Non-catalytic and substrate-free method to titania-doped W 18O 49 nanorods: Growth, characterizations, and electro-optical properties

In the present study, titania-doped (Ti-doped) W ₁₈O ₄₉ nanorods have been prepared using a modified plasma arc gas condensation technique. Characterizations by field-emission gun scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy and high-resolution X-ray photoelectron spectroscopy indicate that the as-prepared nanorods with a singlecrystalline monoclinic W ₁₈O ₄₉ phase are of 20-100 nm in diameter and several micrometers in length. The Raman peaks of the Ti-doped W ₁₈O ₄₉ nanorods show a red-shift Raman peaks, and an additional greenemission peak at 497 nm is observed in the photoluminescence (PL) spectrum compared to pure W ₁₈O ₄₉ nanorods. Field-emission (FE) measurements reveal that the turn-on (E _to) and threshold (E _thr) voltages of the Ti-doped W ₁₈O ₄₉ nanorods are 2.2 and 3.4 V/lm, respectively. A vapor-solid process that does not involve the use of catalyst is proposed for the nanorod growth mechanism. Experimental results show that the additional defects resulting from titania doping are responsible for the enhancement of the optical and FE properties of the pure W ₁₈O ₄₉ nanorods.