Aleksandr Noy

Frictionless sliding of single-stranded DNA in a carbon nanotube pore observed by single molecule force spectroscopy.

Smooth inner pores of carbon nanotubes (CNT) provide a fascinating model for studying biological transport. We used an atomic force microscope to pull a single-stranded DNA oligomer from a carbon nanotube pore. DNA extraction from CNT pores occurs at a nearly constant force, which is drastically different from the elastic profile commonly observed during polymer stretching with atomic force microscopy. We show that a combination of the frictionless nanotube pore walls and an unfavorable DNA solvation energy produces this constant force profiles.

Growth Kinetics of Vertically Aligned Carbon Nanotube Arrays in Clean Oxygen-free Conditions

Vertically aligned carbon nanotubes (CNTs) are an important technological system, as well as a fascinating system for studying basic principles of nanomaterials synthesis; yet despite continuing efforts for the past decade many important questions about this process remain largely unexplained. We present a series of parametric ethylene chemical vapor deposition growth studies in a hot-wall reactor using ultrapure process gases that reveal the fundamental kinetics of the CNT growth. Our data show that the growth rate is proportional to the concentration of the carbon feedstock and monotonically decreases with the concentration of hydrogen gas and that the most important parameter determining the rate of the CNT growth is the production rate of active carbon precursor in the gas phase reaction. The growth termination times obtained with the purified gas mixtures were strikingly insensitive to variations in both hydrogen and ethylene pressures ruling out the carbon encapsulation of the catalyst as the main process termination cause.