Raman spectra in vanadate nanotubes revisited

In this letter we report the Raman spectra of vanadate nanotubes (VONTs). The spectra present a clear signature that can be used for probing the tubular structure. The temperature effects on the structure of dodecylamine- and Cu-intercalated VONTs were studied by changing the laser power density during the Raman measurements. We have found that low laser power densities promote the decomposition of VONTs, leading to the collapse of the tubular structure and converting the nanotubes into V2O5 oxide. The decomposition occurs through an intermediate compound that is isostructural to V2O5 xerogel. The Raman experiments in VONT-based systems should be performed at extremely low laser power densities.