Reliable NO2 sensing and alert system based on Pd-PdO thin film with sub ppm level detection at room temperature

Abstract

Human and environmental health is greatly affected due to toxic gas emissions in the environment from power generation, transportation and other industries. For real time monitoring of polluting gases, gas sensor should be reliable, robust and stable in all environmental conditions. We report, nanostructured PdO thin film based portable and low voltage (< 5 V) operating NO2 sensor for sensing sub-ppm level of NO2, with limit of detection (LOD) 80 ppb at room-temperature. To optimize the sensor response of PdO thin film prepared by cost effective self-assembly technique films were calcined at 200 °C, 300 °C and 400 °C. Effect of calcination temperatures on film’s surface morphology, composition and energy band gap have been studied using various techniques. The charge carrier concentration, charge carrier transport mechanism, sensitivity, selectivity, repeatability, reproducibility, reliability, linearity etc. have been studied. PdO thin films calcined at 400 °C are most sensitive with approx. 60% and 100% response for 500 ppb and 1 ppm NO2, respectively at room-temperature. After stable response upto 6 months and more was obtained for these, a portable, pocket size electronic device of size (8 × 5 cm) was fabricated and tested successfully, coupling with the sensor film to prepare a wearable sensor.