Ruthenium-decorated tungsten disulfide quantum dots for a CO 2 gas sensor

In this work, a selective chemiresistive gas sensor for carbon dioxide gas detection at room temperature (∼25 °C) was successfully fabricated, where ruthenium-decorated tungsten disulfide (Ru@WS 2 ) quantum dots (QDs) have been used as the sensing material. A mixed solvent of lithium hydroxide (LiOH · H 2 O) and N-methyl-2-pyrrolidone (NMP) was used to obtain the Ru-decorated WS 2 QDs from the exfoliated WS 2 nanoflakes. Then, the prepared WS 2 QDs and Ru@WS 2 QDs were confirmed using different material characterization techniques. The gas sensors were prepared by spraying the WS 2 QDs and Ru@WS 2 QDs on gold interdigitated electrodes (IDE), and were then exposed to various concentrations of CO 2 gas in dry air conditions. Also, the effect of humidity on both sensors in 5000 ppm CO 2 gas has been studied. The Ru@WS 2 QD based sensor showed superior sensitivity and good selectivity to CO 2 gas in comparison with isopropanol, acetone, ethanol, methanol and benzene at room temperature than the WS 2 QD. The sensor showed an increase in resistance when exposed to CO 2 gas ranging from 500 to 5000 ppm, indicating p-type characteristics. The Ru@WS 2 QD shows less effects at different humid conditions compared to WS 2 QD as a CO 2 gas sensor.