High-resolution transmission electron microscopy mapping of nickel and cobalt single-crystalline nanorods inside multiwalled carbon nanotubes and chirality calculations

TLDR

The study investigates the inclination of nickel and cobalt nanorod crystal planes relative to the carbon nanotube axis, examining elastic energy and surface tension effects. Nickel and cobalt nanorods (6–20 nm diameter, 0.29–0.9 µm length) were grown inside multiwalled carbon nanotube templates, and the nanotube chirality was mapped by Ni–C atom mapping in a graphene sheet to analyze plane inclination. The nanorods are perfect single crystals with (111) planes inclined at 39.6°/39.4° for fcc Ni/Cu and (002) planes at 53.4° for hcp Co, indicating that controlling chirality could enable synthesis of tubes with known chirality.

Abstract

The nickel and cobalt nanorods of the diameters in the range of 6–20nm with lengths of 0.29–0.9μm are formed using multiwalled carbon nanotubes as templates. The nickel and cobalt nanorods as described in our letter are perfect single crystals inside the nanotube with their Miller planes inclined with respect to the tube axis in a particular fashion. The (111) planes of face-centered-cubic nickel and cobalt are inclined at angles 39.6° and 39.4°, respectively, while the hexagonal-closed-packed cobalt (002) planes incline at an angle 53.4°. The inclination of these planes is studied in detail and results are discussed in terms of elastic energy and surface tension. The chirality of the carbon nanotubes, in intimate contact with the nanorod, is determined using the mapping of Ni and C atoms in a graphene sheet. We believe this could pave a way for synthesizing the tubes with known chirality.