Long-term aging of multiwall nanotubes and fullerene-like nanoparticles of WS2

Abstract

Tungsten disulfide is an important compound with layered structure (2D-material). Chemically it is less stable than tungsten trioxide and hence undergoes oxidation upon exposure to the ambient atmosphere. Although nanoparticles of tungsten disulfide are metastable, hollow-closed nanostructures, i.e. fullerene-like WS₂ (IF-WS₂) and nanotubes thereof are kinetically stabilized because they present their basal (001) surface to the outer world. In this work, the oxidation of IF-WS₂ and nanotubes stored under different conditions for 17–26 years have been studied. It was found that the degree of oxidation depends on the storage conditions. In fact, nanoparticles which were stored for long time and protected from the ambient atmosphere oxidized only marginally, while others kept under less favorable conditions suffered severe oxidation. Furthermore, the degradation of the IF nanoparticles is autocatalytic with clear acceleration over time. This work has also practical significance, since the shelf-life of IF-WS₂ nanoparticles, which are used as solid-state lubricants commercially have not been studied before.