Carbon-Encased Metal Nanoparticles and Sponges, Methods of Synthesis, and Methods of Use

Abstract

We disclose novel metallic nanoparticles coated with a thin protective carbon shell, and three-dimensional nano-metallic sponges; methods of preparation of the nanoparticles; and uses for these novel materials, including wood preservation, strengthening of polymer and fiber/polymer building materials, and catalysis.

1 . A core-shell nanoparticle comprising a metallic-core and a carbon-shell; wherein the diameter of said metallic-core is about 10 μm or less; wherein said carbon-shell completely encloses said metallic-core, so that said metallic-core has no exposed surface; wherein the thickness of said carbon-shell is about 20 nm or less; and wherein substantially all of said metallic-core has a zero oxidation state. 
     
     
         2 . A nanoparticle as recited in  claim 1 , wherein said metallic-core does not comprise a noble metal, and wherein the enclosure of said metallic-core by said carbon-shell is such that substantially all of said metallic-core will remain in a zero oxidation state after said nanoparticle has been exposed to air or water for six months at 25° C. and 1 atmosphere pressure. 
     
     
         3 . A nanoparticle as recited in  claim 1 , wherein said metallic-core is selected from the group consisting of Group IIA metals (Be, Mg, Ca, Sr, Ba, Ra); Group IIIA metals or semi-metals (B, Al, Ga, In, Tl); Group IVA metals or semimetals (Si, Ge, Sn, Pb); Group VA metals or semi-metals (As, Sb, Bi); Group VIA semi-metals (Te, Po); Group IIIB metals (Sc, Y, La, Ac); Group IVB metals (Ti, Zr, Hf): Group VB metals (V, Nb, Ta); Group VIB metals (Cr, Mo, W); Group VIIB metals (Mn, Tc, Re); Group VIII metals (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt); Group IB metals (Cu, Ag, Au); Group IIB metals (Zn, Cd, Hg); Lanthanides (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu); and Actinides (Th, Pa, U, Np, Pu, Am). 
     
     
         4 . A nanoparticle as recited in  claim 1 , wherein said metallic-core is selected from the group consisting of Cu, Ag, Ni, and Gd. 
     
     
         5 . A nanoparticle as recited in  claim 1 , wherein said metallic-core comprises Cu. 
     
     
         6 . A nanoparticle as recited in  claim 1 , wherein said metallic-core comprises Ag. 
     
     
         7 . A nanoparticle as recited in  claim 1 , wherein said metallic-core comprises Ni. 
     
     
         8 . A nanoparticle as recited in  claim 1 , wherein said metallic-core comprises Gd. 
     
     
         9 . A nanoparticle as recited in  claim 1 , wherein said metallic-core comprises Pt. 
     
     
         10 . A nanoparticle as recited in  claim 1 , wherein said metallic-core comprises Pd. 
     
     
         11 . A nanoparticle as recited in  claim 1 , wherein said metallic-core is selected from the group consisting of W, Au, Zn, Cr, and Re. 
     
     
         12 - 29 . (canceled) 
     
     
         30 . A plurality of nanoparticles as recited in  claim 1 . 
     
     
         31 . A method for making metallic-core carbon-shell nanoparticles, said method comprising the steps of:
 (a) impregnating biological fibers with a solution of metal ions in an aqueous or non-aqueous solvent;   (b) removing the solvent, while leaving at least some of the metal ions impregnated in the fibers; and   (c) heating the metal-ion-impregnated fibers in a non-oxidizing atmosphere or in a vacuum to a temperature that carbonizes at least some of the fibers, that does not vaporize most of the carbon, that reduces at least some of the metal ions to metal particles in a zero oxidation state, and that causes a carbon-shell to form around and to completely enclose most of the zero-oxidation-state metal particles.   
     
     
         32 - 53 . (canceled) 
     
     
         54 . A method for protecting wood, said method comprising impregnating the wood with a plurality of metallic-core carbon-shell nanoparticles as recited in  claim 1 , wherein the metallic core is selected from the group consisting of aluminum, magnesium, copper, zinc, and chromium, in an amount sufficient, in comparison to otherwise similar but untreated wood, to substantially inhibit the growth of mold in the wood, or to substantially inhibit fungal decay of the wood, or to substantially inhibit destruction of the wood by termites, or to substantially inhibit destruction of the wood by wood-destroying insects other than termites. 
     
     
         55 - 57 . (canceled) 
     
     
         58 . A composition of matter comprising wood impregnated with a plurality of copper-core carbon-shell nanoparticles as recited in  claim 5  in an amount sufficient, in comparison to otherwise similar but untreated wood, to substantially inhibit the growth of mold in said wood, or to substantially inhibit fungal decay of said wood, or to substantially inhibit destruction of said wood by termites, or to substantially inhibit destruction of said wood by wood-destroying insects other than termites. 
     
     
         59 - 64 . (canceled) 
     
     
         65 . A method for making metallic nanosponges, said method comprising the steps of:
 (d) impregnating biological fibers with a solution of metal ions in an aqueous or non-aqueous solvent;   (e) removing the solvent, while leaving at least some of the metal ions impregnated in the fibers; and   (c) heating the metal-ion-impregnated fibers in a non-oxidizing atmosphere or in a vacuum to a temperature or temperatures that initially carbonize at least some of the fibers, that then reduce at least some of the metal ions to metal particles in a zero oxidation state, and that then vaporize the carbon to produce a metallic, highly porous nanosponge comprising zero-oxidation-state metal.   
     
     
         66 - 90 . (canceled) 
     
     
         91 . A metallic nanosponge comprising a plurality of interconnecting, open metal tubes, wherein said tubes comprise porous walls, wherein most of said tubes are less than about 1 mm in diameter, wherein said porous walls comprise pores between about 1 μm and about 10 nm in diameter, and wherein the thickness of said walls is non-uniform, and is between about 1 μm and about 50 nm. 
     
     
         92 - 107 . (canceled) 
     
     
         108 . A method for catalytically converting NO x  from vehicle exhaust gas, comprising contacting the exhaust gas with a plurality of metallic nanosponges as recited in  claim 91 , wherein said metal is selected from the group consisting of Pt and Pd. 
     
     
         109 . A method for catalytically generating energy in a fuel cell, comprising contacting a gas with a plurality of metallic nanosponges as recited in  claim 91 , wherein the metal is selected from the group consisting of Pt and Ni. 
     
     
         110 . A method for strengthening fiber/polymer composites, said method comprising impregnating the fiber/polymer composite with a plurality of metallic-core carbon-shell nanoparticles as recited in  claim 1 , in an amount sufficient, in comparison to an otherwise similar but unimpregnated fiber/polymer composite, to substantially strengthen said fiber/polymer composite. 
     
     
         111 - 115 . (canceled) 
     
     
         116 . A composition of matter comprising fiber/polymer composites impregnated with a plurality of metallic-core carbon-shell nanoparticles as recited in  claim 1 , in an amount sufficient, in comparison to an otherwise similar but unimpregnated fiber/polymer composite, to substantially strengthen said fiber/polymer composite. 
     
     
         117 . (canceled)