Room temperature responses of visible-light illuminated WO3 sensors to NO2 in sub-ppm range

In this paper, the effects of visible-light illumination on sensing properties of tungsten trioxide (WO3) sensors have been investigated. WO3 sensitive films are prepared on alumina substrates by screen-printing. WO3 sensors illuminated by visible/ultra-violet lights are submitted to sensing tests with 160 and 320 ppb nitrogen dioxide (NO2) at room temperature. NO2 sensing characteristics of the WO3 sensor are significantly improved by illumination as compared to that in the dark. Influences of light wavelength and light intensity on the sensing characteristics are further studied. The results show that visible light can effectively activate the WO3 sensors and blue light is a good choice to produce room-temperature devices which are suited for NO2 sensing applications. A sensing mechanism is proposed according to a simple adsorption–photodesorption model.