1. Electrophoretic Separation
Novel, Ultra-Low Resistance Materials Prepared by Chemical Separation of Metallic Single Walled Carbon Nanotubes
Michael S. Strano, Department of Chemical Engineering, Massachusetts Institute of Technology
Selective Functionalization
Diazonium selectively functionalizes metallic over semiconducting single-walled carbon nanotubes (SWNT), due to the higher electron-transfer capability of metallic SWNT. Among various diazonium reagents, di-carboxy benzene diazonium showed exclusively high selectivity for metallic SWNT, due to its high oxidation potential.
Separation of metallic SWNT using chemical handle via electrophoresis
Hydroxy / carboxy phenyl group (chemical handles) deprotonate in solution and induces a negative charge on the functionalized metallic SWNT. Selectively reacted samples are separated into non-mobile (semiconducting) and negative electrophoretic mobility (metallic) fractions by the induced difference in electrophoretic mobilities during free solution electrophoresis. The speed of motion is approximately twice higher for di-carboxy than 4-hydroxy phenylated SWNT, indicating that higher separation efficiency is expected with di-carboxy phenylated SWNT.
Metallic SWNT film
The measured sheet resistance of metallic SWNT film is 46% lower than that of SWNT mixture film, indicating that metallic SWNT has higher conductivity than unseparated SWNT mixture.
Charged density is doubled O O- H+
Increase µ by
1.7x10-8m2/Vs
(+)
Reacted
M SWNT
Electrophoretic Separation
Metallic SWNT Film