Gold nanoparticles decorated WS${}_2$ microflakes (Au/WS${}_2$) have been synthesized by an in situ chemical reducing process. A chemiresistive-type sensor using as-synthesized Au/WS${}_2$ heterostructures as sensing materials shows an improved response to different concentrations of ammonia compared to pure WS${}_2$ at room temperature. As the concentrations of gold nanoparticles increased in heterostructures, response/recovery speeds of the sensors became faster although the sensitivity of the sensor was compromised compared to the sensitivity of the sensor with lower concentrations of Au. In addition, the Au/WS${}_2$-based sensor indicated excellent selectivity to formaldehyde, ethanol, benzene and acetone at room temperature. The improved performance of the sensors was attributed to the synergistic effect of electronic sensitization and chemical sensitization between WS${}_2$ and Au.

Tungsten sulfide decorated with indium oxide nanoparticles (In₂O₃/WS₂) was studied for a chemiresistive-type NH₃ sensor at room temperature. It was found that the responses of the developed In₂O₃/WS₂ heterostructure nanocomposite-based sensors are significantly improved to 3.81 from 1.45 for WS₂. The response and recovery time of the heterostructure-based sensor was found to significantly decrease to 88 s/116 s (10 ppm) from 112 s/192 s for the WS₂-based one. The sensor also exhibits excellent selectivity and signal reproducibility. In comparison to WS₂ decorated with both ZnO and SnO₂ in similar ways, the In₂O₃-decorated WS₂ has overall better sensing performance in terms of sensitivity, selectivity and response/recovery speeds for NH₃ from 1 ppm to 10 ppm at room temperature. The improved sensing properties of WS₂ incorporating In₂O₃ could be attributed to the joint enhancement mechanisms of the “electronic and catalytic” sensitizations.