Temperature-tuned dual-selective NO2/diisopropylamine sensor based on (NH4)0.33WO3 doped γ-WO3 nanosheets-assembled hollow microspheres via simple pyrolysis of commercial ammonium metatungstate

The efficient and synchronous monitoring of diverse harmful gases by one portable sensor has recently become a hot topic due to the vast majority of reports for only sensing a given gas. Herein, two types of hollow microspheres cross-linked through γ-WO 3 nanosheets were controllably prepared by simple pyrolysis of commercial ammonium metatungstate (AMT). Among, the orange product obtained by air calcination at 400 °C is trace (NH 4 ) 0.33 WO 3 doped γ-WO 3 composite, and has broad mesoporous structure, rich oxygen vacancies and the synergistic catalysis of surface W 6+ Lewis acid. These unique factors help to promote the diffusion of gas molecules, expose more active sites for chemical reaction, increase the conductivity of sensitive material and modulate the state of surface adsorbed oxygen species, which in turn effectively improve its sensitive capability toward diverse noxious gases. The (NH 4 ) 0.33 WO 3 /WO 3 sensor achieves response values of 234 for 5 ppm NO 2 at low 50 °C and 170 for 100 ppm diisopropylamine (DIPA) at 170 °C. Meanwhile, it also displays low detection concentrations, good reversibility and moisture resistance, as well as practical detection for vehicle exhaust and prometryn. This is also the first report of a WO 3 -based sensor that can simultaneously achieve dual-detection of trace NO 2 and DIPA. Moreover, the temperature-tuned dual-response mechanism has also been discussed in detail.