... sensitivity to ppm NO2 and operating temperature (a) WO3 nanoparticles deposited at 1, 3, and 10 kPa and annealed at 600 8C (b) WO3 nanoparticles deposited at kPa and annealed at 400 and 600 8C ... for the sensors made of WO3 nanoparticles deposited at 1, 3, and 10 kPa and annealed at 600 8C while Fig 5(b) shows the results for the sensors made of WO3 nanoparticles deposited at kPa and annealed ... FE-SEM images of WO3 nanoparticles deposited at 1, 3, and 10 kPa, respectively, and annealed at 600 8C (d)–(f) FE-SEM images of WO3 nanoparticles deposited at kPa and annealed at 400, 600, and 800...