Covalent functionalization/polycarboxylation of tungsten disulfide inorganic nanotubes (INTs-WS₂)

Inorganic nanotubes of tungsten disulfide (INTs-WS₂) are insoluble in common solvents and practically inert, hindering their usefulness in both research and commercial applications. The covalent attachment of functional species onto the surface of INT-WS₂ is a critical first step in realizing the potential that INT-WS₂ offer for high-performance materials and products. Although a few attempts have been reported regarding preparing modified nanotubes, only a limited range of surface functionalities is possible with these methods. We have developed a versatile method, based on a modified, highly electrophilic acidic Vilsmeier-Haack reagent, to produce covalently bonded, polycarboxylated functional WS₂ nanotubes that are dispersible in polar liquids, including water. The surface polycarboxylated shell provides a means for additional derivatization, enabling matching compatibility of derivatized nanotubes to both hydrophobic and hydrophilic materials. Nanocomposites incorporating derivatized INT-WS₂ are expected to show improved properties as a result of enhanced interfacial compatibility, made possible by the large number of classes of functionalization available through the initial polycarboxylation step. [Figure not available: see fulltext.]