Doping of MoS₂ and WS₂ Nanostructures

Layered compounds like WS₂ or MoS₂, have strong (covalent) bonds in the layer (a-b plane) and weak van der Waals forces along the c-axis. The high energy stored in the dangling bonds at the periphery of these nanoscopic sheets may induce formation of inorganic nanotubes and fullerene-like nanoparticles (INT and IF) [1]. Due to their unique properties and applications, the study of these nanostructures is a rapidly growing field.
Here, the existing synthetic methods for production of INT-WS₂ method was substantially modified and improved. Interestingly, it was found that by slight changes of the conditions, such as temperature, pressure or gas flows rate, we get a variety of different nanostructures (i.e. WO_2.78 nanowires, WO_2.78@WS₂ core shell nanowires, WS₂ scrolls, IF nanoparticles, thin sheets, spear-like nanotubes and more). Since the IF/INT are semiconductors, their properties can be controlled by doping. Indeed, it was shown that doping of the IF/INT with a few hundred ppm of Re atoms leads to their increased conductivity and to substantial decrease in friction and wear [2]. Study of the optical properties of the Re doped IF-MoS₂ revealed that these NPs undergo Burstein-Moss optical shift due to band filling [3]. Inspired by the fascinating properties of the doped IF/INT, the optical and electronic properties of the undoped counterparts were reconsidered. Herein, it was found that the IF-MoS₂ and INT-WS₂ maintains not only the excitonic structure of the bulk, but also the plasmonic scattering (which does not exist in the bulk) [4]. The strong light-matter interaction in the IF/INT-MS₂ suggests that they can operate as a plasmonic device at room temperature.
1. Tenne, R., et al., Nature, 1992.
2. Yadgarov, L., et al., Angew. Chem. Int. Ed., 2012.
3. Sun, Q.C., Yadgarov, L., et al., ACS nano, 2013.
4. Yadgarov, L., et al., ACS nano, 2014.