Ruthenium-decorated tungsten disulfide quantum dots for a CO₂ 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@WS₂) quantum dots (QDs) have been used as the sensing material. A mixed solvent of lithium hydroxide (LiOH · H₂O) and N-methyl-2-pyrrolidone (NMP) was used to obtain the Ru-decorated WS₂ QDs from the exfoliated WS₂ nanoflakes. Then, the prepared WS₂ QDs and Ru@WS₂ QDs were confirmed using different material characterization techniques. The gas sensors were prepared by spraying the WS₂ QDs and Ru@WS₂ QDs on gold interdigitated electrodes (IDE), and were then exposed to various concentrations of CO₂ gas in dry air conditions. Also, the effect of humidity on both sensors in 5000 ppm CO₂ gas has been studied. The Ru@WS₂ QD based sensor showed superior sensitivity and good selectivity to CO₂ gas in comparison with isopropanol, acetone, ethanol, methanol and benzene at room temperature than the WS₂ QD. The sensor showed an increase in resistance when exposed to CO₂ gas ranging from 500 to 5000 ppm, indicating p-type characteristics. The Ru@WS₂ QD shows less effects at different humid conditions compared to WS₂ QD as a CO₂ gas sensor.