Selective Methane Sensors Based on Tungsten Carbides/Tin Oxide and Tungsten/Tin Oxide Core–Shells Modified on Interdigitated Electrodes

Abstract

Selective methane (CH 4 ) sensors were fabricated based on interdigitated electrodes individually modified with core-shells of tungsten carbides-tin oxide (WC/W 2 C@SnO 2 ) and tungsten-tin oxide (W@SnO 2 ) by thermoreduction method using different percentages of carbon nanotubes and tungsten powder. The morphology of the synthesized core-shells was evaluated by different methods such as patterned X-ray diffraction, particle size analyzer, scanning electron microscopyand transmission electron microscopy. In the fabricated CH 4 sensors, change in resistance was considered as the detection system. Figures of merit such as linearity, specificity, and response time were also evaluated. No serious interference was evaluated via introduction of at least 500 folds excess of different foreign gases to a certain concentration (∼ 1000parts per million, ppm) of CH 4 . Limit of detection was also evaluated to ∼ 45.0 ppm. The relative standard deviation during at least 10 replicate analyses of 1000 ppm of CH 4 standard solution was evaluated to 4.31%. Fast response time (∼ 8.0 s) and recovery time (∼ 11.0 s) have been obtained for the CH 4 sensor fabricated using 5.0%W@SnO 2 .