Quantum Conductance Steps in Solutions of Multiwalled Carbon Nanotubes

We have prepared solutions of multiwalled carbon nanotubes in Aroclor 1254, a mixture of polychlorinated biphenyls. The solutions are stable at room temperature. Transport measurements were performed using a scanning-tunneling probe on a sample prepared by spin coating the solution on gold substrates. Conductance steps were clearly seen. A histogram of a high number of traces shows maximum peaks at integer values of the conductance quantum $G_0=2e^2/h$, demonstrating ballistic transport at room temperature along the carbon nanotube over distances longer than $1.4\mu \mathrm{m}$.