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 chemi-resistive 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 sensitivity, 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. [Display omitted] • ZnO nanorod networks were synthesized in low temperature hydrothermal method. • ZnO nanorod network sensor shows a unique selectivity switching in VOC detection. • Selectively detect methanol (R ∼ 600) at RT and formaldehyde (R ∼ 12000) at high temperature (≥ 50 °C). • Activation energy values has been correlated to explain the sensing mechanism behind selectivity switching. [ABSTRACT FROM AUTHOR]