Imaging of Pristine and Functionalized Carbon Nanotubes by Scanning Tunneling Microscopy

Covalent side-wall functionalization of single-walled carbon nanotubes has been achieved with a variety of schemes and continues to be pursued for modifying carbon nanotube properties for applications in composite materials, sensors and molecular electronics. However, information about specific locations of functional groups along nanotube sidewalls is still lacking. Here we present images of clean and functionalized single-walled carbon nanotubes taken by scanning tunneling microscopy (STM) using highly ordered pyrolytic graphite as a substrate. We demonstrate the distinction of nanotubes from artifacts such as graphene step edges and grain boundaries. Since this is a tedious process, however, we also explored gold as an alternative substrate and present first images of functional groups along nanotube sidewalls.