metal such as B, Mg, Al, Mn, Co, Ni, Cu, Fe Sm, Ln, Yb, Dy, Gd or Er and Nb. The magnetic core is polycrystalline particles which are superspin glass magnetic materials having coercivity greater than zero and magnetic remenance greater than zero at room temperature. Magnetic moment of these superspin glass magnetic materials at low field show increasing with temperature over room temperature. An in situ hydrolysis/precipitation method from precursor metal salts is used to form the polymer-encapsulated magnetic particles.

1 - 13 . (canceled) 
     
     
         14 . A method of making a magnetic particle, comprising:
 forming a solution including a metal precursor, an oxidizing agent or reducing agent, a polymer source, and a basic compound; and   increasing the solution temperature to at least 50° C. to form magnetic particles having a magnetic core and a polymer coating that surrounds and encapsulates the magnetic core.   
     
     
         15 . The method of  claim 14 , wherein the solution is aqueous. 
     
     
         16 . The method of  claim 14 , wherein a mass ratio of metal to polymer in the solution ranges from 1:0.05 to 1:20. 
     
     
         17 . The method of  claim 14 , wherein the magnetic particles are formed in the absence of a polymerization reaction. 
     
     
         18 . The method of  claim 14 , wherein the magnetic core comprises a metal, metal alloy, or metal oxide of at least one of B, Mg, Al, Mn, Co, Ni, Cu, Fe, Nb, Sm, La, Yb, Dy, Gd, or Er. 
     
     
         19 . The method of  claim 14 , wherein the magnetic core comprises polycrystalline particles which are superparamagnetic and coalesced to form a superspin glass magnetic core. 
     
     
         20 . The method of  claim 19 , wherein the polycrystalline particles of the magnetic core are the same crystalline phase. 
     
     
         21 . The method of  claim 19 , wherein the polycrystalline particles which have coalesced to form a superspin glass magnetic core is a soft magnetic material. 
     
     
         22 . The method of  claim 14 , wherein the magnetic particle exhibits a coercivity of greater than 0 to less than 300 Oe and magnetic remanence greater than 0 and less than 12 emu/g. 
     
     
         23 . The method of  claim 22 , wherein the magnetic remanence is between 3 and 10 emu/g. 
     
     
         24 . The method of  claim 22 , wherein the coercivity is between 30 and 150 Oe. 
     
     
         25 . The method of  claim 14 , the magnetic particle having a particle size of 500 nm or less. 
     
     
         26 . The method of  claim 14 , wherein the magnetic moment of the magnetic particle increases as the temperature increases above room temperature. 
     
     
         27 . The method of  claim 14 , wherein the magnetic particle comprises a saturation magnetization greater than 50 and less than 100 emu/g at room temperature. 
     
     
         28 . The method of  claim 14 , wherein the solution comprises a non-aqueous solvent comprising at least one of polyethylene glycol (PEG), dimethylformamide (DMF), and tetrahydrofuran (THF). 
     
     
         29 . The method of  claim 14 , wherein the solution comprises greater than 0 wt. % to 40 wt. % of the metal precursor, greater than 0 wt. % to 50 wt. % of the oxidizing agent or reducing agent, greater than 0 wt. % to 30 wt. % of the polymer source, and greater than 0 wt. % to 110 wt. % of the basic compound.