Continuous flow synthesis of nanomaterials using ionic liquids in microfluidic reactors

Abstract

A method for manufacturing metal nanoparticles includes the use of a microfluidic device. The microfluidic device has a first channel having a first inlet; a second channel having a second inlet; a third channel having a third inlet; and a main channel having a main inlet and an outlet. The first channel, second channel, and third channel all lead into the main channel. The method involves injecting a solution of a metal/ligand into the first inlet, injecting a solution of a reducing agent into the second inlet, injecting a solvent comprised of an ionic liquid into the third inlet, and injecting an inert carrier into the main inlet. The solution of the metal/ligand, the solution of the reducing agent, the solvent and the inert carrier are combined together in the main channel, and the metal/ligand and the reducing agent are reacted for a time sufficient to form a metal nanoparticle.

What is claimed is: 
     
         1 . A method for manufacturing metal nanoparticles by the use of a microfluidic device,
 the microfluidic device comprising:
 a first channel having a first inlet; 
 a second channel having a second inlet; 
 a third channel having a third inlet; and 
 a main channel having a main inlet and an outlet, wherein the first channel, second channel, and third channel all lead into the main channel, 
   the method comprising the steps of:   injecting a solution of a metal/ligand into the first inlet,   injecting a solution of a reducing agent into the second inlet,   injecting a solvent comprised of an ionic liquid into the third inlet, and   injecting an inert carrier into the main inlet,   combining the solution of the metal/ligand, the solution of the reducing agent, the solvent and the inert carrier together in the main channel, and   reacting the metal/ligand and the reducing agent for a time sufficient to form a metal nanoparticle.   
     
     
         2 . The method of  claim 1 , wherein the microfluidic device is comprised of a polymeric material. 
     
     
         3 . The method of  claim 2 , wherein the polymeric material comprises silicon. 
     
     
         4 . The method of  claim 3 , wherein the polymeric material is poly(dimethylsiloxane). 
     
     
         5 . The method of  claim 1 , wherein the first channel, the second channel, the third channel, and the main channel each have a width in a range of from about 100 μm to about 2000 μm. 
     
     
         6 . The method of  claim 1 , wherein the first channel, the second channel, the third channel, and the main channel each have a depth in a range of from about 20 μm to about 200 μm. 
     
     
         7 . The method of  claim 1 , wherein the first channel, the second channel, the third channel, and the main channel have a hydrophobic coating. 
     
     
         8 . The method of  claim 7 , wherein the coating comprises a fluoropolymer. 
     
     
         9 . The method of  claim 1 , wherein the metal/ligand solution is comprised of a mixture of a metal and a ligand capable of stabilizing the metal. 
     
     
         10 . The method of  claim 9 , wherein the metal is at least one selected from the group consisting of gold, silver, cobalt, copper, platinum, and palladium. 
     
     
         11 . The method of  claim 9 , wherein the ligand is comprised of an ionic liquid. 
     
     
         12 . The method of  claim 11 , wherein the ionic liquid is an imidazolium based compound. 
     
     
         13 . The method of  claim 1 , wherein the reducing agent is an imidazolium based borohydride. 
     
     
         14 . The method of  claim 1 , wherein inert carrier comprises a hydrophobic liquid. 
     
     
         15 . The method of  claim 14 , wherein the hydrophobic liquid comprises a fluorocarbon. 
     
     
         16 . The method of  claim 1 , wherein a ratio of the rate of injection of the inert carrier compared to the rate of injection of the solution of the metal/ligand, the solution of the reducing agent and the solvent is from about 2:1 to about 20:1. 
     
     
         17 . The method of  claim 16 , wherein a flow rate of the inert carrier is about 1 mL/hour to about 10 mL/hour. 
     
     
         18 . The method of  claim 1 , wherein a flow rate of the inert carrier is such that when the solution of the metal/ligand, the solution of the reducing agent and the solvent are combined with the inert carrier in the main channel, a droplet comprised of metal/ligand, the reducing agent and the solvent is formed. 
     
     
         19 . The method of  claim 1 , wherein a ratio of the rate of injection of the solution of the metal/ligand to the solvent is from about 1:1 to about 3:1. 
     
     
         20 . The method of  claim 1 , wherein a ratio of the rate of injection of the solution of the reducing agent to the solvent is from about 1:1 to about 3:1. 
     
     
         21 . The method of  claim 1 , wherein a ratio of the rate of injection of the solution of the metal/ligand to the solution of the reducing agent is from about 0.5:1 to about 2:1. 
     
     
         22 . The method of  claim 1 , wherein the metal nanoparticle formed has a diameter of from about 3 nm to about 6 nm. 
     
     
         23 . The method of  claim 1 , wherein the metal nanoparticle formed has a spherical shape. 
     
     
         24 . The method of  claim 1 , wherein the time of the reaction of metal/ligand and the reducing agent is from about 5 to about 60 seconds. 
     
     
         25 . The method of  claim 1 , wherein after reacting the metal/ligand and the reducing agent, the nanoparticle formed is deposited through the outlet of the main channel.