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.