Remskar et al. Nanoscale Res Lett 2011, 6:26 http://www.nanoscalereslett.com/content/6/1/26 absorption peak centered at the 472 nm, revealing changes in the direct transitions from the valence band to the conduction band. Besides these differences, the spectrum of MoS2 nanotubes matches well with the spectrum belonging to the dispersed MoS2 polycrystal- line sample. Morphology of MoS2 Nanotubes The MoS2 multiwall nanotubes gained by the sulfuriza- tion after complete iodine removal keep the shape of the precursor Mo6S4I6 nanowires (Figure 3a). The nano- tubes are still organized in hedgehog-like groups (Figure 3b). The tube walls with a typical thickness below 10 nm are strongly defected (Figure 3c). The lat- tice defects condensate forming faceting of the dome closure or disorder areas near stacking faults of MoS2 layers. Some inner cylinders can be terminated by curved players of outer cylinders (Figure 3d) revealing a dominant tendency of self-termination of surface mole- cular layers, while the inner ones did not gain sufficient energy for a closure. Page 5 of 6 Transport Measurement on a Single MoS2 Nanotube Two-terminal device was fabricated from MoS2 nano- tubes to measure transport properties (Figure 4a). The tubes were placed on a thermally-oxidized, heavily- doped p-Si substrate with a 90-nm-thick SiO2 overlayer. Titanium/gold contacts 20/220 nm in respective thick- ness were formed by electron beam evaporation using a photolithographic lift-off process with separations between the electrodes of 5 μm. Two-terminal measure- ments on a MoS2 nanotube, 105 nm in diameter, show a metallic (approximately ohmic) conduction. No photo- conductivity was observed between measurements taken in the dark and under strong microscope illumination using a halogen lamp (Figure 4b). In addition, the wire conductivity could not be modulated independently on light illumination when backgated through the p + Si substrate in the range from -50 to +50 V with a tube bias ranging from 0 to 5 V, consistent with the metallic character of the nanotube. The nanotube conductivity is estimated to about 2 mS/cm by assuming that the wall thickness is 10 nm, which is the most frequently Figure 3 The MoS2 nanotubes: a A typical TEM image of a bunch of nanotubes grown from sacrificed Mo6S4I6 nanowires keeping their outer geometry; and b self-organization in hedgehock-like groups revealed by SEM; c HRTEM image of a nanotube’s wall with resolved MoS2 molecular layers, stacking faults and atomically rough surface; d TEM image of a single nanotube cap of a nanotube with inner cylinders terminated by curved layers of outer cylinders.