The WS2 nanoflakes based chemiresistive-type sensors were fabricated by dip-coating method. The as-milled WS2 nanoflakes were thus deposited on an alumina substrate preprinted with interdigitated gold electrodes (electrode gap: 200 micrometers). The chemiresistive sensors were tested in a sealed chamber in which different concentrations of analytes could be achieved by vaporizing the corresponding liquids [12], [24], [25] and [26]. The resistance of the chemical sensors was measured by using the digital electromultimeter (Agilent 34410A, USA). The response (Rs) of the sensor is defined as the ratio of Ra to Rg, where Ra and Rg are the resistance of the sensor in air and in analytes, respectively. The time taken by the resistor to ramp from Ra to Ra + 90% (Rg − Ra) is defined as the response time, tres, when the sensor is exposed to the analytes. The time taken by the resistor to change from Rg to Rg-90% (Rg − Ra) is defined as the recovery time, trecov, when the sensor is retrieved from the analytes.