Purification of metal nanostructures for improved haze in transparent conductors made from the same

Abstract

Provided are a method of isolating and purifying metal nanowires from a crude and complex reaction mixture that includes relatively high aspect ratio nanostructures as well as nanostructures of low aspect ratio shapes, and conductive films made of the purified nanostructures.

1 . A process of isolating metal nanowires, comprising:
 (a) providing a crude mixture of nanostructures that includes nanostructures having an aspect ratio of 10 or more and nanostructures having an aspect ratio of no more than 10, the crude mixture being suspended in a polyol solvent;   (b) providing a first diluted crude mixture by combining water with the crude mixture;   (c) providing a combined ketone mixture by combining the diluted crude mixture with a ketone;   (d) providing a precipitate comprising nanostructures having an aspect ratio of 10 or more, and a supernatant comprising at least a portion of the nanostructures having aspect ratios of no more than 10, providing the precipitate including allowing sedimentation of the combined ketone mixture; and   (e) removing from the precipitate the supernatant comprising the at least a portion of the nanostructures having aspect ratios of no more than 10.   
     
     
         2 . The process of  claim 1 , further comprising:
 (f) re-suspending the precipitate of (d) in water to provide a second diluted crude mixture; and   (g) repeating steps (c)-(f).   
     
     
         3 . The process of  claim 2  wherein the nanostructures having an aspect ratio of 10 or more are silver nanowires. 
     
     
         4 . The process of  claim 2  wherein the polyol solvent is ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, or glycerol. 
     
     
         5 . The process of  claim 4  wherein the polyol solvent is glycerol. 
     
     
         6 . The process of  claim 2  wherein the ketone is acetone, methyl ethyl ketone (MEK), 2-pentanone, or 3-pentanone. 
     
     
         7 . The process of  claim 2  wherein the ketone is acetone. 
     
     
         8 . An ink composition comprising:
 a plurality of nanostructures having aspect ratios of 10 or more; and   a liquid carrier;   wherein the nanostructures having aspect ratios of 10 or more are purified by:
 (a) providing a crude mixture of nanostructures that includes nanostructures having an aspect ratio of 10 or more and nanostructures having an aspect ratio of no more than 10, the crude mixture being suspended in a polyol solvent; 
 (b) providing a first diluted crude mixture by combining water with the crude mixture; 
 (c) providing a combined ketone mixture by combining the diluted crude mixture with a ketone; 
 (d) providing a precipitate comprising nanostructures having an aspect ratio of 10 or more, and a supernatant comprising at least a portion of the nanostructures having aspect ratios of no more than 10, providing the precipitate including allowing sedimentation of the combined ketone mixture; and 
 (e) removing from the precipitate the supernatant comprising the at least a portion of the nanostructures having aspect ratios of no more than 10. 
 (f) re-suspending the precipitate of (d) in water to provide a second diluted crude mixture; and 
 (g) repeating steps (c)-(f). 
   
     
     
         9 . The ink composition of  claim 8  further comprising a viscosity modifier. 
     
     
         10 . The ink composition of  claim 8  further comprising a surfactant. 
     
     
         11 . The ink composition of  claim 9  wherein the viscosity modifier and the silver nanowires nanowires are in a w/w ratio of 10 to 0.1. 
     
     
         12 . The ink composition of  claim 1  wherein the viscosity modifier is HPMC. 
     
     
         13 . The ink composition of  claim 8  wherein the ketone is acetone, methyl ethyl ketone (MEK), 2-pentanone, or 3-pentanone.