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 (similar to 25 degrees 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.