High-throughput synthesis of metallic nanoparticles

Abstract

This invention relates to cost-effective methods for synthesizing metallic nanoparticles in high yield using non-dendrimeric branched polymeric templates, such as branched polyethyleneimine. This invention also provides a high-throughput apparatus for synthesizing metallic nanoparticles under conditions that produce less waste than conventional nanoparticle synthesis methods. Also provided are metallic nanoparticles and multi-metallic nanoparticle compositions made by methods and high-throughput apparatus of the invention.

What is claimed is: 
     
         1 . A method of synthesizing metallic nanoparticles, the method comprising
 providing a first flow stream comprising an aqueous salt solution comprising ions of a transition metal and a branched polymeric template, wherein the branched polymeric template is not a dendrimer;   subjecting the first flow stream to a reducing agent to reduce the ions of the transition metal to form metallic nanoparticles within the branched polymeric template; and   optionally separating the metallic nanoparticles from the branched polymeric template.   
     
     
         2 . The method according to  claim 1 , wherein the branched polymeric template comprises a branched polymer selected from the group consisting of polyalkyleneimine, polyester, polyether, thioester, and polysulfide polymers. 
     
     
         3 . The method according to  claim 2 , wherein the branched polymeric template is a polyalkyleneimine. 
     
     
         4 . The method of  claim 3 , wherein the branched polyalkyleneimine is polyethyleneimine. 
     
     
         5 . The method according to  claim 1 , wherein the aqueous salt solution is prepared by dissolving at least one transition metal halide, nitrate, sulfate, or phosphate in water. 
     
     
         6 . The method according to  claim 1 , wherein the nanoparticles comprise one or more metals selected from the group consisting of iron, cobalt, rhodium, iridium, nickel, palladium, platinum; copper, silver, gold, zirconium, and titanium. 
     
     
         7 . The method according to  claim 1 , wherein the first flow stream is obtained by combining a flow stream comprising a metal salt solution with a flow stream comprising the branched polymeric template. 
     
     
         8 . The method according to  claim 1 , wherein the step of subjecting the first stream to a reducing agent comprises combining the first flow stream with a second flow stream comprising a chemical reducing agent. 
     
     
         9 . The method according to  claim 8 , wherein the chemical reducing agent is selected from the group consisting of sodium borohydride, lithium aluminum hydride, and lithium triethylborohydride. 
     
     
         10 . The method according to  claim 1 , wherein the metallic nanoparticles have a median diameter in the range of 1 to 10 nm. 
     
     
         11 . The method according to  claim 1 , wherein the step of subjecting the first flow stream to a reducing agent comprises photochemically reducing the ions of the transition metal in the first flow stream. 
     
     
         12 . The method according to  claim 8 , wherein the ions of the transition metal are photochemically reduced using ultraviolet light. 
     
     
         13 . The method according to  claim 9 , wherein the ultraviolet light has a wavelength of 254 nm. 
     
     
         14 . The method according to  claim 1 , wherein the step of optionally separating the metallic nanoparticles from the branched polyalkyleneimine template comprises a ligand exchange reaction that liberates the metallic nanoparticles from the branched polyalkyleneimine template. 
     
     
         15 . The method according to  claim 1 , wherein the ligand exchange reaction comprises exposing the metal nanoparticles in the branched polyalkyleneimine template to an alkanethiol. 
     
     
         16 . An apparatus for synthesizing metallic nanoparticles, the apparatus comprising
 a first device for providing a first flow stream comprising an aqueous salt solution comprising ions of a transition metal and a branched polymeric template, wherein the branched polymeric template is not a dendrimer;   a second device for providing a reducing agent that reduces the ions of the transition metal in the first flow stream.   
     
     
         17 . The apparatus according to  claim 16 , wherein the reducing agent is a second flow stream comprising a chemical reducing agent, and wherein the second device is configured to mix the second flow stream with the first flow stream, thereby causing the formation of metallic nanoparticles within the branched polymeric template. 
     
     
         18 . The apparatus according to  claim 17 , wherein the chemical reducing agent is a metal hydride. 
     
     
         19 . The apparatus according to  claim 18 , wherein the metal hydride is selected from the group consisting of sodium borohydride, lithium aluminum hydride, and lithium triethylborohydride. 
     
     
         20 . The apparatus according to  claim 16 , wherein the reducing agent photochemically reduces the ions of the transition metal. 
     
     
         21 . The apparatus according to  claim 20 , wherein the second device comprises an ultraviolet light source.