Currently tungsten oxide has been widely used in electrochromic intelligent glass, optical device, supercapacitor, gas sensor, photocatalysis, photothermal therapy and other application fields. With the rapid development of nano science and technology, more and more synthesis methods of nano tungsten oxide are available, mainly has there kinds of methods including vapor deposition, liquid-phase synthesis and solid-phase synthesis.
1.0 Vapor deposition
Vapor deposition is widely used in the synthesis of materials. Generally it is a kind of synthetic method of depositing evaporation source onto substrate material by using external energy. In the synthesis process of the tungsten oxide, physical vapor deposition is often used, which is a physical method using external energy (including ion bombardment, thermal evaporation, electron beam bombardment, laser pulse radiation, etc.) to sublimate the raw material onto the target substrate and then condense it. The size, crystallinity and nano morphology of the target product can be adjusted by adjusting the parameters.
2.0 Liquid phase synthesis
The equipment used in gas phase synthesis is expensive, which limits the development and application of gas phase synthesis to some extent. Therefore liquid phase synthesis has its advantage, it can react at a relatively low temperature and still maintain the good property of the product. After years of efforts by many researchers, more and more liquid phase synthetic methods have been applied to the synthesis of nanostructured tungsten oxide such as sol-gel method, template method, hydrothermal method, electrochemical etching method and electrodeposition method etc.
3.0 Solid phase synthesis method
The solid phase method is to use tungstic acid and ammonium tungstate as raw material, directly heat in tube furnace or muffle furnace to decompose and produce nano tungsten oxide. Although the program of this method is simple and easy to get, most of the products are easy to agglomerate and the size is not uniform, therefore its use is limited.
