Transparent conducting films containing single-walled carbon nanotubes dispersed in an azo dye

Abstract

Described are carbon nanotube dispersions containing single-walled carbon nanotubes dispersed in a dispersant solution comprising a solvent (water, organic polar protic solvents, and/or organic polar aprotic solvents), and an azo compound. The single-walled carbon nanotubes are not cross-linked with covalent bonds. The dispersions are useful for fabricating transparent conductive thin films on flexible and inflexible substrates. Methods for making the transparent conductive thin films are also described.

What is claimed is: 
     
         1 . A carbon nanotube dispersion comprising:
 single-walled carbon nanotubes dispersed in a dispersant solution comprising a solvent selected from the group consisting of water, organic polar protic solvents, and organic polar aprotic solvents, and an azo compound comprising at least one azo moiety, wherein the single-walled carbon nanotubes are not covalently cross-linked.   
     
     
         2 . The carbon nanotube dispersion of  claim 1 , wherein the azo compound comprises at least two azo moieties. 
     
     
         3 . The carbon nanotube dispersion of  claim 1 , wherein the azo compound comprises at least one sulfonic acid moiety. 
     
     
         4 . The carbon nanotube dispersion of  claim 3 , wherein the azo compound comprises at least two azo moieties 
     
     
         5 . The carbon nanotube dispersion of  claim 1 , wherein the azo compound comprises at least two sulfonic acid moieties. 
     
     
         6 . The carbon nanotube dispersion of  claim 5 , wherein the azo compound comprises at least two azo moieties 
     
     
         7 . The carbon nanotube dispersion of  claim 1 , wherein the azo compound is selected from the group consisting of: 
       
         
           
           
               
               
           
         
       
       wherein each R is identical or different and each R is independently selected from the group consisting of amino-substituted phenyl and amino-substituted naphthyl, 
     
     
         8 . The carbon nanotube dispersion of  claim 7 , wherein at least one R is further substituted with at least one sulfonic acid moiety. 
     
     
         9 . The carbon nanotube dispersion of  claim 1 , wherein the azo compound is 3,3′-([1,1′-biphenyl]-4,4′-diyl)bis(4-aminonaphthalene-1-sulfonic acid (Congo red). 
     
     
         10 . A flexible, transparent, conductive film comprising a carbon nanotube dispersion as recited in  claim 1 . 
     
     
         11 . A method of making a flexible, transparent, conductive film, the method comprising:
 providing a dispersion of single-walled carbon nanotubes in a solution comprising a solvent selected from the group consisting of water, organic polar protic solvents, and organic polar aprotic solvents, and an azo compound comprising at least one azo moiety;   contacting the dispersion on a substrate, and then   removing the solution;   wherein a flexible, transparent, conductive film is formed on the substrate, and wherein wherein the single-walled carbon nanotubes are not covalently cross-linked.   
     
     
         12 . The method of  claim 11 , comprising contacting the dispersion on a flexible substrate. 
     
     
         13 . The method of  claim 11 , comprising contacting the dispersion on a flexible substrate selected from the group consisting of PET and PDMS. 
     
     
         14 . The method of  claim 11 , comprising contacting the dispersion on a glass substrate. 
     
     
         15 . The method of  claim 11 , wherein the azo compound comprises at least two azo moieties. 
     
     
         16 . The method of  claim 11 , wherein the azo compound comprises at least one sulfonic acid moiety. 
     
     
         17 . The method of  claim 11 , wherein the azo compound comprises at least two sulfonic acid moieties. 
     
     
         18 . The method of  claim 11 , wherein the azo compound is selected from the group consisting of: 
       
         
           
           
               
               
           
         
       
       wherein each R is identical or different and each R is independently selected from the group consisting of amino-substituted phenyl and amino-substituted naphthyl, 
     
     
         19 . The method of  claim 16 , wherein at least one R is further substituted with at least one sulfonic acid moiety. 
     
     
         20 . The method of  claim 11 , wherein the azo compound is 3,3′-([1,1′-biphenyl]-4,4′-diyl)bis(4-aminonaphthalene-1-sulfonic acid (Congo red).