Process for demetallization of carbon nanotubes

Abstract

Processes are provided for removing metal-based catalyst residues from carbon nanotubes by contacting the carbon nanotubes with an active metal agent and carbon monoxide.

1 . A process comprising:
 a) exposing carbon nanotubes comprising metal impurities to flowing carbon monoxide gas;   b) raising the temperature of the carbon nanotubes and flowing carbon monoxide from about 20° C. to a maximum temperature of 200° C. or lower, to produce volatile metal species and carbon monoxide-treated nanotubes;   c) transporting the volatile metal species away from the carbon monoxide-treated carbon nanotubes; and   d) isolating the carbon monoxide-treated carbon nanotubes.   
     
     
         2 . The process of  claim 1  wherein prior to exposing the carbon nanotubes to flowing carbon monoxide gas, the carbon nanotubes are first exposed to an active metal agent selected from the group consisting of lithium, sodium, potassium, cesium, and combinations thereof. 
     
     
         3 . The process of  claim 1 , wherein the process further comprises annealing the carbon monoxide-treated carbon nanotubes. 
     
     
         4 . The process of  claim 1 , wherein the carbon nanotubes are made by laser ablation. 
     
     
         5 . The process of  claim 1 , wherein the carbon nanotubes are made by chemical vapor deposition. 
     
     
         6 . A composition comprising the isolated carbon nanotubes made by the process of  claim 1 . 
     
     
         7 . A screen printable paste comprising the composition of  claim 6 , a solvent, and a binder. 
     
     
         8 . A photopolymerizable paste comprising the composition of  claim 6 , a solvent, a binder, a photoinitiator, a developable binder and a photohardenable monomer. 
     
     
         9 . An electron field emission device comprising the composition of  claim 6 . 
     
     
         10 . A plurality of field emitters comprising the composition of  claim 6 . 
     
     
         11 . The process of  claim 1  wherein the metal residues comprise catalyst metal residues.