Electrochromism refers to the reversible and lasting change of light transmittance and / or reflectivity associated with electrochemical redox reaction when the material is applied with appropriate voltage. The applications of electrochromic devices mainly include: intelligent windows for cars and buildings, controllable light reflection or light transmission display devices (for optical information and storage), controllable aircraft canopies, reusable price tags, spacecraft thermal control, etc.

Tungsten trioxide (WO₃) is an important n-type semiconductor oxide, which has a variety of crystal structures. Due to its unique physical and chemical properties, it has been widely studied, and has been applied in electrochromic, photochromic, sensing and catalytic fields. In order to further utilize the excellent properties of WO₃ and broaden its application field, the best technical way is to reduce its grain size, that is, nano tungsten oxide.

Compared with the traditional tungsten oxide materials, tungsten oxide nanowires have larger specific surface area, which have a wide range of application prospects in gas sensor, electroluminescence, photoluminescence, conductivity electrode and photocatalysis. Especially in the application field of oxide semiconductor gas sensor, tungsten oxide nanowires not only have large specific surface area, but also have larger surface activity and stronger adsorption capacity, which accelerates the reaction with gas, thus greatly improving the sensitivity and further reducing the working temperature of the sensor.

Rare earth trivalent ions have rich 4f energy level configuration, and their fluorescence characteristics are greatly affected by the crystal field environment and the symmetry of the lattice. At present, many scholars use the small size effect of semiconductor nano materials (ZnO, TiO₂) and lattice sensitization to improve the optical properties of rare earth trivalent ions, which are widely used in biological fluorescent probes, optical devices and new luminescent materials.