Optical properties of vanadium oxide nanotubes.

The optical properties of vanadium oxide nanotube dispersions have been characterized using visible and near infrared absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and nonlinear transmission of optical intensities in the visible and near infrared. Using transmission electron microscopy, optical properties have been correlated to the occurrence of two distinct nanoparticle morphologies: nanotubes and unrolled tubes or platelets. Raman spectroscopy indicates that color changes associated with tub unrolling can be attributed to V2O5 formation. The nanotube and platelet morphologies both show strong optical intensity limiting at 532 and 1064 nm. However, dependencies on repetition rate suggest that slightly different mechanisms dominate at the two wavelengths.