Helical Mesoporous Tantalum Oxide Nanotubes: Formation, Optical Activity, and Applications

Nanomaterials with helical morphologies have attracted much attention owing to their potential applications as nanosprings, chirality sensors and in chiral optics. Single-handed helical Ta₂ O₅ nanotubes prepared through a supramolecular templating approach are described. The handedness is controlled by that of the organic self-assemblies of chiral low-molecular-weight gelators (LMWGs). The chiral LMWGs self-assemble into single-handed twisted nanoribbons through H-bonding, hydrophobic association, and π-π stacking. The Ta₂ O₅ nanotubes are formed by the adsorption and polycondensation of Ta₂ O₅ oligomers on the surfaces and edges of the twisted organic nanoribbons followed by removal of the template. The optical activity of the nanotubes is proposed to originate from the chiral defects on the inner surfaces of the tubular structures. Single-handed twisted LiTaO₃ nanotubes can also be prepared using Ta₂ O₅ nanotubes.