Synthesis of Metallic Nanoparticle Dispersions

Abstract

Disclosed are compositions comprising metallic nanoparticles suitable for use in cohesive, highly conductive structures on substrates. Also disclosed are methods for synthesizing the compositions and methods for forming cohesive, highly conductive structures from the compositions.

1 . A composition, comprising: 
 a population of metallic nanoparticles dispersed in an aqueous medium, wherein at least a portion of the population comprising individual metallic nanoparticles characterized as having an average cross-sectional dimension in the range of from about 1 nm to about 100 nm; and,    wherein each of the nanoparticles comprise at least one ligand bound to its surface, the ligand comprising a heteroatom head group bound to the nanoparticle surface and a tail bound to the heteroatom head group.    
     
     
         2 . The composition of  claim 1 , wherein the nanoparticle population further comprises particle agglomerate comprised of two or more individual nanoparticles, nanoparticle floc comprised of two or more individual nanoparticles, or any combination thereof.  
     
     
         3 . The composition of  claim 2 , wherein the ratio, by weight, of the population of individual metallic nanoparticles to particle agglomerate is in the range of from about 1:99 to 99:1.  
     
     
         4 . The composition of  claim 2 , wherein the ratio, by weight, of the population of individual metallic nanoparticles to particle floc is in the range of from about 1:99 to 99:1.  
     
     
         5 . The composition of  claim 2 , a nanoparticle agglomerate has an average cross-sectional dimension in the range of from about 100 nm to about 10000 nm.  
     
     
         6 . The composition of  claim 2 , wherein a nanoparticle floc has an average cross-sectional dimension in the range of from about 100 to about 10000 nm.  
     
     
         7 . The composition of  claim 1 , wherein an individual metallic nanoparticle comprises silver, copper, gold, zinc, cadmium, palladium, iridium, ruthenium, osmium, rhodium, platinum, iron, nickel, cobalt, indium, silver oxide, copper oxide, gold oxide, zinc oxide, cadmium oxide, palladium oxide, iridium oxide, ruthenium oxide, osmium oxide, rhodium oxide, platinum oxide, iron oxide, nickel oxide, cobalt oxide, indium oxide, or any combination thereof.  
     
     
         8 . The composition of  claim 1 , wherein the aqueous medium is capable of solvating the metallic salt in a range of from about 10 grams/liter to about 600 grams/liter.  
     
     
         9 . The composition of  claim 1 , wherein the nanoparticles are present in the range of from about 0.5 wt % to about 70 wt %.  
     
     
         10 . The composition of  claim 1 , wherein the ligand is present in the range of from about 0.5 wt % to about 75 wt %.  
     
     
         11 . The composition of  claim 1 , wherein the medium is present in the range of from about 30 to about 98 wt %.  
     
     
         12 . The composition of  claim 1 , wherein the composition is capable of forming a cohesive structure of less than about 10 μm in thickness following curing at a temperature of less than about 140° C. for less than about 60 seconds.  
     
     
         13 . The composition of  claim 12 , wherein the structure has a resistivity in the range of from about 2 times to about 15 times the bulk resistivity of the corresponding metal.  
     
     
         14 . A composition, comprising: 
 a metallic nanoparticle mixture comprising at least one metallic nanoparticles, capable of forming a cohesive structure of less than about 10 μm in thickness following curing at a temperature of less than about 140° C. for less than about 90 seconds, wherein the cohesive structure has a resistivity in the range of from about 2 times to about 15 times the bulk resistivity of the corresponding metal.    
     
     
         15 . The composition of  claim 14 , wherein the mixture comprises a population of metallic nanoparticles, a ligand, an aqueous medium, or any combination thereof.  
     
     
         16 . The composition of  claim 15 , wherein the nanoparticle population comprises individual nanoparticles, particle agglomerate comprised of two or more individual nanoparticles, particle floc comprised of two or more individual nanoparticles, or any combination thereof.  
     
     
         17 . The composition of  claim 16 , wherein the ratio, by weight, of the population of individual metallic nanoparticles to particle agglomerate is in the range of from about 1:99 to 99:1.  
     
     
         18 . The composition of  claim 16 , wherein the ratio, by weight, of the population of individual metallic nanoparticles to particle floc is in the range of from about 1:99 to 99:1.  
     
     
         19 . The composition of  claim 16 , wherein individual metallic nanoparticles have an average cross-sectional dimension in the range of from about 1 nm to about 100 nm.  
     
     
         20 . The composition of  claim 16 , wherein particle agglomerates have an average cross-sectional dimension in the range of from about 100 nm to about 10000 nm.  
     
     
         21 . The composition of  claim 16 , wherein particle flocs have an average cross-sectional dimension in the range of from about 100 to about 10000 nm.  
     
     
         22 . The composition of  claim 16 , wherein an individual metallic nanoparticle comprises silver, copper, gold, zinc, cadmium, palladium, iridium, ruthenium, osmium, rhodium, platinum, iron, nickel, cobalt, indium, silver oxide, copper oxide, gold oxide, zinc oxide, cadmium oxide, palladium oxide, iridium oxide, ruthenium oxide, osmium oxide, rhodium oxide, platinum oxide, iron oxide, nickel oxide, cobalt oxide, indium oxide, or any combination thereof.  
     
     
         23 . The composition of  claim 15 , wherein the aqueous medium is capable of solvating the metallic salt in a range of from about 10 grams/liter to about 600 grams/liter.  
     
     
         24 . The composition of  claim 15 , wherein the nanoparticles are present in the range of from about 0.5 to about 70 wt %.  
     
     
         25 . The composition of  claim 15 , wherein the ligand is present in the range of from about 0.5 to about 75 wt %.  
     
     
         26 . The composition of  claim 15 , wherein the medium is present in the range of from about 30 to about 98 wt %.  
     
     
         27 . A method for synthesizing a metallic nanoparticle dispersion, comprising: 
 reacting in an aqueous medium:    at least one ligand, wherein the ligand comprises a heteroatom head group bonded to a tail comprising from 1 to about 20 carbon atoms;    at least one reducing agent; and,    at least one metallic salt in an aqueous dispersing solution, wherein the metallic salt is present in the dispersion at a concentration in the range of from about 10 grams/liter to about 600 grams/liter based on volume of the dispersing solution, and wherein the metallic salt comprises at least one cation comprising silver, copper, gold, zinc, cadmium, palladium, iridium, ruthenium, osmium, rhodium, platinum, iron, nickel, cobalt, indium, or any combination thereof.    
     
     
         28 . The method of  claim 27 , wherein the ligand is characterized as being capable of binding by its heteroatom head group to a surface of a metallic nanoparticle so as to give rise to a metallic nanoparticle stabilized at least in part against aggregation.  
     
     
         29 . The method of  claim 27 , wherein the metallic salt further comprises at least one anion.  
     
     
         30 . The method of  claim 27 , wherein the reacting comprises contacting, mixing, stirring, sonicating, agitating, or any combination thereof.  
     
     
         31 . The method of  claim 30 , wherein, after the reacting, one or more ligand heteratomic head groups are characterized as bound to a surface of one or more metallic nanoparticles so as to give rise to one or more metallic nanoparticles stabilized against irreversible aggregation.  
     
     
         32 . The method of  claim 30 , wherein the method further comprises combining the ligand and metallic salt in a respective molar ratio in the range of from about 0.1:1 to about 1:1.  
     
     
         33 . The method of  claim 32 , wherein the method further comprises combining the metallic salt and reducing agent in a respective molar ratio in the range of from about 1:10 to about 4:1.  
     
     
         34 . The method of  claim 32 , wherein the method further comprises adjusting the relative amounts of ligand, reducing agent, metallic salt, aqueous dispersing solution, adjusting the pH of the aqueous medium, or any combination thereof, so as to give rise to a pH in the range of from about 3 to about 12.  
     
     
         35 . The method of  claim 27  wherein the method further comprises heating the aqueous medium, ligand, reducing agent, and metallic salt in aqueous dispersing solution, or any combination thereof, to a temperature of from about 5° C. to about 200° C. prior to reaction.  
     
     
         36 . The method of  claim 27 , wherein the method further comprises heating the aqueous medium, ligand, reducing agent, and metallic salt in aqueous dispersing solution, or any combination thereof, to a temperature of from about 35° C. to about 70° C. prior to reaction.  
     
     
         37 . The method of  claim 27 , wherein the method further comprises heating the aqueous medium, ligand, reducing agent, and metallic salt in aqueous dispersing solution, or any combination thereof, to a temperature of from about 40° C. to about 60° C. prior to reaction.  
     
     
         38 . The method of  claim 27 , further comprising a recovery step following reaction.  
     
     
         39 . The method of  claim 38 , wherein the recovery step comprises allowing the passage of sufficient time such that the concentration of nanoparticles in any aqueous medium present is in the range of from about 0 wt % to about 70 wt %.  
     
     
         40 . The method of  claim 38 , wherein the recovery step comprises allowing the passage of sufficient time such that the concentration of nanoparticles in any aqueous medium present is about 5 wt % and decanting the aqueous medium.  
     
     
         41 . The method of  claim 27 , wherein the reacting comprises continuously introducing the aqueous medium, ligand, and reducing agent into a first stirred reactor capable of fluid communication with the contents of a second stirred reactor.  
     
     
         42 . The method of  claim 41 , wherein the ligand is characterized as being capable of binding by its heteroatom head group to a surface of a metallic nanoparticle so as to give rise to a metallic nanoparticle stabilized at least in part against irreversible aggregation.  
     
     
         43 . The method of  claim 41 , further comprising continuously introducing the metallic salt dispersion to the first reactor.  
     
     
         44 . The method of  claim 43 , wherein the metallic salt further comprises an anion.  
     
     
         45 . The method of  claim 44 , wherein the anion comprises acetate, nitrate, carboxylate, sulfate, chloride, hydroxide, or any combination thereof.  
     
     
         46 . The method of  claim 43 , wherein the dispersing medium comprises an aqueous medium substantially free of organic solvents.  
     
     
         47 . The method of  claim 44 , wherein the ligand and metallic salt are introduced to the first reactor at a respective molar ratio of from about 0.1:1 to about 1:1.  
     
     
         48 . The method of  claim 43 , further comprising adjusting the relative amounts of ligand, reducing agent, metallic salt, aqueous dispersing solution, adjusting the pH of the aqueous medium, or any combination thereof, so as to give rise to a pH in the range of from about 3 to about 12.  
     
     
         49 . The method of  claim 48 , wherein the method further comprises heating the aqueous medium, ligand, reducing agent, and metallic salt in aqueous dispersing solution, or any combination thereof, to a temperature of from about 5° C. to about 200° C. before reaction.  
     
     
         50 . The method of  claim 43 , wherein the method further comprises heating the aqueous medium, ligand, reducing agent, and metallic salt in aqueous dispersing solution, or any combination thereof, to a temperature of from about 35° C. to about 70° C. before reaction.  
     
     
         51 . The method of  claim 43 , wherein the method further comprises heating the aqueous medium, ligand, reducing agent, and metallic salt in aqueous dispersing solution, or any combination thereof, to a temperature of from about 40° C. to about 60° C. before reaction.  
     
     
         52 . The method of  claim 43 , wherein the residence time of the first reactor is sufficient so as to give rise to the reaction progressing to substantial completion.  
     
     
         53 . The method of  claim 43 , further comprising continuously transporting the contents of the first reactor to the second reactor.  
     
     
         54 . The method of  claim 53 , wherein the residence time in the second reactor is sufficient to allow the reaction to progress to essentially total completion.  
     
     
         55 . The method of  claim 54 , further comprising a recovery step following reaction.  
     
     
         56 . The method of  claim 55 , wherein the recovery step comprises allowing the passage of sufficient time such that the concentration of nanoparticles in any aqueous medium present is about 5 wt %.  
     
     
         57 . A method for forming a conductive structure on a substrate, comprising: 
 depositing a composition onto the substrate, wherein the composition comprises at least one population of metallic nanoparticles, wherein at least a portion of the population comprising individual metallic nanoparticles characterized as having an average cross-sectional dimension in the range of from about 1 nm to about 30 nm;    wherein each of the nanoparticles comprise at least one ligand bound to its surface, the ligand comprising a heteroatom head group bound to the nanoparticle surface and a tail bound to the heteroatom head group; and,    curing the deposited composition.    
     
     
         58 . The method of  claim 57 , wherein depositing comprises a printing method.  
     
     
         59 . The method of  claim 58 , wherein the printing method comprises flexographic printing, rotogravure printing, lithographic printing, intaglio printing, relief printing, screen printing, inkjet printing, laser printing, or any combination thereof.  
     
     
         60 . The method of  claim 57 , wherein the nanoparticle population comprises individual particles, nanoparticle agglomerate comprised of at least two individual nanoparticles, nanoparticle floc comprised of at least two nanoparticles, or any combination thereof.  
     
     
         61 . The method of  claim 57 , wherein an individual metallic nanoparticle comprises silver, copper, gold, zinc, cadmium, palladium, iridium, ruthenium, osmium, rhodium, platinum, iron, nickel, cobalt, indium, silver oxide, copper oxide, gold oxide, zinc oxide, cadmium oxide, palladium oxide, iridium oxide, ruthenium oxide, osmium oxide, rhodium oxide, platinum oxide, iron oxide, nickel oxide, cobalt oxide, indium oxide, or any combination thereof.  
     
     
         62 . The method of  claim 57 , wherein one or more ligands are characterized as bound to a surface of one or more metallic nanoparticles so as to give rise to one or more metallic nanoparticles stabilized against aggregation.  
     
     
         63 . The method of  claim 57 , wherein the nanoparticles are present in the range of from about 0.5 to about 70 wt %.  
     
     
         64 . The method of  claim 57 , wherein the ligand is present in the range of from about 0.5 to about 75 wt %.  
     
     
         65 . The method of  claim 57 , wherein the composition further comprises a rheology modifier.  
     
     
         66 . The method of  claim 65 , wherein the rheology modifier comprises an associative thickener.  
     
     
         67 . The method of  claim 65 , wherein the rheology modifier comprises a thickening agent.  
     
     
         68 . The method of  claim 67 , wherein the thickening agent comprises an alkali-soluble emulsion.  
     
     
         69 . The method of  claim 65 , wherein the rheology modifier is present in the range of from about 0 wt % to about 15 wt %.  
     
     
         70 . The method of  claim 57 , wherein the composition further comprises a binder.  
     
     
         71 . The method of  claim 70 , wherein the binder is present in the range of from about 0 wt % to about 20 wt %.  
     
     
         72 . The method of  claim 57 , wherein the substrate comprises a glass, a ceramic, a polymer, a silicon, a nitride, a carbide, a ceramic precursor, fabric, or any combination thereof.  
     
     
         73 . The method of  claim 72 , wherein the polymer comprises a polyester, a polyolefin, a polycarbonate, an acrylic polymer, polyethylene naphthalate, polyimide, polyamideimide, polyvinyl chloride, polypropylene, a liquid crystal polymer, polycarbonate, or any combination thereof.  
     
     
         74 . The method of  claim 72 , wherein the substrate further comprises paper, synthetic engineered paper, cardboard, a coated corrugated cardboard, an uncoated corrugated cardboard, or any combination thereof.  
     
     
         75 . The method of  claim 72 , wherein at least a portion of a surface of the substrate is capable of being modified to give rise to a surface capable of adhering to the deposited composition.  
     
     
         76 . The method of  claim 57 , wherein the composition further comprises metallic particles.  
     
     
         77 . The method of  claim 76 , wherein the metallic particles have a width in the range of from about 200 nm to about 20000 nm.  
     
     
         78 . The method of  claim 76 , wherein a metallic particle comprises silver, copper, gold, zinc, cadmium, palladium, iridium, ruthenium, osmium, rhodium, platinum, iron, nickel, cobalt, indium, silver oxide, copper oxide, gold oxide, zinc oxide, cadmium oxide, palladium oxide, iridium oxide, ruthenium oxide, osmium oxide, rhodium oxide, platinum oxide, iron oxide, nickel oxide, cobalt oxide, indium oxide, or any combination thereof.  
     
     
         79 . The method of  claim 57 , wherein curing comprises exposing the deposited composition to a temperature of less than about 140° C. for less than about 90 seconds.  
     
     
         80 . The method of  claim 57 , wherein the structure has a thickness of less than about 20 μm.  
     
     
         81 . A method for forming a conductive structure, comprising: 
 depositing a metallic nanoparticle composition comprising at least one metallic nanoparticle onto the substrate, wherein the composition is capable of forming after curing at a temperature of less than about 140° C. for less than about 90 seconds a cohesive and conductive structure having a resistivity in the range of from about 2 times to about 15 times the bulk resistivity of the corresponding metal and having a thickness of less than about 20 μm; and,    curing the deposited composition.    
     
     
         82 . The method of  claim 81 , wherein depositing comprises a printing method.  
     
     
         83 . The method of  claim 82 , wherein the printing method comprises flexographic printing, rotogravure printing, lithographic printing, intaglio printing, relief printing, screen printing, inkjet printing, laser printing, or any combination thereof.  
     
     
         84 . The method of  claim 81 , wherein the composition comprises a population of metallic nanoparticles, a ligand, a medium, or any combination thereof.  
     
     
         85 . The method of  claim 81 , wherein the nanoparticle population comprises individual nanoparticles, nanoparticle agglomerate, nanoparticle floc, or any combination thereof.  
     
     
         86 . The method of  claim 85 , wherein individual metallic nanoparticles have an average cross-sectional dimension in the range of from about 1 nm to about 100 nm.  
     
     
         87 . The method of  claim 85 , wherein nanoparticle flocs have an average cross-sectional dimension in the range of from about 100 to about 10000 nm.  
     
     
         88 . The method of  claim 84 , wherein an individual metallic nanoparticle comprises silver, copper, gold, zinc, cadmium, palladium, iridium, ruthenium, osmium, rhodium, platinum, iron, nickel, cobalt, indium, silver oxide, copper oxide, gold oxide, zinc oxide, cadmium oxide, palladium oxide, iridium oxide, ruthenium oxide, osmium oxide, rhodium oxide, platinum oxide, iron oxide, nickel oxide, cobalt oxide, indium oxide, or any combination thereof.  
     
     
         89 . The method of  claim 84 , wherein one or more ligands are characterized as bound to a surface of one or more metallic nanoparticles so as to give rise to one or more metallic nanoparticles stabilized against irreversible aggregation.  
     
     
         90 . The method of  claim 84 , wherein the nanoparticles are present in the range of from about 0.5 to about 70 wt %.  
     
     
         91 . The method of  claim 84 , wherein the ligand is present in the range of from about 0.5 to about 75 wt %.  
     
     
         92 . The method of  claim 84 , wherein the medium is present in the range of from about 30 to about 98 wt %.  
     
     
         93 . The method of  claim 84 , wherein the composition further comprises a rheology modifier.  
     
     
         94 . The method of  claim 93 , wherein the rheology modifier comprises an associative thickener.  
     
     
         95 . The method of  claim 93 , wherein the rheology modifier is present in the range of from about 0 wt % to about 15 wt %.  
     
     
         96 . The method of  claim 84 , wherein the composition further comprises a binder.  
     
     
         97 . The method of  claim 96 , wherein the binder comprises a latex, a polymer latex, an emulsion polymer, polyimide, a silicone, a fluorocarbon, a polyamic acid, a polyurethane, a polyester, an epoxy, or any combination thereof.  
     
     
         98 . The method of  claim 96 , wherein the binder is present in the range of from about 0 wt % to about 20 wt %.  
     
     
         99 . The method of  claim 81 , wherein the substrate comprises a glass, a ceramic, a polymer, a silicon, a nitride, a carbide, a ceramic precursor, fabric, or any combination thereof.  
     
     
         100 . The method of  claim 99 , wherein the polymer comprises a polyester, a polyolefin, a polycarbonate, an acrylic polymer, polyethylene naphthalate, polyimide, polyamideimide, polyvinyl chloride, polypropylene, a liquid crystal polymer, polycarbonate, or any combination thereof.  
     
     
         101 . The method of  claim 99 , substrate further comprises paper, synthetic engineered paper, cardboard, a coated corrugated cardboard, an uncoated corrugated cardboard, or any combination thereof.  
     
     
         102 . The method of  claim 99 , wherein at least a portion of a surface of the substrate is capable of being modified to give rise to a surface capable of adhering to the deposited composition.  
     
     
         103 . The method of  claim 84 , wherein the composition further comprises metallic particles.  
     
     
         104 . The method of  claim 103 , wherein the metallic particles have a width in the range of from about 200 nm to about 20000 nm.  
     
     
         105 . The method of  claim 103 , wherein a metallic particle comprises silver, copper, gold, zinc, cadmium, palladium, iridium, ruthenium, osmium, rhodium, platinum, iron, nickel, cobalt, indium, silver oxide, copper oxide, gold oxide, zinc oxide, cadmium oxide, palladium oxide, iridium oxide, ruthenium oxide, osmium oxide, rhodium oxide, platinum oxide, iron oxide, nickel oxide, cobalt oxide, indium oxide, or any combination thereof.