Rectifying diodes from asymmetrically functionalized single-wall carbon nanotubes.

Asymmetrically functionalized single-wall carbon nanotubes (SWNTs) have been prepared by a covalent reaction of an 11-mercaptoundecanol-modified Au surface with oxidized SWNT cylinders. While one end of the tubes is attached to gold substrate via ester groups, the free carboxylic substituents on the other end can be either ionized (CO2-) or esterified (CO2Et), creating a donor-acceptor asymmetric and acceptor-acceptor symmetric SWNT, respectively. Study of the SWNT monolayer conductance in Hg drop junction experiments reveals a pronounced diode-like behavior for donor-SWNT-acceptor junctions, while acceptor-SWNT-acceptor junctions are electrically symmetric.