A surfactant-assisted sol-gel route was chosen in order to synthesize low temperature nanostructured V₂O₅ thin films of orthorhombic structure. The effects of the surfactants on the final structure of vanadium oxide films have been evaluated by XRD, SEM and Raman and XAS spectroscopy.

No traces have been found of hydrated phases. On the contrary, Raman and EXAFS show a high degree of equatorial and axial order, comparable or, for Brij^®76 and Tween-60, enhanced with respect to commercial crystalline V₂O₅ powder, even in films annealed at 300 °C.

The removal of surfactants from the host metal oxide network as a function of the thermal annealing has been monitored by Raman and EXAFS. Brij^®76, Triton X-100 and Tween-60 are extracted around 300 °C, while CTAB persists in the matrix at temperatures up to 400 °C. This was confirmed by XRD measurements, too.

The morphologies are mostly driven by the strong anisotropic requirements of the oxide network, forcing the stacking of V₂O₄ chains in lamellar structures. In all cases the spin-coating/evaporation process leads to the deposition of more or less ordered lamellar particles on the substrate. Two different behaviours, related to the persistence of surfactant aggregates during the thermal treatment, may be evidenced:

• In the case of CTAB, the surfactant is still present when the extended crystallization of the oxide network starts around 300 °C; the sintering process becomes effective only after surfactant extraction (around 400 °C): at this stage the nanoparticles are mostly isolated and randomly oriented, so that V₂O₅ lamellas and nanorods elongate at random out of plane distribution with increasing temperature.

• If the surfactant is removed when the crystallization starts (as for other surfactants employed), the in-plane growth of the crystallites is much less perturbed, leading to textured coverage of the substrate by nanobelts and nanorods.

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