Submillimeter-Long WS2 Nanotubes: The Pathway to Inorganic Buckypaper

WS₂ nanotubes present many new technologies under development, including reinforced biocompatible polymers, membranes, photovoltaic-based memories, ferroelectric devices, etc. These technologies depend on the aspect ratio (length/diameter) of the nanotubes, which was limited to 100 or so. A new synthetic technique is presented, resulting in WS₂ nanotubes a few hundred micrometers long and diameters below 50 nm (aspect ratios of 2000–5000) in high yields. Preliminary investigation into the mechanistic aspects of the two-step synthesis reveals that W₅O₁₄ nanowhisker intermediates are formed in the first step of the reaction instead of the ubiquitous W₁₈O₄₉ nanowhiskers used in the previous syntheses. The electrical and photoluminescence properties of the long nanotubes were studied. WS₂ nanotube-based paper-like material was prepared via a wet-laying process, which could not be realized with the 10 μm long WS₂ nanotubes. Ultrafiltration of gold nanoparticles using the nanotube-paper membrane was demonstrated.