Strong p-type doping of individual carbon nanotubes by Prussian blue functionalization.

Numerous efforts have been devoted to the application of single-walled carbon nanotubes (SWCNTs) in nanoscale electrical devices, including field-effect transistors (FETs), memories, and (bio)chemical sensors. These activities have strongly benefited from the development of methods enabling the controlled chemical functionalization of CNTs. Among these techniques, noncovalent modification schemes have found application in the chemical doping of nanotubes, for example for the conversion of semiconducting SWCNTs from pto n-type, and the fabrication of p-n junctions within individual SWCNTs. Such doping has mainly been realized using alkali metals and amino-polymers (e.g., polyethyleneimine) for n-type, and halogens or FeCl3 [11] for ptype doping. A class of potential dopants that has received comparatively little attention so far is that of metal coordination compounds. One such compound, Prussian Blue (PB) (Fe4[Fe (CN)6]3 nH2O (n1⁄4 14–16)), has been utilized as an electrocatalytic material to modify bulk CNT electrodes with the aim of fabricating amperometric biosensors. However, while these studies have addressed the electrochemical properties of the resulting modified electrodes in detail, the impact of the PB layer on the electronic properties of the underlying nanotubes remained unexplored. Furthermore, decorating CNTs with PB is of interest because of the fact that PB is a molecular magnet displaying ferromagnetic properties below its Curie temperature of Tc1⁄4 5.6K, which potentially opens up the possibility for their application in spintronic devices. In the present work, we focus on the electrical properties of individual SWCNT