Effect of copolymer and additive concentrations on the behaviors of mesoporous tungsten oxide

Nanostructured tungsten oxide films exhibit a series of interesting behaviors due to their excellent properties of photochromic reaction and gas sensing. Mesoporous films with a large surface area are desirable to improve their performance. The main purpose of this study is to elucidate the effects of the copolymer and additive concentrations on the microstructure of the mesoporous tungsten oxide prepared by a sol-gel method. The typical calcined tungsten oxide samples synthesized by L62 and P123 exhibit a Brunauer-Emmett-Teller (BET) surface area of 156 and 138 m2/g, respectively. The pore size of 4-10 nm in the sample increases with increasing copolymer concentration. For different additive conditions synthesized by a triblock copolymer, HCl or distilled deionized water (DDW) additive could further promote the BET surface area of mesoporous tungsten oxide than an additive of NaOH, which can be attributed to the stabilization of the micellization in acid media. The sol-gel tungsten oxide involving the use of nonionic triblock copolymer as the templates with disorder pores exhibits outstanding sensitivity in photochromic and gas-sensing properties. Mesoporous tungsten oxide powder synthesized by triblock copolymer exhibits a high transmittance with an indirect EG of 3.73 eV. Gas-sensing measurement reveals excellent recovery and sensitivity under low gas concentration, low operation temperature for mesoporous tungsten oxide film and a sensitivity of 25 as exposed to 20 ppm NO gas at 40 °C.