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