Raman spectroscopic study of oxidation and phase transition in W18O49 nanowires

W₁₈O₄₉ nanowires were synthesized by a high‐temperature physical evaporation technique. The structure, morphology, and composition of the nanowires were characterized by SEM, EMPA, XRD, XPS, and HRTEM techniques. The intrinsic Raman spectrum of W₁₈O₄₉ nanowires was obtained, and the effect of laser power on the change of their structure was also studied. W₁₈O₄₉ nanowires were first oxidized to tungsten trioxide nanowires under irradiation of a certain laser power, and then the tungsten trioxide nanowires underwent a phase transition from monoclinic to orthorhombic with increasing laser power; this phase transition was reversible on turning down the laser power. Copyright © 2006 John Wiley & Sons, Ltd.