Iron nanoparticles and methods of production

Abstract

Techniques and methods are disclosed for producing a plurality of nanoparticles that can be used as catalysts to grow carbon or boron nitride nanotubes. The method includes mixing an iron salt including a ferrous or ferric ion with a long chain amine, thiol or polyphenol in a solvent comprising alcohol to produce a solution. Ferric or ferrous ion is reduced to zero valence iron. Nucleation of iron nanoparticles is initialized. The iron nanoparticles are capped to retard nanoparticle growth. The nanoparticles include an elemental iron core coated with a polyphenol that isolates the core from oxygen. The nanoparticles include an average diameter of less than or equal to 15.8 nanometers. The iron core may further include a secondary metal to form an iron-alloy. The secondary metal, in some applications, can be a transition metal.

What is claimed is: 
     
         1 . A plurality of nanoparticles, each nanoparticle comprising:
 an elemental iron core coated with a polyphenol that isolates the core from oxygen, the plurality of nanoparticles having an average diameter of less than or equal to 50 nanometers.   
     
     
         2 . The nanoparticles of  claim 1 , wherein the nanoparticles have an average diameter within a range from 5 to 25 nm. 
     
     
         3 . The nanoparticles of  claim 1 , wherein the nanoparticles have an average diameter of less than or equal to 15.8 nm. 
     
     
         4 . The nanoparticles of  claim 1 , wherein the polyphenol is one of epigallcatechin gallate, epicatechin, epigallocatechin, and gallocatechin. 
     
     
         5 . The nanoparticles of  claim 1 , wherein the elemental iron core further comprises a secondary metal to form an iron-alloy. 
     
     
         6 . The nanoparticles of  claim 5  wherein the secondary metal is a transition metal. 
     
     
         7 . The plurality of nanoparticles of  claim 1  wherein the nanoparticles have an average diameter of less than or equal to 8.5 nm. 
     
     
         8 . The plurality of nanoparticles of  claim 1  wherein the nanoparticles have an average diameter within a range from 5 to 25 nm and a standard deviation within a range from 1 to 4 nm. 
     
     
         9 . The plurality of nanoparticles of  claim 1  wherein the nanoparticles have a face centered cubic (FFC) crystalline structure. 
     
     
         10 . A method of producing iron nanoparticles, the method comprising:
 mixing an iron salt comprising a ferrous or ferric ion with a long chain amine, thiol or polyphenol in a solvent comprising alcohol to produce a solution;   reducing the ferrous or ferric ion to zero valence iron;   initializing nucleation of iron nanoparticles; and   capping the iron nanoparticles to retard nanoparticle growth.   
     
     
         11 . The method of  claim 10 , wherein the alcohol comprises at least one of methanol and ethanol. 
     
     
         12 . The method of  claim 10 , wherein the iron nanoparticles have an average diameter of less than or equal to 50 nm. 
     
     
         13 . The method of  claim 12 , wherein the diameter distribution of the iron nanoparticles has a standard deviation of less than or equal to 3.7 nm. 
     
     
         14 . The method of  claim 10 , wherein the solution comprises iron at a concentration of less than or equal to 2.5 g/L. 
     
     
         15 . The method of  claim 10 , wherein the solution includes polyphenol at a concentration of less than or equal to 1.5 g/L. 
     
     
         16 . The method of  claim 10 , wherein the solution includes iron at a concentration of greater than or equal to 0.5 g/L. 
     
     
         17 . The method of  claim 10 , wherein the long chain amine, thiol or polyphenol is a polyphenol. 
     
     
         18 . The method of  claim 17  wherein the polyphenol is selected from epigallcatechin gallate, epicatechin, epigallocatechin, and gallocatechin. 
     
     
         19 . The method of  claim 10 , further comprising adding copper to the solution to produce iron nanoparticles comprising copper. 
     
     
         20 . The method of  claim 10  wherein the nanoparticles have an average diameter of less than or equal to 15.8 nm. 
     
     
         21 . The method of  claim 10  wherein the nanoparticles have an average diameter of less than or equal to 5.8 nm. 
     
     
         22 . A method of producing a nanotube, the method comprising:
 providing a plurality of nanoparticles to a furnace, the nanoparticles comprising an elemental iron core coated with a polyphenol that isolates the core from oxygen, the nanoparticles having an average diameter of less than or equal to 50 nanometers;   removing the polyphenol from the plurality of nanoparticles to expose an iron surface of the nanoparticles; and   catalyzing nanotube growth on the exposed surface of the nanoparticles.