WO3 nanowire films have been prepared by thermal evaporation on both a silicon substrate and a quartz substrate. The gasochromic effect and the colouration mechanism of the films are investigated in detail by ultraviolet–visible–near infrared (UV–vis–NIR) spectroscopy, x-ray diffraction (XRD) spectroscopy, micro-Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) and electrical transport measurements. The studies reveal that the gasochromism of WO3 nanowire films is caused by hydrogen injection. Along with the injection, a part of the tungsten ions’ valences and the lattice structure change, giving rise to the colouration of the films. Moreover, electrical transport measurements show the lower conductance of the coloured film, which further confirms the hydrogen injection mechanism. Finally, a gasochromic model of the WO3 nanowire films is proposed.

W 18 O 49 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 W 18 O 49 nanowires was obtained, and the effect of laser power on the change of their structure was also studied. W 18 O 49 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.

Crystalline W20O58 nanowires were grown on silicon substrates by thermal evaporation of tungsten powders in a flow of argon gas without using any catalyst. Scanning electron microscopy shows that typical nanowires vary from 30 to 100 nm in diameter and around 8 µm in length. X-ray diffraction and high-resolution transmission electron microscopy with electron diffraction study reveal that the nanostructures are crystalline. The laser power effect on the structure change of W20O58 nanowires has also been studied, which shows that W20O58 can be directly oxidized to WO3 very easily only by laser heating.

Raman spectroscopic analysis is performed on WO(3) nanowires at room temperature at pressures from ambient conditions to 45 GPa. Linear dependence of the first-order Raman signal on various high-pressure (HP) sections is observed. Upon increasing the applied pressure, the WO(3) nanowires undergo four phase transitions at pressures around 1.7, 4.6, 21.5, and 26.2 GPa, which are all less than that reported for bulk WO(3). When the pressure is up to 42.5 GPa, a new high-pressure phase (HP5) appears. This phase has never been reported and is not reversible while unloading the pressure.