Patent ID: 8349221

Claim:
Prussian blue metal complex nanoparticles, comprising: a crystal of a Prussian blue metal complex comprising a metal atom M A and a metal atom M b crosslinked via a cyano group (CN), and a metal cyano complex anion and/or a metal cation adsorbed on the surface of the crystal, wherein the complex crystal is substantially insoluble in water, and a surface of each fine particle is negatively or positively charged by the adsorption of the anion and/or the cation so as to make the fine particle soluble or dispersible in water, and wherein the adsorbed metal cyano complex anion (C − ) comprises a metal atom M C as a central metal, and the adsorbed metal cation is a cation (D + ) of metal atom M D , wherein: M A is at least one metal atom selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum, and copper; M B is at least one metal atom selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium and calcium; M C is at least one metal atom selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum, and copper; M D is at least one metal atom selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium, and calcium the crystal of a Prussian blue-type metal complex has the metal atom M A and the metal atom M B precipitated by mixing an aqueous solution containing a metal cyano complex anion (A − ) having the metal atom M A as a central metal and an aqueous solution containing a cation (B + ) of the metal atom M B , and the nanoparticle has a structure with a crystal portion made of A − and B + and a surrounding portion made of C − and/or D + .