Temperature dependent selectivity switching from methanol to formaldehyde using ZnO nanorod based chemi-resistive sensor

Operating temperature for detection of a gas/ vapour is an important factor to control the selectivity of a chemiresistive type sensor. By governing the temperature dependent adsorption/desorption process of a gas/vapor on the surface of a sensing prototype, its selectivity can be switched from one target gas to another, which is useful for field applications. In this vision, this study represents a high performance, low temperature, and versatile volatile organic compound (VOC) sensor fabricated by hydrothermally synthesized ZnO nanorod networks. The selectivity of the prepared sensor prototype has been switched from methanol (at low operating temperature i.e < 50(?)C) to formaldehyde (at high operating temperature i.e > 50 C-?) by varying the operating temperature of the sensor. The sensor can selectively detect methanol vapor (400 ppm) with a response value of 600 operating at room temperature (RT, 27 C-?). On the other hand, the same prototype is selective toward formaldehyde (400 ppm) with an extremely high response of 12000 at an operating temperature of 100 C-?. Moreover, high sensi-tivity, selectivity, repeatability, and low response time (4.2 s) towards methanol at room temperature fulfill the purpose of a reliable VOC sensor for practical applications. The mechanism of selectivity switching associated with the present sensor has been correlated with the activation energy values for methanol and formaldehyde. By virtue of temperature driven selectivity switching phenomena, the ZnO nanorod networks based present sensor prototype can be considered as a smart sensing element for a futuristic, versatile, low temperature, dual mode VOC sensor.

Automated summary

The operating temperature is an important factor in controlling the selectivity of a chemiresistive type sensor for gas/vapor detection. By regulating the temperature dependent adsorption/desorption process, the selectivity of the sensor can be switched between different target gases, making it suitable for practical applications. In this study, a high performance, low temperature, and versatile VOC sensor was developed using hydrothermally synthesized ZnO nanorod networks. The selectivity of the sensor prototype was successfully switched from methanol to formaldehyde by adjusting the operating temperature. The sensor exhibited high sensitivity, selectivity, repeatability, and a low response time, making it a reliable VOC sensor for practical applications.